Development of Full Opening Drill Stem Testing Assemblies for Offshore Applications
Authors: Farley D.L. , Jeffords C.M. , Barrington B.Q. 
Published: December 2007

This paper was prepared for the SPE-European Spring Meeting 1974 of the Society of Petroleum Engineers of AIME, held in Amsterdam, the Netherlands, May 29–30, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Netherland Section of the Society of Petroleum Engineers, P. O. Box 228, The Hague, the Netherlands. 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.

Ever increasing needs for longer flow periods, when testing offshore, have resulted periods, when testing offshore, have resulted in development of full opening drill stem test assemblies. This equipment makes the most efficient use of expensive rig time allotted to the evaluation of a well formation. Two full opening tester tools, utilizing different methods of operation, are described and their use in the same DST assembly is shown to be advantageous. A method of operating testing tools by application of annulus hydraulic pressure is also discussed as evidence of the advancement of testing tool technology.

Introduction

Drill stem testing offshore involves many conditions which must be dealt with differently than when performing the same service on land. Higher costs of offshore operations make it necessary to carefully consider any step that requires a significant amount of time. For example, if a long flow period is needed to more fully evaluate a reservoir, it is allowed only after determining the most beneficial way to utilize the time required. Thus, any reduction in time or increase in the efficient use of the allotted flow period is of real value to the well operator. One way to do this is to flow the well at a high rate by using full opening test tools.

When it is realized that drill stem tests often evaluate the need for a five to twenty-five million dollar development-well platform, the importance of obtaining meaningful data concerning formation characteristics is obvious. These tests must supply sufficient evidence of a commercial reservoir to justify such expenditures.

A high flow rate during testing permits a gas reservoir to be drawn down enough to provide an optimum pressure build-up provide an optimum pressure build-up recording to be made when the well is closed-in. Also the higher rate permits a wider radius of investigation for a given flow time, so more of the formation is evaluated.