克深地区井壁稳定性评价及钻井工程应用  

Evaluation of Wellbore Stability in Keshen Area and Drilling Engineering Application

作　　者：王志民 谭丽娟[1] 陈胜[2] 袁芳[2] 韩兴杰[2] 王益民[2] Wang Zhimin;Tan Lijuan;Chen Sheng;Yuan Fang;Han Xingjie;Wang Yimin(School o f Geo-Resources and Information,China University of Petroleum, Qingdao,Shandong,266580, China;Researcli Institute of Exploration and Development,PetoChina Taam Oilfeld Company,Korla,Xinjiang,841000,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]中国石油塔里木油田公司勘探开发研究院,新疆库尔勒841000

出　　处：《天然气与石油》2018年第2期73-78,共6页Natural Gas and Oil

摘　　要：塔里木盆地克深地区裂缝性储层埋藏深,井壁失稳问题严重,建立该区考虑地层各向异性的井壁稳定性评价方法非常重要。通过对现场井壁失稳与地层弱面的相关性研究,发现弱面在强应力、高孔隙压力背景下,将先于岩石本体破坏,产生掉块、垮塌、卡钻现象。若裂缝渗透性较好,钻井液液柱压力大于孔隙压力时即有可能发生漏失,漏失压力不再由破裂压力和最小水平主应力控制,而是取决于裂缝产状和三轴应力状态之间的关系。因此对于强各向异性地层,其强度软弱面上的坍塌压力和漏失压力是钻井稳定性评价中的关键。在核定该区井壁失稳的主控地质因素是强应力背景下的裂缝弱面错动破坏的基础上,评价了克深区带横向各向异性岩体力学的稳定性,建立适用于强各向异性复杂条件下的井壁稳定性评价方法。结果表明克深裂缝性储层的安全泥浆密度窗口普遍较窄甚至无理论安全窗口,提出改善钻井液性能或者采用定向井钻探方案以减少井壁失稳的工程应对方案。现场实践应用表明,钻井液密度调整至合理范围后,井壁失稳明显减少,现场复杂问题得到有效解决。The borehole instability problems are serious in Keshen fractured reservoir with large buried depth in Tarim Basin. It is very important to establish the method of evaluating the stability of the borehole wall with anisotropic formation in this area. Through studies on the correlation of site wall instability and formation weak surface,the existence of the weak plane made the rocks damaged before the rock mass under strong stress and high pore pressure,it will be broken easily and cause collapse and sticking. If the fracture permeability is good,loss may occur when drilling fluid pressure is greater than pore pressure,then loss pressure is no longer controlled by fracturing pressure and minimum horizontal principal stress,but on the relationship between the occurrence of fractures and the triaxial stress state. So for the formation of strong anisotropy,the collapse pressure and loss pressure of weak strength plane is the key parameter in the evaluation of drilling stability. As the main controlling geological factor of the borehole instability in this area that is the failure of the weak surface of the crack under the strong stress background was determined,the stability of the mechanics of transverse anisotropic rock mass was evaluated in Keshen area. A method for evaluating the stability of wellbore under the complex condition of strong anisotropy was established in this paper. The results show that safety mud density windows of fractured reservoirs is generally narrower or even without theoretical safety windows in Keshen. The study shows that the wellbore instability be reduced by improving the performance of the mud or using a directional well drilling scheme. The field practice shows that after the drilling fluid density is adjusted to a reasonable range,the instability of the wellbore is obviously reduced,and the complex problems in the field are effectively solved.

关 键 词：强度各向异性 裂缝 井壁稳定 坍塌压力 漏失压力 

分 类 号：TE24[石油与天然气工程—油气井工程]