Evaluation And Optimization Of Seawater-Based Fracturing Packing Fluid In The N₁m^L Formation Of BZ34-1 Oilfield

The N₁m^L Formation of BZ34-1 is dominated by very shallow water delta sediments and shallow burial.It belongs to under-compacted strata.Its characteristics of high porosity and high permeability,low clay content,and contact cementation make the stratum easy to produce sand.Coupled with the fact that it has been in production for 12years,the production pressure has been increasing,and the water content has been increasing,which has reduced the strength of the original tensile strength of only 0.899MPa.The problem of sand production is urgent.Sand production will not only reduce the production of oil wells,accelerate the wear and tear of equipment,but also cause the collapse of the formations in the mining area,causing oil wells to be scrapped.By comparing mechanical sand control technology,chemical sand control technology,composite sand control technology,and fracturing filling sand control technology,fracturing filling sand control technology is more suitable for sand control in high-permeability loose sandstone oil layers.Fracturing packing fluid is the working fluid during fracturing filling construction.It plays a role in transmitting pressure to form fractures and carrying proppant to support fractures during fracturing.It is very important in fracturing filling.By establishing the theoretical foundation of fracturing filling,a finite element numerical model was constructed,and the conclusion was obtained.As the viscosity of the fracturing packing fluid increases,the flow resistance greatly decreases,and the flow mode is changed to bilinear flow.The pressure gradient can be greatly reduced,which can effectively prevent sand production.But at the same time,it may bring different degrees of damage to the reservoir.Therefore,fully optimizing the fracturing packing fluid formula and correctly evaluating the performance of the fracturing packing fluid have guiding significance for sand fracturing effects.The seawater-based fracturing packing fluid formulations were obtained by selecting the additives and optimizing the concentration of the fracturing fluid.The basic formula of the fracturing packing fluid at 60?is:0.4%thickener+0.5%clay stabilizer+0.2%demulsification and drainage aid+0.08%p H regulator+0.4%cross-linking agent;The basic formulation of the crack packing fluid at 70?is:0.5%thickener+0.5%clay stabilizer+0.2%demulsification and drainage aid+0.08%p H regulator+0.5%cross-linking agent.The subsequent comprehensive performance evaluation of seawater-based fracturing filling fluids showed that the fracturing packing fluid formulation can be prepared using Bohai seawater,the thickening agent dissolution time is less than 15min,the average residue content is 3.8%,and the viscosity after shearing at 60?for 120min is 150m Pa·s.The filtration loss coefficient is:7.15×10^-4(m/(?)min),the demulsification rate is 100%.After shearing at 70?for 120 min,the viscosity is 260 m Pa·s,the filtration loss coefficient is 6.53×10-4(m/(?)min),and the demulsification rate is greater than96.8%.The breaking fluid viscosity is 3 m Pa·s,and the matrix permeability damage rate is less than 20%.It provided technical support for fracturing and filling in the N₁m^LFormation of BZ34-1 Oilfield.