--> Estimating Unconventional Shale-Oil Resources In Selected Lacustrine Self-Sourced Reservoirs Of Southeast Asia

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Estimating Unconventional Shale-Oil Resources In Selected Lacustrine Self-Sourced Reservoirs Of Southeast Asia

Abstract

Lacustrine self-sourced shale reservoirs are predicted to be present in many basins in southeast Asia. The U.S. Geological Survey employed lacustrine shale reservoirs of the Eocene Green River Formation, Uinta Basin, Utah as a geologic and production analog for potential lacustrine self-sourced shales in selected basins in southeast Asia for the purpose of estimating undiscovered shale oil resources. Data from the Eocene Green River Formation included geochemical (total organic carbon, kerogen type, thermal maturity), thickness, degree of tectonic deformation, probability distributions of estimated ultimate recovery (EUR) of oil derived from decline curve analysis, drainage areas of non-interfering wells, and success ratio of drilled and tested wells. With this approach to assessment, one of the significant input variables is the area of potential shale-oil reservoir. Given a distribution of well-drainage areas and EURs based on the Green River Formation analog, the assessment unit area is one of the major inputs in the calculation of volume of potential shale oil resource. Lacustrine shales of the Phitsanulok Basin, Thailand, exhibit favorable geologic characteristics for viable shale-oil resources, but the potential area (748 km2) limits the number of potential well sites for non-interfering wells and thus the calculation of mean resource potential (mean of 53 million barrels of oil, or MMBO). In contrast, the area of potential self-sourced lacustrine shale in the Bohai Bay Basin, China (20,647 km2; mean of 2,036 MMBO) provides for more potential well sites given similar distributions for well-drainage area and EUR. The potential areas of lacustrine shales of the Central Sumatra Basin (6,072 km2; mean of 459 MMBO) and South Sumatra Basin (9,716 km2; mean of 689 MMBO) further demonstrate the importance of potential assessment unit area on resource volumes resulting from the USGS methodology.