Research Of Casing String Strength Optimization Design Of Dongxin Complex Fault Oil Reservoir

Dongxin oil field is a typical complex block oil field, faults are developed there, andfracture system complex. Enter highly water cut stage, due to the characteristics offault-block oilfield, casing damage is seriously, the injection-production pattern iscaused secondary imperfect. How to effectively solve the problem of casing damage,it has became an urgent problem in the development of complex fault-block reservoirs.Therefore, statistical theory is used, the casing damage wells of Dongxin oilfield asthe research, casing damage law is analysis, casing damage mechanism is studied inthis paper. The studies showed that the main reason that casing damage in Dongxinfault-block reservoir is non-uniform extrusion load generated by mudstone creepwhich triggered by high-pressure water injection, stress concentration due tosecondary-order faults formed, shear stress of the secondary-order fault caused byhigh-pressure water injection, and formation water corrosion. Against the unsuitabilityof the conventional casing strength design method at mudstone and fault, andcombined with the casing damage mechanism, a new casing strength optimal designmethod was proposed. Against casing-cementing system is unable resist shear stresscaused by fault slip, a new cementing method that delay casing damage at thesecondary-order slipping fault was proposed. Finally, in the basis of establishing theground stress mathematical model in Dongxin complex fault-block reservoir, a casingstrength optimization design calculator program is complied. Through the study of thepaper, a theoretical basis and foundation was provided for delaying casing damage ofDongxin complex fault-block oilfield.