Near-Bit-Density-Porosity BHA Configuration and Its Utilization in Realtime Geosteering: A Case Study from the Lower Cretaceous Minagish Oolite Limestone Reservoir in Umm Gudair Field, West Kuwait
Authors: Al-Khalifa N. , Joshi D. , Al-Langawi S. , Al-Otaibi S. , Al-Dhafeeri A. , Al-Qazweeni E. , Odiase P. , Mohamed S. B. , Adeniyi A. , John S. 
Published: February 2024

The Lower Cretaceous Minagish formations in Umm Gudair field is a prolific conventional oil reservoir located in onshore West Kuwait. The primary reservoir units are located in thick Oolitic Middle Minagish Member. The long-term field development plan for Umm Gudair field is focused on enhancing hydrocarbon production and extending the plateau rate for its large and matured carbonate reservoirs. Multiple horizontal wells are currently being used to improve well production from the Minagish Oolitic limestone reservoir. The success of these horizontal wells has led to the development of a reactive geosteering technique that allows for optimized placement of horizontal wellbores within the target Oolitic limestones. The geosteering technique is designed to utilize the reservoir character of the Oolitic limestones which in turn requires the implementation of a bottom hole assembly (BHA) configuration that positions the density/porosity logging while drilling (LWD) tool sensors close to the drill bit and ahead of other logging tools. This BHA configuration also provides porosity calculation to as much as close to the bit in TVD and MD mode. This technique has also been useful to steer the well above the barrier and baffle zone (high-density markers) to delay the water cut.

A case study on five horizontal wells drilled in Minagish Oolite limestone reservoir, Umm Gudair field West Kuwait, where the geosteering technique of utilizing the near-bit-density-porosity BHA configuration was implemented. The study aims to highlight the impact of the geosteering technique on horizontal well drilling and hydrocarbon production, as well as explore the merits and demerits of the unique BHA configuration from an application engineering viewpoint.

The positioning of the density/porosity sensors close to the drill bit reduces the reaction time in mitigating against structural play and layers’ property variations resulting in optimized horizontal wellbore placement and hydrocarbon production. This BHA is also helpful to detect early high-density markers within the reservoir which are compared to tight zones in Umm Gudair field. The interpolation of these high-density markers with respect to current oil water contact helps to keep the wellbore above the barrier and baffles lithology to delay water cut from underlying current oil water contact. The density/neutron LWD tool undergo more vibration in the optimized BHA configuration when compared to the conventional BHA configuration due to the components of vibrations being higher closer to the drill bit. This invariably accelerates wear and tear conditions in the fragile density/neutron LWD tool, increasing the likelihood of the tool failure while drilling. However, operational and engineering solutions are successfully being used to mitigate vibration problems associated with the near-bit-density-porosity BHA configuration which eliminates incurring potential additional costs due to the increase frequency of tool maintenance and repair.

Utilizing the near-bit-density-porosity BHA configuration in optimizing horizontal well placement and hydrocarbon production in Oolitic limestone reservoir.