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Results
Abstract The objective is to use future simulated well behavior to optimize well management within a complex reservoir simulation model. This can be used to increase simulated plateau life and reserves. Traditional well management systems often rely on instantaneous well potential to choose guide rates to determine the well allocation within a group of wells. This has proved to be a very effective strategy. However, for the problem of plateau optimization, one can observe the high instantaneous potential of many wells after the plateau is exhausted; this is because the traditional well management system has no knowledge of future behavior. In this work, the future behavior of all the wells and groups with a large and complex giant reservoir simulation model is determined by spawning a coarsened "Look-Ahead model" (LAM). This is performed concurrently, while the main model is still running. After a pre-determined simulation time the LAM model is harvested by the main model, and approximate future behavior is integrated into the well management system of the main model. One simple yet effective technique is to evaluate the current potential of the well to be an average of the current instantaneous potential and the future potential, in, for example, 10 years ahead of the current simulations time. Thus wells whose future performance is inhibited because of high GOR or high water cuts will get there current allocation reduced, and wells with future high potential will get allocated more rate. The use of LAM models is demonstrated in a water flood problem to increase plateau time of a large and complex reservoir model. The LAM model is automatically constructed by collapsing the grid, maintaining some resolution of the current wells and future wells, and coarsening heavily the areas of the grid with spent wells. By doing so a 10x improvement in elapse time of the LAM model, which enables the frequent spawning of LAM models from the main model, and a subsequently the most up-to-date LAM model is integrated into the main well management system. The use of LAM to approximate future behavior of wells, and integrated this behavior into the well management of the reservoir simulator is a novel and practical approach to further optimize the well management system of a reservoir simulator.
Abstract Computational Stratigraphy (CompStrat) is a state-of-the-art earth-modeling method that captures the key heterogeneities in subsurface reservoirs through modeling of the detailed flow and sediment transportation processes in various depositional environments. The method is fully based on physics and generates high-resolution 3D earth models that are much more geologically realistic than those generated by traditional earth-modeling methods. It can accurately predict and preserve those spatially continuous but vertically thin and volumetrically insignificant layers, such as shale layers, thus enabling a much more accurate representation of natural reservoir connectivity. In the past few years, CompStrat has been studied mainly within the earth science community and has yet been broadly applied in reservoir simulation research and practices. Our objective is to bridge this gap and allow this frontier technology to offer geologically realistic earth models for reservoir simulation to better understand how various geological features contribute and control subsurface flow patterns and performance, and subsequently leading to a better integration among earth modeling, flow simulation, and more reliable reservoir performance predictions. CompStrat models often have large number of cells (hundreds of millions or more). A large proportion of them are related to thin shale layers. These thin cells can often cause convergence difficulties in reservoir simulations. We developed a grid coarsening method to drastically reduce the cell number and the simulation time with minimum altering of overall model connectivity characteristics. The method reduces the cell number by 85% to 93% and the simulation time by 94% to 99.4% with limited loss of accuracy for representative examples. Without this method, the simulation may take impractically long time to run for large models with complex multiphase flow dynamics. The successful removal of the computational bottleneck enables the application of this frontier earth-modeling method in high-fidelity reservoir simulation. It also facilitates detailed understanding of the connection between geology and flow to offer valuable insight for reservoir modeling, production forecast uncertainty analysis, and history matching. We developed a method to label, evaluate, and rank geological features based on their influence on flow performance, with shale layers being the specific focus. The labeling is performed semi-automatically and the evaluation and ranking is done efficiently with a reduced-physics solver. The result is statistically consistent across multiple realizations.
- Geology > Sedimentary Geology (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Geological Subdiscipline (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation > Scaling methods (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Summary The representation of faults and fractures using cut-cell meshes often results in irregular non-orthogonal grids. Simple finite volume approaches fail to handle complex meshes because they are highly prone to grid orientation effects and only converges for K-orthogonal grids. Wide stencil approaches and higher order methods are computationally expensive and impractical to adopt in commercial reservoir simulators. In this work, we implement an Enriched Galerkin (EG) discretization for the flow and transport problems on non-orthogonal grids. The EG approximation space combines continuous and discontinuous Galerkin methods. The resulting solution lies in a richer space than the the two-point flux approximation (TPFA) method and allows a better flux approximation. It also resolves the inconsistencies that are usually associated with TPFA scheme. The method is tested for various non-orthogonal mesh configurations arising from different fault alignments. The performance of the scheme is also tested for reservoirs with strong anisotropy as well as reservoirs with heterogeneous material properties.
Abstract Discretization methods have been developed to accompany a novel cut-cell gridding technique for reservoir simulation that preserves the orthogonality characteristic in the lateral direction. A major drawback of the cut-cell gridding method is that polyhedral cells emerge near faults that have relatively small volumes. Pragmatic but non-rigorous approximation methods have been developed in the past to merge these cells with their neighbors so that the grid representation fits the two-point flux approximation (TPFA) framework. In this work, we take a different approach and investigate the global and local applications of select consistent discretization methods in the vicinity of fault representations on cut-cell grids. We develop and test consistent discretization methods that are of low computational cost and do not require major intrusive changes to the solver structure of commercial reservoir simulators. Cell-centered methods such as multi-point flux approximation (MPFA), average multi-point flux approximation (AvgMPFA), and nonlinear two-point flux approximation (NTPFA) methods fit naturally into the framework of existing industrial-grade simulators. Therefore, we develop and test variants of the AvgMPFA and NTPFA methods that are specifically designed to operate on cut-cell grids. An implementation of the well-established but computationally expensive MPFA method is also made for cut-cell grids to serve as a reference to computations with AvgMPFA and NTPFA. All investigated methods are implemented within the framework of a full-physics 3D research simulator with a general compositional formulation, which encompasses black-oil models. We use a set of synthetic cut-cell grid models of varying complexity including conceptual models and a field-scale model. We compare the novel cut-cell adapted AvgMPFA and NTPFA simulation results in terms of accuracy and computational performance against the ones computed with reference MPFA and TPFA methods. We observe that AvgMPFA consistently yields more accurate and computationally efficient simulations than NTPFA on cut-cell grids. Moreover, AvgMPFA hybrids run faster than NTPFA hybrids when compared on the same problem for the same hybridization strategy. On the other hand, the computational performance of AvgMPFA degrades more rapidly compared to NTPFA with increasing "rings" of orthogonal blocks around cut-cells owing to its relatively wider stencil. Auspiciously, only one or two "rings" of orthogonal blocks around cut cells are sufficient with AvgMPFA to deliver high accuracy.
- Europe (1.00)
- North America > United States > Texas (0.46)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (0.93)
- (2 more...)
Implementing a Hardware Agnostic Commercial Black-Oil Reservoir Simulator
Szyndel, Matthew (SLB) | Lemon, Christopher (SLB) | de Brito Dias, Daniel (SLB) | Dodds, Eamon (SLB) | Khramchenkov, Eduard (SLB) | Rinco, Simone (SLB) | Sheth, Soham (SLB) | Tene, Matei (SLB) | Han, Choongyong (Chevron) | Shi, Xundan (Chevron) | Wolfsteiner, Christian (Chevron) | Cao, Hui (TotalEnergies) | Liao, Terrence (TotalEnergies) | Sekachev, Michael (TotalEnergies) | Zaydullin, Rustem (TotalEnergies)
Abstract Commercial reservoir simulators have traditionally been optimized for parallel computations on central processing units (CPUs). The recent advances in general-purpose graphics processing units (GPUs) have provided a powerful alternative to CPU, presenting an opportunity to significantly reduce run times for simulations. Realizing peak performance on GPU requires that GPU-specific code be written, and also requires that data are laid out sympathetically to the hardware. The cost of copying data between the CPU memory and GPU memory at the time of this writing is egregious. Peak performance will only be realized if this is minimized. In paper Cao et al., 2021, the authors establish approaches to enable a simulator to give excellent performance on a CPU or GPU, with the same simulation result using either hardware. We discuss how their prototype was generalized into high-quality, maintainable code with applicability across a wide range of models. Different parts of a reservoir simulator benefit from different approaches. A modern, object-oriented simulator requires components to handle initialization, property calculation, linearization, linear solver, well and aquifer calculations, field management, and reporting. Each of these areas will present architectural challenges when broadening the scope of the simulator from CPU only to supporting CPU or GPU. We outline these challenges and present the approaches taken to address them. In particular, we discuss the importance of abstracting compute scheduling, testing methods, data storage classes, and associated memory management to a generic framework layer. We have created a high-quality reservoir simulator with the capacity to run on a CPU or GPU with results that match to within a very small tolerance. We present software engineering approaches that enable the team to achieve and maintain this in the future. In addition, we present test outcomes and discuss how to achieve excellent performance. To our knowledge, no simulator capable of both CPU simulation and full GPU simulation (meaning simulation with no copies of full grid-size data for purposes other than reporting) has been presented. We will present novel software approaches used to implement the first such commercial simulator.
- North America > United States > Texas (1.00)
- Europe (1.00)
- Asia > Middle East (0.68)
- Europe > United Kingdom > Atlantic Margin > West of Shetland > Faroe-Shetland Basin > Rona Ridge > Block 206/9 > Clair Field (0.99)
- Europe > United Kingdom > Atlantic Margin > West of Shetland > Faroe-Shetland Basin > Rona Ridge > Block 206/8 > Clair Field (0.99)
- Europe > United Kingdom > Atlantic Margin > West of Shetland > Faroe-Shetland Basin > Rona Ridge > Block 206/7 > Clair Field (0.99)
- (2 more...)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- Reservoir Description and Dynamics > Fluid Characterization > Fluid modeling, equations of state (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (0.68)
An Adaptive Grid Refinement Method for Flow-Based Embedded Discrete Fracture Models
Li, Junchao (Xi'an Shiyou University) | Tang, Huiying (Southwest Petroleum University) | Zhang, Yongbin (Research Institute of the Tarim Oilfield, CNPC) | Li, Xin (Research Institute of Petroleum Exploration and Development, CNPC)
Abstract Projection-based embedded discrete fracture models (pEDFMs) are proven effective for modeling flow barrier effects of high-conductivity or impermeable fractures. However, local grid refinements are still needed to improve the accuracy of simulation in flow areas near fractures. In recent years, adaptive grid refinement techniques have received a lot of attention for dealing with highly heterogeneous and fractured models. But few of them are capable of EDFMs. In this paper, an adaptive grid refinement method under flow-based EDFMs (fEDFMs) is proposed for fractured models. The method starts from an fEDFM model which is built by a new technique of transmissibility modification by introducing an artificial pseudo-steady flow near fractures. Adaptive grid refinement and coarsening procedures are designed under an adaptive criterion based on both the fracture distribution and flow solutions. A flow-based upscaling procedure is adopted to form transmissibilities of the hybrid grids and the solution is mapped from the former grid system. The adaptive grid refinement method is applied in a validation case and a real field case, respectively. In each case, comparisons are made between the simulation results of the proposed adaptive grid refinement models and traditional uniform pEDFMs. Besides, comparisons are also made with the overall fine-scale models which serve as the reference models. The comparisons show that the numerical results of the proposed models have a better match to that of the reference models. And it is proven that the approach is more robust when applied to more general flow scenarios with extremely high or completely sealed fractures which could have a great impact on the flow. The proposed method aims to improve the accuracy of numerical simulation for fractured reservoirs.
- Asia > China (0.28)
- North America > United States > Texas (0.28)
An Integrated Modeling Framework for Simulating Complex Transient Flow in Fractured Reservoirs with 3D High-Quality Grids
Liu, Hui (China University of Petroleum Beijing) | Liao, Xinwei (China University of Petroleum Beijing) | Lie, Knut-Andreas (SINTEF Digital) | Klemetsdal, øystein (SINTEF Digital) | Bao, Kai (SINTEF Digital) | Zhao, Xiaoliang (China University of Petroleum Beijing) | Johansson, August (SINTEF Digital) | Raynaud, Xavier (SINTEF Digital)
Abstract Modeling near-well transient flow with complex 3D fracture networks poses several challenges: the multiscale nature (millimeters to kilometers), long and deviating well trajectories, intricate fracture networks with fracture-fracture and fracture-well intersections, and high level of reservoir heterogeneities. We address these difficulties by proposing a comprehensive methodology for meshing, discretizing, and simulating transient flow in complex 3D fracture networks based on discrete fracture-matrix models. Our framework consists of three parts: (i) Given deviating wells and planar or nonplanar fractures and faults, we construct highquality 3D grids conforming to wells, hydraulic fractures, faults, and dominating natural fractures. We ensure sufficient mesh quality near important features using transfinite interpolation near wells and hydraulic fractures, combined with adaptive refinement in regions of interest. (ii) With the generated grid, we discretize the governing equations with a fully implicit finite- volume formulation with an inner-boundary well model and discrete fracture model. (iii) Finally, we analyze the results using suitable visualization tools, both for pressure-transient curves and 3D matrix/fracture data. The framework enables high-resolution numerical modeling of transient flow with complex fracture networks in 3D. We demonstrate the capacities through simple validation cases with comparisons against an industry-standard commercial well-testing software but also present highly complex cases with long and deviating well trajectories and highly detailed fracture networks. We present and analyze flow-transient behavior coupling the wellbore, the fracture network, and the matrix. We also present an approach to reliably diagnose complex multiple flow regimes on the pressure-transient curves combined with different-scale spatial pressure distribution. Comparison against the commercial software indicates that our framework does not introduce adverse grid-orientation effects for non-K-orthogonal grids which is able to robustly handle the details for fracture-network heterogeneities in 3D reservoirs. Overall, our framework is robust for simulating and analyzing realistic second-level transient effects and short-term well performance with complex fracture networks and heterogeneities. Detailed description of the 3D fracture networks, and accurate simulation of the near-well transient flow behavior can be achieved, which provides confidence to interpret the dynamic flow data at different scales and observe transport mechanisms in unconventional fractured reservoirs with multiple levels of heterogeneity.
- North America > United States > Texas (0.68)
- South America (0.68)
High Performance Computing and Speedup Techniques in Geochemical Modeling of Matrix Acidizing
Wei, Wan (The University of Texas at Austin) | Sanaei, Alireza (The University of Texas at Austin) | Bordeaux Rego, Fabio (The University of Texas at Austin) | Sepehrnoori, Kamy (The University of Texas at Austin)
Abstract Matrix acidizing is a stimulation treatment during which acid is injected below formation fracture pressure. The purpose of acidizing is to enlarge pore space or create channels through dissolution of plugging particles and formation minerals near the wellbore. Simulation of acidizing process is computationally expensive, especially for geochemical simulation which considers full-species transport and complex reactions. In this paper, geochemical modeling of acidizing process is implemented through coupling two simulation models. One is UTCOMP (a 3D reservoir simulator) which is responsible for calculations of fluid flow and solute transport. The other is IPhreeqc (a geochemical package) which is responsible for calculations of kinetic and equilibrium reactions among minerals and aqueous species. Acidizing simulation through the coupled model UTCOMP-IPhreeqc is computationally expensive, and geochemical calculations through IPhreeqc are the computational bottleneck. To improve the computational efficiency, geochemical calculations which take up the majority of the computational time are parallelized. And speedup techniques are implemented to reduce the number of IPhreeqc calls through monitoring the amount change of geochemical components. We have validated the coupled model UTCOMP-IPhreeqc through comparison with the analytical solution in previous work. Parallel performance is measured by comparing total CPU time, CPU time spent on geochemical calculations, and speedup ratios among simulation runs using different processor numbers. For heterogeneous matrix, different dissolution patterns are generated under different injection rates, and the computational time varies depending on the total injection time and the average time step size. For different dissolution patterns, the overall speedup ratio is up to 6.69 when using 16 processors, reducing 85% of CPU time compared with the case using a single processor. The speedup ratio for geochemical calculations is up to 14.21 when using 16 processors, saving 93% of CPU time compared with the case using a single processor. Besides parallel computing, the speedup techniques also improve the computational efficiency, and obtain optimal performance for wormhole dissolution patterns in which most of the geochemical reactions occur in a localized volume. The computational time is reduced to 49% maintaining 96% accuracy compared with the case without using speedup techniques. The coupled model UTCOMP-IPhreeqc has the modeling ability of full-species transport and complex reactions. On this basis, the presented model significantly improves the computational efficiency of UTCOMP-IPhreeqc through parallel computing and speedup techniques reducing the computational time of geochemical calculations.
- Geology > Geological Subdiscipline > Geochemistry (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.46)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (21 more...)
- Well Completion > Acidizing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (1.00)
- Reservoir Description and Dynamics > Fluid Characterization > Geochemical characterization (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (0.70)
Abstract Reservoir simulation studies of the Troll field, from the start with single realization full field simulation models and well simulation models in 1991 until today's complex and large ensemble models, have given important input to the Troll field development, reservoir management and well planning. The main focus in this paper is on Troll Oil simulation model. The effects of hardware and software technology developments are discussed. This includes challenges due to field size, geology, communications, thin oil zone, horizontal wells, gridding, numerics, CPU etc. Troll reservoir simulation has always pushed the limits of the hardware and the software, and this has initiated new solutions in modelling and simulators. The following topics are addressed: General information about the Troll field Troll Oil – how did it start Model size, grid resolution and hardware capacity – pushing the limits Grid construction Well modelling Geological reservoir model From Reference Model to Multiple Realizations
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Sognefjord Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Heather Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 054 > Block 31/6 > Troll Field > Fensfjord Formation (0.99)
- (13 more...)
Abstract Solving the equations governing multiphase flow in geological formations involves the generation of a mesh that faithfully represents the structure of the porous medium. This challenging mesh generation task can be greatly simplified by the use of unstructured (tetrahedral) grids that conform to the complex geometric features present in the subsurface. However, running a million-cell simulation problem using an unstructured grid on a real, faulted field case remains a challenge for two main reasons. First, the workflow typically used to construct and run the simulation problems has been developed for structured grids and needs to be adapted to the unstructured case. Second, the use of unstructured grids that do not satisfy the K-orthogonality property may require advanced numerical schemes that preserve the accuracy of the results and reduce potential grid orientation effects. These two challenges are at the center of the present paper. We describe in detail the steps of our workflow to prepare and run a large-scale unstructured simulation of a real field case with faults. We perform the simulation using four different discretization schemes, including the cell-centered Two-Point and Multi-Point Flux Approximation (respectively, TPFA and MPFA) schemes, the cell- and vertex-centered Vertex Approximate Gradient (VAG) scheme, and the cell- and face-centered hybrid Mimetic Finite Difference (MFD) scheme. We compare the results in terms of accuracy, robustness, and computational cost to determine which scheme offers the best compromise for the test case considered here.
- Geology > Geological Subdiscipline (0.93)
- Geology > Structural Geology > Fault (0.46)