Study On High Temperature And High Density Complex Brine Completion Fluid In Low Permeability Reservoir

The 13th East area is located in the Yinggehai Basin in the western shelf of the northern part of the South Sea of China.The temperature and the pressure in the area is high.Compared with conventional drilling and completion fluids,this area places higher requirements on the thermal performance and density of drilling and completion fluids.High temperatures can easily destroy the performance of drilling and completion fluids,causing drilling and completion fluids to fail,resulting in pore throat blockage and other issues.Large formation pressure requires a higher density,but high density requires the addition of more weighting agents,which makes solid content increase.The increasing of the solid content will greatly increase the probability of sticking,blowouts and other accidents.The clay mineral content in this area is high.To the reservoir,the potential reservoir damage is sensitive damage,solid particle blockage damage,and drilling and completion fluid filtrate damage.In this paper,a series of low-permeability reservoir high-temperature and high-density composite brine completion fluids have been developed through a large number of experiments aiming at the high-temperature and high-pressure conditions in the 13th Dongfang reservoir.The completion fluid uses inexpensive CaCl2 and ZnCl2 as weighting materials,The brine density was increased to more than 1.9 g/cm3 by using solubilizers LAS-30 and SLF4.In order to meet the requirements of high-temperature completion,a number of experiments have been conducted to screen out the high-temperature-resistance tackifier BDV-200.Fluid loss additives Polydrill and BDF-100S;corrosion inhibitor HSJ201 and inhibitor DFFP.Through repeated experiments,a set of compound brine completion fluid system with low cost,excellent performance,density of over 1.90/cm3,and temperature resistance up to 160℃ was developed.The specific formula for the brine system is 2%LAS-30+2%SLF4+102%CaCl2+180%ZnCl2+1.5%DJ-61 +1%BVD-200+1%Polydrill+0.5%BDF-100S+0.4%HSJ201+1%KCl+0.8%DFFP。The system has good rheological,inhibitory and antiseptic properties.The core permeability recovery rate can reach more than 90%,and the reservoir performance is excellent.