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This paper describes the evolution of subsea stimulation treatments within one field including a novel dual vessel approach that was developed and successfully implemented on multiple wells. The methodology that enabled stimulations of high volume, complexity and precision is described, including observed results and opportunities for continuous improvement. In a harsh low oil price environment such cost-efficient stimulations can unlock additional potential for many subsea developments. Three West of Shetlands (WoS) injectors stimulation campaigns successfully delivered 11 subsea well treatments with a novel dual vessel batch approach in 2020 delivering operations of outstanding efficiency and reservoir results while driving costs down. A construction vessel provided remotely operated vehicle (ROV) support including deploying the well control package, whereas the stimulation vessel ran its own downline to facilitate optimized use of its dedicated pumping system and large chemical handling capacity. To enable deep water stimulation, the quick connect downline was engineered and project specific equipment installed onto the stimulation vessel allowing deployment to 450m water depth. Notable cost reductions in excess of 34% were achieved utilizing the efficiency offered by manifold entry for batch treatments to minimise the number of subsea re-connection operations while the stimulation vessel allowed much larger bulk loadouts and optimised the number of vessel loadings for continuous operations. This novel dual vessel approach for batch subsea stimulations allowed multiple well access through ‘daisy chains’ within isolated pipeline segments, while keeping injection operations live to other wells from the Glen Lyon Floating Production Storage and Offloading Vessel (FPSO) in the Schiehallion field. Improved HSE performance was achieved through reduced chemical handling and transportation. Real time data solutions for onshore monitoring were developed which aided the management of COVID-19 risks. The post-stimulation injection rate from the stimulation has signifcantly improved in all wells, resulting in large additional injection capacity for the field. Maintaining increased injection capacity has proved to be a challenge. The acquired understanding regarding water quality and longevity of treatments will allow identification of further continuous improvement opportunities to enable sustainable stimulation results.
This paper describes the evolution of subsea stimulation treatments within one field including a novel dual vessel approach that was developed and successfully implemented on multiple wells. The methodology that enabled stimulations of high volume, complexity and precision is described, including observed results and opportunities for continuous improvement. In a harsh low oil price environment such cost-efficient stimulations can unlock additional potential for many subsea developments. Three West of Shetlands (WoS) injectors stimulation campaigns successfully delivered 11 subsea well treatments with a novel dual vessel batch approach in 2020 delivering operations of outstanding efficiency and reservoir results while driving costs down. A construction vessel provided remotely operated vehicle (ROV) support including deploying the well control package, whereas the stimulation vessel ran its own downline to facilitate optimized use of its dedicated pumping system and large chemical handling capacity. To enable deep water stimulation, the quick connect downline was engineered and project specific equipment installed onto the stimulation vessel allowing deployment to 450m water depth. Notable cost reductions in excess of 34% were achieved utilizing the efficiency offered by manifold entry for batch treatments to minimise the number of subsea re-connection operations while the stimulation vessel allowed much larger bulk loadouts and optimised the number of vessel loadings for continuous operations. This novel dual vessel approach for batch subsea stimulations allowed multiple well access through ‘daisy chains’ within isolated pipeline segments, while keeping injection operations live to other wells from the Glen Lyon Floating Production Storage and Offloading Vessel (FPSO) in the Schiehallion field. Improved HSE performance was achieved through reduced chemical handling and transportation. Real time data solutions for onshore monitoring were developed which aided the management of COVID-19 risks. The post-stimulation injection rate from the stimulation has signifcantly improved in all wells, resulting in large additional injection capacity for the field. Maintaining increased injection capacity has proved to be a challenge. The acquired understanding regarding water quality and longevity of treatments will allow identification of further continuous improvement opportunities to enable sustainable stimulation results.
The global opportunities within the subsea market, in both greenfield and brownfield, have been growing over the years; however, the increasing complexity in subsea fields has brought significant challenges in terms of scale control and management. This is highlighted by the lack of reliable water compositions and resulting uncertainties of scale risk evaluation, the difficulty to control chemical dosage subsea, and well access for intervention which becomes a very costly event. These challenges can greatly impact the operational, contingency, and remediation programs, hence the overall economy of the field. This paper presents a selection of hardware technologies that have been utilized to resolve the challenges associated with scale control in subsea fields. Subsea sampling systems have enabled the collection of representative fluid samples directly from the point of interest. This advanced sample transport and analysis has ensured the supply of representative fluid data into scale risk assessment; while chemical injection metering valves (CIMV) have allowed the correct chemical dosage into the target wells. The evolution of optimized hydraulic intervention technologies have improved the available options for cost-effective well access, leveraging lower cost vessels and improving overall capital and operational expenditures. These recent developments in subsea hardware technologies have enabled the subsea scale control problems to be handled more effectively. Upon the review of these associated scale management challenges, the system layouts and working mechanisms of each applicable hardware technology are illustrated in detail. This is further demonstrated by several successful case histories where reliable scale control, reduced intervention frequency, significant cost saving, and increased uptime are achieved. Moreover, equipment flexibility and adaptability to cover a range of environmental conditions, namely water depth, to provide an optimum hydraulic intervention method that offers a commercially attractive alternative to traditional riser-based techniques. The novel scale remediation solutions discussed in this paper have demonstrated the power of integrating hardware technologies with effective chemicals and suitable intervention methods for successful scale control and management in subsea fields.
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