The mechanism of seepage responding characteristic for the water curtain borehole injection in underground water-sealed oil storage

The seepage responding mechanism of rock mass caused by the borehole water injection was crucial to the safe and economical operation of underground water-sealed storage. This study gave a detailed investigation to the above seepage responding mechanism, reflecting by the variation of relationship between injection pressure and flow volume. The characteristic related to rock mass condition was considered by numerical simulation, including fracture aperture, dip angle, tendency and density. And the orthogonal test was used to give some quantitative evaluation for the influence factors. Some conclusion could be given. Firstly, it could be found that the fracture aperture was determined to have the greatest influence to the relationship between injection pressure and volume from the orthogonal test result. Secondly, there would exist a crucial dip angle to form a relative complete hydraulic connection in the fracture net, which indicated a value of 35° from numerical simulation. The fracture density would also have a crucial value to form a relatively good connectivity fracture net, with the value of 1.67 × 10^− 3n/m³. Thirdly, some enlightenments were given for the water curtain system design mainly about the suggestion for the layout of water curtain borehole in some certain rock mass condition. Suggestion about the geological survey was also given for the water curtain system. The innovation was mainly to reveal the relationship between the injection pressure and flow influenced by the rock mass condition, which would contribute to enrich the seepage mechanism in complex fracture and the theory of water curtain optimization.