摘要
四川盆地北部三叠系海相地层已发现20余口井套管存在不同程度的变形损坏,变形井段主要集中在雷口坡组和嘉陵江组,该井段含有大量膏盐,其中嘉四段膏盐含量高达58%。为此,针对该区域的X区块A1井海相地层套管变形检测结果及膏盐层的蠕变特性,采用有限元方法建立了非均匀外挤载荷反演模型,反演得到了海相地层套管所受的非均匀外挤载荷最大、最小值分别为98.93 MPa、92.85 MPa;通过建立海相地层套管受力分析模型,模拟得到了非均匀外挤载荷状态下φφ177.8 mm套管等效应力分布,计算出作用在套管上的等效外挤载荷为119.68 MPa,而被检测的变形套管抗挤强度仅有89.8 MPa,不能满足抗挤要求,定量揭示出了引发该区套管变形损坏的原因是膏盐层蠕变产生的非均匀外挤载荷。结合该区非常规井身结构应用情况,进一步计算了对应φ190.5 mm和2φ215.9 mm井眼尺寸的2φ168.28 mm、φ193.68 mm和2φ177.8 mm套管的等效外挤载荷,推荐了这3种尺寸的套管选型,其抗挤强度分别大于119.24 MPa、124.29 MPa和119.68 MPa,为该区域海相地层套管柱设计提供了参考数据。
Casing deformation and damage of different degrees occurred at the interval of Triassic marine strata in over 20 wells in the northern Sichuan Basin, and most of which focuses in Leikoupo and Jialingjiang Formations, which contain a large amount of gyp- sums salt, with a content up to 58% in the 4th member of Jialingjiang Formation. Based on the casing deformation test results of ma- rine strata in Well A1 and the creeping properties of gypsum-salt layers, a non-uniform external collapse load inversion model was built by finite element method. It is presented that the maximum and minimum non-uniform external collapse loads acting on the cas- ings in marine strata are 98.93 MPa and 92.85 MPa respectively. The force analysis model of marine strata casings was established to simulate the equivalent stress distribution on Ф177.8 mm casing under the state of non-uniform external collapse load. The calculated equivalent external collapse load acting on casings is 119.68 MPa, but the measured collapsing strength of deformed casings is only 89.8 MPa, which can＇t meet the requirement. It is quantitatively revealed that casing deformation and damage in this block is caused by non-uniform external collapse load which is generated by gypsum-salt creep. Equivalent external collapse loads were calculated for Ф168.28 mm, Ф193.68 mm and Ф177.8 mm casings in Ф190.5 mm and Ф215.9 mm boreholes with the configurations of uncon- ventional wells in this block taken into account. The collapsing strengths of these three types of casings are over 119.24 MPa, 124.29 MPa and 119.68 MPa respectively. This study provides an important reference for casing string design of marine strata in the north-ern Sichuan Basin.
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2015年第8期75-79,共5页
Natural Gas Industry
基金
国家科技重大专项课题"钻井工程设计和工艺软件"(编号:2011ZX05021-006)
关键词
四川盆地北部
三叠纪
海相地层
膏盐层
蠕变
非均匀外挤载荷
套管变形
损坏机理
套管选型
Northern Sichuan Basin
Marine strata
Triassic
Gypsum-salt layer
Creep
Non-uniform external collapse load
Casingdeformation
Damage mechanism
Casing type selection
