摘要
大庆油田部分区域集中出现标准层套管剪切损坏,虽已采用标准层不固井工艺延缓套管损坏,但除此之外,套管壁厚、钢级等参数对标准层套管剪切损坏的临界条件也有影响。为此,考虑套管和地层弹塑性力学特征,针对标准层不固井的工程条件,应用考虑大变形后应力平衡状态的拉格朗日格式有限元方程,提出了地层整体移动剪切套管过程的三维有限元计算方法。考虑套管变形和套管断裂的2种失效条件,计算并对比不同壁厚和钢级套管失效的临界值。结果表明:考虑套管断裂的地层剪切套管临界滑移量明显小于考虑套管变形的临界滑移量;同规格、同钢级套管损坏的临界滑移量随套管壁厚增大呈线性减小,随其延伸率增大近似呈线性增大。因此,在满足强度校核的前提下,大庆油田标准层宜采用低钢级小壁厚套管以延缓套管损坏。
Casing shear damage appeared frequently in the datum bed in the Daqing Oilfield,and an uncementing technology has been adopted to delay casing damage.However,the critical value of marker casing shear damage is related to wall thickness and steel grade of the casing.An analysis was conducted on the elastoplastic mechanical characteristics of casings and formations,and a three-dimensional finite element calculation method was proposed,based on the engineering conditions of uncementing markers,for integral formation movement and shearing casing by using the Lagrange finite element equation,which takes account of the stress equilibrium state after large deformation.Critical values of the casing failure with different wall thickness and steel grade were calculated and compared at two failure conditions,i.e.the casing deformation and casing fracturing.It is shown that the critical slippage of casing with formation shear when the casing was fracturing is much smaller than that of casing deformation.The critical slippage of casing that have the same size and steel grade decreases linearly with the increase of wall thickness,but increases linearly with the increase of elongation rate.To sum up,the casing with small wall thickness and low steel grade should be adopted in datum bed of the Daqing Oilfield to delay casing damage on the condition that strength checks are satisfied.
出处
《石油钻探技术》
CAS
CSCD
北大核心
2015年第6期7-12,共6页
Petroleum Drilling Techniques
基金
国家自然科学基金项目"基于混沌理论煤层气井压裂孔裂隙分形演化与渗流特征研究"(编号:51274067)
东北石油大学研究生创新科研项目"注采诱发地层水平断面滑移和套损规律研究"(编号:YJSCX2015-008NEPU)资助
关键词
标准层
套管损坏
有限元法
几何模型
大庆油田
datum bed
casing damage
finite element method
geometric model
Daqing Oilfield
