Jurassic Tight Carbonate Gas Fields of North Kuwait: Exploration to Early Development

Abstract

Exploration activity during the last eight years, targeting Jurassic carbonate reservoirs in North Kuwait, has culminated in the discovery of six major tight gas fields, encompassing an area of about 1,800 sq km with a reservoir gross thickness of about 2,200 ft. These fields are the first free-gas fields in Kuwait, which were put on early production during 2008. The reservoirs are characterized by dual porosity, dominated by low porosity and permeability, in deep HP/HT conditions, with wide variety of hydrocarbon fluids ranging from black oil to gas condensate with sour gas. Typical per well production rates are up to 5,000 BOPD/BCPD and 10 MMSCFPD, making them an excellent commercial success. Despite the limited number of 38 well penetrations to date in this large Jurassic complex, understanding of the depositional model has improved over time through careful integration and detailed interpretation of log, core, and seismic data. Based on these studies, a depositional model incorporating sabkha, tidal flats, lagoon, backshoal, shoal, shoreface inner shelf, outer shelf, and slope/basin depositional environments has been built. Hypersaline brines were generated in the lagoon and seeped downward, selectively dolomitizing the underlying strata, creating secondary porosity and permeability, and significantly improving the reservoir characteristics in some of these fields. From the early phases of exploration, the role of natural fractures in enhancing the production from these reservoirs was recognized. Accordingly, well data acquisition is designed to maximize reservoir understanding. Delineation and development well placement are optimized to penetrate the most heavily fractured corridors, through a combination of seismic attributes and Discrete Fracture Network modeling, constrained by available well data.

Petroleum Geology of Kuwait

“…The significance of Najmah Sargelu carbonate self-sourced reservoirs has been widely investigated (Siddiqui et al, 2008;Nath et al, 2012). The Najmah Sargelu tight carbonates are considered as naturally fractured, organic-rich prolific reservoirs in west Kuwait (Al-Failakawi et al, 2018;Al-Murakhi, 2019) as well as the north fields (Siddiqui et al, 2008;Al-Eidan et al, 2010). The Sargelu Formation overlies Dhruma calcareous shale formation which is an excellent cap rock for the Marrat Formation.…”