Evaluation Method And Application Of Three-dimensional Fracability For Low Permeability Tight Sandstone Reservoirs

With the expansion of energy demand and the increasing shortage of conventional oil and gas resources,unconventional oil and gas resources have gradually become a hot spot of exploration and development.As a kind of common unconventional oil and gas reservoirs with great development potential,the effective development of low permeability tight sandstone reservoirs depends on hydraulic fracturing.Well layout,fracturing horizon optimization and fracture initiation location optimization are the key to efficient fracturing and development of unconventional reservoirs.Three-dimensional fracability evaluation of reservoirs is the basis for identification and screening of engineering ’ sweet spots ’ in fracturing dominant areas.However,the research on fracability evaluation indexes and three-dimensional fracability evaluation methods of low permeability tight sandstone reservoirs is not deep.In this paper,experimental,theoretical and numerical simulation studies are comprehensively carried out for low permeability tight sandstone reservoirs.Based on the physical and mechanical properties of typical tight sandstone reservoirs,the mechanism and influencing factors of fracture initiation and propagation in low permeability tight sandstone reservoirs,a three-dimensional fracability evaluation method for low permeability tight sandstone reservoirs with cross-scale and multi-factor is established.Based on the verification of actual engineering and production data,the application research of this method in a low-permeability tight sandstone reservoir is carried out.The completed research work mainly includes :(1)Through a series of experimental studies on rock mechanics and microstructure,the mineral composition,deformation and failure mechanical properties(brittleness,compressive strength,tensile strength,fracture toughness)and geological mechanical parameters of typical low permeability tight sandstone reservoirs are revealed,which lays a foundation for the establishment of fracability evaluation indexes suitable for low permeability tight sandstone reservoirs.(2)Combined with the experimental research results,considering the whole process of reservoir hydraulic fracturing,the key evaluation factors are optimized from different scales such as the endogenous endowment of rock matrix,the initiation and propagation of hydraulic fractures,the interaction of fractures and the formation of complex fracture network,and a cross-scale multi-factor coupling fracability evaluation index suitable for low permeability tight sandstone reservoirs is proposed.(3)Based on the three-dimensional geological structure model,through the combination of logging and seismic data,the three-dimensional spatial distribution of rock mechanics parameters and in-situ stress of the reservoir is predicted.The three-dimensional fracability evaluation method of low permeability tight sandstone reservoir based on the combination of logging and seismic data is established.The effectiveness of the method is verified by the engineering data and production data of a typical low permeability tight sandstone gas fields.(4)The proposed three-dimensional fracability evaluation method is applied to a low permeability tight sandstone reservoir.Fracability evaluation of single wells located in the reservoir and three-dimensonal reservoir model is carried out.The distribution of fracturing advantage area of reservoir and fracturing advantage layer position of single well are given,which provides reference for well location arrangement and fracturing layer optimization.