Intervention and Abandonment Operations Utilising a Rigless Well Servicing Unit: Case Studies

Abstract

With depressed oil markets and restrictions on project funding, and the sanctioning of developments, there is an acute focus on identifying areas where capital and operational expenditure can be reduced, maintaining capability and safety. One area of focus is on the conveyance method, namely the structure. With rig costs well construction and de-construction operations typically accounting for over 50% of the project cost base, it has been identified as an area where the introduction of new technology has the potential to significantly reduce overall project costs. The market adoption of alternative technologies, such as the "Rigless" approach is in its infancy in the Indian market, however regions such as the Gulf of Mexico and South East Asia have successful track record in the implementation of the technologies in completions, intervention and abandonment projects.

The paper describes alternative facilitating technology, focused on providing the required level of specification for the operations, with a reduction in the base cost of the technology, namely Rigless operations. The core technology is presented, with key facilitators. The application of the technology is presented in two case studies, each demonstrating the specific challenges of the operations and the novel solutions engineered to address these, and as such the significant potential benefits from a Rigless approach. The detailed and operational engineering presented in the case studies, and the identification of functionality requirements that can be improved to operate in technically challenging high cost projects, demonstrate the potential savings that can be achieved through the core technologies, and bespoke interfacing of them to client requirements.

Case study 1 presents a uniquely challenging abandonment campaign undertaken with a Supermajor in the Gulf of Mexico with a bespoke Rigless Unit. With the platform suffering hurricane damage and listing, bespoke technology was required to mobilize to the structure and safely isolate the hydrocarbon bearing reservoirs.

Case study 2 presents a large integrated well re-entry and abandonment campaign, with multiple partially abandoned and suspended wells. The integration of drilling equivalent circulating density techniques to the technology, present solutions that were devised to re-enter wells with annular communication and potentially underbalanced conditions. The flexibility of the Rigless Unit, and its ability to combine new technologies typically only available to integrate to drilling technologies, presents the value proposition of the Rigless Unit and approach.