Subsea operations in general, attract significant expense; from the requirement of a multi-disciplinary team, through to the logistics of equipment and service conveyance in a harsh offshore enviroment. Costs are typically recovered through the reservoir production potential value over a number of years -this is not the case in abandonment operations. Upon cessation of production, the cost of abandonment is absorbed as a liability; as such the focus on cost efficiency is stringent and acute. It is however an area where the adoption of new and novel technology, allied to an alternative approach to service vessel selected and campaign structure, can achieve significant cost savings.This paper describes the development of a subsea wellhead connector intended for use in well abandonment operations, in rigless decommissioning projects conducted in the UK Continental Shelf. It presents one of alternative rigless approaches to field decommissioning, and through collaboration with operators, cost effective equipment is developed reactively to meet their operational requirements. Deviating from a Jack up/MODU based rig campaign to a Monohull based campaign has shown savings can be achieved through a significant reduction in vessel day rates and personnel costs. The requirement of rigless abandonment technologies and equipment is growing as the market adopts rigless abandonment; as such, collaboration is required to align equipment with operators requirements.The development of the Subsea Wellhead Connector (SWC) was undertaken and delivered in 29 days, with design, application, fabrication, and commissioning expedited to meet an aggressive operations schedule. A dedicated project team allied to robust internal engineering and testing programs, facilitated the delivery and leveraged over twenty years of lessons learned in subsea operations. The SWC is intended for Intervention and well abandonment operations, including: conveyance for mechanical and abrasive cutting, wellbore communication and testing, subsea tree (XT) installation, and well barrier verification, and wellhead retrieval.The SWC has now undertaken five campaigns in the first six months since its market entry, and displayed that collaboration and the pooling of creative talent, can provide tangible and discernible benefits to the stakeholders involved.

The adoption of segregated drilling campaigns is commonplace in an effort to harness economies of scale and reduce well construction costs. In an attempt to increase the financial efficiency of drilling campaigns, the division of the well construction and completions operations can be segregated into two distinct phases. A drilling and casing phase leaving a cased well in a Temporary Abandonment (TA) status, followed by a phase consisting of clean-up, completion and stimulation operations resulting in the handover of the well to production to bring hydrocarbon production online. As such an Intervention and Completion Unit (ICU) with the capability to perform perforation, multi-zone completion installation, stimulation, clean-up operations and well testing has significant advantages when deployed in the later phase of a segregated multi-phase drilling campaign. This paper describes the collaborative development of an ICU that facilitates the installation of multi-zone and smart well completions, conveyance for well servicing operations, well bore clean-up (WBC) activities, well testing and stimulation activities. The challenge of undertaking traditional drilling phase activities with a technically capable, yet cost effective ICU is discussed, particularly the core areas where the reduction in specification through it being redundant for the phased operations. The key parameters driving the ICU development and design are presented from the operator's perspective, based on prior campaign experience utilizing this approach with alternative technology. The process identifying the key requirements of the completion and well servicing operations is described with the selection of implementing new technology solutions in the design. The avoidance of Non-Productive Time (NPT) is a core aspiration in making incremental cost efficiencies. The identification of operations not on the critical path that can be performed simultaneously or as an offline activity, have the potential to make high cost impacts. Through innovative design and the implementation of novel and field tested technology, allied to extensive use of offline activities as concurrent operations, the ICU has the potential to make significant cost savings in a segregated well construction project. Collaboration between the operator and service provider drives a design which provides a technically pragmatic and capable ICU and as such attracting project cost savings allied to lower support equipment costs. Further, the deployment flexibility of the ICU allows it to perform operations ranging from well construction activities such as well slot preparation, completions and intervention, to well deconstruction activities such as heavy workover, Permanent Abandonment (PA) phases and slot recovery. The ability to perform multi-phase operations whilst mobilized to a platform brings further cost benefits and operational flexibility.

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.

Subsea operations—from the need for multidisciplinary teams to delivering equipment and services in a harsh offshore environment—are inherently expensive. These costs are typically recovered through the reservoir production over a number of years. When production ceases, the cost of abandonment is absorbed as a liability, which leads to a stringent focus on cost efficiency. It is, however, an area where the opportunity to achieve significant cost savings through new technologies and an alternative approach to service vessel and campaign structure. This paper describes a facilitating technology—the subsea wellhead connector, or SWC—that enables operators to undertake monohull and even rig-based subsea abandonment campaigns. Deviating from a semi-submersible rig to a monohull-based campaign has reduced vessel day rates and personnel costs by a substantial margin. To maximize the saving potential for rigless abandonment technologies and equipment, however, require collaboration between the operator and service provider. The SWC latches and recovers all common 18.75-in. bore wellhead suspension systems. The system offers mechanical, abrasive, or explosive severance tools for plug-and-abandonment (P&A) campaigns and a small re-entry mandrel seal assembly for intervention. Deployment can range from vertically or horizontally rigged orienttions, and operations are limited by the remotely operated vehicle (ROV) limitations. This paper presents four Phase III campaigns in the North Sea continental shelf as case studies. Each has unique challenges. Monohull vessels were used in the first 3 wells and the final campaign was run from a mobile offshore drilling unit (MODU)—this final approach brough rigless technology to a rig to further enhance operational capability.

In an attempt to reduce the capital expenditure (CAPEX) costs of field development, the development and adoption of focused, bespoke equipment can provide significant cost savings. With rig based technology consistently accounting for over 40% of a well construction or de-construction project, it is an area with significant cost reduction potential if alternative facilitating technology is deployed. The paper describes alternative facilitating technology. Modification and project specific integrated engineering that allows for potential cost reductions, through early engagement with an operator and project stakeholders. A well construction project case study presents the early interfacing with a Yangon based operator, concerning the development of an Intervention and Completions Unit (ICU) for operations in a segregated well construction project, to undertake well completion and stimulation activities. A well rejuvenation project case study presents the engineering modification of a Hydraulic Pulling and Jacking Unit (PJU) to undertake well slot preparation activities for mature asset rejuvenation activities for a Gulf of Mexico (GoM) operator. The focused engineering presented in the well construction and well rejuvenation case studies, and the identification of functionality requirements that can be improved to operate in high cost base projects, demonstrates the potential savings that can be achieved. Detailed operational analysis appraisal, and identification of those activities with empirically high levels of non-productive time (NPT), are categorized and technology solutions are developed. Technology solutions provide the required technical capabilities for the intended operations, whilst reducing the associated base construction, maintenance, certification and operational costs that are commonly experienced with over specified equipment. Both case studies present the benefits to the operator in the pre-engineering and design phases, allied to operational benefits.