Paper A: Reservoir Characterization during Underbalanced Drilling: Methodology, Accuracy, and Necessary Data

Paper A:

Reservoir Characterization

during Underbalanced Drilling:

Methodology, Accuracy, and Necessary Data

Erlend H. Vefring, RF- Rogaland Research, Gerhard Nygaard, Telemark Uni- versity College, Kjell K˚ are Fjelde, Rolf Johan Lorentzen, Geir Nævdal, RF- Rogaland Research, and Antonino Merlo, Agip

This paper SPE77530 was presented at the conference and published in the Proceedings of the SPE Annual Technical Conference and Exhibition held in San Antonio, Texas, U.S.A., 29 September - 2 October 2002.

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Copyright 2002, Society of Petroleum Engineers Inc.

This paper was prepared for presentation at the Annual Technical Conference and Exhibition held in San Antonio, Texas, U.S.A., 29 September – 2 October 2002.

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Abstract

In this paper a novel methodology for reservoir characteriza- tion during underbalanced drilling is presented. In this meth- odology we are using a transient wellflow model coupled to a transient reservoir model, and use estimation techniques to estimate reservoir properties. Our focus is to estimate the per- meability and reservoir pressure along the well, using meas- ured data usually available while drilling. The measured data are outlet rates, pump pressure and downhole pressure. The liquid injection and gas injection rates are used as input to the model.

Our finding is that estimating permeability and reservoir pressure simultaneously is a difficult estimation problem, and may lead to large uncertainties in the estimates. If we assume that the reservoir pressure is known, however, reliable esti- mates of the permeability is obtained. A methodology for un- certainty analysis is also presented and can be used to evaluate necessary measurements for proper reservoir characterization.

SPE 77530

Reservoir Characterization during Underbalanced Drilling: Methodology, Accuracy, and Necessary Data

Erlend H. Vefring, RF- Rogaland Research, Gerhard Nygaard, Telemark University College, Kjell Kåre Fjelde, Rolf Johan

Lorentzen, Geir Nævdal, RF- Rogaland Research, and Antonino Merlo, Agip