Study On Casing Residual Internal Pressure Strength After Wear And The Influence On Safety Well Control

The difficulty and the depth of the current oil and gas drilling is continuously increasing currently, especially in the high pressure gas well drilling, borehole pressure, high temperature, frequent occurrence of overflow ,well control issues become increasingly prominent. In the process of exploration and development in Northwest oil field in China , many factors such as the well depth, long drilling cycle , usage of iron ore et al often lead to increased wear and even worn out casing in many regions. And casing wear and cement loops loss will result in bealoop capacity lower , left for safety hazards duloop Well control operation. If the casing wear and the lack of cement loop cause the internal pressure strength reduced to a certain extent, when the overflow happens ,it can not be effectively shutted and killinged , poseing a serious threat to the following well control operation safety during drillng.The paper first discusses the main features and the mechanism of the casing wear. According to the wear characteristics and the casing type commonly used in western oil field,we established the finite element model of casing wear, and used finite element analysis software to calculate the remaining internal pressure strength after worn casing under the condition of different types, different thickness, different wear, with or without cement loop and occurrence of missing cement loop.Construction of a set of the experimental device for the remainder internal pressure strength after worn casing ,we completed the experiment of reminding casing internal pressure strength in different wear size and lack of different cement sheath. And combined the finite element calculation and analysis,we got the relevant Changes law of internal pressure strength .Through experiment study under the condition of cement loop lose and finite element calculation,we found that it can result in an stress concentration when the cement loop had a lack of a certain sheat, Casing internal pressure strength of cement loop is lower than no protection of cement loop.It can not enhance the ability of internal pressure casing, but reduces the internal pressure strength casingWith cement sheath intact model, we calculated the casing Internal pressure strength under commonly used killing methods, analyzed the variation law of casing under different sets of killing methods and the pressure variation law of the fray, drawing killing curve construction , and proposed the preferred killing method. And combinated the analysis of Le 102 killing case, we got differdent iMPact of a variety of killing methods on well control safety. In this paper how to optimize killing program after casing wear is an innovation.It presents that the reminding internal pressure in the fry is a criteria of the kill maximum allowable casing pressure design.This experimental program and equipment is an entirely new experience in the casing internal pressure strength .Espesically through the lack of cement sheath study ,we found that a certain lack of cement sheath angle can result in stress concentration, and the internal pressure strength of casing down to the extent of no protection of cement loop.So the lack of cement loop has an enormous iMPact on casing.