Optimization Of Completion Fluid For Damage Characteristics Of Shahejie Reservoir In KL Oilfield

Aimed at the serious reservoir damage problem during the drilling and completion in KL oilfield,the potential damage mechanism and sensitivity of Shahejie Formation in KL oilfield were analyzed,the perforation completion fluid system was optimized,built,and successfully applied in field test based on the comprehensive evaluation of the completion fluid system performance.Through the study on reservoir potential damage mechanism of Shahejie Formation in KL oilfield,it was found that the reservoir porosity was 18.15%-24.81%,and the permeability was 15.66×10^-3μm²-1030.79×10^-3μm²,which belonged to the medium porosity and medium permeabilityⅡclass reservoir.The average clay mineral content reached 10%,with kaolinite as the main（average 55%）,followed by illite/smectite formation（average24.34%）,including chlorite,which caused the potential water sensitivity,speed sensitivity and acid sensitivity damage.The pore type was mainly intergranular pore,there was clay mineral in the pores,whose occurrence was pore filling type.The maximum pore throat radius was14.6602μm-3.6928μm,the average pore throat radius was 3.0217μm-0.9366μm.The uniformity coefficient was 0.2115-0.2501,the heterogeneity was strong.The average recovery rate of drilling cuttings was 2.30-8.27%,the hydration was strong.There was the potential particle migration damage because of the hydration and exfoliation in clay mineral.The results of reservoir sensitivity evaluation experiments showed that the total velocity sensitive damage rate of the cores from Shahejie Formation in KL oilfield was 65.08%,which was strong damage,the critical flow rate was 0.5mL/min.The water sensitivity index was54.84%,belonging to the medium to strong water sensitivity.The salinity sensitivity rate was54.84%,belonging to the medium to strong damage,the critical salinity was 8460mg/L.The alkali sensitive damage rate was 19.39%,belonging to the weak sensitivity,the critical pH value was 7.The hydrochloric acid sensitivity damage rate was 5.8%,belonging to the medium to weak damage.The mud acid sensitivity rate was 65.3%,belonging to the strong damage.The stress sensitivity permeability damage rate was 24.36%,belonging to the weak damage.The irreversible permeability damage rate was 29.59%.Through the comprehensive performance evaluation,the rheology filtration performances of the four sets completion fluid systems in KL oilfield were poor,the corrosion rates were little high,the corrosion inhibitions were poor,and the hydration swelling inhibition performances were poor.The anti-water-block invisible acid completion fluid and polyamine completion fluid had good compatibility with formation water,while the invisible acid completion fluid and crude oil drag reduction completion fluid had poor compatibility.Four sets completion fluid systems had the high damage to the core permeability.The core permeability recovery value was less than 80%.The clay stabilizer combination system was optimized as 3%KCl+1.5%HCS,with 1.0%-1.5%HTA,1.5%corrosion inhibitor CA-104,and the anti-water-block agent SATRO-1.The completion fluid system suitable to the Shahejie Formation in KL oilfield was built.It had strong inhibiting hydration swelling performance,dispersibility,good lubricity and compatibility with formation water with free solid.The temperature resistance reached 130℃,which could keep the performance for 32h under 120℃.It had the low corrosion,low imitated work of adhesion,and good removing water block effect.The average permeability recovery value was 88.78%,and the reservoir protection effect was good.The proration was 2-3 times higher than the original completion fluid systems in the field test,the application effect was improved obviously.