Making More Complete Use Of DST Data

Abstract

Publication Rights Reserved This paper is to be presented at the Mechanical Engineering Aspects of Drilling Production Symposium in Fort Worth, Tex., on March 23–24, 1964, and is considered the property of Society of Petroleum Engineers. Permission to publish is hereby restricted to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Engineers or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in JOURNAL OF PETROLEUM TECHNOLOGY or SOCIETY OF PETROLEUM ENGINEERS JOURNAL is granted on request, providing proper credit is given that publication and the original presentation of the paper. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract This paper touches briefly upon the qualitative and discusses more fully the quantitative values that can be derived from a properly conducted drill-stem test. These values are shown to come from the test data obtained from sufficient fluid recovery and adequate shut- in pressure build-ups. A brief discussion is given showing several references for background material in the field of production and DST pressure build-up data analysis. Recognizing that good data is important to complete evaluation, the paper briefly discusses some of the specific data that are needed and how they might be obtained. Some very general rules-of-thumb are given suggesting flow and shut-in time relationships based on surface flow reactions. The results of three separate studies are briefly mentioned showing shut-in time and resulting pressure build-up relationships as indications of completion potential. Eight examples of actual DST results and their corresponding Horner plots are presented and discussed. Interpretations are made on each of these examples based on the information shown and suggested effects are made. A presentation is made of the generally accepted assumptions and empirical equations that are used in DST data analysis. Introduction For many years the DST was used only as a qualitative formation evaluation tool, determining the type of fluid present and an apparent rate of flow. Recent application of pressure build-up curve analysis to the DST pressure build-up has shown that quantitative formation evaluation can also be made with excellent reliability, and prior to setting pipe. Quantitative evaluation requires good pressure build-up data and enhances the importance of the final shut-in pressure build-up portion of the normal DST pressure chart. The natural sequence is followed by discussing some general rules-of-thumb for time allotment that may be applied during the actual operation of the test that will help in getting the necessary data. The authors conclude by making some brief evaluations of particular DST data to illustrate the type of information that can be gleaned from a DST today.