Investigation On Casing Failure's Mechanism And Strategies For Treatment In Dongxin Oilfield

When big oilfields enter into the late development stage, the casing deformation,cracking and leaping happen more and more.The annually increase of the casing damage wells influence the production effect greatly.The factors causing casing failure can be classified into two categories: one is the geologic factors, the other is engineering factors. The wriggling and expanding of the sopping shale, sand production, the slippage of the terrane, faultage movement, earthquake movement and other geologic factors are the inner ones; the cement job quality, the perforation, the choosing of the well site, the water injection, the cracking and other engineering factors are outer factors.This paper has studied casing defection in Guangli oil field and made analsis into geological setting, geostress distribution, reservoir properties and production history, studiedon various reasons of casing defection and given calculation and predictions, therefore making it available for casing defection analysis. The factors causing casing failure in Guangli oil field are the salinity of the formation water is so high, eroding the casing and decreasing its intensity; the stress concentration around the hole, the inhomogeneous load and extrusion damage the casing where the cement job quality is not effective.It is suggested that improving cementing job quality furthest during cementing process, and must calculate anticorrosive capability of casing and how much nonuniform external load works on casing's collapsing strength .In addition, balanced injection and production rate as well as pressure control, water control and preventing water from invading shale is an important method to avoid casing failure.