套管缺陷对电场分布影响研究

On the Electrical Field in a Borehole with a Defective Casing

在套管井中,过套管电阻率测井可实现套管外地层电阻率的测量。通过多物理场耦合COMSOL软件,建立了套管井模型,利用数值分析方法研究了套管缺陷(腐蚀、接箍、断裂以及电导率非均匀等)对电场和二阶电位分布的影响。仿真结果表明,套管缺陷对电场和二阶电位曲线影响具有典型的局部特征,即在缺陷范围附近曲线突变,远离缺陷范围影响消除;不同种类套管缺陷,电场和和二阶电位曲线变化规律不同;实际测井数据处理和测井解释必须结合套管缺陷,以消除套管缺陷对测井的影响。

In cased hole,the resistivity of casing external formation can be detected by using the cased hole formation resistivity technology.The well logging models are built by the COMSOL multiphysics soft,and through numerical calculation,the influences of the casing defects(corrosion,collar,fracture and inhomogeneous conductivity,etc.)on the electrical field and the second order potential are analyzed.The numerical calculation results show that the influences of the casing defects on the second order potential take typical local regular,i.e.,there is the curves mutation in a local defective casing,but no change away from the defective section.Different defects have very different characteristics on the curves of the second order potential.And actually the logging data processing and logging interpretation are used to the casing defects in order to eliminate these influences.