Quantitative Characterization Of Strong Heterogeneity In Tight Sandstone Reservoirs In Shan 234-Shan 235 Wellblock

The heterogeneity in tight sandstone gas reservoir is one of the difficulties in exploration and development of gas fields and the study of its controlling factors has been a hotpot in gas field research.Since Shan 234-Shan 235 well area has a higher reserves and number of wells,Shan 234-Shan 235 well has been taken as the study area in this thesis.The sedimentary environment in study area is mainly the braided river or the meandering river system.Tight sandstone reservoir in study area mostly is characterized by transverse connection and sand body superimposition of longitudinal multi-stage channels which are influenced by frequently channel diversion and vertical erosion.The fluid occurrence and gas saturation in the pore throat space of the tight sandstone are also controlled by the heterogeneity of the pore throat of the reservoir.The heterogeneity is showed by the type of storage space,the number of effective pore throat number and volume of unit volume.Based on the sedimentary tectonic setting analysis,high fine stratigraphic contrast division and logging curve quantitative characterization,the quantitative discriminant model of sedimentary microfacies in the study area is established.The multidimensional heterogeneity of reservoir was quantitatively depicted based on the standard of configuration interface division.Typical characteristic parameters have been also extracted from full scale pore throat test experiment to quantify the heterogeneity of the microscale of the reservoir and further analysis of its influence on the presence of fluid and the gas saturation of the fluid.Taking He-8 member and Shan-1member as examples,the research achieves new ideas as follows:(1)Sandstone reservoir formed in different sedimentary environments can be distinguished in logging curves.The morphological,numerical and wave characteristics of logging curves show obvious changes.According to this,the different sedimentary microfacies of the coring well are calibrated by combining the relative center of gravity value G and the amplitude mean square S.Combining the standard of configuration interface division,established the criteria for determining sedimentary microfacies of coring wells,and quantitatively characterized the multidimensional heterogeneity of reservoir.In the end,the configuration combinations of the study area are divided into 18 types.(2)The relationship between porosity and permeability are not only effected by sedimentary but also by diagenesis.The dissolution pore has an important contribution in improving the reservoir performance especially the seepage capacity.(3)The pore structure development is constrained by diagenetic products and the secondary pores in different samples are varied in a wide range.The R2 between facial porosity and permeability is 0.9329 which means the corrosion pores have an important contribution in improving the reservoir performance,especially reservoir seepage ability.(4)The storage ability of reservoir is affected by effective throat number per unit volume and effective pore throat volume per unit volume and the seepage capacity of reservoir is affected by effective throat volume per unit volume and effective throat number per unit volume.(5)The radius of pore and throat have an impact on gas filling.The lower limit of porosity of gas filling is 5.5% which is determined by pore throat radius-phase infiltration method combining with the core experience statistics method.The lower limit of development saturation can also been gained and it is 44.2%.(6)The characteristics of effective sand distribution in different layer are distinguished by combining the better sedimentary architecture identify which is controlled by lower limit of gas filling and development and logging characteristics of gas layer.