Pattern-Review Technique Maximizes Hydrocarbon Recovery in Complex Brownfield
Authors: Carpenter Chris 
Published: October 2022

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203100, “Maximizing Hydrocarbon Recovery and Water-Injection Support Through Pattern Reviews Between Injector/Producer Pairs in a Large, Complex, and Faulted Brownfield in Southeast Asia,” by Arfan Ali, Manish K. Gupta, and Reza Salleh, Brunei Shell, et al. The paper has not been peer reviewed.

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Large, complex, faulted structures often pose substantial challenges in maximizing hydrocarbon recovery. The work presented in this paper has used what the authors call a “pattern-review” technique in a brownfield containing more than 500 well penetrations in southeast Asia. For the first time in field history, pattern reviews have been used extensively as a tool to understand reservoir connectivity and dynamic fluid movements across the field. An integrated effort involving different data sources and disciplines has provided fresh insights into the reservoirs that would have otherwise been difficult in heterolithic stacked reservoirs.

Introduction
The Champion field is 40 km offshore Brunei Darussalam in water depths of approximately 40 m. The field has a long, complex development history spanning almost 50 years. The field contains more than 45 platforms and well jackets. There are approximately 700 conduits in approximately 450 wellbores. For simplification, the field history has been divided into three main phases:
- Phase I: Period of rapid expansion (focus on development of the Champion field main area)
- Phase II: Period of consolidation (focus on waterflood initiation and development away from the main field area)
- Phase III: Period of rejuvenation (focus on expansion in waterflood development)
Because of the field’s complexity and unmappable flank areas, Phase I progressed outward from the center of the field. Appraisal wells from the existing platforms and other, isolated locations were targeted into unappraised blocks. This method of appraising and developing from known to less-known areas worked well in the initial development of the field. Phase II saw an increased emphasis on drilling water injectors in addition to infill oil producers. The lack of water injection and the resulting depletion in the main producing reservoir sands escalated the need for a Phase III development of the field. This phase heavily emphasized ramping up water injection in the field with the aim of forming a line-drive waterflood pattern between injector/producer pairs.
The primary structure in the Champion field is a large anticline feature that is interpreted as a rollover into a regional west-heading growth fault system. Fault throws and transmissibilities vary across the entire field, with faults sealing increasingly from shallower to deeper reservoirs. Multiple sets of 3D seismic data have been acquired over the history of the field. In early 2020, a seismic ocean-bottom node survey was acquired over the field. In addition to the main bounding faults, several small-scale faults present randomly within the individual fault blocks. Ant-track maps have been used along with the seismic fault-structure map to understand these barriers.
The reservoirs in the field consist of Miocene shallow marine, coastal, and deltaic sediments. The shallow reservoirs are heterolithic in nature. Not many wells have targeted these shallower reservoir intervals. A considerable amount of uncertainty surrounds the oil/water contact (OWC) in the field. As a result, a significant proportion of standard stock-tank oil initially in place remains in the ground.