Application Study Of Cement Slurry System In Long Sealing Section Of XX Structure In Jidong Oilfield

According to the needs of XX structural development in Jidong Oilfield,the completion and cementing of deep wells in this block is required to be cemented by one-time return to the wellhead.The deep drilling depth of the block is generally 4000?5100m,and the sealing section is 1600?5100m.The bottom hole pressure is 35?58MPa,the annual average surface temperature is 20?,the bottom hole temperature is 105?130?,and the top and bottom temperature difference is 85?110?.The geological conditions are complex,in Minghuazhen Group,Guantao Formation and Dongying.There are many leaky layers in the group,which are prone to leakage during the cementing process;multiple sets of pressure systems coexist in the well,and gas enthalpy often occurs in the target layer with high oil layer pressure,which seriously affects the cementing quality.For the long sealing section,the large temperature difference cementing slurry system faces slow development of the top compressive strength,poor settlement stability,and coexisting problems during the cementing process.The design uses conventional density cement slurry to seal the lower production layer and low density cement.The slurry is used to seal the upper non-oil and gas intervals to meet the pressure balance requirements.The materials such as cement slurry reducer,anti-leakage agent and anti-caries agent are optimized,and the leakage prevention of cementing under the condition of large temperature difference satisfying XX structure is developed.Density cement slurry,anti-mite conventional density cement slurry,and field application of 3 wells.The main work and research results of the thesis are as follows:(1)Based on the Darcy's law of coexistence of pore-fracture and the new type of cement slurry loss simulation device,combined with the loss of cement slurry and its plugging process,factors such as leakage pressure,leakage channel structure and apparent viscosity of cement slurry were established.The F-value model of the leakage resistance of cement slurry is proposed.The comprehensive leak-proof evaluation method combining the pressure value Pm and the leakage prevention capacity F value is proposed,and the experiment is verified by multiple sets of different leakage prevention cement slurry.The evaluation method is consistent with the experimental results,indicating that the method can be used to evaluate the leakage resistance of cement slurry.(2)For the long sealing section,the large temperature difference cementing cement slurry should meet the leakage prevention requirements,and also meet the construction requirements at the higher temperature of the bottom of the well and the strength requirements of the cement stone at the lower temperature.Microbeads and micro-silicones are used as lightening and stabilizing agents,modified fiber and rubber particle materials as leak-proof and leak-proof materials,and considering the retardant and water-reducing agent which are sensitive to high temperature and temperature difference,1.35?1.50g/cm3 low-density cement slurry that can meet the bottom hole temperature of 105?130? and the top and bottom temperature difference of 85?110?.The leakage pressure of the cement slurry Pm is greater than 7.0MPa,the leakage resistance F value is 79.82?95.16,the top cement slurry 72?96h condensation strength is greater than 3.5MPa,and the comprehensive performance is well coordinated,which satisfies the large long sealing section of the structure.Temperature difference leakage prevention cementing requirements.(3)On the basis of analyzing the existing problems of common anti-caries agent and cement slurry system of XX structure,liquid silicon is used as anti-caries agent to develop liquid silicon anti-cracking conventional density cement slurry.The experimental test results show that the cement paste static strength transition time is less than The 30min and SPN values are less than 3,and the comprehensive engineering performance is well coordinated,meeting the requirements of the XX structural target layer for preventing flooding.(4)The anti-leakage low-density and anti-gas enthalpy conventional density cement slurry system developed by anti-cracking cementing was applied in three wells in the cementing of the XX structural long sealing section of Jidong Oilfield by step-by-step implementation..The results show that there is no leakage and turbulence in cement injection and coagulation process,and the cementing quality is excellent.It solves the problem of large temperature difference in the long sealing section.The upper section is easy to leak and the cement slurry strength develops slowly,and the target layer is easy to be technical challenge.