a b s t r a c tThe oil field development is a hard and critical task that defines the main procedures to be performed during the oil field productive life. Given the complexity of this planning phase, methods to support decision making have been developed to assist in the proper application of high investments. This paper aims to report a 0-1 Linear Programming Model which minimizes the development costs of a given oil field as a whole. The model seeks to define: the number, location and capacities of production platforms; number and positions of wells; points where manifolds must be installed; interconnection between platforms, manifolds and wells; and which sections of each well should be vertical or horizontal. The model was named Multicapacitated Platforms and Wells Location Problem (MPWLP). Two different scenarios were tested and the results were consistent with reality, computationally feasible and presented innovations compared to models found in literature.
WAG (Water-Alternating-Gas) schemes have been applied in Brazilian carbonate reservoirs aiming to minimize residual oil saturation and gas flaring by recycling CO2 naturally being produced alongside hydrocarbon gas. However, applying WAG injection in highly reactive and heterogeneous carbonate rocks can potentially create severe scaling problems. This work develops a reactive transport simulation-based workflow to evaluate the impact of key WAG design parameters on oil recovery, scale deposition risk and CO2 storage to support multi-objective decision-making. Compositional simulations of WAG scenarios were performed as part of a sensitivity study followed by statistical analysis in order to quantify to what extent the outcomes of interest are sensitive to variations on four WAG design parameters: WAG ratio, CO2 concentration in the injection gas stream, injection rate and solvent slug-size. We established an Equation-of-State (EoS) using PVT data, a representative geochemical model and well constrains designed to control production of injected fluids. Scale risk was assessed by calcite changes around the wells, precipitation in well tubing and surface facilities, and water breakthrough. Results of this study showed that values of calcite rate constant (Ksp) and reactive surface area (A0) assigned in numerical simulations can impact relative calcite changes in the reservoir. Using reactive surface areas from BET studies of crushed rocks can lead to prediction of unrealistic amounts of calcite dissolution. Cases with lower values of (Ksp×A0) appeared to be more numerically stable and more consistent with dissolution/precipitation rates of silicate minerals. Simulation results also suggested that calcite dissolution close to injection wells and precipitation in production wells and surface facilities become more severe as CO2 concentration in injection gas and WAG ratio increases. Based on the design variables and reservoir conditions studied, the most to least crucial factors affecting oil recovery were: CO2 concentration in the injection gas stream, injection rate, WAG ratio and solvent slug-size. From a storage perspective, the impact of the design variables had considerably more impact, with the most influential factor being again CO2 concentration in the injection gas stream, followed by WAG ratio, injection rate and solvent slug-size. Optimization study results suggested that low WAG ratio values combined with low to intermediate gas slug sizes could result in superior profitability and CO2 storage outcomes for this pilot. Ultimately, we demonstrate the importance of integrating multiphase miscible displacement with geochemical reactions while modeling complex CO2-EOR in carbonate reservoirs and address how key design parameters impact our desired outcomes, knowledge that promotes a more robust decision-making framework.
CO2-WAG injection has been applied in offshore Brazilian carbonate reservoirs aiming to improve oil recovery and promote a safe destination to CO2 naturally being produced alongside with hydrocarbon gas. A gas reutilisation strategy can potentially lead to multiple benefits: residual oil saturation reduction, maintenance of reservoir pressure, avoidance of gas flaring and development of the infrastructure and expertise necessary to make CO2 storage more accessible once oil production is complete, paving the path for a low carbon future, whereas mature basins can be a potential hub for Carbon Capture, Utilisation and Storage (CCUS). This study aims to develop a methodology to design CO2-WAG projects that not only achieve a high Net Present Value (NPV) but also maximizes the capacity and safety of geological CO2 storage.
CO2-WAG (Water-Alternating-Gas) has been applied in offshore Brazilian oilfields to improve recovery rates and mitigate the environmental impact that venting produced CO2 would bring. Although CO2 is highly miscible in oil under these reservoirs conditions, this gas is also extremely mobile, and its speciation in the aqueous phase drives reactions with carbonates that can cause severe inorganic scaling problems in production systems. It is crucial, therefore, to effectively design CO2-WAG operations for mobility control and, consequently, enhance reservoir performance, CO2 utilization and flow assurance. This paper addresses the design optimization of coupled CO2-EOR and storage operations applied to the Brazilian Pre-salt offshore context (reservoir properties, infrastructure, regulatory framework and economic characteristics), examining the trade-offs of project profitability, CO2 utilization and calcite scale risk. Several compositional simulations of miscible WAG scenarios were performed and key design parameters were optimized using statistical sampling and evolutionary algorithms. Aqueous and mineral reactions were included in the calculations, allowing us to quantify the calcite mass that can potentially deposit in the perforations and production system. The results showed how optimizing WAG operations can significantly improve the economics and the scale management of oil production from carbonate reservoirs. The optimal WAG design greatly increased incremental NPV per volume of CO2 stored and reduced calcite scale risk by simply rearranging the WAG slugs in a tapered manner. Here we demonstrate that this methodology can be used to determine how to recycle CO2 in a given field for better economics and lower carbon footprint, doing so without triggering calcite mineral deposition to the point of permanent jeopardy of production wells and facilities operability. Therefore, the workflow integrates critical challenges that are correlated, yet often addressed independently, supporting the complex decision-making of CO2-EOR operational design in carbonate reservoirs.
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