Reservoir Simulation Results Research Articles

Pre- and Postprocessing for Reservoir Simulation

Summary This paper describes the functionality and underlying programming paradigms of Shell’s simulator-related reservoir-engineering graphics system. This system includes the simulation postprocessing programs Reservoir Display System (RDS) and Fast Reservoir Engineering Displays (FRED), a hypertext-like on-line documentation system (DOC), and a simulator input preprocessor (SIMPL-SIM). RDS creates displays of reservoir simulation results. These displays represent the areal or cross-sectional distribution of computed reservoir parameters, such as pressure, phase saturation, or temperature. Generation of these images at real-time animation rates is discussed. FRED facilitates the creation of plot files from reservoir simulation output. The use of dynamic memory allocation, asynchronous I/O, a table-driven screen manager, and mixed-language (FORTRAN and C) programming are detailed. DOC is used to create and access on-line documentation for the pre- and postprocessing programs and the reservoir simulators. DOC can be run by itself or can be accessed from within any other graphics or nongraphics application program. DOC includes a text editor, which is the basis for a reservoir simulation tutorial and greatly simplifies the preparation of simulator input. The use of sharable images, graphics, and the documentation file network are described. Finally, SIMPLSIM is a suite of programs that uses interactive graphics in the preparation of reservoir description data for input into reservoir simulators. The SIMPLSIM user-interface manager (UIM) and its graphic interface for reservoir description are discussed.

RESERVOIR SIMULATION FOR RESERVOIR MANAGEMENT

The Hutton reservoir in the Merrimelia Field (Cooper-Eromanga Basin) was the subject of a 3-D reservoir simulation study. The primary objective of the study was to develop a reservoir management tool for evaluating the performance of the field under various depletion options.The study confirmed that the ultimate oil recovery from this strong water drive reservoir was not adversely affected by increasing total fluid offtake rate. However, any decisions regarding changes to the depletion scheme such as increasing production rates, if based solely on computer simulation results, should be viewed with caution. Careful monitoring of any changes to the depletion philosophy and checking of actual data against simulation predictions are essential to ensure that oil production rate and ultimate recovery are optimised.The model assisted in evaluating the economics of development drilling. While the simulation results are dependent on the validity of geological mapping, the model was useful in confirming that, due to very high transmissibility in the Hutton reservoir, additional wells would only accelerate production rather than increase ultimate recovery. The issue of drilling wells thus became one of balancing the benefits of accelerating production against the geological risk associated with that well.Interaction between the reservoir engineer and various disciplines, particularly development geology, is critical in the development and application of a good working simulation model. This was found to be especially important during the history matching phase in the study. If engineers and development geologists can learn more of the others' discipline and appreciate the role that each has to play in simulation studies, the validity of such models can only be improved.The paper addresses a number of the pitfalls commonly encountered in application of reservoir simulation results.

Microemulsion Phase Behavior: A Thermodynamic Modeling of the Phase Partitioning of Amphophilic Species

Abstract A thermodynamic model is presented for modeling the partitioning of amphiphilic species between the different phases of systems typically used for chemical flooding. The model, an extension of the pseudophase model by Biais et al.1 that can analyze only a four-component system, can work with five-component systems, including two partitioning amphiphilic species (e.g., two alcohols or one alcohol and a partitioning cosurfactant species). The self-association of alcohol in the organic phases, which results in a variable alcohol partition coefficient, is considered. Experiments to determine thermodynamic constants (which are entered into the model) are described for four-component systems, including one alcohol. The salinity dependence of these parameters is also studied. Brine/ decane/isobutanol/TRS 10-410 as well as brine/nonane/ isopropanol/TRS 10-80 systems are considered. Some computations of pseudophase compositions for the five-component model and for various overall compositions are included. This partitioning model has been included in the chemical-flooding simulator developed at the U. of Texas; the results of this model have been presented in another paper.2 The model used for the binodal surface that is required to calculate phase compositions from pseudophase compositions is presented in this paper, as well as comparisons with experimental data for both four- and five-component systems. Reservoir simulation results are presented in Ref. 3.

Use of Color Movies for Interpretation and Presentation of Reservoir Simulation Results

Motion pictures made from color-coded spatial distributions for fluid saturations, phase compositions, pressure, and temperature are applied to the interpretation of reservoir simulations. The use of computer animation is described as applied to several enhanced oil-recovery processes. Additional insight into simulation results can increase markedly the potential value of numerical simulation. Introduction Use of mathematical reservoir simulators to correlate reservoir data and to predict the behavior of petroleum reservoir recovery processes has become an important part of modern reservoir engineering. In addition to the major technical difficulties inherent in developing and running these simulators, it has been found that it is frequently difficult and time consuming to interpret and present the results from simulators. One underlying cause of this difficulty of interpretation and presentation of simulator results is the quantity of information provided by simulators. For example, a typical compositional thermal simulation (three components) might employ five wells and 300 grid blocks. At each grid block, temperature, pressure, three saturations, and an additional composition are available at each time step. Well rates and pressures, perhaps at several different completion intervals, also are calculated. If the simulation takes 300 time steps to run to completion, more than 450,000 numbers will represent the "solution" to the particular reservoir engineering problem (approximately 1,350,000 intergrid block fluxes also would have been computed and used by the simulator during the simulation). As several dozen of these simulations might be made during a field study, it is clear that the simulator user can be faced with more information from the computer than can be assimilated or interpreted conveniently.A second source of difficulty is the inherent two- and three-dimensional aspects of many simulations. It is straightforward to represent graphically the dynamic history of one-dimensional quantities such as well rates as a function of time. Two-dimensional quantities, such as water saturation as a function of position in a vertical cross section, are more difficult to display on a graph. One commonly used display method for two-dimensional cross sections is line-printer contour plots (Fig. 1). While contour plots provide for a rapid visual evaluation of spatially distributed quantities, a distinct advantage over tables of numbers, these plots have several disadvantages.1. They have a low information content - i.e., a number of such plots would have to be viewed simultaneously to provide a picture of all the reservoir variables in a given cross section at one point in time.2. The spatial resolution and the contour resolution of the plots are low.3. It is generally difficult to gain an appreciation of reservoir dynamics from these static "snapshot-in-time" representations of reservoir conditions. JPT P. 1331＾