页岩气水平井压裂地层滑移致套损模拟试验研究

Physical Simulation Experiment on Casing Damage Caused by Stratigraphic Slip in Shale Gas Horizontal Well Fracturing

为了了解页岩气在水平井压裂过程中地层滑移导致套管损坏的规律,设计了压裂过程中地层滑移室内模拟试验装置,采用该装置模拟了水力压裂过程中产生的地层不均匀隆起诱发水平层面的滑移过程,并基于非常态相似理论确定了试验模型与地层原型各参数之间对应关系。分析结果表明:地层滑移量主要与距地层变形中心的距离有关,即与距水力压裂点的距离有关,总体上,从地层膨胀中心开始,滑移量逐渐增大,在距中心点14～17 cm范围内达到最大值,之后开始快速下降;不同的地层厚度以及不同的地层埋深影响着地层滑移量的大小,当套管穿过层厚较大的页岩地层时,滑移量要比低厚度地层大,当套管在纵向穿过地层发生多段套损时,其上部剪切滑移程度要大于下面部分。所得结果对认识页岩气井剪切型套管变形及如何预防套管损坏具有一定的理论指导意义。

To understand the casing damage caused by stratigraphic slip during shale gas fracturing,a simulation experiment device for stratigraphic slip during fracturing was designed to simulate the horizontal layer slip process induced by uneven rise of the formation during shale gas hydraulic fracturing.The relation between the experimental model and the parameters of the formation prototype is determined based on the theory of abnormal state similarity.The analysis results show that the stratigraphic slip amount is mainly related to the distance from the deformation center of the stratum,that is,the distance from the hydraulic fracturing point.Generally,from the stratum expansion center,the slip amount gradually increases and reaches the maximum value at 14~17 cm from the center point,and then begins to decrease rapidly.Formation thicknesses and depths influence the amount of slippage.The larger thickness layer can cause larger slippage.When the casing is in longitudinal direction through the formation with multiple casing damages,the upper shear slip is greater than the lower part.The study could provide theoretical guidance for understanding the casing shear deformation of shale gas well and casing damage protection.