| The development of area 1 and area 9 of tahe oilfield has entered the stage of high water cut,with strong reservoir heterogeneity and complex water outlet mechanism of horizontal wells,so the common water plugging method is difficult to meet the current production demand of oilfield.In this paper,the technology of water shutoff combined with throughput agent in horizontal wells is studied to improve the recovery efficiency,which provides technical support for the subsequent crude oil exploitation in this reservoir.The composite technology is composed of gel water plugging technology and huff and puff technology,its core is to develop a new monomer gel plugging agent to effectively seal the high permeability layer of the oil layer,and then effectively sweep and wash the low permeability layer through the surfactant,CO2 and N2 foam reagents,so as to achieve the purpose of improving oil well recovery and reducing water cut of the oil well.Combined with the two-dimensional visualization experiment,the mechanism of the composite technology was further verified,and finally the optimal combination of water shutoff and huff and puff agent was proposed to improve the recovery rate.The main work and results of this paper are as follows:(1)Under the strong heterogeneity with high and low permeability of 400mD/50mD in area 1 and area 9 of tahe oilfield,"bottom water coning" is the main water breakthrough mode,and the watered-out mode is "breakthrough of high permeability?extension of along the well?second high breakthrough?whole well flooding".After oil well flooding,the crude oil in low permeability zone is mainly in the form of "eaves oil".(2)A monomer gel plugging agent was developed.The final formula of gel plugging agent was as follows:the concentration of main agent AM was 7%-9%,the concentration of initiator APS was 0.6%-0.8%,the concentration of cross-linking agent NN+FQ was 0.01%-0.015%,the concentration of auxiliary agent DF+CY was 6%-8%,the gel formation time was 4h-5h,and the gel formation strength reached H level.(3)The experimental results of gel performance evaluation show that:When the salinity is 200000mg/L,the breaking multiple is 13 times.At the temperature of 90,the gel strength can reach H level;pH value of 6?8 is more conducive to the synthesis of high-performance plugging agent;the gel injection pressure was low in fracture core plugging experiment,and the effective plugging rate was up to 99%,indicating that the monomer gel plugging system have good injectivity and plugging ability.(4)The three-dimensional physical simulation experimental results show that,under the 8 MPa back pressure,the compound technology priorities of water plugging and huff and puff to improve oil recovery are as follows:the water plugging+nitrogen foam(improve recovery efficiency 22.15%)>water plugging+surfactant(improve recovery efficiency 21.41%)>water plugging+CO2(improve recovery rate 15.34%),it is recommended that water shutoff+N2 foam composite enhanced recovery technology be used as a composite technical scheme for subsequent exploitation in zone 1 and 9 of tahe oilfield.(5)Two two-dimensional visualized flat plate models of metal model and acrylic glass plate were carried out,the experimental results showed that:the gel plugging agent could effectively block the high-permeability layer,and could achieve the purpose of water control and oil increase by effectively inhibiting the channeling of bottom water and improving the sweep efficiency of bottom water in the low-permeability layer;after the channeling channel on the bottom water is blocked,the surfactant or N2 foam injected will bypass the clogging and sealing zone in the high permeability zone near the well and enter the low permeability zone with high oil saturation to start dead oil and dead pores,thus bringing out "eaves oil";while expanding the sweep volume and the oil reservoir utilization degree,the surfactant's effect of reducing the oil-water interfacial tension and N2 foam's effect of controlling the flow profile should be given full play to improve the oil recovery.The research results of this paper can provide technical support for the horizontal well exploitation of clastic reservoir in zone 1 and 9 of tahe oilfield,and it is of great significance to improve the oil recovery rate and the plane heterogeneity of this oilfield. |
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