Summary Although the stacked reservoirs of the Bokor field, offshore Sarawak, Malaysia, are prone to sand production, the field-development team did not opt a priori for gravel packs in every well. While such completions can indeed eliminate sanding risk, the team also wanted to consider the impact of the completion on the production rate of a well. The optimum completion not only excludes sand, but it also maximizes hydrocarbon production. The team carried out a geomechanics and sand-production study, using readily available data. The paper gives an insight in the physics of sand production and how this process can be modeled geomechanically. It shows how the model is used to select feasible completions and quantify sand-free production rates over the life of the reservoir. One important outcome was that screenless completions were possible in the deeper reservoirs by optimizing perforation orientations. Apart from other advantages of screenless completions, this leads to significant potential increases in sand-free production rates. An integrated sand-management process brought together geomechanics, petrophysics, and reservoir and completion engineering to truly optimize completions. Introduction Certain questions have to be answered before completing a well in a weak-sandstone reservoir: Will sand production be an issue now, or as the reservoir depletes? If so, which completion options are feasible, and when do they need to be installed? Several techniques exist to prevent sand from being produced, from screens, gravel packs, or frac packs to optimized and oriented perforating, each with its own merits. But the choice of completion also has a major impact on hydrocarbon-production rates, and therefore on the lifelong economics of a well. To truly maximize sand-free hydrocarbon production, an integrated approach is needed. This includes reservoir knowledge from petrophysical and geomechanical interpretations, reservoir and production engineering, completion design, and implementation. If it can be shown that sand production is going to be a problem, screens, gravel packs, or frac packs can be run. The choice of sand-exclusion equipment will likely have an impact on productivity, which needs to be considered. The industry has become aware that oriented perforations can prevent sand production in many cases. Oriented-perforation completions have an advantage that they minimize the cost and complexity of the completion. More importantly, they also generally give higher production rates than a screen or gravel pack would give in the same well. Clearly, there is a need to predict reliably under which circumstances the technique of oriented perforating can prevent sand production. Geomechanical analysis can provide the answer. While no generally accepted models exist today that can predict rates or total amounts of sand production, we are able to predict the onset of sand production with reasonable accuracy. In many cases, such a prediction is enough to make an informed decision. The Bokor field in the Baram delta, offshore Sarawak, Malaysia, has produced oil since 1982. Its unconsolidated, stacked reservoirs are prone to sand production and were completed traditionally with gravel packs. In 2003, a full field-review study identified new development opportunities, including deeper, previously untapped reservoirs. Given new developments in geomechanics and sanding-prediction models, the study team did not opt a priori for gravel packs in every well. While such completions can indeed eliminate sanding risk, the team also wanted to consider the impact of the completions on the production rates of the wells. The optimum completion not only excludes sand but also maximizes hydrocarbon production over the life of the well. The team seized the opportunity to conduct a sanding-propensity study to gain an understanding of sand-production risks and to optimize completion designs. Geomechanical modeling played an important role in the study. In this paper, we aim to give an insight into some aspects of the physics of sand production and how the process can be modeled geomechanically. We explain how geomechanical models were built from readily available data and how the models were used to select feasible completions and compute critical drawdown pressures (CDP) for various completion scenarios. We discuss how this helps the Bokor-field study team quantify sand-free production rates, now and over the life of the reservoir, and we comment on the role of geomechanical modeling in the integrated, multidisciplinary approach that is needed to optimize completions.
The Dulang oilfield is located some 130 km offshore Terengganu in Peninsular Malaysia and is structurally complex. Production from the field began in March 1991, and oil recovery averaged 26,000 STB/D with peak production reaching approximately 50,000 STB/D. As with the other field developments in the Malay Basin, sand production was not anticipated under normal drawdown or producing conditions, and thus, all the wells in Dulang field were completed without any sand-control measures.In the later stages of the field's life, however, a significant amount of sand production was observed. This condition gradually increased over time, resulting in reduced hydrocarbon production, additional costs for routine wellbore sand clean-outs, and platform shutdowns for surface vessel sand clean-up.A wellbore opportunity study was initiated in 1999 to revitalize the field. The objectives of the study were to 1) identify remaining reserves, and 2) identify new completion options to maximize recovery. The study identified three major activities that would improve oil production: 1. Develop by-passed reserves behind casing 2. Reactivate idle wells that had been shut-in as a result of sand production. 3. Provide additional drainage points for undeveloped reserves.From the proposed wellbore opportunities study, ten wells were identified for a workover campaign, and six wells were identified for infill drilling or sidetracks.Sand production mitigation using a gravel-pack technique was identified as a requirement in the completion plan for the majority of the targeted reservoirs. However, the increase in mechanical skin that would result from a sand control installation was also recognized. Hence, it was determined that the best approach for production optimization in these wells would be a combination of a sand control and a stimulation technique. Several technologies, which included frac-andpack, extension pack with conductivity enhancer, and highrate water-pack (HRWP) gravel packing, were suggested. The use of a special completion tool that would enable greater flexibility on short string selective production in multi-zone gravel-packed wells was also identified.After careful review of the options, a combination of sand control and stimulation techniques (frac pack, extension pack and high-rate water pack) was selected, and the combined strategies have successfully increased the productivity and prevented sand production in the Dulang wells.
Moving into electronic age, completion tool and accessories are getting advanced. For the past 10 years, permanent downhole gauge (PDG) technology has been supported with tremendous investment in its research and development. This pacing technology is no longer new to the industry oil and gas operators. Some operators have made it as standard practice but however, some operators are still performing financial model analysis to justify for PDG installation. Is it a real need to install PDG or it is just another fancy luxury that give limited financial returns to the project? How much data is required by petroleum and reservoir engineer to understand the reservoir? This paper presents in detailed about the financial model analysis and demonstrates the tangible and intangible benefit of the PDG and the added value to full field life cycle.
The Dulang oilfield is located some 130 km offshore Terengganu in Peninsular Malaysia and is structurally complex. Production from the field began in March1991, and oil production averaged 26,000 STB/D with peak production reaching approximately 50,000 STB/D. As with the other field developments in the MalayBasin, sand production was not anticipated under normal drawdown or producing conditions, and thus, all the wells in Dulang field were completed without any sand-control measures. In the later stages of the field's life, however, a significant amount ofsand production was observed. This condition gradually increased over time,resulting in reduced hydrocarbon production, additional costs for routinewellbore sand clean-outs, and platform shutdowns for surface vessel sandclean-up. In 1991, eight years after initial development, a wellbore opportunity study was initiated to revitalize a section of Dulang field. The objectives of the study were toidentify remaining reserves, andidentify new completion options to maximize recovery. The study identified three major activities that would improve oil production:Develop by-passed reserves behind casingReactivate idle wells that had been closed in, some as a result of sand production.Provide additional drainage points for undeveloped reserves. From the proposed wellbore opportunities study, ten wells were identified for a workover campaign, and six wells were identified for infill drilling or sidetracks. Sand production mitigation using a gravel-pack technique was identified as a requirement in the completion plan for the majority of the targeted reservoirs. However, the increase in mechanical skin that would result from a sand control installation was also recognized. Hence, it was determined that the best approach for production optimization in these wells would be a combination of a sand control and a stimulation technique. Several technologies, which included frac-andpack, extension pack with conductivity enhancer, and highrate water-pack (HRWP) gravel packing, were suggested. The use of a special completion tool that would enable greater flexibility on short string selective production in multi-zone gravel-packed wells was also identified. After careful review of the options, a combination of sand control and stimulation technique (frac pack, extension pack and high-rate water pack) was selected, and the combined strategies have successfully increased the productivity and prevented sand production in the Dulang wells. Introduction The Dulang oilfield is located about 130 km offshore Kuala Terengganu, Malaysia. Fig. 1 shows the Dulang Field location. The main reservoir is comprised of Dulang E sands, which are of late Miocene age and consist ofalternating sequences of sands deposited in a tidal flat environment. The reservoir faults are complex and are in a westward plunging anticline. They compartmentalize the Dulang field into 16 subblocks. Stratigraphically, 20reservoir units have been identified in Dulang field. Drive mechanism is edge water, gas cap expansion and solution gas drive. Fig. 2 is a 3-D visualization of the Dulang Field, and Fig. 3 shows the field blocks. When production from the field began, the average production was 26,000STB/D, and during peak production from the field, it was producing nearly double that amount.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.