Study on physical similarity simulation of coordinated coal and oil and gas exploitation

Abstract

Aiming at the problem that coal seam development disturbs the stability of oil and gas trap layer and oil and gas shaft in the coordinated exploitation of coal and oil and gas, two-dimensional simulation test was used to carry out the research on the response law of coal and oil and gas mining strata. The mining process of “oil and gas first, then coal” was adopted to obtain the stress evolution, fracture deformation characteristics of coal and oil and gas overlaying strata and the deformation and failure law of oil and gas shaft. The results show that: if the intensity of oil and gas extraction to the completion of recovery, the overall structure of the model does not appear obvious disturbance, only the local inter-layer rock stress concentration phenomenon, and the coal seam mining at this time will cause a certain disturbance to the oil and gas layer at 200 m below. In the early stage of mining, the stress above the oil and gas layer recovery boundary keeps rising; there is a phenomenon of stress transfer in the coal seam floor, no obvious stress change in the roof of the coal seam. The initial disturbance range is 100 m, and the secondary disturbance range is 75 m. When the full mining stage is entered, the stress concentration above the oil and gas recovery boundary shifts horizontally to the right side, and the coal seam floor experiences the process of stress concentration-pressure relief successively. The interlayer strata structure tends to be stable, and the strata migration degree gradually shifts to the strata near the top of the coal seam. It shows that coal seam mining has a great influence on the stability of the whole strata in the process of coordinated exploitation of superposed resources, so we should pay more attention to the influence of coal seam mining on coordinated exploitation of coal and oil and gas. The main failure mode of the inner shaft in overlying rock is shear deformation failure, while the lower shaft at the center of the working face is tension-shear deformation failure. Attention should be paid to the shaft protection at the center of the working face.

Keywords

• coal and oil and gas exploitation
• formation response law
• wellbore stability
• analog simulation
• stress concentration