Research On The Mechanism And Application Of Water Injection Huff And Puff For Fracturing Horizontal Fractures In YZM Ultra-low Permeability Reservoirs

The water huff-n-puff is a development method of oil recovery by capillary force.Due to the complex pore structure and small pore radius of the ultra-low permeability reservoir,the water huff-n-puff has better adaptability.At present,water huff-n-puff is mainly used in fault-blocking reservoirs or volumetric fracturing reservoirs.In the development process,there are many problems such as adjacent wells and multiple rounds of poor effect,while YZM blocks are horizontal fractures and the flow characteristics are different.Therefore,it is of great significance to study the microscopic flow of fluid in water huff-n-puff,and to reveal the influence of different production parameters,so as to improve the development effect of ultra-low permeability reservoirs.Based on the capillary model and the particle model,this paper clarifies the flow characteristics of oil and water in different stages of water huff-n-puff,calculates the force of the fluid in the micro-pore,and evaluates the fluid migration distance under different injection speeds by considering the horizontal fracture of the fracture.And derived the formula for calculating the volume of imbibition.Based on the study of geological characteristics and microscopic flow characteristics,numerical simulation is carried out to study the influence of different development parameters and development systems on production results,and provide theoretical guidance for the development of on-site development plans.The research result shows that in the reservoir where the horizontal fracture is generated by fracturing,the fluid mainly flows in the radial direction and oblique direction,and the vertical flow distance is limited.Although the number of driven capillary tubes under the low-speed injection condition is limited,it can supplement the reservoir energy more effectively;The static imbibition experiment shows that high water saturation and poor pore connectivity will lead to a significant reduction in the volume of imbibition recovery;Numerical simulation result shows that the injection volume and injection speed have the greatest impact on oil production,and the well shut-in time has the greatest influence on the water production,and the production pressure difference has the greatest influence on the reservoir pressure distribution.In this model,the injection volume of the injection is 300m3,the injection speed is 10m3/d,the well shut-in time is 30d,the well production bottom pressure is 0.5MPa,and the development method of multi-cycle well group water huff-n-puff is adopted,which can achieve the best development effect.