American Institute of Mining, Metallurgical and Petroleum Engineers Inc.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract

The ultimate implications of bottom-hole pressure data interpretation rarely can be pressure data interpretation rarely can be foreseen in their entirety by the wellsite engineers originally developing those data. This situation is particularly critical in remote area exploration programs where original evaluation procedures are extremely expensive and crucial decisions regarding the future of large areas often depend on a limited quantity of data from very few wells.

This paper illustrates, by a series of examples, that formation pressure surveys may be taken too much for granted and that their contribution to evaluation decisions often are not fully appreciated.

No amount of rigorous mathematical treatment of pressure survey data can compensate for detailed planning and strict attention to the characteristics likely to lead to costly misinterpretation.

Introduction

Considerable attention has been devoted to the application and interpretation of reservoir pressure surveys in advanced oil and gas field pressure surveys in advanced oil and gas field primary and secondary development programs, primary and secondary development programs, while relatively minor importance has been attached to the benefits to be derived from these data in exploration efforts. Similarly, it is often only after field or reservoir development has progressed well beyond the discovery stage that the true value of such basic information is appreciated. It is at this late stage that pressure data, which could have been conclusively obtained during preliminary evaluation, may be found to be unreliable preliminary evaluation, may be found to be unreliable or even unavailable in any form.

This problem involving costly unreliable and/or misleading data may result largely from the fact that the development reservoir engineer often is divorced from the exploration phase, and does not become involved until such phase, and does not become involved until such time as a discovery has been classified as a development project.

ACCURACY OF DRILLSTEM TEST PRESSURE MEASUREMENTS PRESSURE MEASUREMENTS Consider the countless cases where the DST pressure data, especially initial shut-in pressure data, especially initial shut-in pressures, are used ultimately as vital basic pressures, are used ultimately as vital basic data for reservoir evaluation. The care taken in obtaining DST data of maximum accuracy often is appropriate only for qualitative analysis.

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