Study On Damage Mechanism And Prevention Measure Of Thermal Horizontal Well In Shengli Oilfield

Because of the high development efficiency and economic benefits,thermal horizontal well has become an important way in the exploitation of heavy oil resources.But because of the complexity of the subsurface environment,thermal horizontal well happened a lot of damage in the process of application.The damage wells in the research block of Shengli Oil Field account for 26.9% of the total number of thermal horizontal wells,which caused significant economic loss.The purpose of studying on damage of thermal horizontal well is helping prevent damage of thermal horizontal well and reduce economic loss.At first,the paper analyzed the damage characteristics of the damage of thermal horizontal wells of research block.Statistical analysis has been made to find out the damage form of each cycle,the possible reason that made this damage,which points out the direction for later study.Then temperature field model of thermal horizontal wells was used to calculated the horizontal segment of steam temperature and pressure.Then,the paper established thermal stress calculation model of horizontal section of the string,and calculate the change of thermal stress in the different period by writing programs.As a result,the paper got the dangerous zones of horizontal section of string of different periods.At last,the paper analyzed the specific form of damage on the horizontal section of the string.The paper used finite element software ANSYS to calculate the stress of the end of screen in different temperature and different borehole curvature.The paper analyzed the stress of horizontal section of string and the dangerous areas in the case of phenomenons like constriction of wellbore.From the analytical result,we can find that the most happened damaged time of thermal horizontal wells is the first three cycles and cycles after eighth cycles.In the steam period,the first end pipe is subjected to a large compressive stress,and in the soak period,the last end pipe is subjected to a large tensile stress.In the steam period,the end of screen andperforation will be significant stress concentration.