Evaluation On Shale Reservoir And Cap Rock Based On Well Logging Data

With more and more research on shale these years in oil industry,it is found that shale can be seen as source,reservoir and cap at the same time the same location.It has promising petroleum reserves and production.This dissertation studies shale reservoir of the second member of Funing formation in Subei basin as well as the shale cap rock of Huagang Formation and Pinghu Formation in the central tectonic inversion zone in Xihu Depression.Both of the target areas are studied with geological analysis and reservoir or cap rock evaluation with well logging data.In the shale reservoir area,based on well logging data standardization and core depth shift,correlation of different minerals(i.e.clay,feldspar,quartz and carbonates)and sensitive logging respectively according to “mineral-electrical property” relation.TOC values are measured and lithofacies are classified with the method of ?logR;Moreover,well model is established with constraints such as physical properties and geomechanics features for well logging interpretation for each single well.In this study,techniques and methods used are as follows: 1)distribution of mineral components,TOC content,fractures development,physical features and mudstone thickness 2)multifactor superposition and 3)geologic analogy.The result shows that relative thicker favorable lithofacies strata with higher brittleness index and better physical features are promising reservoir.In the second study area with the shale cap rock,well logging interpretation model of inorganic mineral value is made based on shale content measured by VSH equation.Identified from well logging,lithofacies are classified using the method of “quantitative calculation and qualitative identification”.Well logging parameters(e.g.shale cap rock breakthrough pressure,physical properties and geomechanics features)model is established.Each single well interpretation is accordingly conducted.As the target area has a too large coverage with very few wells on this offshore oilfield.It is solved by combining both quantitative and qualitative methods.Quantitative evaluation highlights analyzing and summarizing microcosmic sealing ability of the cap rock which can be used as a tool to recognize impacting factors of physical property sealing,overpressure sealing and hydrocarbon concentration sealing with understandings of breakthrough pressure,porosity,permeability and TOC content from well logging interpretation.Qualitative evaluation,which plays a critical role in cap rock well logging evaluation,emphasizes analyzing macroscopic geological conditions such as cap rock thickness,diagenetic stages and lithofacies distribution.