Study On Fine Logging Evaluation Of Tight Reservoirs In Huagu 101 District

Affected by the long-term heavy activities of the fault zone,the Huagu-101 District has formed the framework with criss-cross faults and the complex tectonic conditions.As a result,fluid property can't be judged accurately during reservoir evaluation and reservoir classification is difficult.Some reservoirs with basically the same porosity have high productivity by self-spraying,and some can achieve industrial oil flow after hydraulic fracturing and some are dry layers.The productivity is controlled by the development level of fractures.In view of the above problems,this paper starts from the three aspects of reservoir validity,heterogeneity,and fractureability,and uses reservoir classification as the ultimate goal to carry out the fine logging evaluation of tight reservoirs in Huagu 101 District.In terms of reservoir validity evaluation,the reservoir parameters calculation models are established on the basis of core depth correction and well logging curves normalization.Simultaneously in consideration of the fractures,complicated pore structure and large variation range of m and n,using NMR datas to calculate variable m and n and furtherly to calculate the water saturation by Archie formula.Summarizing the log responses of the conventional curves and the electrical imaging to the fractures,picking out the acoustic curve and resistivity curve as the sensitive curves,and the composite index of fracture development is constructed to achieve semi-quantitative evaluation of fractures by using wavelet multi-scale decomposition and prediction error analysis techniques.In terms of heterogeneity evaluation,because electrical imaging logging can obtain the information of the two-dimensional data around the borehole wall,so the electrical imaging porosity spectrum analysis technique and the Lorentz curve method can be used to characterize the one-dimensional and two-dimensional heterogeneity.In order to eliminate the influence of lithology,using the difference between the fractal dimension of the acoustic wave and the gamma ray curve by R/S analysis to characterize the reservoir heterogeneity,which is corresponding to the result of electric imaging.In terms of fracability evaluation,combined with the rock mechanics experiments and previous research results,the suitable rock mechanics parameters calculation models are given.Consdering that the rock mineral composition,rock structure,the confining pressure and temperature have effects on the dynamic and static conversion rule,so we use the empirical formula by Bian Huiyuan.The largest principal stress orientation in the Kuishan section of the Huagu 101 District is identified by electrical imaging and array sonic log is North West-South East.Discussing the effects of five factors including brittleness,fracture toughness,horizontal stress difference,uniaxial compressive strength,and fracture on the fracability and then a fracability evaluation model is comprehensively established.In reservoir classification evaluation,the reservoirs'oil quality is light and good,and the lower limit of oil level is oil trace.The lower limit of the porosity is 5%and the permeability is0.07×10^-3um².Porosity,oil saturation,fracture development degree,heterogeneity and fracability index are selected as the sensitive factors to identify the reservoir types.Three discriminant expressions are establish by using Fisher discriminant to classify reservoirs into three categories.