| The problem of casing wear is serious in a certain oil field due to its deep burial and long drilling time.At present,the well structure,casing,drilling fluid and drilling tools used in this oil field have changed greatly compared with the past,and there are many new problems to be solved in casing wear.Therefore,prediction of casing wear degree and evaluation of residual strength under new drilling conditions are of great significance for improving casing design method and well integrity technology.In order to improve the prediction level of wear degree of casing in deep Wells in this oilfield,the following researches are carried out in this paper:First,investigate nine cases of casing wear problems in this oilfield at present,and summarized the main factors affecting casing wear: well quality,wear belt of drill pipe joint and casing material,drilling technology,drilling fluid and drill pipe protector.The key parameters of casing wear prediction were obtained through the physical wear test.In view of the characteristics of ultra-deep Wells in this oilfield,a hard drilling string model based on "wear efficiency" is determined to predict casing wear.Second,Introduced the importance of contact pressure threshold in casing wear prediction,calculates the contact pressure threshold under the drilling condition of this oil field through physical experiment for the first time,and points out that casing wear can be controlled by the control of well quality and the selection of wear belt.Finite element analysis was carried out on two kinds of casing with severe wear in this oilfield,and the residual strength of casing under different wear rates was determined.Third,a matching casing wear prediction software,and the database of drill pipe,casing and wear coefficient used in the oilfield was established.The calculation results of the software were compared with the field measurement results.The results showed that the calculation accuracy of the software could meet the field requirements of casing wear prediction in the oilfield. |
