The first successful natural dump-flood in the Malaysian offshore environment provided numerous lessons learned to the operator. The minimal investment necessary for implementing the dump-flood coupled with the lack of recompletion opportunities in the subject wells suggested that direct execution without spending on expensive data gathering activity and extensive reservoir study makes more sense from a business point of view. A similar oil gain compared to a water injection project can be achieved at a significantly lower cost of USD 0.01 to 0.15 million in an offshore environment through dump-flooding. The existing oil producers in the depleted reservoirs in Field B were originally completed and successfully drained oil from in a high-pressured watered-out reservoir below, making it an ideal dump-flood water source. The dump-flood was initiated by commingling the target and water source reservoir through zone change, allowing water to naturally cross-flow into the pressure depleted target reservoir. Once a memory production logging tool (MPLT) confirmed the cross-flow, the offtake well was monitored to determine the impact of the dump-flood and produce once the pressure was increased. Minimal investment was necessary because the operations were executed using slickline. The reservoir model will be calibrated once the positive impact of dump-flood is realized in the offtake well. The first natural dump-flood in Reservoir X-2 has successfully produced 0.29 MMstb as of August 2018 with 600 BOPD incremental oil gain. The incremental recovery factor (RF) from the first dump-flood is predicted to be from 5 to 8%. Based on this success, it was decided to replicate the dump-flood project in other depleted reservoirs with Reservoir X-2 as an analog. Four reservoirs were subsequently identified, each with an estimated operational cost of approximately USD 0.01 million and potential incremental reserves of 0.10 to 0.20 MMstb per reservoir. The minimal investment necessary, the idle status of the wells and reservoirs, and the potential incremental reserves suggested that it is more appealing to proceed with implementing the dump-flood without undergoing an extensive and costly reservoir study. With reservoir connectivity being important to the success of dump-flooding, a more cost-effective approach would be to confirm the connectivity by monitoring the offtake well after the dump-flood is initiated. This approach provides more value because the cost of interference or pulse testing is significantly more expensive than the cost of the dump-flood itself while reservoir connectivity was already indicated as likely by geological data (map and seismic). Through a value driven approach, these dump-flood opportunities become more economically viable, allowing the operator to prolong the life of the assets and maximize the field profit. This paper discusses using a value driven and business approach to implement the dump-flood in a mature field. Valuable insight into the business and technical considerations of implementing dump-floods are described, which are relevant to the industry, especially in today's low margin business climate.

While it is true that reservoir simulation and new technology applications are crucial to unlocking reserves in a field, the first and most fundamental step in rejuvenating a mature field is to verify the existing data and evaluate the basis of the current understanding. This process, while seemingly "routine", can uncover ambiguous data and questionable interpretations, which can mislead the reservoir simulation results unless corrected. The older and more mature the oilfield, the more ambiguities that can be uncovered. The new understanding can be subsequently converted to "quick-gain" opportunities that can be quickly monetized, while maturing higher investment and more complicated opportunities with reservoir simulation. The approach applied in a sample field named Field B comprised challenging the established interpretation and understanding by taking a more thorough look and applying a different approach with the basic data. There are examples of reinterpreting the seismic data, cross-checking pressure and production reports with geological understanding, cross-checking well intervention reports, production and open-hole log data, and challenging the conventional approach and understanding. On top of the detective work, it is also necessary to judge whether the data "make sense" or seem unreasonable. Although simple, this approach was effective and successful in generating multiple opportunities in Field B. This paper provides valuable insight and examples in data verification and challenging established understanding to generate potential opportunities. Having a good grasp of the fundamentals is a valuable skill in a mature field environment. It pays to thoroughly understand the fundamentals, because otherwise, the "fancy techniques" will not work.

Sarawak offshore wells are mostly completed with dual string completion and are heavily relying on gas lift as the primary artificial lift. Dual string gas lift is an economical way to selectively produce from multi-stacked reservoirs in Sarawak fields. However, it poses great challenges in terms of operations, troubleshooting, allocation and optimization as both strings share a common annulus. Dual string gas lift performance diagnosis need to be done from time to time to ensure the strings production are optimized at well level. Gas injection rate is a critical input in predicting the well performance based on the gas lift performance curve. However, the gas lift injection rate for dual string is measured at well – not at string level. The gas lift injection rate into each string needs to be allocated correctly either through well modelling calibration approach, testing one string while shutting its neighbor or well tracer application. After allocating the gas lift injection rate into each string correctly, well modelling prediction run at done to mitigate multipointing issues, design optimum point of injection, establish optimum injection rate at well level and determine the optimum casing head pressure. The operator has proposed for a workflow to correct the dual gas lift injection allocation based on well modelling calibration. The workflow was implemented and resulted in multiple optimizations in terms of gas lift valve change program, choke optimization and gas lift rate optimization. Apart from that, the paper will also share on the findings from the well tracer application in correcting the gas injection allocation. This paper will focus on the production performance check on dual string gas lift performance at well level. The findings from the study are subsequently monetized as quick-gain opportunities while the operator is embarking into long term study on assessing the alternative artificial lift strategy suitable for a brownfield. The lessons learned will also be applicable to oil fields with similar situations to further improve the fields’ production.

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The Balingian province is located offshore Sarawak, comprising of at least 7 oil fields with its regional geology consisting of a combination of deltaic & shoreface system. Though consisting of clastic reservoirs, the fields are highly sophisticated in terms of reservoir compartmentalization, hence uncertainties in fluid contacts, differing depletion strategies and varying production performance per well. As the regional production has gone into brownfield stage, the challenge is to determine the most suitable secondary recovery method to prolong field life. The subsurface & feasibility studies conducted produced mixed results between application of water & gas injection, giving recovery factors between 30 to 40%, and implementation so much depending on source of water & gas and cost benefit analyses. The application of IOR across Balingian province are executed in pilot mode across all fields. While the pilots are still continuing, this paper is to share the methodology, recovery factors and process of the regional study and some results from the ongoing surveillance post-execution, and the wayforward.