Source Rock Characterization of the Hanifa and Tuwaiq Mountain Formations in the Arabian Basin, Based on Rock-Eval Pyrolysis and the Modified Delta Log R Method

Abstract

AbstractThe Tuwaiq Mountain and Hanifa formations contain both significant hydrocarbon reservoirs and world-class hydrocarbon source rocks. This paper focuses on the characterization of the source rocks within the formations by integrating core-derived geochemical data and well-log responses. The hydrocarbon source rock potential of these stratigraphic intervals in the Arabian intrashelf basin was evaluated using Rock-Eval pyrolysis and the Delta Log R method. Organic geochemical analyses of core samples for S2, total organic carbon (TOC), and hydrogen and oxygen indices were used to determine the quality of organic matter. Most of the source rocks are thermally mature and contain oil-prone Type-II kerogen. The Delta Log R method was used to obtain calculated TOC values to increase the coverage across the zone of interest (uncored intervals) and laterally at the uncored wells. Level of maturity (LOM) is one of the key required inputs for the Delta Log R method. The LOM was derived from predicted vitrinite reflectance values using heat flow distribution within the entire basin. A comparison of TOC values derived from the Delta Log R method with actual laboratory-measured TOC values from core samples shows a very good agreement. This allows confident application of this technique in calculation of TOC values in wells for which no core samples are available. The TOC and effective thickness fairway maps of the Tuwaiq Mountain and Hanifa source rocks generated from this method offer great insights for defining the source rock characteristics.