裂缝型变质岩油藏注气驱机理及驱替效率实验研究

Experimental research of gas injection displacement mechanism and efficiency in the fractured metamorphic rock reservoir

采用物理模拟实验的方法,做注气膨胀实验,评价天然气在原油中的溶解性。通过数模和细管实验,确定目前地层压力和温度下的最小混相压力。开展双重介质变质岩油藏顶部注天然气,底部注水长岩心驱替实验(岩心夹持器呈30°倾斜),得出了裂缝和基质分别对采收率的贡献。驱替压力25.6 MPa和38.6 MPa,均小于最小混相压力,实验中天然气驱替过程为非混相驱。由于裂缝的收缩性远大于基质,衰竭采出的原油可以看作是裂缝的贡献。同时,由于基质与裂缝之间的渗透率相差极大,因此在初期的驱替过程中,裂缝中的原油可以被完全驱出。结合以上分析,可以由最终实验结果得出基质与裂缝系统各自对采收率的贡献。

The swelling test is conducted under physical simulation to analyze the natural gas solvency in the crude oil. MMP is cal？culated by simulation and slim tube experiment under the current pressure and temperature situation. The long core displacement experiment on the double medium metamorphic reservoir rock cores is conducted to get the recovery of the contribution from the matrix and fractures respectively, including natural gas injection on the top and water injection at the bottom of the long core（the core holder is 30＆#176; to the horizontal direction）. The displacement pressure is 25.6 MPa and 38.6 MPa, lower than the MMP, meaning that the whole procedure is immiscible displacement. Contractility of fractures is much larger than matrix, thus the oil recovery from the depletion can be treated as the contribution of fractures. And the assumption can be made that the oil are completely out of the fractures in the initial displacement process because of the great permeability difference between fractures and matrix. Based on the analysis above, the contribution to the final recovery of the fractures and matrix respectively can be obtained from the experi？mental result.