Innovative Measurement-While-Drilling and Mapping-While-Drilling Technologies Enabling Drilling and Geosteering Complex Multilateral ERD Wells—Case Study From Wandoo Field

Abstract The Wandoo Field in the North West Shelf offshore Australia is a mature field that has been in production since 1993. In 2022, two development wells, the trilateral B17 and B18 wells, were planned to target remaining high oil saturations and increase production. Both wells were classified as extended-reach-drilling (ERD) wells due to the shallow true vertical depth[SD1][MR2] of the reservoir resulting in an extreme stepout ratio. In addition, highly complex 3D well paths were required to access the areas of remaining high oil saturations with unswept oil reserves. Geosteering operations were critical for achieving the production objectives. However, the low resistivity contrast of the target sand from the adjacent layers, and the tight window constrained by the moveable oil-water contact (OWC), made geosteering challenging. Besides these, the existing wells in the field posed anticollision issues for all four laterals. Wellbore stability was also a concern here because of the narrow equivalent circulating density margin and the unconsolidated nature of the reservoir rocks. During the planning phase, several new technologies were selected to help tackle these challenges and ensure project success. First, a new measurement-while-drilling tool that could provide a continuous definitive dynamic survey while drilling was included. This could give definite dynamic surveys in real time, enabling the most accurate curve in the most complex 3D well profiles, while also eliminating the static survey time and reducing time to total depth. Second, a high-definition ultradeep-resistivity tool (HD-UDR) was used for mapping the reservoir layers and OWC more than 30 m away from the wellbore for geosteering the wellbores within the target zone. Third, a high-definition deep resistivity tool (HD-DR) was used for providing closer-to-bit high-resolution delineation of nearby boundaries. Finally, the 3D Ultra Deep Azimuthal Resistivity tool [HW3][MN4]was implemented post-drill to obtain a volumetric mapping of resistivity profile around the wellbore and to gain insights on the faults, water coning, and unswept zones. While drilling, the HD-UDR tool facilitated the safe crossings of nearby wells, by providing accurate position within the stratigraphy, and by detecting the water coning caused by nearby producer wells. The 3D reservoir mapping processing, under optimal conditions, [SD5]generate transverse inversion slices every 10 m along the wellbore and provided additional insights into field for future development planning. Due to a range of challenges including the high ROP requirements for wellbore stability and the complex reservoir environment, the 3D reservoir mapping process was delivered post-drilling in this instance. Post-drill resistivity cubes along the lateral were generated, opening possibilities for integration with existing reservoir models. Despite the significant challenges the team faced, the project execution went smoothly, and all four laterals were successfully drilled and completed, achieving the expected production rate and reserves. Geosteering, aided by the advanced technology portfolio, played a critical role in placing the wellbores at the optimal positions in the reservoir.