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Collaborating Authors
Results
Abstract BONGKOT South field is a multilayer retrograde gas condensate reservoirs field. The condensate –gas ratio (CGR) and condensate production forecasts are a major challenge of the field especially with monobore well completion which has limited zonal contribution data. This paper describes how the pressure-based CGR framework with integrated reservoir engineering data analysis is introduced to improve the forecast accuracy and enhance reservoir behavior intuition compared to the existing empirical methodology, CGR versus cumulative production. The framework adopts the pressure-based CGR correlation which can model the retrograde condensation while maintaining simplicity for practical use. The proposed framework is split into 2 sections. The producing CGR parameters are established through history matching with actual production data using integrated information to enhance intuition on the CGR behavior which improve the accuracy of the CGR matching and forecast. The non-producing CGR is estimated using the established CGR correlations which were constructed based on the sample with CVD analysis and all single reservoir production data. The estimated CGR then apply to the simulator result to get the condensate forecast. The forecasted field condensate rate during plateau period ranges between 8,000 to 11,000 STBD with single reservoir initial CGR and field average producing CGR varies in range of 15 – 120 STB/MMSCF and 17-28 STB/MMSCF respectively. Field blind test was also performed to validate the framework which shows mismatch in a total condensate volume of less than 3% over a total raw gas volume of 47 BSCF. Results from various well-level CGR history match show different CGR decline behaviors of retrograde gas condensation and vaporization at lower reservoir pressure. The matching of such behavior can be achieved by the proposed framework which adopts pressure-based correlation while the existing production based correlation cannot. The proposed framework has demonstrated that BONGKOT South operators can accurately predict well producing CGR for prudent reservoir management and development. Well-structured integrated data analysis during CGR history match provides better intuition into reservoir behavior which could guide engineer to better reservoir management decision. The established CGR trend could also be used by external optimizer module, e.g. LINOPT, as CGR decline input to better optimize the longer-term condensate recovery.
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Gas-condensate reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
- Information Technology > Data Science (0.75)
- Information Technology > Modeling & Simulation (0.49)
Abstract The Sarawak Integrated Gas Network is one of the largest and arguably most complicated offshore gas networks in the world due to its intricate physical layout comprising of more than 20 fields producing with total capacity of more than 4000 MMscf/d, supplying to 3 LNG plants. As there are various operators in the network operating different Production Sharing Contracts (PSCs) and Gas Sales Agreements (GSA), commercial arrangements are essential to govern the production policy of the network to ensure PSC and GSA obligations and/or entitlements are honoured. Gas quality management by blending of gas is another aspect to be considered as each of the 3 LNG plants have constraints on contaminants such as CO2 and H2S and each field has varying contaminant levels. Integrated Production Systems Model (IPSM) is used extensively for the production forecast of integrated gas networks as pressure interaction via surface network between the different wells have a significant impact on the reservoir performance. However, due to the combination of physical and commercial constraints of the Sarawak Gas Network and the additional complexity due to contaminants management, generic IPSM models are unable to accurately handle both physical and commercial requirements. As such, the traditional workflow for Sarawak Gas Network required a workaround where IPSM models are used in combination with post processing spreadsheet to manually tweak production forecasts in order to honour commercial and gas quality constraints. This was cumbersome and also negated the real benefits of IPSM. The recent rebuild of the Sarawak IPSM model with the Shell proprietary tool, "Hydrocarbon Field Planning Tool" (HFPT), addresses this challenge by incorporating the commercial arrangements within the model. This is made possible as HFPT allows for flexible scripting which enables asset specific functionality to be modeled. The approach is essentially a 2 step approach within HFPT, where field capacity is derived based on physical constraints (as per generic IPSM models) and a second step where production nomination is managed with a series of rules designed to mimic operational practices to align production nomination with commercial arrangements and for gas quality management. The Sarawak HFPT model has been used extensively for Business Planning and resource reporting exercises to ensure the production forecasts are robust and credible. With this novel approach, the revamped Sarawak IPSM model is capable of generating production forecasts which integrates both commercial and physical constraints as well as contaminants management without the need to evaluate the commercial arrangements as a post processing step.