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Abstract

Well construction reliability is always of great importance especially when it is about drilling in an arid region that contains strategic groundwater reserves. This is the case of Hassi Messaoud and satellite oilfields (HMDs) in Algeria where aquifers of the Northern Sahara System (NSAS) Spread out. Problems closely related to well construction such as casing corrosion, cementing lack and also those of post-abandonment are encountered by Sonatrach and partners there.

The main environmental concern becomes, then, how to ensure a reliable and highly safe well design and structure by improving drilling practices and introducing innovative architecture technologies aiming at significantly reducing aquifers contamination risks.

This paper describes how Sonatrach has been able to deal with such problems. Besides, it points out how risks are assessed according to an appropriate method that was fitted for purpose. On the other hand, field data are used to analyze the occurring phenomena and lessons learned from what is considered as the most tragic disaster related to well construction in Algeria - that occurred in Berkaoui satellite field in 1986 -are stressed.

Furthermore, the paper summarizes the steps and the approach taken along the way in stating new drilling performance objectives for HMDs to meet world-class standards and fulfil NSAS protection commitment.

Introduction

The world of oil and gas drilling achieves every year important progresses, guided by quality and competition requirements, and delimited by HSE requests more and more strict and standardized.

Sonatrach oil and gas Company subscribes its drilling objectives within this frame. Well construction has been performing since two decades tangible qualitative and quantitative improvements. Performance is continuously recorded in terms of duration, footage and spurt productivity and subjected to growing desire to achieve more and more audacious targets.

However, another aspect of performance is still being integrated: durability and integrity. Actually, well construction is facing imposing problems of casing corrosion and/or collapse. The number of workovers due to such problems increased significantly in the mid 1990’s. To a large extent, it is true this is related to monitoring accuracy advances but it is an actual problem all the same.

Drilling days, footage and direct costs shouldn’t be considered anymore as the exclusive performance indicators. It becomes clear that construction quality and well integrity requirements must be covered by the performance concept. As topical concerns, we can cite non-exhaustively: Casing durability, aquifers protection risk analysis, as well as the regularity of the openhole profile.

This paper describes how Sonatrach is dealing with well quality and integrity requirements, focusing on casing corrosion, aquifers protection and post – abandonment problems.