基于漏失压力极限法的压力衰竭气藏大位移水平井井身结构设计  

Structural design of extended reach horizontal wells in pressure depleted gas reservoirs based on the leakage pressure limit method

作　　者：李忠慧[1] 李中 方满宗 楼一珊[1] 陈浩东 刘杰 Li Zhonghui;Li Zhong;Fang Manzong;Lou Yishan;Chen Haodong;Liu Jie(National Engineering Laboratory for Oil and Gas Drilling Technology//School of Petroleum Engineering,Yang-tze University,Wuhan,Hubei 430100,China;CNOOC China Limited Zhanjiang Branch,Zhanjiang,Guangdong 524057,China;Turpan Oil Produetion Plant,PetroChina Tuha Oilfield Company,Turpan,Xinjiang 838000,China)

机构地区：[1]"油气钻井技术"国家工程实验室.长江大学石油工程学院 [2]中海石油(中国)有限公司湛江分公司 [3]中国石油吐哈油田公司吐鲁番采油厂

出　　处：《天然气工业》2018年第8期91-95,共5页Natural Gas Industry

基　　金：国家自然科学基金项目"深水高温高压环境下钻井全过程井壁稳定评价方法"(编号:51774050)

摘　　要：地层压力衰竭气藏在油气压力下降后,岩石特性参数以及地应力会发生改变,如果沿用压力未衰竭时的井身结构设计方案将会导致井身结构设计不合理,易发生井漏、井塌等井下复杂情况。为此,在分析压力衰竭地层大位移水平井钻井难点与对策的基础上,将井筒最大液柱压力与漏失压力平衡作为初步确定套管下深的约束条件,同时考虑循环当量密度的影响,建立了压力衰竭气藏水平井井身结构设计方法,并在莺歌海盆地东方1-1气田进行了现场应用。研究结果表明:(1)井内压力平衡的上限取漏失压力,其值等于水平最小主地应力;(2)水平最小主地应力将随着气藏开采地层流体压力的降低而减小;(3)套管下入极限深度受到钻井液循环当量密度(ECD)的制约,即随着水平段的延伸,环空压耗将增加至压漏临界点深度;(4)东方1-1气田主力储层地层压力衰竭严重,井身结构优化后采用四开井身结构,使得3个不同压力体系的储层不同存于一个裸眼井段,有效地降低了井下复杂情况的发生概率。结论认为,该方法可为压力衰竭气藏的大位移水平井井身结构设计提供理论依据。The rock characteristic parameters and earth stress of pressure depleted gas reservoirs are changed after the oil/gas pressure drops,so the casing program used for undepleted reservoirs is not suitable any longer and it tends to bring about complex downhole situations,e.g.circulation loss and well collapse.In this paper,the difficulties and countermeasures of extended reach horizontal wells in pressure depleted reservoirs were analyzed.Then,a method to design the casing program of horizontal well in pressure depleted reservoirs was developed with the balance between the maximum wellbore fluid column pressure and the leakage pressure as the constraint to determine the casing running depth while considering the effect of equivalent circulation density（ECD）.Finally,this design method was applied on site in the Dongfang 1-1 Gas Field,Yinggehai Basin.And the following research results were obtained.First,the leakage pressure is taken as the upper limit of borehole balance pressure,which is equal to the minimum horizontal major earth stress.Second,the minimum horizontal major earth stress decreases with the drop of the fluid pressure in the producing zones of gas reservoirs.Third,the casing running depth limit is controlled by the ECD of drilling fluid.That is to say the annulus pressure loss will increase to the depth of critical leakage point as the horizontal section extends.Fourth,the pressure of the principal reservoir in the Dongfang 1-1 Gas Field is depleted seriously.And its optimized casing program is four-spudding structure,in which the reservoirs of 3 different pressure systems are not arranged in the same open hole section and the occurrence probability of complex downhole situations is reduced effectively.In conclusion,this method provides a theoretical basis for the design of casing program of extended reach horizontal wells in pressure depleted reservoirs.

关 键 词：压力衰竭 气藏 大位移 水平井 井身结构 漏失压力 循环当量密度 东方1-1气田 莺歌海盆地 

分 类 号：TE243[石油与天然气工程—油气井工程]