Bokor--A New Look at Sand Production in a Mature Field
- Abdullah Bin Kasim (Petronas Carigali Sdn Bhd) | Frank M. Wijnands (PT Schlumberger Geophysics Nusantara) | Surej K. Subbiah (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- December 2008
- Document Type
- Journal Paper
- 415 - 423
- 2008. Society of Petroleum Engineers
- 2.4.5 Gravel pack design & evaluation, 1.2.2 Geomechanics, 5.6.9 Production Forecasting, 5.6.1 Open hole/cased hole log analysis, 1.2.3 Rock properties, 4.1.5 Processing Equipment, 2.2.2 Perforating, 2.4.6 Frac and Pack, 5.5.11 Formation Testing (e.g., Wireline, LWD), 5.3.4 Integration of geomechanics in models, 1.6 Drilling Operations, 2.4.3 Sand/Solids Control, 3.2.5 Produced Sand / Solids Management and Control, 5.1.2 Faults and Fracture Characterisation, 5.5 Reservoir Simulation
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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.
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.
|File Size||4 MB||Number of Pages||9|
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