--> Geology and Geophysics Integrated Quantitative Characterizations of Complex Carbonate Fractured-Vuggy Reservoirs of Central Uplift in Tarim Basin

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Geology and Geophysics Integrated Quantitative Characterizations of Complex Carbonate Fractured-Vuggy Reservoirs of Central Uplift in Tarim Basin

Abstract

The Ordovician carbonate fractured-vuggy reservoirs are deeply buried (exceed 5500 m) in Central Uplift of the Tarim Basin, with extremely irregularity in scale, geometry and spatial distributions, have strong heterogeneity in transport properties, which increase the uncertainty of deep hydrocarbon exploration.

Facing the problems of fine scaled, deeply buried, strong heterogenous deep fractured-vuggy reservoirs, this paper used advanced data-driven technology to integrate geology, geophysics and production data, established a geology-geophysics integrated workflow to quantitatively characterize the reservoirs in the micro-macro-mega scale. (1) Microscopic scale (0.01~0.1 m): Focusing on the effective pore structure in deeply buried carbonate strata and considering the geological processes including sedimentary, diagenetic, and tectonic movements, detailed observations on core samples and thin sections were carried out, and 7 lithofacies and related 19 rock types were divided; (2) Macroscopic scale (0.1~10 m): According to the vertical and horizontal resolution and recognition ability of wireline logging data, a classifier from logging data that was conditioned to core data was created, and 9 electro facies are divided; (3) The megascale (>10 m): Constrained by the rock types and electro facies, a data mining approach was carried on fused spectral-decomposition multi seismic attributes, and 6 types of seismic facies of the fractured-vuggy reservoirs were recognized. Combined with three-dimensional interpretation of strike-slip faults, a three-dimensional framework was established. (4) Fluid property analysis: According to the results of well test, logging interpretations of oil and gas aquifers, combined with well production data, the fluid property in traps was recognized, and the multi-stage hydrocarbon accumulation processes were reversed.

This workflow integrated the geological understanding, geophysical responses and data mining techniques and achieved a seamless connection between the microscopic-macro-macroscopic scales. The workflow was applied to quantitative characterize the deeply buried fractured-vuggy reservoirs and deep carbonate petroleum system analysis, showing a reliable guidance to local oil and gas exploration. The workflow can also be applied to the studies on similar paleo-karst reservoirs and clastic reservoirs.