DEVELOPMENT OF AN EFFECTIVE RESERVOIR MODEL FOR EAGLE FORD SHALE FROM WELLBORE ENVIRONMENT, SOUTH TEXAS

摘要

The Eagle Ford Shale is a major hydrocarbon producing formation deposited on a broad shelf extending from the Mexican border in South Texas to the East Texas Basin. The majority of exploration and production activity within the Eagle Ford shale is focused in South Texas, where the Eagle Ford reaches maximum thickness and produces oil, gas, and condensates. Eagle Ford shale is subdivided into two units based on mineralogy and organic content. The Upper Eagle Ford consists of interbedded calcareous mudstones that contain a lesser quantity of organic matter characterized by low to medium gamma ray response. The Upper Eagle Ford thickens towards the Maverick basin and gradually thins out in the East to Northeast direction towards the Edwards and Sligo shelf margins. In contrast, the organic rich calcareous mudstone of the Lower Eagle Ford is characterized by high gamma ray and extends continuously across the area.Eagle Ford lithofacies and source rock characteristics vary across the basin and influence the petrophysical and geomechanical properties of the reservoir. These reservoir properties are mostly established from analysis of reservoir core plugs that are extracted from either whole cores or from side wall cores. This process consumes considerable time causing long delays in well completions and increased rig time. This paper presents an integrated approach for the reservoir evaluation of the Eagle Ford shale by using a combination of downhole formation evaluation data including, geochemical, nuclear magnetic resonance, and acoustic measurements. Petrophysical and lithofacies models were developed by integration of these measurements for the analysis of lithology, mineralogy, total organic carbon (TOC), and geomechanical properties of formation. Reservoir properties obtained through the presented approach can be used to design hydraulic fracture strategies for optimal well productivity. This approach is applied in multiple wells to develop a good understanding of Eagle Ford heterogeneity in the basin. Derived results highlight the basinal variations in Eagle Ford shale and differences in petrophysical properties of the reservoir.This methodology, supported through reconciliation with extensive core data from the project, enables development of a validated reservoir model and design of an effective log data-acquisition program for future development wells in this basin.