João Carlos von Hohendorff Filho

Evaluation of Explicit Coupling Between Reservoir Simulators and Production System

In recent years, the oil industry has used various methodologies to solve numerical coupling of reservoirs and production systems to properly model complex projects needing an integrated solution of computational models that represent the fluid flow through the reservoir up to the surface. We present a study of explicit coupling methodology testing the production system on common operating conditions, verifying the benefits and quantifying limitations of explicit methodology, due to numerical stability errors reported in literature.

Evaluation of Reservoir and Production System Integration in Production Strategy Selection

In offshore petroleum field studies, the integration between reservoir and production system simulators may improve production forecasts. Therefore, it is important to check if this integration is necessary and a methodology to do it adequately. In this work, we analyzed the influence of this integration in the development of a petroleum field focusing on the effects on the production strategy parameters for a benchmark model based on an offshore field in Brazil. The methodology is based on a 12-step procedure for closed loop reservoir development and management. The production facilities are integrated with the reservoir in Step 11 and we propose to reoptimize the production strategy using information about pressure gradients inside the satellite well pipes for production forecast, while evaluating net present value as the objective-function. We adapted an assisted optimization workflow to include the optimization of new variables such as, pipe diameters of production system, platform position and artificial lift application, and compared this with the production strategy obtained from the same benchmark in a nonintegrated approach. Comparing nonintegrated and integrated production strategies, we observed changes that indicate the need to integrate reservoir and production systems in the decision making process. (1) Platform position was more affected by economic indicators than production loss due to pressure drop in flowlines. (2) Economic return and field oil recovery were significantly affected by the diameters of the production pipes. Artificial lift application with high gas injection rates enhanced well performance. (3) A reoptimization of the number of wells had little effect on the cumulative oil production but larger influence on net present value, indicating potentially unnecessary wells in a nonintegrated project. (4) The integration demanded further optimization of well placement, significantly impacting both net present value and the recovery factor. The integrating production facilities with the reservoir, generated a significant increase in the net present value, maintained the same oil recovery factor and required less investment. All manuscripts will be sent through an XML markup process that will standardize the look and layout of the paper. Figures and table will be placed directly after the first paragraph they are mentioned in. This will not alter the content of the paper in any way. Event specific copyright information will be added during the XML process.

Production Strategy Selection for a Naturally Fractured Carbonate Reservoir from Campos Basin

Post-salt carbonate fields are produced by depletion for more than thirty years in Campos basin, Brazil. Usually, they have recovery factors lower than 10%. This article presents a naturally fracture reservoir (NFR) simulation study with undersaturated pressure with no active gas cap and a small aquifer. This work includes a reservoir decision analysis which was done using uncertainty analysis, assisted optimization, comparison among strategies and a reliability test to check how production strategy results behaves when uncertainty parameters are used. The goal is to present a secondary recovery method to improve oil recovery for this field using the best strategy among water, gas, water and gas and immiscible water-alternating gas (IWAG) injection. Although those methods are highly used for carbonates among oil industries worldwide they are not commonly used in carbonates fields located offshore Brazil, especially in carbonates with oil or mixed wettability. Selection of the best production strategy for this reservoir was determined through a full-field simulation using a commercial simulator with double porosity model. The main application of this work is the possible implementation of a new production strategy that can change paradigm at how carbonates are produced offshore Brazil. The results and conclusion are based on alternatives to maximize oil production and net present value (NPV). Comparison among the production strategies indicated water injection as the best way to produce this type of reservoir. The results showed that this method is robust because its economic results did not alter when different parameters representing the major uncertainties were used. Further studies and implementation of water injection as secondary recovery strategy can boost production at new and mature fields for the huge carbonate play located at the post-salt part of Campos Basin. Indeed, any successful production strategies for carbonates have potential to be extended to pre-salt fields. Introduction Reservoir heterogeneities increase practical and theoretical problems for understanding fluid flow among rocks that contain them. NFR is highly heterogeneous and its characterization, production mechanisms, modeling and simulation are completely different from conventional reservoir. Reservoir production mechanisms in naturally fractured reservoirs are more complex than single porosity reservoirs because, in addition to matrix properties, fracture system properties and factors controlling fluid exchange between the matrix and fractures should be analyzed. Oil recovery factors at this type of reservoir vary greatly because its production depends on matrix flow, fracture system connectivity, matrix-fracture iteration, wettability and how those factors affect the main production mechanism. Early identification of a fractured reservoir is very important to avoid field jeopardy; indeed if the correct treatment and production strategy are applied since the beginning of the field plan, the results will be reliable production curves, good reservoir management and higher recovery efficiency. Depletion in a fractured reservoir generates fluid expansion; fluids are then transferred from matrix to fractures. Simultaneously capillarity, gravity, heterogeneity and capillarity continuity can increase or decrease fluid recovery from matrix system. If injection is performed, fluid injected can easily surpass matrix and reach fractures leaving a lot of bypassed oil what usually results in inefficient displacement.. This is the main reason why the use of secondary recovery for NFR and carbonates is limited in Brazilian’s post-salt carbonate fields. Pressure maintenance is important for reservoir management and this is valid for any type of reservoir, even NFR where higher pressure increases imbibition in spite of rock wettability.

Evaluation on Explicit Coupling Between Reservoir Simulators and Production System

Various methodologies to model the coupling of reservoirs and production systems have been applied in the oil industry in recent years due to the need to model properly the integrated solution of models that represent the flow of fluids through the reservoir to the surface.These methodologies are used to solve the production forecast of multiple reservoirs, sharing production platforms with limited production e injection capacities ruled by complex production systems. They can be grouped into two basic types: implicit and explicit coupling methodologies.Explicit methodology can be an efficient choice to integrate simulations because allows coupling adequate simulators to model the whole system and also to grant flexibility in study of well management alternatives. However, it is necessary to test this type of procedure to check the quality of the results. Therefore, a validation study of explicit coupling methodology is presented in this work where the production system is tested on common operating conditions during production and injection of fluids, verifying benefits and limitations of explicit methodology. Some methods for improving the explicit response are proposed and evaluated.An example of application verifies the gain of flexibility in well prioritization by the group management obtained by use of an external methodology for reservoir simulator.The explicit coupling, as implemented, has shown a satisfactory result for the integration between the simulators, honoring all operating constraints set in evaluation cases. Some correction methodologies are necessaries to obtain stabilized results.© 2012 ASME