Casing Drilling was introduced to optimize the drilling of the top hole section in the Phase 1 wells of the mature Samarang Field re-development campaign. Lost circulation and stuck casing incidents in the surface section had been observed in previous campaigns, and Casing Drilling was identified as a solution to mitigate these problems. Company procedures require that a pilot hole be drilled on the first hole section out of the conductor on the first well drilled during a platform revisit, for shallow gas mitigation. Although the risk of shallow gas was considered low in the Samarang field, the requirement applied to the first well to be drilled in the campaign. In the absence of a conclusive shallow seismic survey, other analyses to evaluate the likelihood of shallow gas were used, and Casing Drilling provided a different approach to mitigating the risk of shallow gas blowout. This paper discusses the benefits of Casing Drilling in Samarang, with special focus on its application as mitigation for a reduced risk of shallow gas blowout. It reviews the modeling and risk analysis conducted to justify and obtain the waiver required to drill without drilling the conventional pilot hole. It also discusses the lessons learned from the execution. The implementation of Casing Drilling in mitigating the shallow gas drilling risk, among other benefits, was a significant milestone in the project. The drilling operations became more efficient based on the substitution of the pilot hole on the first well of the re-development campaign. This has opened the opportunity for potentially valuable savings in the next phase of the project (with seven platform revisits) and other similar brown fields revisit campaigns.

The Late Neogene Baram Delta province developed on an active margin located offshore Borneo in Malaysia. The field has been in production since 1982, and a total of 64 wells have been drilled from three (3) platforms. This paper discusses the process used to locate remaining oil for infill drilling. This involved a multidisciplinary effort including geology and geophysics, reservoir engineering, drilling / completion, and production technology. The geologic and geophysical (G&G) assessment consisted of updating the static model and constructing mobile oil thickness and structural and bubble maps of all reservoirs. These maps were used in conjunction with original and current fluid contacts and helped to identify and locate remaining oil accumulations. The target portfolio was screened and ranked, and preliminary wellbore paths were built. Four (4) new wells and eight (8) sidetracks combining either shallow or deep targets were passed on to the reservoir engineering team for optimisation from simulation models and first-pass estimation of oil incremental reserves. Reservoir simulation focuses on optimising target intervals as determined through G&G work and drilling design. Well constraints are set to be consistent with operating field production practices and facilities constraints. Completion intervals for the dual-string wells are optimized to minimise water cut and maximise oil rates. All simulation results are rigorously checked against offset well production and observed properties. Once drilling targets are risk-assessed on the basis of structural, fluid contacts, and properties uncertainties, the final well trajectories are designed by the drilling team. This study identified and ranked multiple undrained and appraisal areas. A full infill redevelopment consisting of more than 10 accelerated wells planned through the utilisation of existing facilities was presented and approved by PETRONAS Carigali Sdn. Bhd. (PCSB). The well and target portfolio is focused on three (3) main field development areas: Attic oil in shallow Pliocene reservoirsNew development areas in deeper Miocene levels on the southern blockUntapped deep Miocene reservoirs on the northeastern flank in crestal location The first two (2) sidetracks and three (3) workovers were successfully completed in December 2012, and the current oil production is 40% higher than originally estimated. The successes to date have proved the effectiveness of the concepts that were applied to identify and develop the remaining oil, and the field became East Malaysia's top producer.