The Experiment Research On The Deformation And Failure Of Cement Sheath During Steam Injection Or Cementing

After the completion of cementing about infusing cement,mining time and benefits later of the oil shale mines are affected by the interface cementation performance of casing-cement ring.The interface cementation of casing-cement ring is an important component of the integrity of the system interface.Once the effect of interface cementation performance of casing-cement ring is not as ideal as expected and lead to the failure of cementing system,it may cause serious problems such as annular channeling flow of air.So the research on the interface of casing-cement ring is a basic work to improve the cementing quality fundamentally.Finishing the deep investigation and careful analysis on the factors which affect the interface performance of casing-cement ring,the experimental system is designed to study the cementation between the cement ring and two different structure of the casing of straight tube and corrugated pipe under the effect of high temperature.Then this paper analyzes the factors which affect the interface performance of casing-cement ring and the deformation and failure of the interface shape in the mining of steam injection.The test results show that:(1)Due to the differences of straight tube and corrugated pipe structures,when bellows occur expansion deformation at high temperature,strain value of the peaks and troughs is greater than ones of the expansion joint,and some of its deformation can be absorbed by the expansion joint.As a result,strain value of corrugated pipe is lower than that of straight pipe at the same temperature effect,and with the increase of temperature,The difference increased gradually.In the process of destruction and failure,Axial strain and hoop strain of straight pipe will appear at 100? increases greatly at 100?,but strain value of corrugated pipe is linear growth with the change in temperature.(2)In the process of the test,the steel of selected straight pipe and corrugated pipe is same,the proportion of cement ring materials is same,therefore the strain values of system are roughly same when appearing cemented surface seal failure problems under the effect of high temperature.Micro axial strain and toroidal strain values of annular tubes is around 2000.The radial extrusion deformation of casing ring expansion deformation can lead to micro cracks of the cement ring,Axial deformation of casing and cement that is not synchronized can make the system appear cementation failure.And the not-synchronized axial deformation is the main reason that causes the seal failure of casing and cement ring.(3)During the leakage test,when the temperature is 120? and the pressure is 0.75 MPa,the leakage of straight pipe cementing surface takes place,and cementation destroys,seal failures.However,when the temperature is 170? and the pressure is 0.35 MPa,those phenomena take place to corrugated pipe(4)Peaks and troughs have no much effect on the overall heat transfer balance of corrugated pipe in the process of systematic heat transfer and the thickness of cement ring becomes the main factor affecting cement ring heat transferThe comprehensive analysis can come to the conclusion that the interface cementation performance between corrugated pipe and cement ring is better than the straight pipe and cement ring under the effect of high temperature.The test results have certain guiding significance and application value to the prevention of casing-cement ring cementation's damage during the engineering of exploitation of oil and gas of oil shale steam injection.