Experimental study on seepage of shale fractures coupling with confining pressure and temperature
There are widespread distributions and seepage of groundwater in rock fractures. Seepage conditions in the fractures can be affected by stress and temperature conditions. Shale seepage conditions are complicate coupling with stress and temperature. Experiments have been carried out on the shale samples with three types of fractures including: single short fracture (type A), single long fracture (type B), symmetrical short fractures (type C). Three temperature conditions were set for type A. Coefficient C which is the ratio between seepage pressure and flow rate is consistent when the temperature effects are slight. Linear relation curves between coefficient C and temperature are simulated. For type B three confining pressure were applied by heat sheet. As confining pressure increases, the seepage pressure increases. Seepage pressure distribution is nonlinear when the flow rate increases to 6ml/min under the confining pressure of 12MPa. For type C three temperature conditions coupling with three confining pressure conditions are analyzed for the seepage pressure. The effects of confining pressure on seepage pressure are different from type B. Nonlinear curves are shown under 3MPa and 6MPa at 50℃. Seepage pressure values at 70℃ are smaller than those at 30℃ and 50℃. Coefficient C contour is depicted for the scope of experiment temperature and confining. The small value region of coefficient C is about the 6MP and 50℃. Through fractures the nonlinear increase of seepage pressure occurred when the confining pressure is larger for single fracture, and it happens when the confining pressure is smaller for double fractures.