Characteristics of inclusions in chang 7 member and shale oil accumulation stages in Zhijing-Ansai area, Ordos Basin

Wenjie Wu; Jian Wang; Nan Wu; Yong Feng; Yilin Liang; Yulin Chen

doi:10.1371/journal.pone.0302468

. 2024 May 2;19(5):e0302468. doi: 10.1371/journal.pone.0302468

Characteristics of inclusions in chang 7 member and shale oil accumulation stages in Zhijing-Ansai area, Ordos Basin

Wenjie Wu ¹, Jian Wang ^1,^*, Nan Wu ¹, Yong Feng ¹, Yilin Liang ¹, Yulin Chen ¹

Editor: Fabio Trippetta²

PMCID: PMC11065247 PMID: 38696445

Abstract

In order to further clarify the shale oil accumulation period of the Chang 7 member of the Mesozoic Triassic Yanchang Formation in the Zhijing-Ansai area of the central Ordos Basin, Using fluid inclusion petrography analysis, microscopic temperature measurement, salinity analysis and fluorescence spectrum analysis methods, combined with the burial history-thermal history recovery in the area, the oil and gas accumulation period of the Chang 7 member of the Yanchang Formation in the Zhijing-Ansai area was comprehensively analyzed. Sixteen shale oil reservoir samples of the Mesozoic Triassic Yanchang Formation in seven typical wells in the study area were selected.The results show that the fluid inclusions in the Chang 7 member of Yanchang Formation can be divided into two stages. The first stage inclusions mainly develop liquid hydrocarbon inclusions and a large number of associated brine inclusions, which are mainly beaded in fracture-filled quartz and fracture-filled calcite. The fluorescence color is blue and blue-green, and the homogenization temperature of the associated brine inclusions is between 90–110°C. The second stage inclusions are mainly gas-liquid two-phase hydrocarbon inclusions, gas inclusions and asphalt inclusions. Most of them are distributed in the fracture-filled quartz, and the temperature of the associated brine inclusions is between 120–130°C. Fluid inclusions in Chang 7 member of the Yanchang Formation can be divided into two stages. The CO₂ inclusions and high temperature inclusions in the Chang 7 member of the Yanchang Formation are mainly derived from deep volcanic activity in the crust.

Introduction

In the past few decades, with the continuous decline of conventional oil and gas resources, global oil and gas resources are facing great challenges, and the exploration and development of shale oil has always been highly valued by experts and scholars [1].

In the Ordos Basin, the Chang 7 member of the Mesozoic Triassic Yanchang Formation is an important shale oil reservoir with great potential for exploration and development. The Yanchang Formation has experienced many tectonic movements, and the accumulation conditions are extremely complex [2]. Predecessors have done a lot of research work on the oil and gas accumulation periods of the Yanchang Formation. Currently, there are three different viewpoints in the research on the oil and gas accumulation period of the Chang 7: (1) The first stage of charging and accumulation occurred at the end of the Early Cretaceous [3–5]. Some scholars believe that this period is the peak period of basin subsidence and thermal evolution, during which oil and gas accumulation occurred [6]. (2) Two stages of charging and accumulation. One was small-scale oil and gas charging in the Early Cretaceous [7,8], and the other was large-scale oil and gas accumulation in the late Late Cretaceous [9–11]. (3) Three phases of charging and accumulation. The first stage of oil and gas charging occurred at the end of the Middle Jurassic [12–14], and the second stage of large-scale oil and gas migration occurred in the Late Jurassic to the middle of the Early Cretaceous [15–17]. The three phases of oil and gas accumulation occurred in the Late Cretaceous [18,19]. Due to the different understandings of the periods of oil and gas accumulation by the predecessors, the research on the key period of the accumulation age in this area needs to be perfected, and there is a lack of systematic understanding of the oil and gas accumulation in this block. Therefore, it is necessary to conduct further research on the oil and gas accumulation periods of the Chang 7 of the Yanchang Formation in the Zhijing Ansai area of the Ordos Basin.

This research project focused on the Chang 7, carried out experiments through petrographic observation of fluid inclusions, composition analysis, temperature and salt test, to identify the oil and gas accumulation periods of the Chang 7. In this paper, on the basis of systematic sampling and research on the characteristics of the low-permeability sandstone reservoirs of the Mesozoic Yanchang Formation in the Zhijing-Ansai area [20], the microscopic petrographic observation of fluid inclusions, microthermometry characteristics, and burial and thermal history are used to discuss. The stages of oil and gas migration and charging in the Mesozoic Yanchang Formation and the determination of reservoir formation time [21]. The research results help to understand the oil and gas accumulation mechanism of the Yanchang Formation in the Zhijing Ansai area of the Ordos Basin, and can provide theoretical support for the next step of oil and gas exploration in favorable areas in this area.

Geological background

The Ordos Basin is located in the western part of the North China Plate, spanning five provinces of Shanxi, Gansu, Ningxia, Mongolia, and Shanxi, with an area of about 370,000 square kilometers [22]. The geological background of the Ordos Basin is complex, and its tectonic activities include six first-order tectonic units: Yimeng Uplift, West Margin Thrust Zone, Tianhuan Sag, Yishan Slope, Jinxi Flexure Belt, and Weibei Uplift [23,24]. The period of the Chang 7 member of the Triassic Yanchang Formation in the Ordos Basin was the heyday of the lake basin, and the Late Triassic was the most important stage for the development of geological structures in the basin, and it was also one of the periods when the oil and gas system was extremely developed (Fig 1). The Chang 7 member in the Ordos Basin belongs to the heyday of basin development and evolution. The complex geological history and a series of sedimentary structures make the Chang 7 member the most important source rock development layer and key productivity layer in the Ordos Basin [25,26].

Fig 1 — (Modified from Liu et al., 2015) [27] (https://www.cia.gov/the-world-factbook/countries/china/map).

The research area is the Zhijing-Ansai area of the Ordos Basin, and the Chang 7 member oil layer group in the research area can be divided into three sublayers, Chang 7₁, Chang 7₂ and Chang 7₃ according to the depositional cycle from top to bottom. The lithology of the reservoir is mainly feldspathic sandstone and lithic sandstone, with high content of clay minerals, the reservoir is compact, and intergranular dissolution pores and intragranular dissolution pores are developed. The Chang 7 member mainly develops delta front subfacies and shore-shallow lake subfacies, partially develops semi-deep lake subfacies, and delta front mainly develops underwater distributary channels, flow separately bays and mouth bar microfacies [28].

Materials and methods

Samples and equipment

The samples collected for this study were collected from 7 typical wells in the Zhijing Ansai Block, including Well Xin 140, Well Xin 283, Well Shun 37, Well Shun 111, Well Gao 135, Well Wu 100, and Well Qiao 136. Select 16 samples of Chang 7 member for preparation. Under the indoor conditions of room temperature 20°C and air humidity 30%, make double-sided polished thin slices, and further carry out petrographic observation, composition analysis and temperature and salt test of fluid inclusions. The equipment used in this experiment is a Nikon Eclipse 80i dual-channel fluorescence microscope equipped with ultraviolet (UV) and transmitted light (TR). The excitation wavelength of ultraviolet light is 330-380nm, and the micro fluorescence spectrometer adopts the Maya 2000 Pro fiber optic spectrometer in the United States.

Fluid inclusion analysis

The composition of fluid inclusions represents the original mineral composition of past geological periods. The formation of inclusions runs through the entire geological process. It records and preserves the physicochemical characteristics of different stages of geological processes [29]. By describing the morphology and spatial distribution characteristics of inclusions under fluorescence and transmitted light by microscopy, oil and gas inclusions and brine inclusions can be identified. Under the excitation of ultraviolet light, hydrocarbon inclusions generally emit various fluorescences, and the organic molecular structure in the inclusions is the main factor controlling the fluorescence intensity and color [30]. Oil inclusions with different fluorescent colors represent different maturity. Using Spectra Suite software to calculate the spectral parameters of hydrocarbon-bearing inclusions one by one, the maturity of individual inclusions can be judged.

The liquid hydrocarbon inclusions and gas-liquid two-phase brine inclusions with different occurrences in different periods were selected, and their homogeneous temperatures were measured respectively, and the measured brine temperature in the same period was used to approximate the geothermal temperature when the oil inclusions were trapped.

Temperature measurement and salt measurement experiments were carried out under transmitted light, using the British Linkam THMSG600 microscopic cold-hot stage, using the thermal cycle method proposed by Goldstein and Reynolds (1994), to measure the hydrocarbon-containing inclusions with stable beating and regular shape and the brine inclusions in the same period the homogeneity temperature (Th) and the freezing point temperature (Tm) of the body were measured.

After being captured, inclusions will be affected by the temperature and pressure of the formation, which will cause deformation and greatly affect the uniform temperature. However, the formation of inclusions is complicated and there are many damage factors. As far as possible, samples consistent with the FIA concept were screened for experimental test analysis to ensure the reliability of experimental data [31,32]. FIA refers to "the most detailed group of related inclusions that can be classified petrographically" or "a group of inclusions that can be distinguished by petrographic methods and represent the most finely divided inclusion capture event" [33,34]. Each FIA is based on a petrographic relationship rather than a similarity in thermometric data representing a temporally finer-grained inclusion storage event [35,36]. The basin simulation software PetroMod was used to draw a burial-thermal history map combined with the uniform temperature of the fluid inclusion body temperature and salt test to determine the time of fluid inclusion capture [37], which provided a basis for correctly dividing the oil and gas migration and charging periods of the Yanchang Formation. This experiment was completed in the National Key Geochemical Laboratory of Yangtze University in Wuhan City, Hubei Province.

Results and discussion

Reservoir diagenesis

The diagenesis of the reservoir affects the physical properties of the reservoir, which is the basis for the division of inclusions [38]. The products and traces of diagenesis represent the activity information of deep formation fluids, which are of great significance to oil and gas migration and accumulation [39]. The tight sandstone in the reservoir in the study area is mainly composed of arkose and lithic arkose, with a small amount of medium sandstone and coarse sandstone. Its diagenetic process is complex. Previous studies have shown that the Chang 7 member reservoir in the study area mainly experienced diagenesis including compaction, cementation, micro-fractures, and dissolution [40]. The sandstone reservoirs of the Chang 7 member are mainly in the middle diagenetic stage A (Fig 2). According to the study of the burial history, the sandstone of the Chang 7 member has experienced a burial depth of 3000 m, and the compaction is relatively developed. During the early diagenesis stage A, the paleogeothermal temperature was low, the organic matter was immature, and mechanical compaction was the main action, accompanied by early chlorite appearing in the form of film, and a small amount of calcite cement was produced. The authigenic clay minerals in the reservoir are mainly chlorite, illite, kaolinite and illite-smectite mixed layer. In the early diagenetic stage B, the paleogeothermal temperature was 65–85°C, and as the buried depth increased, the compaction gradually increased. At this time, the Ro was 0.35–0.5%, the fluid was weakly acidic, and the feldspar began to dissolve. Its dissolution is mainly the dissolution of clastic particles and the dissolution of interstitials, and the types of pores are residual intergranular pores and secondary dissolved pores. The feldspar dissolution is mainly along the feldspar cleavage seam, forming dissolution pores in the feldspar grains, and the feldspar and cuttings are completely dissolved to form cast film pores (Fig 3). The intergranular dissolution pores and intragranular dissolution pores formed by dissolution make the reservoir pores larger and the physical properties better, which is the most important diagenesis for the development of the Chang 7 member reservoir [41].

Fig 3 — (a) Well Qiao136, 1578.25m, intergranular dissolution pores, (b) Well Wu 100, 1937.5m, feldspar dissolution pores.

Salt physology observation and composition characteristics of inclusions

The fluid inclusions in the reservoir samples of the Chang 7 member of the Yanchang Formation mainly occur in the quartz grains, mainly in single liquid phase, gas-liquid two-phase, and pure gas phase (Fig 4). Gas-liquid two-phase inclusions include brine inclusions in which bubbles move randomly and gas-rich inclusions (Fig 8).

Fig 4 — (a) Well Xin 283, 2004.30m, liquid hydrocarbon inclusions, 50 times transmitted light. (b) Well Xin 283, 2004.30m, blue-green fluorescence and a in the same field of vision. (c) Well Xin 283, 2004.30m, fluorescence spectra of oil inclusions. (d) Well Xin 140, 2073.55m, Gas-liquid two-phase hydrocarbon inclusions, 50 times transmitted light. (e) Well Xin 140, 2073.55m, blue luminescence. (f) Well Xin 140, 2073.55m, fluorescence spectra of oil inclusions. (g) Well Gao 135, 1783.60m, gas-liquid two-phase hydrocarbon inclusions, 50 times transmitted light. (h) Well Gao 135, 1783.60m, bluish green fluorescence. (i) Well Gao135, 1783.60m, fluorescence spectra of oil inclusions. (j) Well Qiao 136, 1584.50m, liquid hydrocarbon inclusions, 50 times transmitted light. (k) Well Qiao 136, 1584.50m, blue luminescence. (l) Well Qiao136,1584.50m, fluorescence spectra of oil inclusions.

Fig 8 — (a) Well Gao 135, 1783.60m, 50 times transmitted light, rich gas phase inclusions. (b) Well Xin 283, 2013.10m, 50 times transmitted light, CO₂ inclusions. (c) Well Gao135, 1790.55m high, 10 times transmitted light, asphalt.

Through microscope transmitted light and fluorescence observation, blue fluorescent and blue-green fluorescent oils were observed in thin slices of samples collected in Well Xin 283, Well Xin 140, Well Wu 100, Well Shun 111, and Well Shun 37 in the Chang 7₁ Formation inclusions. It is mainly distributed in quartz particles, the gas-liquid ratio is 3–9%, and the size of a single inclusion is between 5–10 μm. Its shape is mostly irregular round and long strips, and most of them are produced in the shape of beads. The reasons for the different fluorescence intensities of inclusions are the differences in maturity and shape of inclusions. The measured oil inclusions in the Chang 7₁ segment have differences in the peak morphology of the microfluorescence spectrum (Fig 4), and the measured GOI value of the oil inclusions is about 8–15%.

In the thin sections of samples collected from Well Qiao 136 and Well Gao 135 in the Chang 7₂ member of the Yanchang Formation, it was observed that inclusions are usually developed in mineral fractures and asphaltenes. Most of them are gas-liquid two-phase inclusions, the gas-liquid ratio is 3–9%, and the size of a single inclusion is relatively large, mostly between 7–10 μm (Table 1). The shape is nearly round and rhombus, mostly in single output, and it is light yellow and colorless under single polarized light. Under fluorescence excitation, it shows blue fluorescence with high abundance, and the peak range of the microfluorescence spectrum is 450-491nm.

Table 1. Statistical table of microscopic temperature measurement of inclusions in Chang 7 member in Zhijing-Ansai area.

Well	Layers	Depth /(m)	Number of test inclusions/piece	Size/(μm)	Gas-liquid ratio/%	Temperature/°C	Freezing point/°C	GOI/%
Xin283	Chang7₁	2004.3	9	5–8	3–6	92.6- 105.7	-3.2–4.1	13
Xin140	Chang7₁	2073.55	8	5–7	3–7	90.1- 109.7	-2.8–3.6	8
Qiao136	Chang7₂	1584.5	11	7–9	5–8	119.3- 125.7	-6.6–2.1	11
Gao135	Chang7₂	1783.6	13	7–10	6–9	121.6- 128.9	-7.7–3.5	10
Wu100	Chang7₁	1935.2	9	5–7	3–5	93.7- 106.72	-6.1–3.6	12
Xin283	Chang7₁	1995.7	8	7–9	7–8	90.8- 110.3	-2.2–3.8	9
Shun111	Chang7₁	1756.3	9	5–10	6–9	91.2- 103.1	-1.9–3.3	13
Shun37	Chang7₁	1917.25	10	6–8	5–8	91.3- 107.6	-3.5–3.8	10

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According to the different phase distribution and composition characteristics of the inclusions, the inclusions measured in the Chang 7 member of the Triassic Yanchang Formation in the study area can be divided into the following four types:

The first type is a single liquid hydrocarbon-containing inclusion, which is mostly taupe under transmitted light, and blue-green or blue under fluorescence. Mainly trapped and fracture-filled in quartz (Fig 4B).

The second type is gaseous hydrocarbon inclusions, which are gray under a single polarizer, and mainly occur in quartz filled with fractures (Fig 8B).

The third type is gas-liquid two-phase salt water inclusions (Fig 4A and 4J), which are transparent under a single polarizer and mostly irregular oval and long strips. It mainly occurs in fracture filling quartz and fracture filling calcite.

The fourth type is bitumen (Fig 8C), dark brown under a single polarizer, no fluorescence display, low abundance, captured in fracture-filling quartz minerals.

The second type is gaseous hydrocarbon inclusions, which are gray under a single polarizer, and mainly occur in quartz filled with fractures (Fig 8B).

The fourth type is bitumen (Fig 8C), dark brown under a single polarizer, no fluorescence display, low abundance, captured in fracture-filling quartz minerals.

Thermometric characteristics of inclusions and oil and gas accumulation and charging stages

Inclusion microthermometry experiments were carried out in the Chang 7 member of the Yanchang Formation, and the results showed that: Well Xin 283, Xin 140, Shun 111, Wu 100 and Gao 135, The inclusions developed in Well Qiao 136 have similar physical properties. The FIA representing the two-stage oil and gas charging process was detected, and the detection results proved that there were two stages of oil and gas charging in the Chang 7 member in the Zhijing-Ansai area. The detected oil inclusions with two fluorescent characteristics are generally distributed in diagenetic fractures within quartz grains, which corresponds to early capture events. Due to the different structural positions, there are certain differences in the burial history-thermal history evolution of single wells, resulting in a certain degree of difference in the homogeneity temperature of the associated brine inclusions of oil inclusions. The homogeneous temperature of brine inclusions in the first stage is distributed between 90–110°C, with an average of 106.8°C, the homogeneous temperature of brine inclusions in the second stage is mainly distributed between 120–130°C, with an average of 126.7°C (Fig 5).

The salinity value of the fluid inclusions is indirectly obtained from the measurement of the freezing point temperature of the inclusions, and the salinity value of the fluid inclusions is between 5.35–13.06%. The intersection graph of the homogeneous temperature and salinity of the inclusions shows that there is no obvious correlation between the homogeneous temperature of the inclusions in the two stages and the salinity (Fig 6).

According to the burial thermal evolution history of the Chang 7 member and the measured homogeneous temperature of the associated brine inclusions in the same period, the oil and gas charging time was estimated. The results show that the Chang 7 member is mainly formed in two phases. Phase I oil and gas inclusions are the period of large-scale oil and gas accumulation. Combined with the homogeneous temperature of brine inclusions in this period of oil inclusions in the same period and the simulation results of thermal history restoration, it is judged that the oil and gas charging period corresponds to about 120–100 Ma ago, which is the Early Cretaceous late stage (Fig 7). In the second stage of accumulation, the abundance of oil and gas inclusions in the stage is relatively high. Combined with the homogeneous temperature of brine inclusions associated with oil and gas inclusions in this period and the paleogeothermal history of the reservoir, the corresponding time is about 100–90 Ma, which means that the second oil and gas charge was in the early Late Cretaceous (Fig 7). Since the Late Triassic-Early Cretaceous was the formation stage of the Ordos Inland Basin, the platform subsidence amplitude was roughly the same, and the measured oil and gas charging times of the two periods were close.

Discussion on the source of CO₂ inclusions and high temperature inclusions

While hydrocarbon-related inclusions were observed in the Chang 7 member reservoir, gas-rich phase inclusions, CO₂ inclusions, and high-temperature inclusions were also observed. It is mostly trapped in the quartz minerals with developed fractures.The samples of CO₂ inclusions and high-temperature inclusions in brine in the same period were tested, and it was found that the freezing point ranged from -5.2 to 6°C, and the uniform temperature was greater than 180°C (Fig 8).

The sources of CO₂ in crustal-surface sedimentary fluids and natural gas are mainly divided into organic sources and inorganic sources [42–44]. The inorganic origin can be divided into mantle origin and petrochemical origin. One is that volcanic activity is accompanied by the eruption of a large amount of high-temperature gas [45]. During the up welling of magma, the temperature and pressure drop, and the carbon dioxide it carries is released. The second is formed by the decomposition of calcium carbonate in the formation under the high temperature action of magma or thermal fluid [46].

The main source of carbon dioxide formation in the Ordos Basin is related to the late Paleozoic volcanic activities [47]. Extensive volcanic activity occurred during this period, and magmatic fluids associated with volcanic activity may contain dissolved carbon dioxide. This carbon dioxide can be released during volcanic eruptions, or it can be transferred to the sedimentary rocks around the basin through fractures, pores, caves, unconformities and faults [48].

As far as the Yanchang Formation is concerned, CO₂ inclusions can come from CO₂-rich fluids or deep formations. CO₂ in the strata can migrate vertically through different geological structures [49]. Thermal fluids can transport carbon dioxide from deeper formations to shallower formations through fractures and faults as a medium. As the hot fluid continues to rise and the pressure gradually decreases, CO₂ dissolves from the magma, forming gas bubbles, some of which can be trapped in the volcanic rock or released into the surrounding environment. The burial and heating of these volcanic rocks resulted in the release of CO₂ as a by-product, leading to the formation of CO₂ inclusions [50].

According to Ren et al. (2020), a tectonic thermal event occurred during the Early Cretaceous. The large-scale generation and accumulation period of oil and gas accumulation in the Ordos Basin was in the Early Cretaceous [51]. The tectonic thermal events in the Early Cretaceous controlled the oil and gas generation and accumulation periods of the main source rocks in the Mesozoic, which corresponds to the accumulation time of the inclusion test analysis. It is speculated that the source of CO₂ inclusions and high temperature inclusions in the Chang 7 member of the Mesozoic Yanchang Formation in the Zhijing-Ansai area originated from the up welling of as the no spheric materials in the deep Ordos Basin in the Early Cretaceous. It is speculated that the CO₂ inclusions and high-temperature inclusions in the Chang 7 member in the Zhijing-Ansai area originated from the up welling of deep as the no spheric materials in the Ordos Basin during the Early Cretaceous. The specific formation reasons and the accumulation time of CO₂ inclusions need further experimental research.

Conclusions

The fluid inclusions in the Chang 7 member reservoir of the Mesozoic Triassic Yanchang Formation in the Zhijing-Ansai area of the Ordos Basin are mainly gas-liquid two-phase brine inclusions and liquid hydrocarbon inclusions. It also includes a small amount of gaseous hydrocarbon inclusions and asphalt, and the main component of gaseous hydrocarbon inclusions is CO₂.

The fluid inclusions developed in the reservoirs of the Mesozoic Triassic Yanchang Formation in the Zhijing-Ansai area can be divided into two stages. Among them, the phase I inclusions are mainly liquid hydrocarbon inclusions and a large number of associated brine inclusions, mainly showing blue and blue-green fluorescence. Predominantly beaded distribution of early fracture-filled quartz and fracture-filled calcite. The peak homogeneity temperature of its associated brine inclusions is between 90–110°C. Phase II inclusions mainly develop gas-liquid two-phase hydrocarbon inclusions, associated brine inclusions and a small amount of CO₂ inclusions and bitumen. It mostly occurs in the form of bands in fracture-filled quartz, and the peak homogeneity temperature of its associated brine inclusions is between 120–130°C.

The Chang 7 reservoir of the Yanchang Formation in the Ordos Basin mainly experienced two stages of oil and gas charging. The first period occurred in the late Early Cretaceous. It is a period of massive oil and gas charging, and it is the period of oil and gas generation and accumulation of main source rocks. The second charge occurred in the early Late Cretaceous.

The formation of CO₂ inclusions and high temperature inclusions in Chang 7 member of Zhijing-Ansai area is related to the late Paleozoic volcanic activity, which is mainly derived from the up welling of deep as the no sphere in the Ordos Basin in the early Cretaceous.

Data Availability

All relevant data are within the manuscript and its Supporting Information files.

Funding Statement

This work was supported by Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences), Ministry of Education (Grant number TPR-2022-12), and the National Nature Science Foundation of China (Grant numbers 42172179). The project fund is hosted by Professor Nan,Wu.

References

1.Zou C. N., Pan S., Q., Horsfield B., et al. Oil retention and intrasource migration in the organic-rich lacustrine Chang 7 shale of the Upper Triassic Yanchang Formation, Ordos Basin, central China. AAPG Bulletin, 2019. 103(11): 2627–2663. [Google Scholar]
2.Liu R. C., Ren Z.L., Ma K., et al. Classification of Hydrocarbon Accumulation Phases of Yanchang Formation in Southern Ordos Basin. Geoscience, 2019, 33(06), 1263–1274. [Google Scholar]
3.Wilkinson J. J., Lonergan L., Fairs T., and Herrington R. J. “Fluid inclusion constraints on conditions and timing of hydrocarbon migration and quartz cementation in Brent Group reservoir sandstones, Columbia Terrace, northern North Sea,” Geological Society, London, Special Publications, 1998. vol. 144, no. 1, pp. 69–89. [Google Scholar]
4.Shi L., Wang X. Z., Fan B. Z., et al. Characteristics of sandy lamination and its hydrocarbon accumulation, Yangchang Formation, Ordos Basin.Oil & Gas Geology, 2018, 39(3), 522–530. [Google Scholar]
5.Wang Z. Y., Zhou N. W., Lu S. F., et al. Generation, accumulation, and distribution of Upper Paleozoic tight sandstone gas in the northeastern margin of the Ordos Basin, Marine and Petroleum Geology, 2023, Volume 156. [Google Scholar]
6.Ma G. L. Hydrocarbon accumulation in the Yanchang Formation,Majiatan Oil Field, Ordos Basin. Sedimentary Geology and Tethyan Geology, 2015, 35(02), 35–44. [Google Scholar]
7.He H. Q., Guo X. J., Zhao Z. Y., et al. New understandings on gas accumulation and major exploration breakthroughs in subsalt Ma 4 Formation of Ordovician Majiagou Formation, Ordos Basin, NW China,Petroleum Exploration and Development, Volume 49, Issue 3, 2022, Pages 489–501. [Google Scholar]
8.Yu B., Zhou K., Guo Q.,et al. Hydrocarbon Accumulation Models and the Main Controlling Factors for the Lower Formation of the Upper Triassic Yanchang Formation in the Wu-Ding area of the Ordos Basin. CEOLOGY AND EXPLORATION, 2012, 48(04), 858–864. [Google Scholar]
9.Liang Y., Ren Z. L., Shi Z., et al. Classification of hydrocarbon accumulation phases of the Yanchang Formation in the Fuxian-Zhengning area, Ordos Basin. Acta Petrolei Sinica, 2011, 32(05), 741–748. [Google Scholar]
10.Liang Y., Ren Z. L., Wang Y.L., et al. Characteristics of fluid inclusions and reservoiring phases in the Yanchang Formation of Zichang area, the Ordos Basin. Oil & Gas Geology, 2011, 32(2), 182–191. [Google Scholar]
11.Li J., Zhao J. Z., Wei X. S., et al. Gas expansion caused by formation uplifting and its effects on tight gas accumulation: A case study of Sulige gas field in Ordos Basin, NW China, Petroleum Exploration and Development, 2022, Volume 49, Issue 6, Pages 1266–1281. [Google Scholar]
12.Bloch Salman, Lander R. H., Bonnell L. Anomalously high porosity and permeability in deeply buried sandstone reservoirs: origin and predictability. AAPG Bull, 2002.86, 301–328. [Google Scholar]
13.Liu C., Wang Z. L., Liu C. Y., et al. Characteristics of fluid inclusions in Yanchang Formation of the Yanchang oilfield, Ordos Basin. Acta Geoscientica Sinica, 2009, 30(2), 215–220. [Google Scholar]
14.Burruss R. C. Practical aspects of fluorescence microscopy of petroleum fluid inclusions. In: Barker C.E., Kopp O. (Eds.), Luminescence Microscopy: Qualitative and Quantitative Applications, 1991, vol. 25. Society for Sedimentary Geology (SEPM) Short Course, pp. 1–73. [Google Scholar]
15.Cheng F. P., Shi B., Li R. X., et al. Oil-Gas Accumulation Phases and Fluid Inclusion Proof of Chang 4+5 Reservoir in Jiyuan Area in Ordos Basin. Xinjiang Petroleum Geology, 2011. 32(4), 366–369. [Google Scholar]
16.Fu J. H., Liu G. D., Yang W. W., et al. A study of the accumulation periods of low permeability reservoir of Yanchang Formation in Longdong Area, Ordos Basin. Earth Science Frontiers, 2013. 20(2), 125–131. [Google Scholar]
17.Luo C. Y., Luo J. L., Luo X. R., et al. Characteristics of fluid inclusions and its application in analysis of hydrocarbon accumulation stages from the Chang 8 sandstone in the middle west area of Ordos Basin. Geological Journal of China Universities, 2014, 20(4):623–634. [Google Scholar]
18.Xu Z. J., Liu L. F., Wang T. G., et al. Analysis of the accumulation force of Chang 7 lacustrine tight oil of the permian triassic in the Longdong Area of Ordos Basin. Bulletin of Mineralogy Petrology and Geochemistry, 2017. 36(4), 637–649. [Google Scholar]
19.Song S. J., Liu S., Liang Y. X. Timing and chronology of hydrocarbon accumulation phases of Chang 8 tight reservoir in southwest of Ordos Basin. Fault-Block Oil and Gas Field, 2018, 25(2), 141–145. [Google Scholar]
20.Zhu S. F., Zhu X. M., Jia Y., et al. Diagenetic alteration, pore-throat network, and reservoir quality of tight gas sandstone reservoirs: A case study of the upper Paleozoic sequence in the northern Tianhuan depression in the Ordos Basin, China. AAPG Bulletin, 2020, 104(11): 2297–2324. [Google Scholar]
21.Ge X., Shen C B., David Selby, et al. Petroleum evolution within the Tarim Basin, northwestern China: Insights from organic geochemistry, fluid inclusions, and rhenium–osmium geochronology of the Halahatang oil field.AAPG Bulletin 2020; 104 (2): 329–355. [Google Scholar]
22.Li M. R., Hou Y. C., Xie X. K., et al. Hydrocarbon accumulation mode and exploration prospect of Triassic Yanchang Formation in Pingliang-Yanwu area, Ordos Basin. Acta Petrolei Sinica, 2023, 44(3),433–466. [Google Scholar]
23.Wu Y., Zhang J. G., Yin J. T., et al. The high resolution sequence stratigraphic framework and palaeo-geomorphologic restoration of Yanchang Formation in Triassic system in Fuhuang exploration area of Ordos Basin. Journal of Northwest University, 2019, 49(01), 132–143. [Google Scholar]
24.Song L. J., Wang Z. Z. Late Triassic tectonic stress field of the southwestern Ordos Basin and its tectonic implications: Insights from finite-element numerical simulations. Geosphere, 2023.19(3): 770–781. [Google Scholar]
25.Niu X., Yang T., Thomas J. H. Dodd, et al. Characteristics and formation mechanisms of gravity-flow deposits in a lacustrine depression basin: Examples from the Late Triassic Chang 7 oil member of the Yanchang Formation, Ordos Basin, Central China. Marine and Petroleum Geology, 2023, 148: 106048. [Google Scholar]
26.Jiang F. J., Zhang C. l., Wang K., et al. Characteristics of micropores, pore throats, and movable fluids in the tight sandstone oil reservoirs of the Yanchang Formation in the southwestern Ordos Basin, China. AAPG Bulletin, 2019, 103(12): 2835–2859. [Google Scholar]
27.Liu Z L., Shen F., Zhu X M.,et al. Formation Conditions and Sedimentary Characteristics of a Triassic Shallow Water Braided Delta in the Yanchang Formation, Southwest Ordos Basin, China.[J].PloS one, 2015. doi: 10.1371/journal.pone.0119704 [DOI] [PMC free article] [PubMed] [Google Scholar]
28.Eenglish K. L., Redfern J., Corcoran D. V., et al. Constraining burial history and petroleum charge in exhumed basins: New insights from the Illizi Basin, Algeria. AAPG Bulletin, 2016, 100(4): 623–655. doi: 10.1306/12171515067 [DOI] [Google Scholar]
29.Liu W. H., Wang X. F., Zhang D. D., et al. Restudy on geochemical characteristics and genesis of Jingbian gas field in Ordos Basin. Journal of Northwest University, 2022, 52(06), 943–956. [Google Scholar]
30.Hao F. et al. “Kinetics of hydrocarbon generation and mechanisms of petroleum accumulation in overpressured basins,” Science Press, Beijing, 2005. [Google Scholar]
31.Zheng Q., Liu Y. Q. The diagenesis and diagenetie litbofucies of tight reservoir of Chang 4+5 member of Yan chang Formation in Huaqing area, Ordos Basin. Advances in Earth Science 2015, 30(1), 78–90. [Google Scholar]
32.Goldstein R.H. Fluid inclusions in sedimentary and diagenetic systems. Lithos, 2001, 55, 159–193. [Google Scholar]
33.Liu B., He S L., Meng L D., et al. Sealing mechanisms in volcanic faulted reservoirs in Xujiaweizi extension, northern Songliao Basin, northeastern China.AAPG Bulletin 2021; 105 (8): 1721–1743. [Google Scholar]
34.Li R. X., Jin K. L., Liao Y. S. Analysis of organic inclusions using micro-FT.IR and fluorescence microscopy and ITS singnificance. Geochimica, 1998, 27(3), 244–250. [Google Scholar]
35.Goldstein R. H. Petrographic analysis of fluid inclusions Fluid inclusions analysis and interpretation. Mineralogical Association of Canada, Short Course Series, 2003, 32, 9–53. [Google Scholar]
36.Goldstein R. H., Reynolds T. J., et al. Systmatics of fluid inclusions in the diagenetic mineral. SEPM Short Course, 31, 1994, 1–85. [Google Scholar]
37.Xiao X. M., Liu Z. F., Liu D. H. Aplic ations of fluid inclusions in the reservoir to the studies of gas pool forming time. Chinese Science Bulletin, 2002, 4(12), 957–960. [Google Scholar]
38.Wang J. B., Guo R. T., Xiao X. M., et al. Timing and phases of hydrocarbon migration and accumulation of the formation of oil and gas pools in Lunnan Low Uplift of Tarim basin. Acta Sedimentologica Sinica, 2020. 20(2), 320–326. [Google Scholar]
39.Hu Z. Q., Zheng H., Yin W., et al. Comparison of diagenetic characteristics and pore evolution in outcrops and cores of tight sandstone reservoirs in the Triassic Yanchang Formation, the Ordos Basin, China. AAPG Bulletin, 2020, 104(11): 2429–2452. [Google Scholar]
40.Li Y., Fan A., Nils S., et al. Sedimentary facies control on sandstone reservoir properties: A case study from the permian Shanxi Formation in the southern Ordos basin, central China. Marine and Petroleum Geology, 2021, 129: 105083. [Google Scholar]
41.Zhou K. Trap Assessment of Chang-8 section in Ansai Oilfield of Ordos Basin. Petrochemical Industry Technology, 2015, 22(11), 223–224. [Google Scholar]
42.Chen R. Y., Luo X. R., Chen Z. K., et al. Estimation of Denudation Thickness of Mesozoic Stata in the Ordos Basin and Its Geological Significance. Acta Geologica Sinica, 2006, 685–693. [Google Scholar]
43.Guo X. H., Tan C. Q., Zhao J. H., et al. Different influence of diagenesis on micro pore-throat characteristics of tightsandstone reservoirs: Case study of the Triassic Chang 7 member in Jiyuan and Zhenbei areas, Ordos Basin. Natural Gas Geoscience, 2021, 32(6), 826–835. [Google Scholar]
44.Lu P., Bai Y., Liu W. G., et al. Optimization of favorable areas for carbon dioxide geological storage in Majiagou Formation in Ordos Basin. Geological Review, 2021, 67(03), 816–827. [Google Scholar]
45.Hanson A. D., Ritts B. D., Moldowan J. M. Organic geochemistry of oil and source rock strata of the Ordos Basin, north-central China. AAPG Bulletin, 2007, 91(9): 1273–1293. [Google Scholar]
46.Wang F., Dai S. X., Zhu W., et al. Migration law of CO₂ storage in low-porosity and low-permeability reservoirs—Taking Ordos Basin as an example. Geology in China, 2020, 1–18. [Google Scholar]
47.Zhao Y., Li M., Wan C. L., et al. Analysis on characteristic and origin of carbon dioxide, Guxi area, Zhanhua depression. Petroleum Geology and Recovery Efficiency, 2011, 18(2), 38–40. [Google Scholar]
48.Zhang W. Z., Yang H., Peng P. A., et al. The Influence of Late Triassic volcanism on the development of Chang 7 high grade hydrocarbon source rock in Ordos Basin. Geochimica, 2009, 38(06), 573–582. [Google Scholar]
49.Yang H., Zhao X. S., Kang Y. L., et al. Evaluation on geological sequestration suitability and potential of CO₂ in Ordos Basin. Climate Change Research, 2019, 15 (1), 95–102. [Google Scholar]
50.Lu S., Deng J., Bai H. Analysis on genesis of carbon dioxide gas reserevoir in ordovician subsalt in ordos basin. Petrochemical Industry Application, 2013, 32(05), 77–81. [Google Scholar]
51.Ren Z. L., Qi K., Liu R. C., et al. Zhang Y.Y., Yang G.L., Ma Q. Dynamic background of Early Cretaceous tectonic thermal events and its control on various mineral accumulations such as oil and gas in the Ordos Basin. Acta Petrologica Sinica, 2020, 36(4), 1213–1234. [Google Scholar]

PLoS One. doi: 10.1371/journal.pone.0302468.r001

Decision Letter 0

Fabio Trippetta

10 Dec 2023

PONE-D-23-39049Characteristics of Inclusions in Chang 7 Member and Shale Oil Accumulation Stages in Zhijing-Ansai Area, Ordos BasinPLOS ONE

Dear Dr. Wang,

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Reviewers' comments:

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Comments to the Author

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The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

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Reviewer #1: Yes

Reviewer #2: Yes

**********

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Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The paper analyzes fluid inclusions in reservoir samples from the Chang 7 member of the Yanchang Formation in the Ordos Basin using microscopic observation, temperature measurement, and fluorescence spectroscopy.

It identifies two stages of oil and gas accumulation based on the characteristics of fluid inclusions, including inclusion type, temperature, and fluorescence. The first stage occurred in the late Early Cretaceous and the second in the early Late Cretaceous.

It discusses the sources of CO2 inclusions and high-temperature inclusions, relating them to volcanic activity in the Early Cretaceous.

The study helps understand the oil and gas accumulation mechanisms and periods in the Yanchang Formation to guide exploration in the area.

The study uses multiple well-established petrographic techniques to analyze fluid inclusions and comprehensively interpret the oil and gas accumulation history.

It relates the inclusion data to burial history modeling and tectonic events to constrain accumulation timings.

The findings provide insights on the key accumulation periods to inform exploration in the region.

Questions for Authors:

What criteria were used to select inclusions for analysis (e.g. inclusion size, shape)?

How was the microscope stage calibrated and what was the estimated temperature uncertainty?

Have other inclusion studies in the area reported consistent or differing accumulation timings? If differing, how do the authors reconcile the interpretations?

The study presents a comprehensive inclusion analysis and ties the findings to the geological evolution of the area. While some methodological details could be improved, it provides useful insights for the basin. The questions aim to strengthen the reliability and contextualize the conclusions.

Reviewer #2: The topic of this article is relatively new, and the views are clear and correct. The article conforms to the purpose of this journal, and also reflects strong innovation and practical application. The structure of the full text is basically reasonable, the ideas are clear, and the levels are clear. The expression of opinions is basically accurate, and the arguments and arguments are basically consistent.

This article requires the following changes from the author:

1. The referenced literature needs to be closely integrated with the topic and paper materials, and it is recommended to use newer references.

2. It is recommended to supplement the experimental data in Table 1.

3. It is recommended that a scale bar be added to Figure 8.

4. The title "chang 7" in Figure 6 is not standard and should be changed to "chang 7 member".

5. The marked range in Figure 4 is not clear, replace it with an obvious outline.

6. Finally, pay attention to the writing format of experimental data in the article.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Reviewer #1: Yes: Xu-Guang Guo

Reviewer #2: Yes: Wei Lin

**********

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PLoS One. 2024 May 2;19(5):e0302468. doi: 10.1371/journal.pone.0302468.r002

Author response to Decision Letter 0

18 Mar 2024

Responses to Editor

I have received your email, for your proposed amendments, I am deeply grateful. I have modified according to your opinion, and submitted the modified paper in the journal paper system.

If you have any questions, please feel free to contact me. I will address them promptly and make the necessary corrections.

Responses to Reviewer 1

Thank you for your comments, we have studied the valuable comments from you and

tried our best to revise the manuscript. All the modified parts are marked up using

“track changes” fuction of Word. The details are as follows:

1.Comment:What criteria were used to select inclusions for analysis (e.g. inclusion size, shape)?

Response:Thank you for your question. According to the People 's Republic of China oil and gas industry standard SY /T 6010-1994 sedimentary rock inclusion homogenization temperature and salinity determination method, the inclusion test was carried out. In theory, any mineral crystallized from the fluid will contain inclusions. The main mineral ( quartz ) grains with good transparency and good crystallinity were selected for microscopic observation from low to high magnification.

2.Comment:How was the microscope stage calibrated and what was the estimated temperature uncertainty?

Response:Thank you for your question. Firstly, the microscope is placed under the light source, and the brightness and uniformity of the light source are adjusted to make the observation area have enough light and appropriate contrast. The second step is to adjust the eyepiece. Next, adjust the focal length of the eyepiece, so that the field of view of the eyepiece is clear and without distortion. It can be achieved by rotating the focusing wheel of the eyepiece. The third step is to adjust the objective lens : select the appropriate objective lens, adjust the focal length of the objective lens, so that the image of the observed sample is clearly visible. Similarly, it can be achieved by rotating the focusing wheel of the objective lens. Step 4 Calibration scale : In the field of view of the microscope, there is usually a scale to measure the length or diameter of the sample. First, a standard sample with a known length is measured under a microscope, and then the scale of the microscope is adjusted to match the standard length. The fifth step of calibrating the eyepiece micrometer is to use a standard sample with a known length to measure under the microscope, and then adjust the scale of the eyepiece micrometer to make it consistent with the standard length. Finally, check the microscope 's focusing system to ensure that clear images can be obtained under different observation conditions. The measurement error of the micro cold and hot stage instrument is ± 0.1 °C.

3.Comment:Have other inclusion studies in the area reported consistent or differing accumulation timings? If differing, how do the authors reconcile the interpretations?

Response:Thank you for your question. Other scholars in the Yanchang Formation of the Ordos Basin have studied the accumulation period of inclusions. The reservoir accumulation period of Mesozoic Yanchang Formation in southeastern Ordos Basin is mainly Early Cretaceous ( 93-120Ma ). This paper is aimed at the accumulation period of the Yanchang Formation in Zhijing Ansai area. Although it is affected by the region, the recovery of the accumulation period echoes with previous scholars.

Responses to Reviewer 2

Thank you for your comments, we have studied the valuable comments from you and

tried our best to revise the manuscript. All the modified parts are marked up using

“track changes” fuction of Word. The details are as follows:

1.Comment:The referenced literature needs to be closely integrated with the topic and paper materials, and it is recommended to use newer references.

Response:Thank you for your suggestions. I have made modifications to the questions raised and highlighted them.

2.Comment:It is recommended to supplement the experimental data in Table 1.

Response:Thanks for your valuable advice. All relevant data are within the paper.

3.Comment:It is recommended that a scale bar be added to Figure 8.

Response:Thank you for your question. I will make modifications to Figure 8 and highlight it in the manuscript.

4.Comment:The title "chang 7" in Figure 6 is not standard and should be changed to "chang 7 member".

Response:Thanks for pointing out the error.I have made corrections to this issue.

5.Comment:The marked range in Figure 4 is not clear, replace it with an obvious outline.

Response:Thanks for your valuable advice.I have made corrections to the images, please refer to the manuscript.

6.Comment:Finally, pay attention to the writing format of experimental data in the article.

Response:Thank you for pointing out the error. I have made modifications to the format.

Attachment

Submitted filename: Response to Reviewers.docx

pone.0302468.s001.docx^{(15KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0302468.r003

Decision Letter 1

Fabio Trippetta

4 Apr 2024

Characteristics of Inclusions in Chang 7 Member and Shale Oil Accumulation Stages in Zhijing-Ansai Area, Ordos Basin

PONE-D-23-39049R1

Dear Dr. Wang,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Fabio Trippetta, Ph.D.

Academic Editor

PLOS ONE

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #2: Yes

**********

6. Review Comments to the Author

Reviewer #2: The revised manuscript is generally satisfactory, and most of my concerns have been well addressed, my recommendation is for acceptance.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No

**********

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Attachment

Submitted filename: Response to Reviewers.docx

pone.0302468.s001.docx^{(15KB, docx)}

Data Availability Statement

All relevant data are within the manuscript and its Supporting Information files.

[pone.0302468.ref001] 1.Zou C. N., Pan S., Q., Horsfield B., et al. Oil retention and intrasource migration in the organic-rich lacustrine Chang 7 shale of the Upper Triassic Yanchang Formation, Ordos Basin, central China. AAPG Bulletin, 2019. 103(11): 2627–2663. [Google Scholar]

[pone.0302468.ref002] 2.Liu R. C., Ren Z.L., Ma K., et al. Classification of Hydrocarbon Accumulation Phases of Yanchang Formation in Southern Ordos Basin. Geoscience, 2019, 33(06), 1263–1274. [Google Scholar]

[pone.0302468.ref003] 3.Wilkinson J. J., Lonergan L., Fairs T., and Herrington R. J. “Fluid inclusion constraints on conditions and timing of hydrocarbon migration and quartz cementation in Brent Group reservoir sandstones, Columbia Terrace, northern North Sea,” Geological Society, London, Special Publications, 1998. vol. 144, no. 1, pp. 69–89. [Google Scholar]

[pone.0302468.ref004] 4.Shi L., Wang X. Z., Fan B. Z., et al. Characteristics of sandy lamination and its hydrocarbon accumulation, Yangchang Formation, Ordos Basin.Oil & Gas Geology, 2018, 39(3), 522–530. [Google Scholar]

[pone.0302468.ref005] 5.Wang Z. Y., Zhou N. W., Lu S. F., et al. Generation, accumulation, and distribution of Upper Paleozoic tight sandstone gas in the northeastern margin of the Ordos Basin, Marine and Petroleum Geology, 2023, Volume 156. [Google Scholar]

[pone.0302468.ref006] 6.Ma G. L. Hydrocarbon accumulation in the Yanchang Formation,Majiatan Oil Field, Ordos Basin. Sedimentary Geology and Tethyan Geology, 2015, 35(02), 35–44. [Google Scholar]

[pone.0302468.ref007] 7.He H. Q., Guo X. J., Zhao Z. Y., et al. New understandings on gas accumulation and major exploration breakthroughs in subsalt Ma 4 Formation of Ordovician Majiagou Formation, Ordos Basin, NW China,Petroleum Exploration and Development, Volume 49, Issue 3, 2022, Pages 489–501. [Google Scholar]

[pone.0302468.ref008] 8.Yu B., Zhou K., Guo Q.,et al. Hydrocarbon Accumulation Models and the Main Controlling Factors for the Lower Formation of the Upper Triassic Yanchang Formation in the Wu-Ding area of the Ordos Basin. CEOLOGY AND EXPLORATION, 2012, 48(04), 858–864. [Google Scholar]

[pone.0302468.ref009] 9.Liang Y., Ren Z. L., Shi Z., et al. Classification of hydrocarbon accumulation phases of the Yanchang Formation in the Fuxian-Zhengning area, Ordos Basin. Acta Petrolei Sinica, 2011, 32(05), 741–748. [Google Scholar]

[pone.0302468.ref010] 10.Liang Y., Ren Z. L., Wang Y.L., et al. Characteristics of fluid inclusions and reservoiring phases in the Yanchang Formation of Zichang area, the Ordos Basin. Oil & Gas Geology, 2011, 32(2), 182–191. [Google Scholar]

[pone.0302468.ref011] 11.Li J., Zhao J. Z., Wei X. S., et al. Gas expansion caused by formation uplifting and its effects on tight gas accumulation: A case study of Sulige gas field in Ordos Basin, NW China, Petroleum Exploration and Development, 2022, Volume 49, Issue 6, Pages 1266–1281. [Google Scholar]

[pone.0302468.ref012] 12.Bloch Salman, Lander R. H., Bonnell L. Anomalously high porosity and permeability in deeply buried sandstone reservoirs: origin and predictability. AAPG Bull, 2002.86, 301–328. [Google Scholar]

[pone.0302468.ref013] 13.Liu C., Wang Z. L., Liu C. Y., et al. Characteristics of fluid inclusions in Yanchang Formation of the Yanchang oilfield, Ordos Basin. Acta Geoscientica Sinica, 2009, 30(2), 215–220. [Google Scholar]

[pone.0302468.ref014] 14.Burruss R. C. Practical aspects of fluorescence microscopy of petroleum fluid inclusions. In: Barker C.E., Kopp O. (Eds.), Luminescence Microscopy: Qualitative and Quantitative Applications, 1991, vol. 25. Society for Sedimentary Geology (SEPM) Short Course, pp. 1–73. [Google Scholar]

[pone.0302468.ref015] 15.Cheng F. P., Shi B., Li R. X., et al. Oil-Gas Accumulation Phases and Fluid Inclusion Proof of Chang 4+5 Reservoir in Jiyuan Area in Ordos Basin. Xinjiang Petroleum Geology, 2011. 32(4), 366–369. [Google Scholar]

[pone.0302468.ref016] 16.Fu J. H., Liu G. D., Yang W. W., et al. A study of the accumulation periods of low permeability reservoir of Yanchang Formation in Longdong Area, Ordos Basin. Earth Science Frontiers, 2013. 20(2), 125–131. [Google Scholar]

[pone.0302468.ref017] 17.Luo C. Y., Luo J. L., Luo X. R., et al. Characteristics of fluid inclusions and its application in analysis of hydrocarbon accumulation stages from the Chang 8 sandstone in the middle west area of Ordos Basin. Geological Journal of China Universities, 2014, 20(4):623–634. [Google Scholar]

[pone.0302468.ref018] 18.Xu Z. J., Liu L. F., Wang T. G., et al. Analysis of the accumulation force of Chang 7 lacustrine tight oil of the permian triassic in the Longdong Area of Ordos Basin. Bulletin of Mineralogy Petrology and Geochemistry, 2017. 36(4), 637–649. [Google Scholar]

[pone.0302468.ref019] 19.Song S. J., Liu S., Liang Y. X. Timing and chronology of hydrocarbon accumulation phases of Chang 8 tight reservoir in southwest of Ordos Basin. Fault-Block Oil and Gas Field, 2018, 25(2), 141–145. [Google Scholar]

[pone.0302468.ref020] 20.Zhu S. F., Zhu X. M., Jia Y., et al. Diagenetic alteration, pore-throat network, and reservoir quality of tight gas sandstone reservoirs: A case study of the upper Paleozoic sequence in the northern Tianhuan depression in the Ordos Basin, China. AAPG Bulletin, 2020, 104(11): 2297–2324. [Google Scholar]

[pone.0302468.ref021] 21.Ge X., Shen C B., David Selby, et al. Petroleum evolution within the Tarim Basin, northwestern China: Insights from organic geochemistry, fluid inclusions, and rhenium–osmium geochronology of the Halahatang oil field.AAPG Bulletin 2020; 104 (2): 329–355. [Google Scholar]

[pone.0302468.ref022] 22.Li M. R., Hou Y. C., Xie X. K., et al. Hydrocarbon accumulation mode and exploration prospect of Triassic Yanchang Formation in Pingliang-Yanwu area, Ordos Basin. Acta Petrolei Sinica, 2023, 44(3),433–466. [Google Scholar]

[pone.0302468.ref023] 23.Wu Y., Zhang J. G., Yin J. T., et al. The high resolution sequence stratigraphic framework and palaeo-geomorphologic restoration of Yanchang Formation in Triassic system in Fuhuang exploration area of Ordos Basin. Journal of Northwest University, 2019, 49(01), 132–143. [Google Scholar]

[pone.0302468.ref024] 24.Song L. J., Wang Z. Z. Late Triassic tectonic stress field of the southwestern Ordos Basin and its tectonic implications: Insights from finite-element numerical simulations. Geosphere, 2023.19(3): 770–781. [Google Scholar]

[pone.0302468.ref025] 25.Niu X., Yang T., Thomas J. H. Dodd, et al. Characteristics and formation mechanisms of gravity-flow deposits in a lacustrine depression basin: Examples from the Late Triassic Chang 7 oil member of the Yanchang Formation, Ordos Basin, Central China. Marine and Petroleum Geology, 2023, 148: 106048. [Google Scholar]

[pone.0302468.ref026] 26.Jiang F. J., Zhang C. l., Wang K., et al. Characteristics of micropores, pore throats, and movable fluids in the tight sandstone oil reservoirs of the Yanchang Formation in the southwestern Ordos Basin, China. AAPG Bulletin, 2019, 103(12): 2835–2859. [Google Scholar]

[pone.0302468.ref027] 27.Liu Z L., Shen F., Zhu X M.,et al. Formation Conditions and Sedimentary Characteristics of a Triassic Shallow Water Braided Delta in the Yanchang Formation, Southwest Ordos Basin, China.[J].PloS one, 2015. doi: 10.1371/journal.pone.0119704 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0302468.ref028] 28.Eenglish K. L., Redfern J., Corcoran D. V., et al. Constraining burial history and petroleum charge in exhumed basins: New insights from the Illizi Basin, Algeria. AAPG Bulletin, 2016, 100(4): 623–655. doi: 10.1306/12171515067 [DOI] [Google Scholar]

[pone.0302468.ref029] 29.Liu W. H., Wang X. F., Zhang D. D., et al. Restudy on geochemical characteristics and genesis of Jingbian gas field in Ordos Basin. Journal of Northwest University, 2022, 52(06), 943–956. [Google Scholar]

[pone.0302468.ref030] 30.Hao F. et al. “Kinetics of hydrocarbon generation and mechanisms of petroleum accumulation in overpressured basins,” Science Press, Beijing, 2005. [Google Scholar]

[pone.0302468.ref031] 31.Zheng Q., Liu Y. Q. The diagenesis and diagenetie litbofucies of tight reservoir of Chang 4+5 member of Yan chang Formation in Huaqing area, Ordos Basin. Advances in Earth Science 2015, 30(1), 78–90. [Google Scholar]

[pone.0302468.ref032] 32.Goldstein R.H. Fluid inclusions in sedimentary and diagenetic systems. Lithos, 2001, 55, 159–193. [Google Scholar]

[pone.0302468.ref033] 33.Liu B., He S L., Meng L D., et al. Sealing mechanisms in volcanic faulted reservoirs in Xujiaweizi extension, northern Songliao Basin, northeastern China.AAPG Bulletin 2021; 105 (8): 1721–1743. [Google Scholar]

[pone.0302468.ref034] 34.Li R. X., Jin K. L., Liao Y. S. Analysis of organic inclusions using micro-FT.IR and fluorescence microscopy and ITS singnificance. Geochimica, 1998, 27(3), 244–250. [Google Scholar]

[pone.0302468.ref035] 35.Goldstein R. H. Petrographic analysis of fluid inclusions Fluid inclusions analysis and interpretation. Mineralogical Association of Canada, Short Course Series, 2003, 32, 9–53. [Google Scholar]

[pone.0302468.ref036] 36.Goldstein R. H., Reynolds T. J., et al. Systmatics of fluid inclusions in the diagenetic mineral. SEPM Short Course, 31, 1994, 1–85. [Google Scholar]

[pone.0302468.ref037] 37.Xiao X. M., Liu Z. F., Liu D. H. Aplic ations of fluid inclusions in the reservoir to the studies of gas pool forming time. Chinese Science Bulletin, 2002, 4(12), 957–960. [Google Scholar]

[pone.0302468.ref038] 38.Wang J. B., Guo R. T., Xiao X. M., et al. Timing and phases of hydrocarbon migration and accumulation of the formation of oil and gas pools in Lunnan Low Uplift of Tarim basin. Acta Sedimentologica Sinica, 2020. 20(2), 320–326. [Google Scholar]

[pone.0302468.ref039] 39.Hu Z. Q., Zheng H., Yin W., et al. Comparison of diagenetic characteristics and pore evolution in outcrops and cores of tight sandstone reservoirs in the Triassic Yanchang Formation, the Ordos Basin, China. AAPG Bulletin, 2020, 104(11): 2429–2452. [Google Scholar]

[pone.0302468.ref040] 40.Li Y., Fan A., Nils S., et al. Sedimentary facies control on sandstone reservoir properties: A case study from the permian Shanxi Formation in the southern Ordos basin, central China. Marine and Petroleum Geology, 2021, 129: 105083. [Google Scholar]

[pone.0302468.ref041] 41.Zhou K. Trap Assessment of Chang-8 section in Ansai Oilfield of Ordos Basin. Petrochemical Industry Technology, 2015, 22(11), 223–224. [Google Scholar]

[pone.0302468.ref042] 42.Chen R. Y., Luo X. R., Chen Z. K., et al. Estimation of Denudation Thickness of Mesozoic Stata in the Ordos Basin and Its Geological Significance. Acta Geologica Sinica, 2006, 685–693. [Google Scholar]

[pone.0302468.ref043] 43.Guo X. H., Tan C. Q., Zhao J. H., et al. Different influence of diagenesis on micro pore-throat characteristics of tightsandstone reservoirs: Case study of the Triassic Chang 7 member in Jiyuan and Zhenbei areas, Ordos Basin. Natural Gas Geoscience, 2021, 32(6), 826–835. [Google Scholar]

[pone.0302468.ref044] 44.Lu P., Bai Y., Liu W. G., et al. Optimization of favorable areas for carbon dioxide geological storage in Majiagou Formation in Ordos Basin. Geological Review, 2021, 67(03), 816–827. [Google Scholar]

[pone.0302468.ref045] 45.Hanson A. D., Ritts B. D., Moldowan J. M. Organic geochemistry of oil and source rock strata of the Ordos Basin, north-central China. AAPG Bulletin, 2007, 91(9): 1273–1293. [Google Scholar]

[pone.0302468.ref046] 46.Wang F., Dai S. X., Zhu W., et al. Migration law of CO₂ storage in low-porosity and low-permeability reservoirs—Taking Ordos Basin as an example. Geology in China, 2020, 1–18. [Google Scholar]

[pone.0302468.ref047] 47.Zhao Y., Li M., Wan C. L., et al. Analysis on characteristic and origin of carbon dioxide, Guxi area, Zhanhua depression. Petroleum Geology and Recovery Efficiency, 2011, 18(2), 38–40. [Google Scholar]

[pone.0302468.ref048] 48.Zhang W. Z., Yang H., Peng P. A., et al. The Influence of Late Triassic volcanism on the development of Chang 7 high grade hydrocarbon source rock in Ordos Basin. Geochimica, 2009, 38(06), 573–582. [Google Scholar]

[pone.0302468.ref049] 49.Yang H., Zhao X. S., Kang Y. L., et al. Evaluation on geological sequestration suitability and potential of CO₂ in Ordos Basin. Climate Change Research, 2019, 15 (1), 95–102. [Google Scholar]

[pone.0302468.ref050] 50.Lu S., Deng J., Bai H. Analysis on genesis of carbon dioxide gas reserevoir in ordovician subsalt in ordos basin. Petrochemical Industry Application, 2013, 32(05), 77–81. [Google Scholar]

[pone.0302468.ref051] 51.Ren Z. L., Qi K., Liu R. C., et al. Zhang Y.Y., Yang G.L., Ma Q. Dynamic background of Early Cretaceous tectonic thermal events and its control on various mineral accumulations such as oil and gas in the Ordos Basin. Acta Petrologica Sinica, 2020, 36(4), 1213–1234. [Google Scholar]

PERMALINK

Characteristics of inclusions in chang 7 member and shale oil accumulation stages in Zhijing-Ansai area, Ordos Basin

Wenjie Wu

Jian Wang

Nan Wu

Yong Feng

Yilin Liang

Yulin Chen

Roles

Abstract

Introduction

Geological background

Fig 1. The main tectonic units and the location of the study area in the schematic diagram of Ordos Basin.

Materials and methods

Samples and equipment

Fluid inclusion analysis

Results and discussion

Reservoir diagenesis

Fig 2. Diagenetic evolution sequence of Chang 7 member in Zhijing-ansai area.

Fig 3. Characteristics of dissolution pores in Chang 7 member.

Salt physology observation and composition characteristics of inclusions

Fig 4. Fluorescence spectral characteristics of inclusions in Chang 7 member.

Fig 8. Numerous gas, CO2 and asphalt inclusions in Chang 7 member.

Table 1. Statistical table of microscopic temperature measurement of inclusions in Chang 7 member in Zhijing-Ansai area.

Thermometric characteristics of inclusions and oil and gas accumulation and charging stages

Fig 5. Histogram of homogeneous temperature distribution of inclusions in Chang 7 member.

Fig 6. Scatter diagram of homogeneous temperature-salinity of inclusions in Chang 7 member.

Fig 7. Burial history-thermal restoration map of Mesozoic Triassic Yanchang Formation in Zhijing-Ansai area, Ordos Basin.

Discussion on the source of CO2 inclusions and high temperature inclusions

Conclusions

Data Availability

Funding Statement

References

Decision Letter 0

Fabio Trippetta

Roles

Author response to Decision Letter 0

Decision Letter 1

Fabio Trippetta

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

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Fig 8. Numerous gas, CO₂ and asphalt inclusions in Chang 7 member.

Discussion on the source of CO₂ inclusions and high temperature inclusions