Tithonian Basal Makhul Shale: A Frontier Shale Resource Play in Kuwait

Husain, Riyasat¹; Al-Khamis, Awatif; Hussain, Fida; Prakash, Anand; Rabie, Ahmed; and Al-Fares, Abdulaziz
¹[email protected]

The lower part of the Makhul Formation comprises a transgressive sequence of organic rich argillaceous limestones, calcareous mudstones and dark euxinic bituminous rich claystones. The unit called as the ‘Basal Makhul Shale’ is emerging as a promising exploratory target for shale oil. The Basal Makhul Shale was deposited during the latest Tithonian (Jurassic) in the mid to distal outer ramp setting within an anoxic intrashelf basin of deposition on the carbonate ramp system of the Arabian shelf. The thickness of the unit gradually increases to the north. The present TOC values range from 0.35 to 7.51%. The hydrogen index shows low values, indicating nearly inert type II marine to mixed gas- and oil-prone source potential. The average Vitrinite reflectance values ranging from 0.72% to 0.86% and Pyrolysis Tmax values ranging from 406°C to 460°C suggest middle to earliest late maturity window for oil generation. The transformation ratio is about 68% and the hydrocarbon saturation varies from a minimum of 70% in the southwest to a maximum of 96% in the north. Generally the unit is over pressured at 0.80-0.92 psi/foot with formation pressures increasing to the north and northwest. The dominant lithology is bituminous calcareous mudstone rich in kerogen and appears to be brittle. The fracture sets seen on the image logs strike in NE-SW and NW-SE directions. Majority of the fractures are cemented/sealed fractures and are envisaged to act as weak zone during stimulation. Present day stress orientation is within a small range of N32°E-N52°E and consistent across major fault systems. The formation appears to be experiencing consistent strike-slip stress regime. The Basal Makhul Shale has flowed measured quantities of gas and oil on testing in different fields. High gas chromatographic readings have been recorded within the unit in the wells drilled in the northern Kuwait. Synergistic studies involving organic richness, maturity, overpressures, hydrocarbon saturation and sedimentary facies suggest shale oil potential of the unit in the northern Kuwait. The play is comparable to the Eagle Ford Shale play of North America. Key exploration challenges include paucity of sub-surface information and lack of expertise for drilling, testing, completion and stimulation of these challenging resources. Application of unconventional exploratory workflows and appropriate drilling, completion and stimulation practices are vital for exploration success.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013