Deepwater Extended Well Testing In The Gulf Of Mexico
Authors: Cribbs M.E. , Voss J.D. , DeCarlo L.J. 
Published: October 2008

This paper examines deepwater Gulf of Mexico well testing and the need for extended well testing from the oil company's perspective. Well test objectives together with possible facility arrangements are examined as they integrate with the DeepStar project's modular field development facility arrangement.

INTRODUCTION

Development cost for future deepwater projects are anticipated to be substantial with large projects potentially costing more than $1.0 billion. Because of the cost magnitude, development decisions need to be made on accurate and reliable information; both for the anticipated performance of the reservoir, and for the appropriateness of the development concept as well. Generally the more accurate and reliable (or predictable) the information, the less risk will be assigned to the development decision. Such risk reduction is the primary concern of most managers. There is a compromise that managers must make, however, with regard to the accuracy / confidence in the reservoir information relative to the cost associated with its acquisition. An appropriate mix of drilling additional delineation wells, well testing and extended well testing is required to establish a development decision based on an acceptable level of risk. Such an approach is necessary because none of the alternatives provide all of the needed information. Many of the key parameters of reservoir performance are time dependent and can only be assessed via extended production activity. Specialized test ships and equipment have been developed to perform extended well tests and many managers perceive a similar equipment need for the Gulf of Mexico. However, the cost of an extended well test program relative to the limited information that is acquired is difficult to justify.

This paper is intended to evaluate the need for extended well testing in the deep water of the Gulf from the perspective of management, the facilities engineer and the reservoir engineer. The conclusions that have been drawn indicated that:Production from extended well tests would not generate sufficient revenue to support a leased extended well test facility;The longest duration, anticipated for any GOM extended well test would mostly likely not exceed two month, typical durations being less than one with months;The cost for an extended well test on its own is not justified relative to the new information that it will provide.

The paper is also intended to provide an alternative approach of evaluating long term reservoir performance as well as the development concept to be employed. The concept allows the development to be staged, thus limiting management's exposure to risk.

CONVENTIONAL WELL TESTING

Conventional Well Testing, as defined by this paper, is conducted in an effort to acquire data that can be used to characterize the near-wellbore region of a reservoir and to determine the minimum reservoir size by a short duration (hours) flow test. The principles of Pressure Transient Analysis are used to interpret the time-dependent response of the well/reservoir system. The objective of the analysis is to determine if the data exhibits features consistent with the reservoir models created by the geoscientist, petrophysicist and reservoir engineer.