Safety evaluation of production casing in staged stimulation of ultra-deep horizontal wells

Abstract

In view of the influence of high temperature formation fluid during the staged stimulation of ultra-deep oil and gas wells, the change of wellbore temperature field may cause casing rupture and compression. Based on the law of momentum conservation and energy conservation, an iterative calculation model of deep annulus pressure is established to study the variation law of confined annulus between packers. According to casing wear shape, the calculation model of residual strength and safety evaluation are established. The casing annulus pressure of L-3 well is predicted by casing annulus pressure prediction model, and the sensitivity analysis is carried out. The results show that the errors between the measured and predicted values of casing annulus are within the allowable range and the model accuracy is high. The effects of annulus liquid and tubing coefficients on annulus pressure are studied, and the effect of wear depth on casing safety factor is studied. In this paper, the effects of annulus pressure and casing wear on wellbore integrity in ultra-deep wells are considered comprehensively, and a method for production casing safety evaluation is developed.