Evaluation of Upper Marrat Formation through an Integrated Approach Utilizing Secondary Porosity Index and Seismic Facies Analysis, West Kuwait

M.F. Fahmy¹, R. Morakhi¹, A.A. Jalil¹, and I.A. Al-Shammak¹

Abstract

The Marrat formation is considered to be one of the most important carbonate oil reservoirs in West Kuwait oil fields. It is divided into three main parasequences, upper, middle and lower. Wells and 3D seismic data have been used to identify main structural elements of West Kuwait and their tectonic evolution, particularly Marrat basin architecture and depositional fabric during Jurassic time. The west Kuwait area including four main anticlinal structures namely Abduliyah, Dharif, Minagish and Umm Gudair with known multiple Jurassic oil entrapments. The porous and permeable Middle Marrat constitutes the main oil accumulations where reservoir quality is strongly controlled by structure, primary depositional fabrics, as well as extensive dolomitization. This paper focuses on upper Marrat parasequence mainly in Abduliyah and Dharif oil fields. The petrophysical analysis at wells indicated that Upper Marrat formation consists of argillaceous limestone based on density-neutron and potassium- thorium cross plots corroborated by well cuttings. Although the said formation represents tight carbonates, there is porosity enhancement at wells. The integration between secondary porosity index and high resolution seismic data revealed good correlation between impedance and porosity with well log data interpretation. Structural attributes such as coherency and curvature are employed for seismic facies analysis and fracture detection. Upper Marrat formation productivity may be emphasized by increasing in upper Marrat formation pressure followed by well kick during drilling one of the Abduliyah wells. This integrated approach was used utilizing petrophysical data, supplemented with seismic facies and real time well data. This resulted in the identification of sub-seismic 'fracture corridors', which generally created by the action of some cross faults and the dolomitization affected the study area to enhance the effective porosity development. Moreover, the hydrocarbon play in these areas has been the combination of moderately porous carbonate reservoir and open fracture networks to enhance the formation productivity.

AAPG Search and Discovery Article #90188 ©GEO-2014, 11th Middle East Geosciences Conference and Exhibition, 10-12 March 2014, Manama, Bahrain