Production allocation is required in hydrocarbon accounting to determine the hydrocarbon volume at the point of sale and for back allocation to the field, platform, well, and down to the individual reservoir levels. Production allocation is not only important for the purpose of reporting to the host government but also to understand the remaining hydrocarbon reserves which are crucial for reservoir management and input to the full field review studies. For wells producing from commingle zones, the individual zonal contribution determination is important. The Production Logging Tool (PLT) is commonly used to measure each reservoir's contribution downhole. Latest technology advancement in directional drilling over time has allowed for more deviated and horizontal wells. Well deviation is one of the factors affecting fluid flow pattern in a borehole apart from the phase holdups and fluid properties (PVT). As production fluid flows upwards in a deviated well, the movement of the lighter phase to the high side of the well displaces the dominant heavier phase liquid, causing it to flow downwards. This borehole phenomenon is commonly known as Apparent Down Flow (ADF). A standard PLT has a centralized spinner configuration and when run in wells experiencing ADF will likely cause the spinner to measure an incorrect fluid velocity. Depending on the degree of the holdup of the heavier phase, the spinner may show a reduced or even negative rotation if it is immersed in the heavier phase fluid. Conversely, the spinner may show faster rotation if it is located in the lighter phase fluid. The advanced PLT, with its array of mini spinners and holdup sensors, was developed in part, to measure the effects of ADF and was designed to cover the well's cross section area, giving a more accurate description of the flow behavior; thus better measurement and understanding of ADF phenomena. It has been observed from many production logging surveys that were conducted using a standard PLT, where the spinner shows negative readings during the flowing condition, indicating fluid re-circulation (or fluid fallback). However, information from other sensors such as fluid density identifier and temperature tool does not support these findings (of fluid re-circulation), which results in inaccurate rate calculation to determine zonal contribution. To overcome this challenge, the advanced PLT can be used to measure the contribution for each zone more accurately as the effects of ADF can be further understood. The calculated production rates from the advanced PLT were found to be more representative despite the presence of ADF in the wells. This paper discusses some case studies on the application of the advanced PLT in overcoming the challenges of quantifying zonal contribution in wells experiencing ADF.

This paper discussed Operator's experience on integrated downhole logging suite to diagnose multi-phase flow and to improve multi-reservoirs flow allocation in deviated wells, offshore Borneo Island. Field A is located in the West Balingian geological province of the Sarawak Basin, 140km offshore Bintulu in a water depth of 165ft. It was discovered in by Exploration Well #1 (EW#1), followed by downflank Appraisal Well #2 (AW#2) in 1982 and second Appraisal Well #3 (AW#3) in 2000, to address some of the significant subsurface uncertainties impacting on the field development plan. Phase-1 development wells (e.g. DW#1 and DW#2) was drilled and completed in 2014, with 7″ × 4-1/2″ cemented liner as lower completion across the clastic reservoirs. During pre-development in 2016, additional perforation in DW#1 oil zones were added whereas additional perforations in DW#2 oil zones were added in 2019. The two (2) relatively new wells produce commingled from several oil-bearing and gas-bearing zones. Developing highly compartmentalized multi-stacked reservoirs via simplified well completions, poses a great challenge for subsurface data acquisition when it comes to determining production allocation, managing flow assurance issues, understanding reservoir connectivity, surveillance of individual well performance and generating total field production forecasting. Conventional production logging result conducted in 2016 was unsatisfactory to explain some of the wellbore and reservoir flow peculiarities. Since it was important to know which zones contributed to the production, diagnostic of wellbore/reservoir flows and coupled with well integrity issues, Spectral Acoustic Logging with Thermo-Hydrodynamic Modeling was conducted to obtain the valuable information and to perform well/reservoir diagnostic. Remote platform location put an additional challenge to the logging campaign, as such the logging program was customized to satisfy the logging objectives while comply with HSE requirement. The collaborative approach between Operator and Service provider as solution partners, established a new finding for the formulation of remedial treatment to increase production and recovery from the wells by ensuring that each well operates to the maximum of its abilities.

In today's business paradigm, early monetization of resources is a key competitive edge. This requires an effective development plan fostered via sound cost-benefit analysis followed by the systematic and timely implementation of said plan. The drive to obtain faster oil has led to a comprehensive collaboration between PETRONAS and PSC Contractors in one of its biggest oil fields. Daisy Field is situated 170km off the coast of Terengganu, Malaysia and the first oil was discovered in 1991. The field reached its peak production in 1999 (90,000 bopd) and has undergone steep decline since then, with current average production of ~25,000 bopd. Using extensive historical surveillance and production data, an initiative was taken to identify and unlock remaining reserves. A new approach to an existing engineering technique called Locating the Remaining Oil (LTRO) has been applied in Daisy Field as an alternative to time consuming static-dynamic modelling. This new approach integrates cased hole log information, production data and decline curve analysis in order to identify bypassed or undrained oil that can be monetized through behind casing or infill drilling. This paper is a case study on the utilisation of LTRO for brownfield rejuvenation. LTRO is a low-cost but effective solution for idle well reactivation; it may accelerate identification of opportunities, which could be exploitable even during low oil prices, as prevailing currently. Following its deployment within the collaboration, reserves addition has been realized, value created and the cycle time for brown field development plan approval was reduced significantly. This paper will also demonstrate how integrated collaboration between host government, operator and service provider can be a good synergy for effective brownfield rejuvenation.