Abstract

Interpreting pressure transient tests in complex faulted and stratigraphic environments can be difficult. In fluvial depositional environments, where sand continuity is a significant uncertainty, pressure transient test interpretation can generate several non-unique solutions, all of which may match test data. Using seismic attribute analysis to constrain pressure transient test interpretation leads to better understanding of reservoir heterogeneities and boundaries, and is the central theme of this paper. Additionally, seismic data can guide the design of pressure transient tests, especially the test duration to evaluate key seismic anomalies. Other data such as production history, core data, formation evaluation from well logs, analog information on channel geometry etc. is also important in getting a better understanding of reservoir description. While we briefly discuss all relevant data, the focus of this paper is primarily on integrating seismic amplitude response with pressure transient test interpretation.

The interpretation of the pressure transient test is done numerically, guided by an initial interpretation of point bar and channel system geometry from seismic attribute analysis. The analysis of the build-up pressure derivative clearly shows the impact of point bar boundaries and connectivity across point bars. For the reservoir evaluated, there was fluid and pressure communication across the point bars, and this was reflected in the transient pressure analysis of the build-up and also from historical production data. The results presented in this paper illustrate the value of integrating geology, geophysics and production data with well test interpretation for a fluvial reservoir.

Introduction

The integration of geology with well test interpretation has been discussed by Massaonnat and Bandiziol (1991) and subsequently by Corbett et al. (1998). The latter paper concludes that the integration of geoscience and well testing results in reduction of uncertainty in reservoir description, especially in fluvial reservoirs. Zheng et al. (2003) illustrate this integration using geological, petrophysical, seismic attribute and well test data from a fluvial reservoir in the Gulf of Thailand. More recently, Zheng (2006) concludes that numerical well test interpretation which incorporates reservoir geology and heterogeneity (rock and fluid) is the future of well testing. Raghavan et al. (2000) provide another example of a fluvial gas condensate reservoir where the integration of geologic and geophysical interpretations with measurements from flow tests helped in reservoir characterization. The authors discussed the advantages of using numerical interpretation of well tests as compared to classical analytical interpretation. They also noted that sub seismic features may be identified and their properties estimated by conducting flow tests.

Rooij et al. (2002) studied point bar geometry, connectivity and well test signatures in fluvial systems, focusing on the lateral connectivity between point bars. Their work investigated the effect of different types of channel fill sequences on well test signatures and connectivity across channel fills. Toro-Rivera et al. (1994) summarized that flow characteristics of a fluvial reservoir can be better understood by the integrated interpretation of well test pressure data in a geologically coherent fashion.

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