Case Study: Drilling Performance in a Thin Oil Rim Carbonate Pinnacle:Central Luconia, Sarawak

摘要

Drilling into carbonate reservoirs presents challenges involving damaging vibrations to drilling assemblycomponents, encountering total drilling fluid losses, formation damage, potential loss of directional controlif drilling into karst structures, and formation evaluation, particularly with high reservoir uncertainty. Thesechallenges are exacerbated by the need to drill a long, relatively smooth 6,000-ft horizontal ERD wellfor autonomous inflow control device (AICD) smart well completion at 45 ft TVDss below the GOC.This paper describes collaborative efforts amongst different facets of drilling, fluids, and drill bits with theoperator drilling team. Planning, risk assessment, directional drilling, and formation evaluation solutionsare discussed for total drilling performance from spud to well TD for three wells in Phase 1 of this campaign. The elongated narrow nature of the carbonate pinnacles and optimal oil ultimate recovery dictateshorizontal production hole placement in the mid-point of the thin oil rim. Well designs were optimized withconsideration for anticollision risk, optimum reservoir recovery, karst avoidance, shallow hazard, extendedreach drilling the long horizontal section with minimal undulation, in-field referencing (IFR) surveys tominimize well bore uncertainty, fluid management for optimum hole cleaning, and drill bit designed forpenetration rate and minimal vibration. BHAs were modeled for directional control, drilling efficiencyand damaging vibrations from drill-bit and BHA components. BHA simulation incorporating downholevibration isolation tool mitigates and decouples damaging vibrations. The high fluctuation of 5 to 40 kpsi compressive strength from offset Carbonate sections induces vibrationdamage to drill-bit cutters if not designed out. Fluids design focused on drilling using a waterbased mud andreadiness to combat severe or total losses. Fluids design for the horizontal section requires both an easy toclean filter-cake if switched to Pressurize Mud Cap Drilling (PMCD), and on acid-degradability of the filter-cake if drilled using conventional drilling allowing the application of an in-situ acid generator filter-cakebreaker system, optimized fluid performance for hole cleaning, pressure management, and torque and dragreduction by means of nondamaging lubricants. The ultradeep-resistivity inversion successfully mappedand reduced seismic uncertainties and achieved optimal well placement within the thin oil rim.