The Dynamic Numerical Simulation in Flowlines (DNSFL) is an alternative tool adapted to handle Dynamic Models in Fine Scale. This feature has been particularly relevant for studying the current case, a huge multilayered waterflooding process developed in a giant field of great extension reservoirs with considerable facial and stratigraphical variations. The DNSLF develops these tasks suitably because uncouples reservoir geometry and heterogeneity from transport equations, solving the problems dominated by convective flows in a faster and computationally more efficient way. This allows to build models of greater space discretization and, therefore, to represent better the heterogeneity of the reservoirs. The analyzed field is constituted by fluvio-lacustrine deposits, nine sand-clay cycles of normal grading (only eight of them were modeled), partially connected reservoirs; with 250 actives wells in commingled production and water injection; and with a long and detailed history of simultaneous primary and secondary events. In a previous paper (SPE 94815) a Streamline-based Global History Matching of this field was presented. This process enabled to achieve the Geological Modeling Calibration, a clear conceptualization of the current primary and secondary production mechanisms, its productive behavior, and to evaluate the geostatistical and Upscaling procedures to apply for the definition of the Simulation Model. This paper illustrates how the Integral Model achieved, with a detailed Streamline-based History Matching, is used for Waterflooding Design Optimization, Surveillance and Monitoring, showing that these principles are key factors to understanding reservoir performance and identifying opportunities that will improve the ultimate recovery. During the detailed History Matching process CPU runtimes around 200 minutes were achieved using a 1225000 grid cells Model, with 190 timesteps, quarterly at the starting, and monthly after, based in a Pentium 4 PC, 3.2GHz CPU and 2GB RAM. It showed that it is possible to work with a big Streamline-based Model in relatively short processing time. Introduction The classical techniques of waterflooding surveillance, including methods like: mapping (gas-oil ratio, water cut, pressure, etc.) total liquid production vs. time, injected poral volumes vs. recovery factor, Hall plots, etc., jointly with the monitoring process have backed-up successful Exploitation Optimization processes[1]. Most of these techniques, as those mentioned above, are 0D; some recent practices made 1D or 2D spatial distribution of the relevant characteristics to the process, essentially productions and injections, but without integrating the pressure fields. Streamline simulation goes further and incorporates pressure fields, which determine streamline as the most probable way of fluid movement. In this sense, and always in the pressure field, there are two well differentiated work levels in the waterflooding projects[2] (Fig. 1):The first level, called "Production-injection surveillance" based on the historic analysis of the waterflooding, allows for the examination of injectors and producers, identifying well and poorly swept areas.The second level, "Streamline-based simulation" based on a detailed geological model, fluid physics and history matching, which allows, in addition to the previous one, for an integral redesign and forecast of the waterflooding towards its optimization. Both levels are sustained and fed by monitoring the field process; as it is clear, the development of the second level, as in the example of Puesto Hernández Rayoso Field- Block 4, implies achieving the first level.
The Dynamic Numerical Simulation in Flowlines (DNSFL) is an alternative tool adapted for handling Fine Scale Dynamic Models. DNSLF uncouples reservoir geometry and heterogeneity from transport equations, solving problems dominated by convective flows in a faster and computationally more efficient way. This allows to build Models of greater spatial discretization and, consequently, to better represent reservoir heterogeneity. This feature has been particularly relevant for studying the current case, that consists of great extension reservoirs with considerable facial and stratigraphical variations. In this paper a workflow is presented, using the above DNSLF properties, in a Global History Matching to develop the "Fine" Scale Geologic Model Calibration and the Definition of a Preliminary Static-Dynamic Model of a giant field of Neuquén Basin, Argentina. The analyzed field is constituted by fluvio-lacustrine deposits, nine sand-clay cycles (only six of them were modeled), partially connected reservoirs; with 380 actives wells in commingled production and water injection; and with a long and detailed history of simultaneous primary and secondary events. CPU runtimes around 70 minutes were achieved using a 808860 grid cells Model, with 111 quarterly based timesteps in a Pentium 4 PC, 2.2GHz CPU and 2GB RAM. This showed that it was possible to work with a big Model in short processing time. With this preliminary model, based on a well-groups-level global history matching, a clear conceptualization of the current primary and secondary production mechanisms, and its productive behavior, was obtained. This reservoir conceptualization was a strong guide for the Global History Matching process. Geostatistical and Upscaling procedures applied for the definition of the Simulation Model could be evaluated by means of sensitivities analysis on some model parameters. This preliminary model allowed sensitivities to make recommendations on future work stages, including Geological Model refinements and detailed History Matching. Introduction The Puesto Hernández Field, with approximately 147 km2, is located in the "Neuquén Engulfment" environment, on the northeast margin of the Neuquén Basin, in the northern part of Neuquén province, Argentina (Fig. 1). Reservoir Description The producing reservoirs in the field, the Rayoso, HuitrÍn and Agrio Fms, are of Cretaceous age (Fig. 2). This work presents the modeling tasks carried out for the Rayoso Fm, the main producer in the field (38% of total production). The Rayoso Fm is part of a clastic-evaporitic unit deposited in a predominantly continental medium of fluvio-lacustrine character. The clastic section is the one showing prime economic interest, where nine sand-clay cycles have been recognized. Of these, the six most important were modeled. The cycles are truncated towards the E-NE by the inter-Cenomanian unconformity at the top of the Rayoso Fm, and show different water-oil contacts1. The producing levels are relatively shallow (at depths of less than 600 mbgl), and have good petrophysical characteristics, low reservoir pressures, and oil viscosities that vary laterally and with depth. All reservoirs in the Puesto Hernández area are part of a SW dipping homoclinal structure, with an average dip of 5º. An E-W extensional fault system splits the field into 4 major Blocks, the hydrodynamic communication of which was analyzed in this work (Fig. 3).
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