Mix-n-match Reservoir Coupling in Integrated Modeling and Optimization
Authors: Rahmawati Silvya Dewi , Hoda Mohammad Faizul , Wagner Daniel , Kuntadi Arif 
Published: March 2015

Reservoir Coupling (running multiple reservoir models in a concerted manner) features have been offered by software vendors for some time but with severe limitations. The participating models necessarily use the same vendor simulators and the models are usually limited to black-oil versions. This paper presents an integrated modeling and optimization solution with vendor independent participating simulators. The three reservoir models use simulators from different vendors (SENSOR®, ECLIPSE®, and MORE®). One model uses a black-oil PVT formulation while the other uses compositional PVT.

The reservoir with the black-oil PVT model will be post-processed using consistent and accurate black-oil to compositional stream conversions. Stream conversion will utilize split factor tables to convert each phase volumetric rate to component molar rates. The split factors are a function of pressure and phase and are pre-generated simultaneously with the black-oil PVT tables. Streams from a "reduced" compositional PVT reservoir model are post-processed with another set of split factor tables, which are also a function of phase and pressure. This will allow the automated conversion of the reduced (or pseudoized) molar rates to equivalent "process" feed molar rates.

The resulting comingled molar rates are delivered to the surface process simulator. An open source process simulator DWSIM® is used to model the common process facility. The sales products (gas, natural gas liquid (NGL), and oil) from the process facility model are priced in an economic model and the final results are in terms of the net present value (NPV). The optimization formulation maximizes the NPV while controlling key operating parameters of the integrated model.

The approach presented in this paper can be used for integrated modeling within production sharing contracts where different companies may insist on using different reservoir simulators.

Introduction

Integrated modeling and optimization are important tools in the oil and gas production business both for engineers or management. The advantage of having an integrated field modeling simulation from surface to sub-surface for a petroleum engineer are 1) helping to make decision regarding the field production with consideration of all aspects that are related to maximizing oil production and 2) thorough field production capabilities can be easily analyzed. While for the management team, the asset evaluation is the most important part in order to gain the highest profit and to make decisions that could increase company value during operation time.

This paper presents a reservoir coupling model in an integrated scheme between surface and sub-surface. The dynamic communication between the reservoir and surface facility is kept tight by introducing a project time step. The project time step will represent the time when the surface model is run and the input is updated based on the reservoir simulation results. Reservoir coupling is a part of the oil and gas industry, that could represent ownership from different companies/vendors. Each company usually runs the simulation using various simulators and/or PVT models. In this paper, the different reservoir simulation results will be honored and become an input to the surface facility model. The reservoirs will share the same surface facility model.