Reducing Geological Uncertainty and Enhancing Reservoir Navigation in A Complex Clastic Reservoir Through Integration of Extra-Deep Azimuthal Resistivity Inversion and Litho-Density Imaging: A Case Study on Minagish Field in West Kuwait

Abstract

Abstract The Upper Burgan Reservoir located in west Kuwait is a diverse and intricate clastic reservoir, presenting challenges in well placement due to structural and sedimentological factors, as well as uncertainty regarding the Oil Water Contact (OWC) of the reservoir. To address these uncertainties a real-time resistivity inversion coupled with the near-bit-gamma ray and litho-density image interpretation were used to map remote conductive boundaries and to provide invaluable information on the reservoir structural architecture. A geo-navigation model was created using offset well gamma ray, resistivity, and bulk density measurements. The offset wells bulk density and resistivity measurements were further used as inputs in generating synthetic high-density images and forward resistivity inversion solutions along the planned well path trajectory. The resistivity inversion solutions provided a visualization of the logging while drilling (LWD) tool’s simulated azimuthal resistivity curves at varied depths of investigation within the specific Upper Burgan target reservoir environment and was a key factor in determining the tool’s look-ahead capability. The implemented BHA comprised of a rotary steerable system, near-bit-gamma, azimuthal and extra-deep resistivity, and the density-porosity-image technologies. The resistivity inversion results acquired from the extra-deep azimuthal resistivity measurements in real-time provided the look-ahead capability used in detecting the target UB1 reservoir ahead of the drill-bit allowing for timely adjustments to the wellbore trajectory resulting in accurate positioning of the wellbore within the productive zone of the target Upper Burgan UB1 reservoir. The extra-deep azimuthal resistivity real-time measurements also provided a means of visualizing the Upper Burgan UB1 reservoir architecture on a seismic scale and were key in making the geosteering decision to divert from the original well plan maximum wellbore inclination adjusting in steps up to 94.0 degrees to align the wellbore parallel to the formation dip thereby optimizing well bore placement. A combination of the Litho-density image and the deep and shallower azimuthal resistivity measurements provided important reservoir scale structural information. These were used to successfully navigate the wellbore within the productive zone of Upper Burgan UB1 target reservoir for +/-1300-ft MD footage of the drain section achieving 100-% reservoir contact. A petrophysical evaluation of the drilled interval in the Upper Burgan UB1 target reservoir identified excellent reservoir properties. The integration of the extra-deep azimuthal resistivity and litho-density image technologies in providing detailed seismic and reservoir scale structural and geological information proved invaluable in making geosteering decisions to achieve a more accurate positioning and subsequent navigation of wellbores within a complex siliciclastic environment. This strategy has resulted in an enhanced recovery of bypassed oil located in thief zones.