应用流固耦合理论研究套损机理

Casing damage mechanism by applying theory of fluid-solid coupling

根据油藏渗流与变形耦合作用理论,应用三维有限元模拟软件,对注水井泄压过程中井底套管内流体压力与地层中孔隙压力巨大压差导致套管外载的增加进行计算模拟.以实测岩石和套管强度参数为依据,采用调整地层压力、渗透率、有效厚度等条件,对不同泄压速度产生的压力变化规律进行了研究.研究结果表明,在其他地层条件都相同的条件下,渗透率越低,放喷相同流量时套管承受的挤压力越大;压差越大,套管承受的挤压力越大.由泄压与套管挤压力关系图版可以确定注水井作业、测试、洗井等过程中的允许泄压速度界限,控制该界限能防止套管损坏.

The load increasing of casing is numerically simulated which is caused by the great pressure difference between the fluid pressure in casing and the pore pressure in formation in the pressure relief process of water injection wells.Based on the actually measured rock parameters and the strength parameters of casing,the variation law of the pressure difference under different pressure-relief rates is studied by adjusting formation pressure,formation permeability and wall thickness of casing.It is shown that,the case other conditions are the same,the lower the permeability,the greater the extrusion pressure born by the casing;the greater the pressure difference,the greater the extrusion pressure born by the casing.The allowable pressure-relief rate limits in water injection,well testing,well washing etc.processes can be determined according to pressure-relief—casing extrusion-pressure relation type-curve,to control the limits can prevent casing damage.