Optimizing Brownfield Redevelopment With Decision/Risk Assessment: Case Study
Authors: Denney Dennis 
Published: February 2015

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 87047, "Optimizing Brownfield-Redevelopment Options Using Decision/Risk Assessment: Case Study - Bokor Field, Malaysia," by B. Wongnapapisan, SPE, S. Flew, SPE, and F. Boyd, SPE, Schlumberger, and Z. Hassan, Petronas Carigali Sdn. Bhd., prepared for the 2004 SPE Asia Pacific Conference on Integrated Modeling for Asset Management, Kuala Lumpur, 29-30 March.
Revitalization of the Bokor field was affected by many surface-facility constraints as well as the subsurface complexity of laminated stacked reservoirs. These complex problems required use of an integrated multidisciplinary team method that used a decision- and risk-assessment (DRA) approach to screen development options.

Introduction
Field redevelopment requires identification of system bottlenecks and proposals to remove them, but, often, only the facilities level is considered. In proposing a revitalization plan for the Bokor field, the team developed a decision-making process to select an optimal development plan that would solve the constraints while minimizing unit technical operating cost (UTOC) and maximizing production.
Often, brownfield redevelopments are limited to maximizing existing facilities (e.g., well slots or the processing plant). In the case of Bokor, essentially no additional oil could be produced because of a lack of gas lift and export compression. Thus, an approach was required that solved the existing bottlenecks and provided sufficient additional capacity to sustain a cost-effective revitalization plan. The process had to be iterative and assess the risks and uncertainties of each approach as well as the economic effects.
The solution considered each reservoir target on a discounted-cumulative-oil basis, producing a ranked list of opportunities that could be added together to form any development scenario. Rather than running a reservoir simulation on each development case, multiple facility-development options were evaluated quickly. Each development scenario then was analyzed with a tornado chart, to prepare a decision tree that yielded the most likely outcome. This approach allowed options as diverse as subsea tiebacks or fully integrated platforms with many electrical submersible pumps (ESPs) to be risked and ranked equitably within a reasonable time frame.
The full-length paper details the comprehensive multidisciplinary integration process required for brownfield redevelopment by use of a DRA approach for screening, ranking, and evaluating the redevelopment options and eventually selecting the most appropriate option.
The existing facilities comprise five main structures: three drilling platforms, a production-station structure where the liquid-production separation and handling process takes place, and a gas-compression structure for gas lift and export. The Bokor field is interlinked with the Betty field for gas import (very high pressure, high pressure, and low pressure), the Baronia field for gas export (gas from Bokor and Betty), and the Bakau field for liquid export.