Evaluation Of Mechanical Properties And Casing Deformation Resistance Of Rubber Elastomeric Cement

In recent years,with the large-scale development of shale gas blocks in Changning,Sichuan,the problem of casing deformation and damage caused by fault slippage has caused significant economic losses.This paper puts forward the concept of "overcoming rigidity with softness".By adding elastic material to the cement slurry,the strength of cement stone can be reduced,and the accommodating space for fault displacement can be provided,so as to prevent and slow down casing deformation.In order to explore the elastic modification mechanism of rubber particles on cement stone,quantitatively analyze the elastic enhancement effect of rubber particle content on cement stone,and evaluate the ability of rubber elastic cement stone to prevent casing damage during the fault sliding process.Experiments and numerical simulations were carried out on cement stone samples with rubber particle content,and the main conclusions were as follows:(1)Scanning electron microscope was used to observe the rubber elastic cement stone,and qualitatively explore the elastic modification mechanism of rubber particles to cement.The results show that with the increase of the content of rubber particles in the cement stone,the microstructure angle increases.The content of calcium hydroxide crystals of elastic modulus decreased significantly,and the content of network,cluster,and fibrous calcium silicate hydrate crystals increased significantly,and when the curing period increased to 7 days,the hydration products near the rubber particles inside the sample were in the form of fibers.It is mainly composed of calcium silicate hydrate gel,and a large number of pores and cracks will make the sample show lower elastic modulus and hardness.(2)The experimental methods of triaxial compression and nanoindentation were used to explore the elastic modification effect of different rubber contents on cement stone at the macro and meso scale.When the 2% increase to 8%,the compressive strength and elastic modulus of the cement stone show a rapid linear decline,and the decline ratios are as high as 21.1% and 64.3%,respectively.The ratio of low-hard mineral clusters to low-hard mineral clusters showed an upward trend,and the ratio of medium-hard mineral clusters to hard mineral clusters showed a downward trend.The lattice indentation interpolation cloud map also showed that the incorporation of rubber particles effectively reduced the overall modulus and hardness levels.(3)Carry out the numerical simulation of the deformation process of the fault sliding extrusion casing.The simulation results show that: at the interface between the fixed rock layer and the sliding fault,the casing has the largest stress level and the largest diameter reduction.The casing is dislocated as a whole and does not reduce in diameter.Under the condition that the fault slip is 30 mm,the maximum stress on the casing is 1.9GPa,and the maximum diameter reduction is 8.98 mm.The influence of diameter reduction is within 1%,and with the increase of rubber particle content and the decrease of elastic modulus of rubber-enhanced cement stone samples,the deformation degree of casing decreases significantly,and the maximum reduction of diameter decreases by 36.5%,and the elastic modulus of rubber increases.Cement can effectively slow down casing diameter reduction in the process of fault sliding.