Research On The Effect Of Segmental Fracturing Process On The Integrity Of Cement Annulus In Horizontal Wells

Horizontal well technology is a commonly used to increase the production of oil and gas wells at present.Research on the effect of multi-stage fracturing of horizontal wells on the integrity of cement annulus can provide targeted measures to reduce the possibility of cement annulus damage,increase the working life of oil and gas wells,and reduce oilfield costs.This paper theoretically studies the stress of casing-cement annulusformation system under non-uniform ground stress conditions.Numerical simulation of horizontal fracturing conditions in horizontal wells is performed using finite element software and discrete element software.First,using finite element software to establish a finite element model to obtain the change of plastic zone in the multi-stage fracturing process of the cement annulus,and then using discrete element software to analyse the unit with the largest plastic deformation in the finite element to obtain the number of micro-cracks in the unit along with the fracturing process.The cement annulus’ s integrity can be reflected to some extent by the change of the cement annulus plastic zone and the number of micro-cracks.According to the simulation results of finite element software and discrete element software,it can be obtained that the cement annulus integrity deteriorates when the internal stress of the cement annulus exceeds the average value of the in-situ stress in the cross-section direction of the wellbore.Cement annulus integrity will increase as the stiffness ratio between casing and cement annulus increases.The nonuniform coefficient of the casing increases,the integrity of the cement annulus weakens.The more horizontal fracturing sections,the poorer the cement annulus integrity.Defective cement annulus can make its integrity worse...