Development of Tight Gas Fields
- 2. About OSL OSL is a multi-disciplined team of creative, forward-thinking technical specialists, working collaboratively with the energy and related sectors to provide quality implemented solutions. Our speciality is front-end engineering and provision of innovative solutions for Gas and Oil Processing, Transport and Storage - both onshore, offshore and subsea. OSL has extensive experience in the energy sector, including environmentally friendly technologies such as carbon capture, bio-fuel and biogas. Our highly skilled team undertake a wide range of projects for a variety of major and independent energy companies and we pride ourselves on our clever thinking, quality, timeliness and the cost effectiveness of our delivery. We are the leading authority in the design and optimisation of gas compression systems both on and offshore. This is achieved by “cradle to grave” engineering and design support through innovative thinking based on sound engineering practices, reinforced by our extensive operational experience.
- 3. Development of Tight Gas Fields The Industry Challenge In recent years, the exploration of gas fields in the Southern North Sea (SNS) has often avoided exploring tight gas reservoirs due to high field development costs. As a result of this, many gas discoveries and fields have been left undeveloped. There are two fundamental challenges in developing tight gas fields, the first of which is the cost. Apart from developing a topside platform, there is significant and often uncertain expense in the drilling and fracking that is required to release the gas reserves in the reservoirs. The cost of drilling is particularly high when drilled horizontally for long distances before initiating the fracking process. The second being the presence and flow-back of solids in the form of sand or proppants from the hydraulic fracturing. Unconventional gas fields require hydraulic fracturing in order to recover natural gas at economic rates, solids flow-back can cause pipeline and equipment internal erosion and solids deposition. Therefore, solids production management is a critical issue to address and is essential to prolong the operational lifespan of pipelines and associated production equipment. OSL has developed a subsea solution that addresses both of these problems hugely reducing the drilling costs whilst assuring the life of pipelines and associated equipment. A comprehensive methodology entailing production, processing, transportation and solids removal is included in this package, which will turn tight gas field development into a highly profitable investment. The overall infrastructure investment is approximately one- third of the investment required for a standard topside facility.
- 4. OSL Subsea Separation Solution Having a wealth of experience in the SNS, OSL has undertaken a detailed analysis of the challenges and conditions associated with fields that may contain high quantities of sand and/or proppants at the wellhead. We have created a solution for these fields designed to be compact and simple, with minimal maintenance requirements using standard subsea components. This solution enables tight gas wells to be developed in the absence of topside structures as well as advanced and expensive drilling techniques. The skid in our design can be placed on the seabed and the extraction can proceed with a more cost-effective drilling technique, without a long run of horizontal wells. The OSL solution includes a self- contained subsea separation unit, which will be installed on the seabed by a drilling rig on the well conductor without the need for piling. The unit is capable of being handled and installed by a standard jack- up rig and has a standard subsea tree guide frame. It is designed to allow for easy removal for either decommissioning or relocation as and when a new low reserve gas field needs to be developed. The main components within the package are industry standard and include the wellhead, separation unit, solids accumulator, fiscal metering station and umbilical installations. The process will be controlled by a standard Subsea Control Module (SCM), which will contain electronics, instrumentation, hydraulic components and chemicals to provide well control functions during well production. The package will be tied back into an existing platform. This will ensure that the platform’s life is extended as it will become a hub for these new subsea wells. The processed gas can then be transferred as per every client’s need.
- 5. Wellhead and Christmas Tree Solids Separation Equipment Solids Accumulator Choke Valve and Isolation System Flow Metering Device Adjacent Subsea Installation or Topsides Onshore or Offshore Processing FacilitiesSubsea Export Pipeline Umbilicals Termination Assembly Process Chemical Injection Hydraulic Oil Power Supply Control Signal Subsea Separation Skid The solids disposal process from the solids accumulator will be completed by periodically using a Remotely Operated Vehicle (ROV) without any diver intervention. Our unique pressure reduction approach has been devised to ensure the safety of both personnel and the environment during the solids removal procedure. This method is designed to be simple, inherently safe and cost-effective.
- 6. System Design The OSL solution is very flexible and has been designed to operate over a wide range of operating conditions. Marginal tight gas fields that exhibit the following properties are ideal applications for this comprehensive package. The flexibility of the solids separator operation is an essential element of this package. Each gas field possesses unique associated solids characteristics therefore the ability to optimise the separator design using Computational Fluid Dynamics (CFD) techniques is a substantial benefit. The package has stringent erosion monitoring to track the mechanical integrity of the equipment exposed to solids to prevent any damage. However, in the unlikely event of excessive erosion over time, the package design enables easy replacement of equipment if and when required. The package is contained within a standard skid design, which is compact and provides ease of access for ROV operations. The square shaped skid is 5.8m wide, 6.4m high and weighs 82 tonnes. It has been optimally loaded and can be installed on the seabed without the need for piling using standard jack-up drilling rig deck cranes. The steel structure will provide adequate support, dropped object protection and trawler board protection to the separator, solids management system and other components of the skid. The equipment contained within the package has been optimally sized to reduce total investment whilst maintaining accessibility.
- 7. Benefits This subsea separation package provides the following benefits: • Complicated drilling time is minimised, reducing drilling costs significantly • Capital investment is reduced by approximately one-third, compared with conventional development • Shorter time to reach first gas • No need for topside facilities • Mechanical integrity issues of the pipeline and processing equipment are minimised • Process safety is never compromised through OSL's Process Safety in Design (PSiD) • Using standard subsea components, the system has been designed for high reliability, ease of connection to ROVs for solids production management, removal and inspection, as well as simple maintenance and servicing • Close monitoring of any critical equipment degradation allows immediate and proactive action to be taken • Optimisation of the separator design using CFD • Easy removal of skid for either decommissioning or relocation which provides a cost-effective long-term solution • No negative impact on the sea life and its environment through simple and compact technology This solution provides a significant opportunity to reconsider some of the unexploited fields at a cost effective price point. Thus - tight gas fields in the SNS have not been more attractive to develop.
- 8. Engineering Creative Solutions for our Energy Future /oslconsulting @oslconsulting OSL Consulting OSL Consulting OSL House Henry Boot Way Priory Park East Hull HU4 7DF View this document online at www.issuu.com/oslconsulting Tel: +44 (0) 1482 626400 www.oslconsulting.com info@oslconsulting.com