A Study On The Relationship Between Geological Stress And Casing Failure In Chaoyanggou Oilfield

As a low permeable oilfield, the number of casing failure wells increased year by year since the first casing failure well occurred in 1990 in Chaoyanggou oilfield. In order to solve this problem, this paper statistical analysis the situation of casing failure of this oilfield from eight different aspects, such as the depth, type, layer, injection production ratio and so on. It found that the depth of casing failure focused on the oil layer, the type of casing failure is deformation, and the number of casing failure increased with the increasing of injection pressure. When the injection pressure decreased, the number of casing failure is also deduced. So to evaluate accurately the relationship between injection pressure and casing failure has an important significance for the further exploitation by water flooding and preventation casing failure.Therefore, this paper determined the size and direction of three main earth stress with hydraulic fracture, viscous remanent magnetization, differential strain analysis, and acoustic emission methods. On the basis of the result and the destabilizing norm of rock, this paper calculate the critical injection pressure to prevent stratum slippage. And point out calculation method of the injection pressure in the oilfield on the considering two factors of initial burst pressure and overburden pressure. This gave a therotical basis for reasonable controlling injection pressure and effectively preventing casing failure.Besides, this paper emphasized on the research of the relationship between the injection pressure and casing failure. Based on rock and fluid coupling theory, applying finite elements analysis method and considering the interference among the wells, the paper simulated the distribution of pore pressure and seepage pressure under different permeability condition by using finite elements analysis software. it obtained the relation that the Mise stress of casing increases with the increasing of injection pressure. Intergrated with the geological characteristic that it has the upper and nether planes of weakness of oil layer, it also simulated the deformation of casing when the planes of weakness exist. It found that if both the upper and nether planes of weakness exist, the shift of casing deformation is the largest. According to the simulation of the stress on casing, the paper put forward the measures that is to control injection pressure and enhance the casing strength of the weakness place to prevent building pressure in oil layer.