| The Chang 6 reservoir in Zhengzhuang district is an ultra-low permeability reservoir with problems of high injection pressure in production wells during the process of water flooding,which seriously affect the production and development effect of oil field.Aiming at Chang 6 reservoir in Zhengzhuang district,this paper systematically analyzes the factors that lead to the difficulty of water injection,and develops the targeted application technology based on the mechanism of influencing factors to provide technical support for the effective water flooding development of the Chang 6 ultra-low permeability reservoir in Zhengzhuang district.Around the problem of high injection pressure at the field,based on the analysis of reservoir geological characteristics and pore throat structure,through the core damage assessment experiment,the influence of clay swelling and migration on reservoir damage was ascertained.Besides,the influences of scaling blockage on water injection pressure were determined through analysis of water injection process and water quality.By the means of comprehensive analysis,scaling,clay swelling and scaling of oil and water pipelines were the main factors that affect the effective water injection of Chang 6 ultra-low permeability reservoir in Zhengzhuang district.Thus,a series of application techniques for preventing and controlling formation scaling and clay swelling and migration had been developed to ensure the effective implementation of water injection development technology in the Chang 6 ultra-low permeability reservoir in Zhengzhuang district.According to the manufacturing rules of the magnetizer,the magnetic material is optimized,and the parameters of the magnetizer are optimized before the magnetic circuit calculation,so as to make the pipe flow applying magnetizing scale inhibitor which conforms to the water quality of Zhengzhuang district(magnetic course:200mm;magnetic field intensity:300?800mT).After two months' field test of high magnetic intensity processor treatment,the results showed a good anti-scaling effect that the scaling of pipeline had been reduced,and the scaling inhibition rate had finally reached more than 90%.By analyzing the scaling mechanism and tendency of the reservoir in this district,it was known that injected water was easy to generate dispersed CaC03 precipitation and corrosive scaling such as Fe(OH)3 precipitates in the formation.Through the evaluation of the anti-scaling effect of 4 kinds of anti-scaling agents,the anti-scaling agent with best effect was selected and applied in 10 wells of Chang 6 reservoir in Zhengzhuang district.The significant anti-scaling effect showed that the workover cycle was extended by 3-4 times with a maximum extension of 6 times and the cost of workover caused by scaling and clogging was significantly reduced.Based on the analysis of clay mineral composition and potential swelling and migration mechanism,it was found that injectability,washing-out resistance and low cost are the main factors hindering the application of conventional clay stabilizers.Therefore,three kinds of polyquaternium clay stabilizers with high washing-out resistance and scaling resistance under low concentration were developed by using the principle of multi-point adsorption and bridging adsorption to solve the long-term effective adsorption of clay stabilizers,and polydimethylamine-epichlorohydrin(CS-1)with best performance was selected.Aiming at effective anti-scaling and economic applicability,12 kinds of small molecular hydrochloride clay stabilizers with low cost,high anti-swelling rate and excellent injectivity were developed,and tetraethylenepentamine hydrochloride was preferred.Two kinds of clay stabilizers,tetraethylenepentamine hydrochloride and polydimethylamine-epichlorohydrin(CS-1),were compounded to optimize the compounding system with a mass ratio of 4:6.The system had excellent anti-scaling effect,strong washing-out resistance and low application cost. |
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