Evaluation Of Micro-damage And Fluidity Of Slickwater On Shale Reservoir

Shale oil and gas reservoir has become the main target of development and exploitation of major oil fields.Shale oil and gas reservoirs are characterized by fine lithology,poor physical property,large seepage resistance,strong heterogeneity,strong sensitivity,and high difficulty in exploitation.The fracturing fluid reservoir reconstruction technology can effectively improve the exploitation effect of shale oil and gas reservoirs by constructing artificial fractures with high conductivity performance,but it will also cause damage to the reservoirs to a certain extent.In this paper,five kinds of slickwater are configured for shale oil reservoir core.Using NMR,CT scanning,scanning electron microscopy and other experimental means,the differences of core porosity and permeability characteristics,pore throat structure,surface morphology and element composition before and after the action of five kinds of slickwater are analyzed at the microscopic level,and then the microscopic damage degree of different slickwater to reservoir is studied.On this basis,the adaptability of slickwater to shale oil reservoir is evaluated.In addition,based on the influence of slick water on the pore structure of shale core,the pore network model before and after slick water damage is established by using the slice images obtained from CT scanning and core pore data.The open source package OpenPNM written in python is used for seepage calculation,and the changes of oil-water relative permeability curve of shale core before and after slick water damage are simulated and compared at the macro level.To determine the effect of micro-damage of slickwater on shale oil extraction.By comparing the experimental results of NMR,CT scan and SEM at the microscopic level,the shale oil reservoir adaptively selects slickwater 5,and slickwater 1,2 and 3 can be used as alternatives.The permeability damage degree and pore binding degree of slickwater 5are relatively low,and the damage to shale oil reservoir is low,which is conducive to fracturing fluid flowback.Slick water 5 causes a low porosity reduction,a large increase in total porosity,an increase in the number of fractures,and a better permeability,which is conducive to oil and water migration and fracturing fluid injection and flowback.The chemical element adsorption caused by slippery water 5 is light,the pore filling is not serious,the element migration is prominent,the intergranular pores increase,and the damage to shale oil reservoir is weak.At the macro level,through comparative analysis of five phase permeability curves and data,slick water 5 has the best adaptability to shale oil reservoir.The co-permeability area of core phase permeability curve after slick water 5 is nearly 4 times that of dry sample,which is much higher than other cores,indicating that slick it has the best influence on the oil displacement effect of core.Only the oil-phase permeability curve of the cores treated with slick water 4 is lower than that of the dry samples,indicating that all the cores except slick water 4 have better effects on the oil-phase fluidity of the cores.The residual oil in the core phase permeability curve after the action of slickwater 5 is twice that of dry sample,which is much higher than other slickwater,indicating that it has the best effect on the core water phase mobility.The results show that the micro damage of slippery water to core can also affect the macro level.The research of this paper provides theoretical support and experience for the development of oilfield slick water system.