深井安全钻井液密度窗口影响因素  

Analysis on influential factors for safe window of drilling fluid density in deep well

作　　者：李玉伟[1] 艾池[1] 王志成 胡超洋[1] 郝明[1] 栗爽[1] 

机构地区：[1]东北石油大学教育部提高油气采收率重点实验室,黑龙江大庆163318 [2]中国海洋石油工程股份有限公司设计公司工艺部,天津300451

出　　处：《油气地质与采收率》2013年第1期107-110,118,共4页Petroleum Geology and Recovery Efficiency

基　　金：国家自然科学基金项目"水力压裂岩体损伤演化与微裂缝形成研究"(50974028);国家青年科学基金项目"基于分数阶理论泥岩动态蠕变细观损伤机理研究与套管外挤损坏判别标准制定"(51104032);黑龙江省研究生创新科研基金项目"基于分形与损伤理论的巷道围岩稳定性研究"(YJSCX2011-115HLJ)

摘　　要：考虑钻井液渗滤造成井壁岩石孔隙压力变化和钻井液与地层岩石温差产生的附加应力和应变,推导了孔隙度与孔隙压力和温差的理论关系,建立了考虑孔隙压力、温差及孔隙度变化的深井安全钻井液密度窗口计算模型。应用模型计算结果表明:①深井钻井井壁岩石与钻井液温差一定时,随着钻井液渗滤作用的增强,井壁岩石孔隙压力增加,导致坍塌压力增大,破裂压力减小,安全钻井液密度窗口变小,不利于安全钻井。②当井壁岩石孔隙压力一定时,若钻井液使井壁岩石降温,则随着温差的增加,坍塌压力减小,破裂压力增加,安全钻井液密度窗口范围变大,有利于安全钻井;若钻井液使井壁岩石升温,则随着温差的增大,坍塌压力增大,破裂压力减小,安全钻井液密度窗口变小,不利于安全钻井。Considering the pore pressure variation of sidewall rock, which is caused by drilling fluid filtering, and additional stress and strain which is caused by temperature difference between drilling fluid and formation rock, the theoretical model of variation of porosity, which has considered variation of pore pressure and temperature difference, is derived, and the calculation model of safe window of drilling fluid density in deep well, which has considered variation of porosity, temperature difference and pore pressure, is finally established. Application of this calculation model shows that: when temperature difference between sidewall rock and drilling fluid in deep well is definite, with increased function of drilling fluid filtering, as increased as pore pressure of sidewall rock, the caving pressure is increased, fracturing pressure is decreased, safe window of drilling fluid density is narrowing, and unfavorable for safety drilling; and when pore pressure of sidewall rock is definite, if drilling fluid lower the temperature of sidewall rock, then as increased as temperature difference, the caving pressure is decreased, fracturing pressure is increased, safe window of drilling fluid density is widen, and favorable for the safe drilling. Moreover, if drilling fluid rises the temperature of sidewall rock, then as increased as temperature difference, the caving pressure is increased, fracturing pressure is decreased, safe window of drilling fluid density is narrowing, and unfavorable for the safety drilling. In this paper, the effects of drilling fluid filtering and temperature difference between drilling fluid and formation rock on safe window of drilling fluid density are theoretically explained, which is a of significance to the present calculation model of safe window of drilling fluid density.

关 键 词：深井 井壁 安全钻井液密度窗口 坍塌压力 破裂压力 

分 类 号：TE22[石油与天然气工程—油气井工程]