| With the adoption of various enhanced oil production measures,the working conditions of casing of oil and water wells have become more and more deteriorated,and nearly all oil fields are now confronted with a universal problem:casing damage,which is increasingly aggravated year by year and brings about enormous loss of manpower,material resources and financial resources to oilfield. 8000 oil and water wells were damaged cumulatively,and 80 hundred million Yuan (RMB) were lost directly in Daqing oilfield. Research on the mechanism of casing damage and relative workover technology has both theoretical and engineering significance.Casing damage is a complex problem involving geo-mechanics , fluid mechanics and material theories. According to statistics of Daqing oilfield, the creeping of shale after soaking, gliding of layers and hydraulic fracturing are the main reasons for casing damage in water injectation oilfields. The main types of casing damage in Daqing oilfield include deformation, leak, dislocation and compression. This paper analyzes the present situation of research on casing damage mechanism in the world studies systematically the casing damage in Daqing oilfield brought by water injection and fracturing,and mainly focuses on analyzing deformation and comprepression. The influence factors of casing damage are found out. Based on the above analysis the problems existing in the old casing design methods are studied and new methods for casing loading anylysis and optimized design are built up. In addition the analysis of influence of cement on casing is carried out.At present it is very difficult to repair complex casing damage wells, so it is very necessary for developing new workover technology. This paper presents the technology for casing reshaping and casing patching. The mechanical characteristic of special downhole tools are analyzed, which improves the performance and dependability. It provides oilfields new approaches to casing repair .
|
PDF Full Text Request