基于漏失机理的碳酸盐岩地层漏失压力模型  

The lost circulation pressure of carbonate formations on the basis of leakage mechanisms

作　　者：李大奇[1] 康毅力[1] 刘修善[2] 曾义金[2] 杜春朝[3] 

机构地区：[1]西南石油大学油气藏地质及开发工程国家重点实验室,四川成都610500 [2]中国石化石油工程技术研究院,北京100101 [3]中国石化西北油田分公司,新疆乌鲁木齐830013

出　　处：《石油学报》2011年第5期900-904,共5页Acta Petrolei Sinica

基　　金：国家重点基础研究发展规划(973)项目(2010CB226705);国家科技重大专项(2008ZX05049-003-07HZ和2008ZX05005-006-08HZ)联合资助

摘　　要：漏失压力预测是防漏堵漏的关键。在孔隙型或含微裂缝的砂、泥岩地层中,依据破裂压力设计钻井液安全密度上限值是比较合理的,然而在缝洞发育的碳酸盐岩地层中,往往使得钻井液设计密度值偏大。为了保障安全顺利钻井,亟需建立碳酸盐岩地层的漏失压力预测理论。基于对碳酸盐岩地层钻井液漏失机理的新认识,建立了压裂性漏失、裂缝扩展性漏失、大型裂缝溶洞性漏失的漏失压力模型。压裂性漏失主要抵抗地应力,漏失压力近似等于地层破裂压力;裂缝扩展性漏失需要抵抗地应力和地层压力,漏失压力一般小于地层破裂压力;大型裂缝溶洞性漏失只需抵抗地层压力,漏失压力一般略大于地层压力。实例分析表明,漏失压力模型科学依据更加充分,也更具针对性,预测结果与实际情况比较吻合,为合理的钻井液密度设计及防漏堵漏提供了依据。因此,建议将漏失压力纳入到钻井工程设计中。The prediction of lost circulation pressure is a key to leak resistance and sealing.It is reasonable for sandstone or mudstone formations with small pores or microcracks to design the upper safe density limit of drilling fluids based on fracture pressure,which,however,often results in a higher safe density value of drilling fluids for carbonate formations with developed fractures or caverns.Therefore,it is necessary to establish a theoretic foundation for the prediction of lost circulation pressure in order to guarantee safe drilling in carbonate formations.Based on the newly obtained cognition on lost circulation mechanisms of drilling liquids in carbonate formations,we established a lost circulation pressure model suitable to different leakage in carbonate formations,such as fracturing leakage,fracture expansion leakage and large-scale fracture or cavern leakage.The fracturing leakage deals mainly with in-situ stress for its lost circulation pressure is approximately equal to the fracture pressure of formations,the fracture expansion leakage is related with both in-situ stress and the formation pressure because the lost circulation pressure is commonly smaller than the fracture pressure of formations,while the large-scale fracture or cavern leakage is merely involved in the formation pressure for the lost circulation pressure is often slightly higher than the formation pressure.Case analyses have proved that this lost circulation pressure model is of sufficiency in scientific bases and pertinence.The prediction result derived from the model is relatively consistent with the actual situation and consequently provides a substantial basis for a rational design of the drilling fluid density as well as the leak resistance and sealing.Therefore,it is suggested that the design of drilling engineering should take the lost circulation pressure into consideration.

关 键 词：破裂压力 防漏堵漏 安全密度窗口 储层损害 碳酸盐岩 

分 类 号：TE21[石油与天然气工程—油气井工程]