Reservoir Navigation in Njaba Field – Challenges, Procedure and Results

Due to the low oil price, Exploration and Production (E&P) companies are driven to reduce the cost per barrel of oil equivalent (BOE). The application of reservoir navigation services, in the placement of high angle and horizontal (HAHZ) wells in the sweet spot of reservoirs, has aided in meeting this economic need of the E&P, while also improving hydrocarbon recovery. Reservoir navigation services (RNS) can be regarded as another tool for improving the odds of success while drilling of HAHZ wells. This service involves the integration of real-time data (deep-reading azimuthal resistivity, gamma-ray, density image, resistivity image logs, near bit inclination and a fit for purpose rotary steerable system) to accurately position the well-bore relative to specific subsurface targets, while remaining within the constraints of the drilling and completion program. RNS also require a software package capable of pre-well modeling, displaying the acquired real-time data and interactively adapting the model to the real-time data. Geosteering in Njaba field involved a comprehensive pre-well planning, discussions, documentation and management approved decision-tree. Using three wells for this study, this paper describes the challenges, procedures and results of geosteering in Njaba Field located on-shore Niger-Delta. From different entry points, wells NJX1, NJX2, and NJX3 were planned to drain the same reservoir and optimize hydrocarbon recovery within the reservoir. Some of the challenges encountered includes geosteering the wellbore above a pre-determined production TVD hardline while simultaneously avoiding drilling into an overlying undulating shale cap rock, vertical seismic uncertainty and undulating formation boundaries.