STABILITY ANALYSIS AND NUMERICAL SIMULATION OF WELLBORE DURING OIL AND GAS DEVELOPMENT IN SAND CONGLOMERATE RESERVOIRS

摘要

In order to improve the development efficiency of oil and gas resources and to reduce the occurrence of complex situations and accidents during drilling operations in sand conglomerate reservoirs in the Mahu Sag, Xinjiang Oilfield, two instability modes of gravel shear failure and sliding failure between sand conglomerate matrix and gravel are considered in this paper. A solution model for the collapse pressure of the borehole wall considering the cementation strength of the sand conglomerate was established, and the minimum in-well pressure for maintaining the stability of the borehole wall of the sand conglomerate reservoir was predicted. RFPA software was used to establish a numerical model for sand conglomerate reservoirs to study the effect of gravel on crack propagation around the well. The results showed that, considering the sliding failure of the fracture surface of the sand conglomerate reservoir rock mass and shear failure of the rock body, the occurrence of sliding failure of the fracture surface can be reduced by controlling the angle between the drilling direction of the wellbore and the fracture surface. As the horizontal wellbore extension direction is consistent with the minimum horizontal principal stress, the crack initiation pressure will increase significantly. Therefore, we need to pay attention to the change of pump pressure when hydraulic fracturing of this type of well. The research results from this study provide guidance and suggestions for the efficient and low-cost development of sand conglomerate reservoirs.