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Abstract

In practice, a reservoir test that is successfully executed according to a specified pragmatic design will provide interpretable results satisfying the test objectives. Usually, there is an optimal test design among several options which will minimize the cost of the test, without jeopardizing the likelihood that useful interpretations will ensue. Consequently, as numerous testing configurations have been introduced, it has become necessary to develop interpretation procedures which are as straightforward as the conventional techniques while offering a more reliable or refined answer. The use of downhole flow and pressure measurements, or even downhole shut-in devices, pressure measurements, or even downhole shut-in devices, are cases in point. With proper design, execution and interpretation, tests which employ these configurations can provide reservoir properties that could be much more provide reservoir properties that could be much more difficult to obtain by other means.

One objective of this paper is to present a methodology for reservoir test interpretation. This defines the hierarchy and sequence for employment of all analysis techniques, and is intended to be general enough in concept to accomodate any type of test. Field examples are used to illustrate the merits of specific acquisition procedures, and also how the methodology can aid in achieving the test objectives with consistent and coherent analyses.

Introduction

Dynamic downhole measurements such as pressure, flowrate, density, and temperature, are acquired routinely by production logging and testing devices. Production production logging and testing devices. Production logging (or PL) surveys versus depth under stabilised flowing or shut-in conditions are used to diagnose and monitor well performance. Surveys versus time with the tool in a fixed position in the wellbore yield the reservoir's transient response pattern to rate perturbations. This response is used to help define the well/reservoir model and to quantify well performance. By production log testing is understood the synergy between the 'versus depth' and 'versus time' acquisition schemes.

The acquisition and interpretation procedures used in this paper have been extensively employed. Experience with wellbore flowrate and pressure measurements has resulted in the guidelines offered herein for designing tests which maximise the desirable characteristics of the downhole sensors. The purpose of this paper is to discuss when and why a particular testing configuration is preferable over another, and to define a sequence of interpretation steps that accomodates any type of test while also providing a mechanism for consistently correct analysis.

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