Table 4.
Recovery rate of permeability of artificial fractured core (2# oil-based drilling fluid).
| experiments | weighting agent | core | pressure difference of flow-back (MPa) | recovery rate (%) | permeability before damage (10−3 µm2) | permeability after damage (10−3 µm2) |
|---|---|---|---|---|---|---|
| without acid dissolution | standard barite | ADD11 | 2.52 | 35.51 | 1.1134 | 0.3954 |
| ADD12 | 2.46 | 33.59 | 1.2547 | 0.4214 | ||
| submicron barite | ADD13 | 2.11 | 38.11 | 0.8548 | 0.3258 | |
| ADD14 | 2.23 | 36.79 | 0.9631 | 0.3543 | ||
| superfine manganese ore | ADD15 | 1.98 | 48.55 | 0.8267 | 0.4014 | |
| ADD16 | 2.01 | 45.91 | 0.7968 | 0.3658 | ||
| with acid dissolution | standard barite | ADD17 | 1.99 | 55.19 | 0.9257 | 0.5109 |
| ADD18 | 1.89 | 63.06 | 0.7459 | 0.4704 | ||
| submicron barite | ADD19 | 1.74 | 55.86 | 0.8569 | 0.4787 | |
| ADD20 | 1.63 | 70.99 | 0.9646 | 0.6848 | ||
| superfine manganese ore | ADD21 | 0.22 | 92.99 | 1.1039 | 1.0265 | |
| ADD22 | 0.27 | 91.48 | 0.8853 | 0.8099 |