Study On Improving The Accuracy Of Water Lock Damage Test In Coal And Rock Reservoirs

Accurately testing the degree of water lock damage in coal and rock reservoirs is closely related to increasing coalbed methane production capacity.However,the existing CBM reservoir water lock damage test method has many problems,and it is impossible to accurately test the degree of water lock damage,which in turn leads to the inability to prevent water lock damage on the spot.By investigating the basic theory,evaluation method and lifting measures of water lock damage in conventional reservoirs and coal-rock reservoirs,the difficulties in the indoor test method of water-locking damage in coalbed methane reservoirs are summarized,and the basic physical properties and pilot-sensitive experiments of reservoir cores are carried out.The water lock damage experimental conditions and experimental equipment were optimized,and the degree of water lock damage was tested more accurately.The physical property experiments show that the throat type of DZ-9 coalbed methane reservoir in Shanxi is mainly bundle bundle throat,which belongs to low porosity and low permeability reservoir.Pilot-sensitive experiments found that:(1)the sensitivity of the DZ-9 coal-rock reservoir is weak,and the critical flow rate is 1.00 m L/min;(2)salting-out phenomenon during the water-sensitivity experiment can produce additional reservoir damage.,affecting the relationship between single factor and reservoir damage degree;(3)the water sensitivity of DZ-9 coal reservoir is moderately strong to strong;(4)the stress sensitivity of DZ-9 coal reservoir is moderately strong to Stronger,the critical stress is 3.5 MPa.In short,the relevant sensitivity damage may increase the water lock damage permeability damage value.Based on the conventional oil and gas reservoir test methods,the experimental materials and instruments were improved,and the coal and rock reservoir water under the influence of different experimental conditions,such as different flow rates,salinity,clay mineral content,net confining pressure and reservoir lamination,were carried out.Lock experiment:(1)It is verified that different experimental conditions will increase the added value of reservoir damage,affecting the accuracy of water lock damage test;(2)the maximum value of water lock damage under different experimental conditions is 53.93%,the minimum value is 29.62 %,the water lock damage intensity is weak to medium strong.Under the different experimental conditions,the average value of the water lock damage rate is 45.19%,that is,the corresponding water lock damage intensity is moderately weak;(3)Negative pressure difference condition Water lock damage still occurs,and the water lock damage in the same layer core is lower than that of the positive pressure difference,so it has a good protection effect on the reservoir.