摘要
针对油井长期服役过程中的固井界面微间隙产生机理及规律问题,对比国外学者的经典试验,利用ABAQUS有限元软件对套管内压交变作用下的固井界面力学响应进行了模拟分析。分析结果表明,当套管和水泥环应力均处在弹性范围内时,没有微间隙产生;而在高应力作用下水泥环中存在塑性残余变形时,套管内压交替变化将导致套管、水泥环和地层界面变形不再协调,将可能脱开产生微间隙。因此得出结论:套管内压交变作用下的水泥环塑性残余变形是导致微间隙产生的主要原因之一。进一步对影响微间隙尺寸的关键因素及规律进行分析,指出套管内压值越大,产生微间隙的可能性就越大,套管内交变压差越大,微间隙的尺寸就越大;在套管内交变压力作用下,软地层比硬地层固井界面更容易产生微间隙;同时,选用低弹性模量水泥固井界面产生微间隙的可能性则会降低。研究结果对环空带压和环空窜流的产生原因及预防具有重要意义。
In order to figure out cementing interface micro-annulus generation mechanism and rules during long well life, simulation analysis is conducted for cementing interface mechanical response under alternating cas- ing pressure by using the ABAQUS software based on classic experiments of foreign scholars. Analysis results show that, there is no microgap when the casing and cement sheath have a stress within an elastic range; alternating change of internal casing pressure will cause coordination failure of casing-cement sheath-formation interface de- formation so as to generate microgaps when the cement sheath has residual plastic deformation under high stress ac- tion. A conclusion is made that, residual plastic deformation of the cement sheath under alternating change of inter- nal casing pressure is one of primary causes for microgaps. Key factors and pattern of influencing mircrogap size are analyzed to show that mierogap possibility improves with increase of internal casing pressure and microgap size in- creases with alternating pressure difference in the casing; under alternating internal casing pressure, soft formation cementing interface is easier to generate microgaps than hard formation; it is less possible for the cementing inter- face with a low elasticity modulus to generate mircrogaps. The study results have an important significance on cause analysis and prevention of annulus pressure and annular fluid channeling.
出处
《石油机械》
2015年第4期22-27,共6页
China Petroleum Machinery
基金
国家973计划项目"深井复杂地层安全高效钻井基础研究"(2010CB226706)
中央高校基本科研业务费专项资金资助项目(27R1202015A)
关键词
微间隙
套管
水泥环
固井界面
塑性残余变形
有限元模拟
microgaps
casing
cement sheath
cementing interface
residual plastic deformation
finite element simulation
