3d Compositional Reservoir Simulation in Conjunction With Unstructured Grids

Abstract

-In the last decade, unstructured grids have been a very important step in the development of petroleum reservoir simulators. In fact, the so-called third generation simulators are based on Perpendicular Bisection (PEBI) unstructured grids. Nevertheless, the use of PEBI grids is not very general when full anisotropic reservoirs are modeled. Another possibility is the use of the Element based Finite Volume Method (EbFVM). This approach has been tested for several reservoir types and in principle has no limitation in application. In this paper, we implement this approach in an in-house simulator called UTCOMP using four element types: hexahedron, tetrahedron, prism, and pyramid. UTCOMP is a compositional, multiphase/multicomponent simulator based on an Implicit Pressure Explicit Composition (IMPEC) approach designed to handle several hydrocarbon recovery processes. All properties, except permeability and porosity, are evaluated in each grid vertex. In this work, four case studies were selected to evaluate the implementation, two of them involving irregular geometries. Results are shown in terms of oil and gas rates and saturated gas field.

Development of an embedded discrete fracture model for 2D and 3D unstructured grids using an element-based finite volume method

“…The EbFVM is a general approach that can be applied to both 2D and 3D unstructured grids. Because of its flexibility in the discretization of the domain and convenience of implementation in simulators that can construct arbitrary connections between gridblocks, this approach was implemented in UTCOMP-RS, an in-house, multi-component reservoir simulator for both two-and three-dimensional simulations (Marcondes and Sepehrnoori, 2010;Marcondes et al, 2013;Araújo et al, 2016;Fernandes et al, 2016). The simulator uses an implicit-pressure, explicit-composition (IMPEC) formulation.…”

“…11d) pyramid elements. This grid was used by Araújo et al (2016) for a gas-flooding simulation. As can be seen, a "hole" was added in this grid to represent a low-permeability zone.…”

“…Unstructured grids have been used in reservoir simulation to represent geologically complex reservoirs (Fung et al, 1992;Durlofsky and Chien, 1993;Verma and Aziz, 1997;Prévost et al, 2002Prévost et al, , 2005Edwards, 2002;Hoteit and Firoozabadi, 2006a;Vitel and Souche, 2007;Sepehrnoori, 2007, 2010;Araújo et al, 2016;Fernandes et al 2016Fernandes et al , 2017Samier and Masson, 2017). In comparison with structured grids, unstructured grids are more capable of representing irregular reservoir structures and reservoir boundaries, as they provide more flexibility regarding the geometry of gridblocks and their discretization.…”

Development of a fully implicit approach with intensive variables for compositional reservoir simulation

“…UTCOMPRS is a modified version of the UTCOMP simulator, which initially was developed by Chang (1990), Chang et al (1990), Perschke (1988), Perschke et al (1989a), andPerschke et al (1989b) that considers up to four phase flow (water, oil, gas, and a second oleic phase) with rigorous flash and phase stability calculations. UTCOMP was originally implemented using the Acs et al (1985) IMPEC approach using Cartesian grids and since the original implementation has been the subject of several improvements and the addition of new capabilities such as unstructured grids (Fernandes et al, 2012;Araújo et al, 2016), corner point (Fernandes et al, 2014a), TVD schemes for unstructured grids (Fernandes et al, 2013;(Fernandes et al, 2015a), high performance computing (Doroh, 2012), to name few improvements in the UTCOM-PRS simulator. The enhanced simulator is referred to as UTCOMPRS.…”

A TVD scheme for 3d unstructured grids applied to compositional reservoir simulation

“…The EbFVM implemented in the UTCOMP simulator are based on Marcondes and Sepehrnoori (2010), Marcondes et al (2013) and Santos et al (2013) for the General Purpose Adaptive Reservoir Simulator (GPAS). In UTCOMP, the implementation for 2D and 3D unstructured grids using the EbFVM and the IMPEC approach are presented in Fernandes et al (2012) and Araújo et al (2016). Additionally, IMPSAT (Implicit Pressure and Saturations) approaches (Fernandes et al, 2014;Fernandes et.…”