Offshore Reservoirs--A Different Engineering Approach Is Required
Authors: Mcintosh I. , Baxendale D. 
Published: March 2010

An increasing number of Canadian companies are becoming involved in East Coast offshore exploration. This exposes more petroleum engineers, for the first time in their careers, to the unique complexities of offshore petroleum engineering. Experience in Western Canada has given engineers a well founded knowledge of onshore oil and gas development however, when faced with offshore field assessment this experience often cannot be directly applied. The engineer is faced with relatively familiar engineering problems but in an unfamiliar context. The solutions to these problems are unlikely to be identified intuilively. This paper attempts to identify the different approach required to solving offshore petroleum engineering problems. The cost benefits of sophisticated data acquisition programs, and the need for extensive pre-development engineering are addressed.

Introduction

Although there is, as yet, no offshore production in Canada there have been a number of significant discoveries which are involving petroleum engineers in field appraisal and development studies.

A petroleum engineer whose experience has been obtained in Western Canada should have no major problems in undertaking an evaluation of an offshore reservoir however there are significant differences, which must be appreciated by the engineer. Development constraints dictate that those offshore reservoirs which can be developed are typically large, deep and have high deliverability. Oil reservoirs generally contain medium to high gravity crudes. Such reservoirs may not be familiar to some engineers, however, the differences faced by the engineer relate more to the opportunities for, and importance of, reservoir data acquisition and the level of subsequent interpretation of the data required prior to production start-up.

This paper attempts to explain why a different approach is required when evaluating offshore wells and conducting subsequent reservoir studies. It is based on the author's experience of North Sea fields and Western Canada oil and gas operations. There are references to previously published material, produced by engineers involved in the early days of North Sea development in particular. North Sea reservoir developments provide excellent examples of the problems petroleum engineers wilt face in developing East Coast fields.

In attempting to demonstrate the differences in engineering approach to offshore fields, there are no new theories expounded but an attempt is made to remind engineers of the principles of reservoir evaluation in order to avoid applying Western Canada experience where it is not appropriate.

The paper makes a case for good petroleum engineering practice which is equally applicable to onshore oil and gas fields. It hopefully does not promote over-engineering but attempts to justify the appropriate level of engineering given the impact on the development process.

The paper is subdivided into three pans for the readers benefit. A discussion of the principles of offshore reservoir appraisal and development is followed by details of offshore well evaluation and lastly by offshore development planning.

There is an emphasis on oil fields in this paper due to the more severe technical problems associated with development on the Grand Banks.