S. I. SCJGE-1 2019 Petrophysical analysis of Upper Qishn Clastic Member Reservoir, Tawila Oilfield, Yemen Adel Al-Johi 1 & Elkhedr Ibrahim 1 & Saad Mogren 1 & Aref Lashin 2,3 Received: 10 July 2020 /Accepted: 2 October 2020 # Saudi Society for Geosciences 2020 Abstract A comprehensive petrophysical study of the Upper Qishn Clastic Member reservoir was conducted at Tawila oilfield in Yemen. An integrated well-logging dataset was analyzed to detect the reservoir properties and hydrocarbon potential. Lithologic data, shale/matrix models, elastic, seismo-facies, and fluid analytical analyses and crossplots were generated to characterize the reservoir. The clastic reservoir was subdivided into four petrophysical zones (S1A, S1B, S2, and S3) having different reservoir properties and hydrocarbon content. Crossplots of dia-porosity, apparent-matrix density, and elastic rock properties revealed a reservoir with mixed rock types primarily composed of quartz, calcite, and feldspars, with rare kaolinite and heavy minerals. A laminated-shale model was found to apply to the S2 and S3 reservoir zones, while dispersed- and structural-shale models best describe the S1A and S1B zones. Pickett and Buckles saturation crossplots indicated that the reservoir is not at irreducible water saturation. The Qishn reservoir exhibits regular and uniform facies of similar thickness throughout the study area with a slight dip toward the northwestern part of the oilfield. Estimated petrophysical parameters for the reservoir are represented by vertical petrophysical analogs and property distribution maps. The vertical petrophysical analogs show that the S2 and S3 zones attained clearly defined reservoir properties compared to S1A and S1B zones. The S2 zone has an effective porosity of 11–19%, permeability of 2–670 mD, and hydrocarbon saturation < 57%. The S3 zone offers an effective porosity of 12–21%, permeability of 4–2000 mD, and hydrocarbon saturation < 61%. Both S1A and S1B zones show weak petrophysical parameters and low hydrocarbon content. Hydrocarbon-distribution maps reveal significant hydrocarbon saturation north of the main east–west- trending fault reaching a maximum associated with low shale volume and excellent effective porosity and permeability values. It was concluded that the S2 and S3 zones are the most hydrocarbon-rich zones in the reservoir and should be further studied and mapped across the study area and the nearby oilfields. Keywords Well-logging datasets; . Reservoir properties; . Hydrocarbon potential; . Upper Qishn Clastic Member reservoir; . Tawila oilfield; . Yemen Introduction The Republic of Yemen is located in the southwestern part of the Arabian Peninsula, adjacent to the world’s most produc- tive and valuable hydrocarbon reserves. The exploration his- tory of the Yemen sedimentary basins dates back to the middle of the last century, when the Iraqi Petroleum Company Ltd. conducted a preliminary geological exploration in Hadhramout and in the southern part of the Al Mahrah Provinces. The company established the first detailed strati- graphic divisions in the region, including southern Al Mahrah Province and the Wadi Al Masila Basins (Beydoun 1996). From the 1970s to the 1980s, the southern and northern Yemeni concession blocks were offered to petroleum compa- nies, with commercial discoveries forthcoming in the 1980s. This article is part of the Topical Collection on Current Advances in Geological Research of Egypt * Elkhedr Ibrahim eibrahim@ksu.edu.sa 1 Department of Geology and Geophysics, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia 2 Petroleum and Natural Gas Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia 3 Geology Department, Faculty of Science, Benha University, P.O. Box 13518, Benha, Egypt Arabian Journal of Geosciences (2020) 13:1114 https://doi.org/10.1007/s12517-020-06077-0