The objective of this project is to design, engineer, construct/fabricate, test, and qualify a full-scale prototype subsea chemical storage and injection system (Subsea ShuttleTM) for low dosage rate production chemicals to enhance offshore oil production. The aim of this project to develop and qualify this new technology which will help reduce the cost of subsea well tie-backs and extend their reach to unlock stranded resources.

Subsea Shuttle LLC, Houston, TX 77024

Ultra-deepwater oil and gas production systems routinely cost multiple billions of dollars and require multiple appraisal wells at costs in the hundred-million-dollar range (each) to justify sanction, followed by years of delayed production while designing, constructing, and installing the required facilities. According to numerous industry forecasts, a growing number of oil and gas accumulations in deepwater will be developed via long tie backs of subsea wells to existing host facilities. One of the key challenges to the success of these subsea well tie backs is to safely and reliably supply the necessary chemicals to maintain wellbore integrity and flow assurance in the long-distance flowline. 

Virtually all wells, particularly subsea wells require production chemicals to prevent and/or mitigate corrosion within the wellbore and flowline blockage from wax, paraffin, hydrate and other deposition. Onshore and offshore dry tree (platform-based production systems) well treatment is straight forward with direct (surface – platform) access to point of chemical need. For subsea wells, current technology is to deliver these chemicals via an umbilical; a complex, multi-component, wire, fiber and chemical conduit tubes bundled together and positioned across the seafloor from host platform to subsea well. The umbilical is purpose engineered for each application, has long delivery schedules and is expensive to build and install. Once installed they are prone to clogging if chemical usage is changed, as is often necessary over the life of a well. Even if the umbilical doesn’t clog or corrode over the life of the well, at abandonment they are expensive to remove and are not reusable. Even more problematic, for long offsets subsea wells, the umbilical cannot flow the required volumes of high viscosity chemicals across the significant offset distances and still have sufficient pressure to flow into high pressure subsea wells. By providing the required chemical injection local to need, subsea, the most expensive part of the umbilical, the chemical tubes can be removed, significantly reducing umbilical cost and allow much longer offsets to host platform facilities. 

While individually subsea wells are usually exploiting smaller resource plays and may have less reserves when compared to the giant offshore platform developed fields, in aggregate and particularly in the Gulf of Mexico (GOM), they could represent significant reserve and production potential. They are much cheaper than dry tree wells (which require a platform) and can be developed much more quickly.

This project represents new and novel technology and to date no specific industry design or regulatory standards have been promulgated or adopted.  However, there are several existing, relevant analogs for guidance as well as components, equipment, and technologies, that have been re-purposed and integrated into the subject SCSI to help insure safe, reliable, and environmentally compliant operation. Phase I Report, appendix 1 presents some of the standards and recommended practices that were applied to the design. From these and with guidance from regulators and potential customers, a set of Functional Design Specifications (FDS) were developed.

The general design consists of three (3) systems, a dual barrier subsea chemical storage system (Storage), a subsea process module (Process Module), and a host platform power regulator and control module (PRCM), taken together the system is commonly referred to as a Subsea Chemical Storage and Injection System (SCSI). The Storage system is innovative and patented. It features a flexible, engineered fabric bladder, resistant to chemical degradation and is totally enclosed within a hard, metallic pressure vessel, which is rated and qualified for surface storage and transportation. The Process Module sits on the same skid as the Storage unit and has two (2) connection points, one is electrical power and control which attaches to an existing field umbilical and the second, a fluid connection to the existing wellhead and/or flowline. 

Ultra-deepwater oil and gas production systems routinely cost multiple billions of dollars and require multiple appraisal wells at costs in the hundred-million-dollar range (each) to justify sanction, followed by years of delayed production while designing, constructing, and installing the required facilities. According to numerous industry forecasts, a growing number of oil and gas accumulations in deepwater will be developed via long tie backs of subsea wells to existing host facilities. One of the key challenges to the success of these subsea well tie backs is to safely and reliably supply the necessary chemicals to maintain wellbore integrity and flow assurance in the long-distance flowline. 

Virtually all wells, particularly subsea wells require production chemicals to prevent and/or mitigate corrosion within the wellbore and flowline blockage from wax, paraffin, hydrate and other deposition. Onshore and offshore dry tree (platform-based production systems) well treatment is straight forward with direct (surface – platform) access to point of chemical need. For subsea wells, current technology is to deliver these chemicals via an umbilical; a complex, multi-component, wire, fiber and chemical conduit tubes bundled together and positioned across the seafloor from host platform to subsea well. The umbilical is purpose engineered for each application, has long delivery schedules and is expensive to build and install. Once installed they are prone to clogging if chemical usage is changed, as is often necessary over the life of a well. Even if the umbilical doesn’t clog or corrode over the life of the well, at abandonment they are expensive to remove and are not reusable. Even more problematic, for long offsets subsea wells, the umbilical cannot flow the required volumes of high viscosity chemicals across the significant offset distances and still have sufficient pressure to flow into high pressure subsea wells. By providing the required chemical injection local to need, subsea, the most expensive part of the umbilical, the chemical tubes can be removed, significantly reducing umbilical cost and allow much longer offsets to host platform facilities.

While individually subsea wells are usually exploiting smaller resource plays and may have less reserves when compared to the giant offshore platform developed fields, in aggregate and particularly in the Gulf of Mexico (GOM), they could represent significant reserve and production potential. They are much cheaper than dry tree wells (which require a platform) and can be developed much more quickly.

Offshore, ‘enhanced oil recovery’ can be the difference between economically drilling a subsea well and achieving primary and often secondary (usually water injection) recoveries (50/60%) versus leaving the resources in the ground (0% recovery) due to the high cost of dry tree, platform supported wells. 

Without the development and commercialization of this technology, billions of barrels of oil equivalent could go undeveloped or unrecovered. This project will help safely develop and enhance recovery of resources from these long offset reservoirs, adding royalty revenues, jobs, and energy security, which are of particular importance in today’s unpredictable environment. Also, the additional production from subsea wells feeding a host platform may both 1) extend the potential life of the host facility and 2) generate better host facility economics by spreading host facility’s fixed cost over more barrels of through-put added from the subsea tie-back. 
 

• Stakeholder day, site meeting (2022-05-13)
  • Approximately 50 participants including representatives from BSEE met at facility and reviewed equipment and discussed forward plans
• SSS is awarded Offshore Technology Conference (OTC) Spotlight on New Technology award.

The System Integration Test (SIT) was completed, and the report submitted. Subsequently, the Phase I report was completed and submitted. The submission of the Continuation Application (CA) is planned. With CA approval, the project will move into Phase II. Key objectives of Phase II, Budget Period 3 (BP3) are:

• Planning and coordination of offshore demonstration of the Integrated Unit, including regulatory review and approval process
• Acquisition and fabrication of all site specific (offshore field demonstration location) components
• Offshore deployment, operation, and Integrated Unit recovery 
• Onshore post-demo Integrated Unit inspection and review and Integrated Unit decommissioning
• Final technical report including engineering drawings

RESULTS OF PHASE I
Engineered, compliant and qualified components were specified, then procured and then manufactured / fabricated into full-scale subassemblies which were tested. The subassemblies were assembled into a full-scale prototype unit and then qualified with a Factory Acceptance Test (FAT), first on shop floor, and then emersed in the outdoor test tank. The Systems Integration Test (SIT) connected the three (3) sub-assembles and provided an overall system qualification. 

All equipment performed proving functionality and fit for purpose for the prototype full-scale system. 

• The prototype SIT test proved the entire system works both on the surface and underwater.  There remains improvements and optimization that may be made as more experience is gained working with the system. But the system with the new-build prototype tank and bladder is ready to be built, deployed, and used subsea for chemical injection.
• System safety is a primary feature of the prototype minimizing risk to people working around the unit and to the environment.  When operating on the surface or subsea, the system Fails-to-Safe conditions (stop pump and close isolation valve(s).  This fail-to-safe condition may be automatic (when a setpoint is exceeded) or it may be manually started (ESD).  All automatic and all manual ESD conditions were tested and qualified as operational.
   

$2,998,962.00

$2,237,000.00

NETL – David P. Cercone (David.cercone@netl.doe.gov or 412-386-6571)
Subsea Shuttle LLC – Art Schroeder (art@SubseaShuttle.com or 713-681-1482) 
James Chitwood, Principal Investigator (jec@chitwoodengineers.com)

Offshore Technology with Art Schroeder. Ep184 - Oil & Gas Upstream (oilandgasonshore.com), November 2022

Energy Tech Venture Forum XVIII 2020 Presentation Rice Alliance for Technology and Entrepreneurship [PDF], September 2020

Subsea Shuttle Subsea Chemical Storage Unit 2020 06 08 Draft 7 [Youtube], June 2020