钻井液浸泡下深部泥岩强度特征试验研究  

EXPERIMENTAL STUDY OF STRENGTH PROPERTIES OF DEEP MUDSTONE UNDER DRILLING FLUID SOAKING

作　　者：卢运虎[1,2] 陈勉[1] 金衍[1] 滕学清[1,2] 吴文[3] 刘绪全[1] 

机构地区：[1]中国石油大学油气资源与探测国家重点实验室,北京102249 [2]中国石油塔里木油田分公司,新疆库尔勒841000 [3]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,湖北武汉430071

出　　处：《岩石力学与工程学报》2012年第7期1399-1405,共7页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家重点基础研究发展计划(973)项目(2010CB226700);"十一五"国家科技重大专项项目(2011ZX05031–004–005 HZ);国家自然科学基金资助项目(51074171)

摘　　要：针对钻井液作用下深部泥岩破坏的关键技术难题,通过室内试验分析钻井液浸泡下深部泥岩强度弱化规律,并从微观角度分析试样发生变化的机制。研究结果表明:(1)钻井液浸泡下,随取芯夹角增大,岩石强度先增大后减小,岩石强度降幅高达49.5%～54.7%;随着围压增加,取芯夹角为0°和90°时岩石强度增幅较低,仅为26.4%～39.2%。(2)泥岩弹性模量随钻井液作用时间的增加而降低,随取芯夹角的增加呈现先增大后减小的变化规律,泊松比变化规律则相反。(3)与内摩擦角相比,泥岩黏聚力变化规律性强,0°和90°条件下黏聚力降低幅度较大,最高达67.3%;其他情况下泥岩黏聚力变化幅度不大。(4)钻井液滤液的渗入导致泥岩内部裂缝缝尖应力强度因子增加、临界断裂韧性降低、裂缝扩展,这是泥岩强度降低的根本原因。同时,钻井液滤液改变了层理面填充物的矿物成分,降低裂缝面的摩擦因数,加剧岩石强度的降低。According to the key technical problem of deep mudstone failure under drilling fluid soaking, the weakening law of strength is analyzed by the laboratory test; and the changing mechanism of core samples is analyzed through microcosmic angle. The result shows that： （1） Under the drilling fluid soaking, the mudstone strength increases first and then decreases with increase of coring angle. The decreasing range of strength is up to 49.5% - 54.7%. With the increase of confining pressure, the increasing range of strength is lower and it is only 26.4%- 39.2% with coring angles of 0° and 90°. （2） The elastic modulus of mudstone decreases with the increase of soaking time, and increases first and then decreases with the increase of coring angle. But the change law of the Poisson＇s ratio is opposite with that of the elastic modulus. （3） Comparing with the internal friction angle, the change of mudstone cohesion presents stronger regularity. The decreasing range of cohesion is larger with coring angles of 0° and 90°, and it reaches 67.3%; but the change range of cohesion is small under other coring angles. （4） Because of the invasion of drilling fluid, the stress intensity factor of crack at the tip increases; the critical fracture toughness decreases and the cracks propagate, which is the basic reason for strength decrease of mudstone. Simultaneously, mineral composition of the fitting in bedding surface is changed by the action of drilling fluid. So, the friction factor crack face decreases and the decrease ofmudstone strength is intensified.

关 键 词：岩石力学 深部泥岩 强度 取芯夹角 浸泡时间 钻井液界面性质 

分 类 号：TU45[建筑科学—岩土工程]