Study on seepage law of horizontal well during pumping in low-permeability aquifers

The exploitation technology of horizontal well is widely applied in fields such as groundwater and oil and gas extraction. However, the permeability law during the exploitation of horizontal well in low-permeability formations remains to be further proved. Based on the principle of similarity and the seepage theory, this paper adopted a self-designed indoor simulation testing system for horizontal well and combined the monitoring of pore water seepage pressure to collect the seepage laws of groundwater around it in real time under the stable flow and unstable flow conditions for the horizontal well during pumping process. And the following conclusions were obtained: (1) During the early stage of pumping test for horizontal well under unstable flow condition, the pore pressure dropped rapidly. After that, the decrease of pore pressure slowed down and tended to stabilize; Moreover, the variation range of pore pressure in the front section of the horizontal well was greater than that in the back section; There was a phenomenon of incomplete unwatering for the horizontal well in low-permeability aquifers (that was, the drawdowns did not coincide with the screen pipe of the horizontal well). (2) In the pumping test of horizontal well under stable flow condition, there was a dominant pore pressure drop curve. The changes of pore pressure from the supply end to the front end of the horizontal well was from large to small, and it formed a gentle drop funnel-shaped shape on the axial profile. In conclusion, it can provide a reference basis for the exploitation of horizontal well in low-permeability aquifers.