Abstract
The Late Jurassic Meem Shale Member is widely exposed within the Sabatayn Basin, including in the Al-Jawf sub-basin. In this study, a total of 49 shale samples of the Meem Shale Member from two exploratory wells; Dahmar Ali - 01 (28 samples in the depth range 1441-2351 m) and Kamaran-01 (21 samples in the depth range 2275-3011 m) in the south-eastern portion of the Al-Jawf sub-basin were studied as possible source rocks. Evaluation of source rock geochemistry including total organic matter (TOC) and Rock-Eval pyrolysis analyses was performed. The results of this study provided information regarding significant exploration of oil and gas resources from the Meem Shale Member in the Al-Jawf sub-basin.
Both the incident light microscopic results and the Rock-Eval geochemical study have indicated that the analyzed shale samples contain predominantly Type III kerogen with minor contributions of Type I/II and IV, so as to they can generate both oil and gas. The values of hydrogen index (HI) are decreased with increasing thermal maturity and varied between 34 and 803 mg HC/g TOC. Based on the measured VRo% range of 0.63 and 2.00, the Meem shales are currently within the oil- and gas-generation window, thus, they are considered as shale-oil and-gas resource possible plays.
The geochemical results were integrated with geological data of the Al-Jawf sub-basin and incorporated into a basin model to simulate petroleum generation and/or retention in the Meem Shale Member. The constructed basin models illustrated that the Meem Shale Member displayed a peak oil generation window during the Late Jurassic to Early Miocene, where large amounts of oil were generated, with a conversion ratio of 10-75 TR%. Further, the high heating rates from local volcanic rocks from the Early Miocene till date have caused gas generation from both of the original Type III kerogen and from secondary cracking of retained oil in the Meem Shale Member. However, the main contribution of gas generation within the Meem Shale Member came from secondary cracking processes through geologic time. The good thickness (736-910 m) of the organically-rich, high genetic potential and matured Meem Shale Member is expected to provide large amounts of oil and gas within the south-eastern portion of Al-Jawf sub-basin. Therefore, the Al-Jawf sub-basin can be considered as a rich oil and gas exploration province.