Study On The Compound Displacement Technology Of Weak Gel-Surfactant In The Reservoir Of Gaoqianbei Area

The geological reservoir of the Gaoqianbei reservoir is 1450×104t,the reservoir temperature is 65?,and the formation water salinity is 1584mg/L.The average effective permeability of the reservoir is 442.3mD,and the average porosity is 30.3%.It is a high-porosity and high-permeability reservoir.Heterogeneity of the reservoir layers is mostly medium-heterogeneous,but intra-layer and plane heterogeneity are strong,and large pore channels develop.The Gaoqianbei reservoir was put into development in 1991.After the oil well producing water,the water content rose rapidly.The water in the edge and bottom continued to advance,the flooding situation was complicated,and the remaining oil was highly dispersed.After 2000,the profile adjustment began,and good results were obtained initially.However,after the fifth profile adjustment,the effect of profile control deteriorated and the water content increased.The reservoir is currently in a state of high moisture content(97.31%)and low recovery(20.29%),and it is necessary to explore effective water control and oil increasing methods.The Gaoqianbei area reservoir adopts gel profile modification to improve the inter-layer heterogeneity of the reservoir and has achieved certain results.However,as the profile adjustment cycle increases,the effect of profile modification gradually deteriorates.The serious heterogeneity in the reservoir layer will have a serious impact on the sweep efficiency of the displacing fluid.The weak gel deep regulation will improve the heterogeneity within the layer.At present,the remaining oil in the reservoir is highly dispersed,and the active system is used to reduce the oil-water interfacial tension of the remaining oil,start the remaining oil,and improve the washing efficiency.Therefore,this paper proposes the use of weak gel-surfactant compound modulation flooding technology to improve the development of reservoirs.The weak gel system injected into the formation can increase the fluidity of the water phase,control the viscous fingering phenomenon,and expand the sweep volume.The surfactant has the effect of reducing the interfacial tension and emulsifying the crude oil,and can further increase the oil displacement.Efficiency,thereby achieving a significant increase in water drive reservoir recovery.In this paper,the weak gel system and its properties,the interaction between the weak gel and the surfactant,the adjusting and displacing parameters of the complex modulation and the flooding mechanism were studied through laboratory experiments.The following research results were obtained:(1)A weak gel system has been developed,which is suitable for high-permeability and high-permeability reservoirs in the Gaoqianbei area.The formulation of the weak gel system was:1600-1800mg/L HPAM + 160-200mg/L cross-linking agent FA+ 150mg/L oxygen scavenger.The weak gel system has good temperature resistance,salt resistance and long-term stability,and has good adaptability in an oil reservoir environment.The core flow experiment shows that the weak gel can effectively adjust the water-absorbing profile and the cross-section improvement effect is good.And the larger the permeability difference,the better the water-absorbing profile is improved.(2)In compound flooding,the concentration of surfactant JDYQ-2 is 2000mg/L,the interfacial tension is 1.35×10-3mN/m,and it reaches the order of 10-3mN/m,and the surfactant has good properties of temperature resistance,salt resistance and anti-absorption.Surfactant JDYQ-2 can work in the order of 10-3mN/m,regardless of the weak gel system before or after gelation.The compatibility of the surfactant JDYQ-2 with the weak gel is good,but before the gel formation,the weak gel system is in direct contact with the surfactant solution,and the surfactant will adversely affect the gelation performance of the weak gel.The interaction of a weak gel with a surfactant will have an adverse effect on the microstructure of the weak gel,the network structure is destroyed,the gap between the molecules is reduced,and the arrangement is irregular.(3)The parallel core flooding experiments show that compared with the surfactant flooding and the weak gel flooding drive,the weak gel-surfactant complex flooding effect is better,and its enhanced oil recovery rate is 17.23%.The optimal injection method of weak gel-surfactant compound flooding is to inject the surfactant after injecting the weak gel first,and the injection slug size is 0.2PV weak gel + 0.3PVJDYQ-2 solution.The adjustment drive was performed in three rounds,which is appropriate.(4)Visual flooding experiments show that the weak-gel-surfactant hybrid flooding mechanism is mainly driven by weaker gels and surfactants acting synergistically.The injected weak gels preferentially enter the large pore area.The reservoir's heterogeneity is adjusted,and the subsequent injection of a weak gel into the small pore area of the lower permeability can significantly activate the remaining oil.After injecting the surfactant solution,the surfactant solution enters the low-permeability zone under the action of the pre-weak gel to achieve liquid flow turning,and the surfactant also has the effect of reducing the oil-water interfacial tension and emulsifying the crude oil,thereby expanding the swept volume and displacement efficiency are affected.In this paper,a weak gel-surfactant composite flooding drive technology has been studied for high-porosity and high-permeability reservoirs in the Gaoqianbei area.The research results obtained provide references for field application of water-controlling and oil-enhancing technologies in the field of Gaoqianbei reservoir.At the same time,it can also provide reference for the application of enhanced oil recovery technologies in the other oilfields of the same type.