Real-Time Fluid Mapping Ensures Reserve Development Via Optimized High-Angle Infill Drilling

Abstract

Reservoirs containing complex structures require additional technology to obtain optimum performance from planned production wells. In this scenario, logging-while-drilling (LWD) technologies play an important role in well construction from purely geometric trajectories to the real-time trajectory steering and formation and fluid characteristics measurements. A North Sea Alvheim field case study is presented in this paper. During the exploration and initial development phase of the field, the oil/water contact (OWC) varied to 7 m due to the presence of mudstone baffles and faults. The field has been on production since 2008 using bottom-aquifer drive, and current fluid contacts have shifted from their initial levels. To enhance field recoverable reserves, an infill development plan was required to place the wells within a thin oil rim between the gas/oil contact (GOC) and the OWC. Field objectives included achieving optimal well landing, identifying the moveable oil in situ, mapping the hydrocarbon-bearing reservoir, and identifying the hydrocarbon type (oil or gas) along the wellbore trajectory. To address the challenges, an integrated drilling bottomhole assembly (BHA) consisting of a deep-directional resistivity (DDR) tool to refine the reservoir delineation and structural positioning, a downhole fluid analyzer (DFA) using optical spectrometry to identify in-situ fluids, and advanced petrophysical measurements provided a complete quantitative reservoir evaluation during well construction. This paper presents the design, execution, and interpretation of the acquisition program to achieve the well objectives, including positioning the producer well in the desired moveable fluid zone. The final results demonstrated that integrating LWD measurements in the operation added significant value toward achieving the desired wellbore trajectory by optimally positioning the wellbore in the desired reservoir fluid layer.