Numerical Simulation And Prevention Measures On Casing Damage Of Thermal Production Well

The thermal heavy oil production technology has been widely applied to enhance oil rate. But the casing bore great thermal stress which caused by the high temperature of injected steam, and then reduced casing service life, especially on bending part. During steam injection, the casing stress was influenced by many factors. But the main factor has a close connection with the coupling interaction of oil reservoir thermal field and stress field. It is the coupling interaction that caused the stress concentration and casing damage. So it is necessary to consider the coupling interaction of oil reservoir thermal field and stress field when analyzing the mechanism of casing damage in thermal heavy oil production, which has great importance in both theory and application.Based on thermo-structural coupling theory, by numerical analysis on the stress in bent casing of thermal production well, the thermal stresses under different geological conditions and different hanging heights of screen liner were simulated. The results can provide theoretical guidance to analyze casing stress status and prevent casing damage. The main research is listed as follows:(1) On the base of plenty of field data, casing damage is happened in bent pipe easily, and then the object and method of study are definite.(2) The finite element model of composite element of casing-cement sheath-surrounding rock was built, and the elastic-plastic model of the casing composite element was numerical calculated. The feasible method of equivalent parameters was received.(3) By the method of equivalent parameters, the thermal stresses under different geological conditions and different temperatures of casing were simulated.(4) By numerical simulation on the influence of complex geological strata on stress distribution of bent casing in thermal production well, the thermal stresses under different hanging heights of screen liner were simulated. (5) Based on numerical analysis on the influence of steam temperatures on stress distribution of bent casing in thermal production well, the laws between stress of bent casing and thermal stress, different geological conditions, different hanging heights of screen liner were received. The results can offer reference for analyzing the reasons of casing damage and preventing casing damage in advance.