Study on damage of follicle drilling with fuzzy-ball fluid in coal measures three gas combined production

The engineering operation effect and reservoir damage control effect of fuzzy-ball in unconventional reservoirs such as single coalbed methane reservoirs and tight sandstone gas reservoirs all meet the field requirements.However,due to the lack of appropriate evaluation methods, the laboratory still lacks the formation damage test evaluation to the combined production reservoir, which is applied to the coal-measure combined mining formation.The laboratory test uses a reservoir damage evaluation system that can separately measure the flow and pressure of single-layer and multi-layer combined mining to simulate the pressure and temperature conditions of the Linxing coal-measure reservoir. A total of seven sandstones in the Shihezi Formation and Taiyuan Formation are selected. Adopting the gas constant flow method to test four sets of tests in the sand/coal single-layer mining mode, the “sand + coal” double-layer combined mining mode, and the “sand + sand + coal” three-layer combined mining mode.The test records seven sets of stable flow rates before and after the damage of each layer of single mining and multi-layer combined mining, and 14 sets of inlet and outlet pressures when stable. seven sets of permeability data are calculated by Darcy′s law. which was used as the basic data. The comparative flow method is used to evaluate the overall damage degree of the reservoir caused by the fleece drilling and completion fluid. The test results show that:①When sand and coal are mined in a single layer,the steady flow damage rates are 7.96% and 7.91% respectively,which are close to 8.48% and 8.55% in the permeability damage rate.②In the case of double-layer mining,the stable overall flow damage rate is 7.24%.The overall permeability damage rate cannot be calculated, and the single-layer permeability damage rates are 7.24% and 7.81%,respectively.③When three layers are mined together,the overall flow damage rate is 8.83%,and the overall permeability damage rate cannot be calculated.The single layer permeability damage rate was 6.48%,11.97%,and 9.68% respectively.The results show that the indoor evaluation of formation damage results of Fuzzy-ball drilling and completion fluids in multi-layer co-production meets the requirements of of on-site damage control, and at the same time confirms that the flow method can replace the permeability method to evaluate the damage degree of working fluid reservoirs. The application of on-site optimization technology provides a new evaluation method.