Abstract
Tight carbonate reservoirs of north Kuwait present many challenges for field development due to the inherent low porosity and permeability characteristics. The reservoirs are characterized by an average matrix porosity from 2 to 6% and permeability from 0.01 to 1.5 md. Near critical gas and volatile oil fluids produce mainly from Middle Marrat carbonate multi flow unit reservoirs. Natural fractures play a primary role in the producibility of these reservoirs and understanding the fractures and rock texture are important to the characterization and subsequent stimulation strategies for production.
High deviated well is commonly used to intersect the potential natural fractures and connect the multi flow unit inside Middle-Marrat carbonate. Multiple pressure regime encounter from the upper part of Jurassic layer resulted in the required 6in slimhole to be used to drill the target Middle-Marrat formation. Drilling risks are aplenty in downhole conditions made hostile by high viscosity synthetic mud with high solid content for a 6-in deviated hole going through varying pressure profile amidst high torque and drag. These challenges and slimhole size often limit the technology availability on acquiring high quality measurement especially with a borehole imager for fracture characterization.
The new logging-while-drilling (LWD) tool presented in this paper overcomes these challenges while delivering services in 18 to 19 lbm/gal (ppg) of synthetic-oil-based-mud (SOBM). The tool features an extremely compact 5 ft long LWD sub, which includes a power source, memory and directional sensors for azimuth and high side offset detection. The compact size sub allows for placement near the bit and reduces overall required bottom-hole-assembly (BHA) length. The torque and drag of the logging run in the cleaning out assembly were studied to ensure smooth acquisition minimizing risk of stuck pipe.
