北特鲁瓦地区裂缝性碳酸盐岩地层井壁稳定性研究

北特鲁瓦地区石炭系中统巴什基尔阶(KT-Ⅱ)碳酸盐岩地层裂缝发育,钻井过程中井壁垮塌问题严重.为提高钻井效率,研究了 KT-Ⅱ碳酸盐岩地层裂缝产状及缝间充填物质,测试了碳酸盐岩基质及缝间充填物组分,分析了裂缝发育对碳酸盐岩地层孔渗特性、力学强度的影响.同时,耦合地应力场、渗流场及裂缝力学弱面效应等因素,建立了裂缝性碳酸...

Study on the Wellbore Stability in Fractured Carbonate Formations in North Truva Area

The fracture development of carbonate formation in the Carboniferous Middle Bashkir Order (KT-II) in North Truva area has caused serious wellbore collapse during drilling.In order to improve the drilling efficiency,the fracture occurrence and inter-fracture filler of KT-II carbonate formation were studied,the carbonate matrix and inter-fracture filler components were tested,and the influence of fracture development on the pore permeability characteristics and mechanical strength of the carbonate formation was analyzed.At the same time,a theoretical model of wellbore instability in fractured carbonate formations was established by coupling the ground stress field,seepage field and fracture mechanical weak plane effect,and the prediction of wellbore stability in KT-II carbonate formations in North Truva area was carried out.The results show that:the development of fractures in the KT-II carbonate formation in the North Truva area and the prominent inter-fracture mechanical weak plane effect are the dominant factors inducing the wellbore collapse; the development of fractures strengthens the seepage migration of drilling fluid along the fractures and weakens the supporting effect of the drilling fluid on the wellbore; the fracture occurrence and wellbore trajectory have obvious effects on the stability of the wellbore in the carbonate formations,drilling in the direction of 180° to the dip angle of the fracture plane can bring the optimal wellbore stability,and optimizing the wellbore trajectory can effectively improve the wellbore stability in fractured formations.The results of the study reveal the mechanism and main influencing factors of the wellbore instability in fractured carbonate formations,and provide a reference for the design of wellbore trajectory and the selection of engineering parameters in fractured carbonate formations.