Abstract

Shell Petroleum Development Company of Nigeria Limited (SPDC) recently embarked on a campaign to abandon some wells in line with a corporate drive to enhance the safety of the wells in her portfolio. It is also to ensure that SPDC as a responsible operator aims to safeguard people and environment as required by law. The campaign is part of a larger campaign that had the objective of enhancing safety integrity in SPDC. It will also afford the opportunity to carry out relatively inexpensive repair and recompletions.

A total of six wells were abandoned in the land and swamp terrain within a year period utilising the Hydraulic Workover Units (HWU) for Land anda combination of the HWU and Self Elevating Workover Platform (SEWOP) in the Swamp. The 6 wells were amongst the most critical wells for abandonment based on SPDC defined criteria (e.g wells in Navigable water ways or in built up neighborhoods). In one of the wells on land, human habitation had since grown close to its proximity and the well experienced high annular pressures, hence the need for the abandonment. The others are in the waterways in the swamp with other technical problems. Most of the wells were drilled over 30 years ago and they have either outlived their useful life or there is plan to recover the remaining reserves in other offset wells.

The abandonment involved full subsurface and surface abandonment with the entire wellhead and casing structures removed from below the mudline or cellar (for land). The use of the HWU / SEWOP arrangement brought significant cost savings (25 - 50 %) when compared to the cost of using conventional workover rig. This paper reviews the work that was carried out in the abandonment and highlights the challenges as well as strategies that were applied towards the successful abandonment operations.

Introduction

Although, Well abandonment (decommissioning) is part of a Field development Plan, this activity has often being delayed because it is a non-oil generating activity. Moreso, it is most often ranked low when competing for the limited funds with other oil generating activities.

However, SPDC has recognised the need to accommodate ‘limited’ well abandonment activities every year to ensure that as a responsible operator it aims to safeguard people and the environment as required by law.

The well abandonment campaign is part of SPDC corporate drive to enhance the safety of some critical wells in its portfolio and to ensure that all wells are operated within the acceptable safe envelope.

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