超深层碳酸盐岩裂缝面形态与摩擦因数研究

Research on fracture surface morphology and friction coefficient of ultra-deep carbonate rock

潘冠昌 杨斌 张浩 常坤 冯云辉

成都理工大学油气藏地质及开发工程国家重点实验室，四川 成都 610059 中国石化茂名石化公司，广东 茂名 525000

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059,China Maoming Petrochemical Company, SINOPEC, Maoming 525000, China

岩体裂缝面摩擦特性是影响裂缝地层井壁稳定性的重要因素。文中选取川西雷口坡组超深层碳酸盐岩井下岩心为研究对象，对充填、未充填天然裂缝面和抛光裂缝面摩擦因数进行测试，分析微凸体、充填物和钻井液浸泡对裂缝面摩擦因数的影响，建立了未充填裂缝面粗糙度与摩擦因数关系模型。结果表明：超深层碳酸盐岩充填裂缝面摩擦因数（0.307~0.391）要低于基质裂缝面（未充填裂缝面为0.520~0.550、抛光裂缝面为0.420~0.441）；钻井液浸泡后摩擦因数降低，且裂缝面越光滑，摩擦因数下降幅度越大。分析认为：相对于白云石基质，方解石充填物矿物颗粒间黏着摩擦较弱，以及裂缝面形态更为平坦，是导致充填裂缝面摩擦因数较低的主要原因，而钻井液浸泡岩心裂缝面后产生的润滑效应也会导致摩擦因数降低。研究成果能够为超深层裂缝性碳酸盐岩地层井壁稳定性评价提供重要的实验参数支撑，为封堵防塌钻井液优化提供基础指导。

The friction characteristic of rock fracture surface is an important factor affecting the wellbore stability in fractured formation. The ultra-deep carbonate rock core of the Leikoupo Formation in western Sichuan was selected as the research object to test the friction coefficients of unfilled and filled natural fracture surfaces and polished fracture surfaces, and to analyze the influence of asperity, filling, and drilling fluid on the friction coefficient of the fracture surface. The results show that the friction coefficient (0.307￣0.391) of the ultra-deep carbonate filling is lower than that of the matrix fracture surface (0.520￣0.550 for the unfilled fracture surface and 0.420￣0.441 for the polished fracture surface), and the friction coefficient decreases further after the drilling fluid immersion. The smoother the fracture surface is, the greater the friction coefficient decreases. According to the analysis, compared with dolomite matrix, the main reasons for the lower friction coefficient of the filled fracture surface are the weak adhesive friction between mineral particles and the flatter fracture surface morphology of calcite filling. The friction coefficient decreases due to the lubrication effect of the drilling fluid soaking the fracture surface. The research results can provide important experimental parameter support for wellbore stability evaluation of deep fractured carbonate formations and basic guidance for optimization of plugging and anti-sloughing drilling fluid.

10.6056/dkyqt202206012