oa Integrated fracture characterization of Najmah-Sargelu Reservoirs, Umm-Neqa structure, Kuwait: Its implications on hydrocarbon exploration

The recent exploratory efforts in the Umm-Neqa structure, in northern Kuwait, established the presence of light oil and gas in the Najmah and Sargelu reservoirs. These reservoirs are very tight carbonates with a matrix porosity of between 2.0% to 4.0% and permeability of less than 0.01–1.0 mD. Despite the low matrix permeabilities, the presence of natural fractures in the reservoirs is believed to have enhanced the permeability by several folds, as is evident by the high production rates. This presentation shows the results of fracture characterization studies to provide a better understanding of the complex fractured Najmah and Sargelu reservoirs in Umm Neqa structure. The study was based on the integration of core and borehole image log data from the two wells drilled in the structure. The natural fractures in the reservoirs were characterized in terms of size, aperture, density, orientation and sealing properties. The fractures mostly range from 5–8 inches in height; however some fractures are longer and a few exceed 3 ft in height. The fracture aperture varies between 0.2–0.3mm. Most of the fractures are open or partially open and steep (70–80o). Two dominant fracture sets were identified using borehole images; one set trends NNE-SSW and the other NW-SE. Borehole breakouts suggest that the direction of principal horizontal compressive stress is NE-SW, and natural fractures that strike in this direction are mostly open. These fractures are capable of transmitting fluids and enhancing the permeability. Horizontal boreholes,<br>oriented perpendicular to the strike of high-permeability fracture sets, hold great promise for maximizing primary production.