Study On Adjustment Method For Water Injection Wells In Low Production Area Of Y30 Area Of Ultra-low Permeability Reservoir

Y30 area of ultra-low permeability reservoir in Ordos Basin is developed by water flooding.Due to poor formation physical properties and strong heterogeneity,it is difficult to inject water into some well groups and establish effective displacement.Repeated fracturing of water injection well is an adjustment method to improve water injection capacity and development effect.Some tests have been carried out in the some reservoirs and certain results achieved.However,it is still unclear to adopt continuous water flooding or converted production after repeated fracturing of water injection well.The applicability of the two adjustment methods of water injection well is also lack of theoretical study,which restricts the further popularization and application.In this paper,focused on the adjustment method of water injection wells in ultra-low permeability reservoirs,the relevant reservoir engineering method and numerical simulation have been used to carry out researches.Firstly,in this paper,aiming at the water flooding effect of Y30 ultra-low permeability reservoir,the dynamic mode and analyzes the main control factors,summarizes the main contradictions of low production and low efficiency well groups have been divided,the effect of continuous water injection test and transfer production after repeated fracturing of water injection wells and depletion development test of converted production wells have been evaluated,and the feasibility of the two adjustment methods of water injection wells have been defined;Secondly,the numerical simulation is carried out for the two adjustment methods of water injection wells,and the variation law of the seepage field and adaptability of the two adjustment methods have been analyzed.The results show that the continuous water flooding method after repeated fracturing of water injection wells can effectively expand the swept area and produce the remaining oil between injection and production wells.This method is suitable for well groups with good sand body connectivity,few fractures between injection and production wells and good early water injection effect;For the mode of conversion to production depletion development after repeated fracturing of water injection wells,it can improve the near well seepage capacity of conversion wells and effectively produce vertical residual oil.This mode is suitable for well groups with short waterflood front and vertical untapped potential layers;Then,combined with the main control factors and adaptability,using the fuzzy comprehensive evaluation theory,the optimization method of water injection well adjustment mode is established,and the python program module is compiled to determine the well location and layers of water injection wells which need to be adjusted in Y30 area;Finally,the numerical simulation and historical fitting research of Y30 area of the actual reservoir are carried out,and the fracture length and injectionand-production parameters of the adjustment scheme of water injection wells are optimized.It is predicted that the recovery degree of water injection wells will be increased by 1.98% in 10 years.The results of this paper provide a theoretical basis for the adjustment of water injection wells in ultra-low permeability reservoirs.A method reference for the optimization of layers of adjusted wells are provided,which has a guiding significance for establishing water injection development adjustment scheme in ultra-low permeability reservoirs.