For its operations in the shallow Ebok field offshore Nigeria, Afren wanted to drill horizontal wells shoe to shoe as efficiently as possible in the soft formation. The unconsolidated formation, shallow TVDs, and long wells with tortuous paths presented challenges to achieving good dogleg assurance. Dogleg severity (DLS) was an issue in the 16-in and 12¼-in sections because trajectory had to be maintained while drilling through complex anticollision conditions and fault access windows incorporated at the well-planning stage. The 16-in surface holes in some of the wells were drilled to an 82° inclination at section TD. Failing to cross any unanticipated fault could result in mud losses and POOH to either plug back and replan the trajectory or a cement squeeze job.
SLB provided an integrated team approach and collaborative project management, from planning and engineering to execution and drilling, through its PetroTechnical Engineering Centers (PTECs). Experienced petrotechnical experts and wellsite engineers at PTECs design and execute operations using advanced software and technology to engineer drilling fluid systems and drilling assemblies that maximize ROP and daily footage.
For this operation, the team selected a low-flow configuration of the PowerDrive Xceed RSS, a point-the-bit system that reduces the tendency of the hole to spiral due to variations in trajectory. The team fitted the RSS with a SHARC high-abrasion-resistance PDC drill bit for enhanced hole cleaning practices, especially in the 12¼-in section.
PeriScope HD service was used in four wells because it provides a more precise delineation of reservoir boundaries and fluid contacts. The service is the industry’s first to provide deep, directional electromagnetic LWD measurement to continuously monitor the position of formation and fluid boundaries.
Mud engineering design was provided by VIRTUAL HYDRAULICS™ drilling fluid simulation software. The software was used to monitor and predict critical drilling parameters to help Afren achieve a high-quality wellbore under optimal operating conditions while reducing rig time and lowering costs.
In the 12¼-in section, the PowerDrive Xceed RSS saved half a day for every 1,000 ft drilled as compared with the PDM that had been previously used. Drilling runs for two of the wells took only 30 days, saving 8.4 rig days compared with using a PDM.
Two wells were drilled ahead of AFE, saving Afren 25% off AFE. Both wells were drilled shoe to shoe in single runs with an improvement in below-rotary ROP of 76% as compared with offset wells drilled in the area, and there was only minimal wear to the PDC cutters at the end of the run.
