水泥石初始压力特征分析

固井水泥浆注入井内后,在水泥石形成之前会出现失重现象,从而使水泥浆浆柱压力逐渐降低,如果没有引起其压力升高的因素,水泥浆柱压力会降为水柱压力.但事实上,在水泥浆失重期间,水泥浆柱压力下降会引起套管扩张变形和地层收缩变形,这两种变形都将挤压失重的水泥浆.这种挤压失重水泥浆的过程会持续到水泥石形成.水泥石形成时,重新建立起套管、水泥石、地层之间的压力平衡,此时水泥石承受的压力就是水泥石的初始压力.水泥石初始压力对水泥石、套管、地层体系以后的受力变形极为重要.

ANALYSIS OF INITIAL PRESSURE FEATURE OF SET CEMENT

After cement slurry is injected into well,weight loss occurs before set cement formed,which makes fluid column pressure of slurry decline step by step,and fluid column pressure of slurry is to decrease to water column pressure if there is none of other factors that can result in higher pressure.During weight loss of cement slurry,declining of fluid column pressure of slurry arouses extension distortion of annular tube and contraction of formation,which both compress weightless cement.This process would go on until set cement shaped.When it formed,the pressure balance was achieved once more among casing,set cement and formation,and the pressure that the cement stands was its initial pressure.The initial pressure of set cement was of great importance to cement,casing and formation system deformation.