Semi-Automatic History Matching Using the Pilot Point Method Including Time-Lapse Seismic Data

Abstract

Abstract In this paper, we evaluate the benefit of using time-lapse seismic in reservoir simulation and handle some of the associated challenges. The problem is tackled from a reservoir engineering perspective, focusing specifically on the use of time-lapse seismic in history matching. A semi-automatic history-matching procedure is presented that uses both production and time-lapse seismic data as conditioning data. The actual integration of the production and time-lapse seismic data is handled in the objective or misfit function, which expresses the misfit between modeled and observed reservoir behavior. The pilot point method was chosen to reduce the large history matching parameter space1–5. The optimum permeability values at the pilot points were determined using the Levenberg-Marquardt optimization algorithm. The semi-automated method is tested on a 2D synthetic reservoir. The results indicate that for a case with abundant production data, time-lapse seismic sometimes yields only minor improvements in the final history matched model. However, when production data is limited, time-lapse seismic improves the history-matched permeability fields considerably by correctly identifying and locating the major heterogeneities of the permeability field. In addition, the sensitivity studies show that if pilot points are located in or near heterogeneities, the automatic history-matching algorithm has a better chance of correctly locating the heterogeneities. Furthermore, a seismic noise sensitivity analysis shows that seismic noise impedes accurate determination of the history-matched parameters. The results of this research demonstrate that a history-matching procedure including time-lapse seismic can improve reservoir characterization and modeling. It can be used as a reservoir management tool to optimize in-fill well locations, enhanced oil recovery projects, and economic evaluations. The semi-automated procedure allows engineers to work more efficiently with larger reservoir models and extensive dynamic conditioning data sets. Introduction 4D seismic is the process of repeating 3D seismic surveys over a producing reservoir in time-lapse mode. It has a potentially huge impact in reservoir engineering because it is the first technique that may allow us to directly image dynamic reservoir properties such as fluid movement, pressure build-up, and heat flow in a reservoir in a true volumetric sense. Seismic images are sensitive to spatial contrasts in two distinct types of reservoir properties:non-time-varying static geology properties such as lithology, porosity, shale content; andtime-varying dynamic fluid-flow properties such as fluid saturation, pore pressure and temperature. Given a single 3D seismic survey, representing a single snapshot in time of the reservoir, the static geology and the dynamic fluid-flow contributions to the seismic image are non-uniquely coupled and therefore difficult to separate. For example, it may be impossible to distinguish an oil-water contact from a horizontal depositional boundary in a single seismic image. However, with 4D seismic surveys, examining the difference between time-lapse 3D seismic images allows the non-time-varying geologic contributions to cancel, resulting in a direct image of the time-varying changes caused by the reservoir fluid flow. Potential applications of 4D seismic include mapping fluid contacts with time, estimating pressure compartmentalization and fault seal, and locating bypassed oil.