RESERVOIR CHARACTERIZATION OF UNCONVENTIONAL DADAŞ FORMATION IN SOUTHEASTERN TÜRKİYE: FACIES DISTRIBUTION AND FRACTURE MODELLING IMPLICATIONS

Date

2024-8-27

Author

ÖZKUL, CANALP

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The Early Silurian (Llandovery) to Early Devonian (Lochkovian) Dadaş Formation in the Diyarbakır Basin represents the most important unconventional play in Southeast Türkiye. The Dadaş-I Member, the lowermost part of the Dadaş Formation, constitutes self-contained source and reservoir rocks potentially the most promising sources of hydrocarbon reserves. The prolific interval of the Llandovery-age Dadaş-I Member is delineated and divided into four distinct lithofacies (L1, L2, L3, and L4) by the application of a new multidisciplinary and multiscale methodology integrating the assessment of facies heterogeneity, petrophysical parameters, geochemical and geomechanical properties and natural fracture characterization. Petrophysical and geochemical properties of L3 lithofacies, characterized by organic matter-rich shales, show remarkable unconventional hydrocarbon potential, while L1, which consists of shale dominated siltstone and sandstones interbeds has good petroleum generative potential. L4, comprised of carbonate rich shales with siltstones appears to be a potentially good target for hydrocarbon generation, especially for hydraulic fracturing operations due to more favorable geomechanical properties. However, the L2, shale with siltstone interlaminations, shows almost no hydrocarbon potential. Two prominent fracture sets were systematically developed in the Dadaş-I Member. In L4 facies, natural fractures display unique orientations, mostly striking parallel to an E-W-directed major fault group. However, the rest of the natural fractures in L1, L2 and L3 facies are striking NE-SW, parallel to the secondary group of faults. The geomechanical properties of each lithofacies show that L4 facies has relatively higher elastic parameters and higher brittleness with higher strength properties. Throughout the complex deformation history in the region, L4 formation has accumulated more tectonic stresses and naturally fractured prior to the other facies (L1, L2, and L3). Fracture intensity variations in the Dadaş-I Member appear to control reservoir pressures and the migration of the generated hydrocarbon. The highest fracture intensities by mostly critically stressed fractures were associated with high water rate in the flow-back operations indicating an inverse relation between fracture intensity and production results. The presence of higher natural fracture intensity supporting the fluid-flow dynamics in low-matrix-permeability shale reservoirs may be an obstacle to the desired high production rates in the Dadaş-I reservoirs.

Subject Keywords

Unconventional reservoir, Dadaş Formation, Natural Fracture Characterization, Facies Heterogeneity.

URI

https://hdl.handle.net/11511/111308

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Graduate School of Natural and Applied Sciences, Thesis