Design for Reliability in Testing from Floating Drilling Vessels
Authors: Harris L.M. 
Published: December 2007

This paper was prepared for the Second Annual European Meeting of the Society of Petroleum Engineers of AIME, to be held in London, England, April 2–3, 1973. 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 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.

Well tests can be made from floating drilling vessels with better success than normally experienced in land-based operations. Technology and equipment are available today to insure full safety and reliability. Tests designed for full safety invariably include standards conducive to maximum efficiency and to the lowest ultimate cost.

Policies should be established early that will contribute to the recovery of maximum reservoir data without incurring operating risks or increasing costs. Tests should be attempted only in cased holes and certain tool manipulations restricted to only daylight hours. Limits should be established for surface pressures and, basically, all pressure drop taken in the bottom of the hole.

Equipment should be selected to provide compensation for vessel motion, to consider water depth and well depth and to provide full control of the formation fluids and pressures to be encountered. Just as in all other parts of the floating drilling system, the provision of redundancy is the key to protection from equipment malfunction and/or other emergencies. Preferably, tests should be made through tubing Preferably, tests should be made through tubing test strings rather than drill pipe.

Operating procedures should be prepared with forethought to assigning job responsibilities in detail, to monitoring tool performance and well behavior and to insuring full control of the well under any set of conditions that could occur.

Numerous tests have been performed safely in water depths in excess of 1000 feet without difficulties. Complete safety can be maintained without reducing the quantity or the quality of the data obtained from the test.

Introduction

Drill-stem testing has been used by the oil industry for more than 30 years as a means to evaluate the productive potential of a well prior to final completion. Its original purpose prior to final completion. Its original purpose was primarily to test in the open hole and to determine if an investment in the casing and the completion of the well were justified. The tests were flowed through the drill pipe used in drilling. Hence, the term "drill-stem test" arose.