Managing an oil rim type reservoir has constantly been a great challenge and understanding the oil rim movement has remained as one of the main subsurface uncertainties. Prudent reservoir management through an active reservoir, well and facilities management (RWFM) plan is key to realizing the uncertainties, optimizing production and reserves of brownfields. Monitoring the oil rim through cased-hole reservoir saturation logging has been identified as a de-risking method, planned and executed for two consecutive years in the field to minimize the oil rim uncertainty. The field studied is one of the brownfields in offshore Sarawak, Malaysia, which has been on production for more than 40 years. Results acquired from the cased-hole logs have triggered the need to optimize the location of an infill oil producer planned in the Field Development Plan. The cased-hole results indicated that the original oil target in the N reservoir had mostly been swept by water. Through thorough studies and modeling, an opportunity to the western flank in M reservoir, located close to a proposed workover well, was suggested. Furthermore, latest input on the proposed workover well and facilities health check suggested the workover candidate was not favourable due to its location on an aging single well monopod structure with complex well mechanical problems. Thus, the planned infill oil producer was recommended to replace the workover well and recover the reserves. Integrated studies incorporated cased-hole results with reservoir modeling indicated that the new infill location would yield a total of 5.7MMSTB reserves with initial production rate of 1215BOPD. In addition, through integration of a multi-disciplinary team, revision to the infill location was timely and the infill was also accelerated from Phase II to Phase I of the development plan as a rig filler for cost optimization. Well test result successfully validated the reservoir productivity of 1238BOPD with no water production. This paper presents the integrated subsurface and surface solutions and criticality of proactive data acquisition, field monitoring and collaborative team work strategies to maximize the recovery from a brownfield.
This paper discusses a comprehensive study to address the uncertainties and troublesome major field development. The west Malaysia field has 7 platforms, and 110 wells. Production started in 1979. The highly complex, elongated anticline structure, possess over 330+ interpreted normal, reverse and wrench faults. It is deposited in Lower Coastal Plain within transgressive system tract. Despite the strong and consistent reservoirs production, recovery Factor (RF) remained at 19% indicating potential remaining value. The new look requirement were imposed as a result of disappointing drilling results mainly due to Key uncertainties in hydrocarbon redistribution, sand continuity and its quality, oil production across adjacent fault blocks. Multicomponent seismic was acquired, to establish an updated reservoirs framework and assist in mapping hydrocarbon, water as well as lithology identification (sand/shale/coal). Several wells were suspended based on the indicative study result. 85 new opportunities were identified, and tiered based on technical confidence and risk appetite. A roadmap consists of detailed development strategies spanning over 5 years and beyond associated with ~100MMstb reserves value that will bring the RF to 31% were proposed. Main study outcomes resulted of reducing sand distribution uncertainty, reservoir extension was clarified and confirmed with the new seismic interpretation result. By passed oil were mapped.
To further develop and recover reserves volume from a major oil field in Malaysia utilizing the latest and most premium seismic technology 3D 4C OBC. The overall field development was imposed due to a disappointing drilling results. Field A, located offshore West Malaysia, is a laminated Lower Coastal Plain sandstone deposited with occasionally marine transgressions. A highly complex, elongated anticline structure that possess over 330 interpreted normal, reverse and and wrench faults (normal, reverse and wrench). Production started in 1979. Despite the strong and consistent production, the Recovery Factor (RF) remains at 19% indicating potential remaining value. The time-consuming and costly azimuth 3D 4C OBC was acquired in 2015, to benefit from its capability in mapping hydrocarbon and water as well as lithology identification (sand/shale/coal). The 4C data was processed using 3D pre-stack. An improved continuity and sharpness of the main reflectors on the P/Z cube was clear to allow an efficient brown field redevelopment analysis specifically in the areas of infill and injectors well placements. Attributes maps were calibrated with newly acquired logs, and combined with re-evaluation of existing well logs and production data to ascertain development areas, and potential secondary recovery mechanism. Results were translated to static and dynamic models where possible, with 2D volumetric exercise for the smaller, and non-producing reservoirs. The opportunities identified were classified according to risk matrix, and uncertainties, an overall full-field redevelopment plan was proposed including an aggressive project tiring approach with fast execution process and higher risk appetite. Results coming from PP PSDM and PS PSDM confirmed the reasoning behind unsatisfactory outcome of 2015 infill campaign. The previously high uncertainty in sand distribution and reservoir extensions were clarified and confirmed with the new seismic interpretation result. Two wells were suspended based on the indicative result that showed addition of fault planes within the area. Subsequently, moving forward a total of 85 areas of new opportunities were identified and tiered based on technical confidence and risk appetite. A roadmap consists of detailed development strategies spanning over 5 years and beyond associated with ~100MMstb reserves value that will bring the RF to 31% were proposed and proceeded towards project sanctioning. The first four wells of its campaign was sanctioned, executed and spudded in August 2018. The objective while developing existing producing area is to target virgin location for additional data and to de-risk the undeveloped areas. The results from the first two wells allowed clearer picture of the complexity of the fields with mixed results combined with the operational challenges due to unexpected reservoir losses. Immediate recovery plans and decision matrix were quickly devised and re-entry and deviations were made to the original plans. The completed wells successfully produce up to 1100 stb/d, which was higher than the planned 750 stb/d. In addition to the completed targets, 6 BCO targets were also identified for future production enhancement activities.
Injecting energy into the reservoir is a suite of injection techniques used by the oil and gas industry for producing more oil. Injecting a large amount of water is called ‘waterflooding’ which improves oil production by sweeping the hydrocarbon fluids towards the producer well and by increasing the reservoir pressure. Waterflooding imposes a new set of challenges to understand the connectivity between wells, fault compartments, and reservoirs. Water flooding in mature fields offers a significant increase in secondary oil recovery and enhances the economic life of a field. However, to optimize the waterflood program, the level of detailed understanding of reservoir architecture has always been a challenge in complex structural regime field. This study presents innovative methods of integrating the seismically derived geo-cellular model into the dynamic model of closing the loop for improved understanding of the reservoir. The example presented here is from an offshore field, Sarawak Malaysia. The study area lies in the North West Balingian sub-province in Malaysia where the main reservoirs are of Oligocene to Lower Miocene age. Target reservoir consists of stacks of lower coastal plain sandstones interbedded with shale and coal that were deposited in an overall transgressive setting. The field consists of a very complex structural regime with multiple stacked reservoirs. There were more than 1200 faults captured in the structural interpretation of seismic data. Capturing the features of the fault compartments and defining the communications between blocks are important for predicting the water pathway, breakthrough time, and identifying beneficial wells. Due to the complex structural configuration with more than 250 fault compartments, it was challenging to design a fully integrated simulation model to examine in detail all aspects of the historical and planned development. This being the most challenging case a model was constructed which aimed to identify the location of the remaining oil for infill drilling, likely future production, and establish reservoir connectivity between the injectors and oil producers. In the constructed model seismic data was utilized in a unique way by integrating very detailed reservoir probabilities from stochastic inversion into rock physics modeled logs, sedimentological information, and geo-cellular model. At this stage, dynamic properties were integrated into the geo-cellular model to study the fault block communication. In the end, four unswept zones have been identified for future development. The necessity of optimizing secondary recovery in re-development campaign with fit-for-purpose seismically assisted simulation models designed in the ongoing brownfield development program. The integrated interpretation of detailed reservoir probabilities together with geo-cellular and dynamic modeling helped in understanding reservoir architecture. The study offers substantial benefits in order to plan the waterflood program for secondary oil recovery.
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