Improve Efficiency Tight Gas Fields

Doc. No.: OS-INT-0092-SPR-0007 Improving Efficiency Tight Gas.docx
Date: 27 Nov 2015
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WHITE PAPER:
IMPROVING EFFICIENCY AND
REDUCING COST WHILST GETTING TO
THE TARGET
Neil Harvey, Abdullah Khan, Sermsak Manalertsakul
OSL Consulting, Hull, November 2015

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TABLE OF CONTENTS
1. EXECUTIVE SUMMARY ..........................................................................................3
2. INTRODUCTION ....................................................................................................5
3. REDUCING COSTS WHILST TARGETING TIGHT GAS............................................6
4. THE CLEVER THINKING ®
APPROACH.................................................................10
5. THE SOLUTION....................................................................................................14
6. CONCLUSION ......................................................................................................18
7. REFERENCES .......................................................................................................20

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1. EXECUTIVE SUMMARY
Developing stranded tight gas reserves has become one of the key issues in recent years, as
more conventional fields become depleted. Directional drilling from a platform is used to
develop single and multiple well gas fields. However, this method has high cost implications
for single well and dual well developments and may not be economically viable for low
reserve fields. Finding ways of improving the economic viability of tight, low reserve gas fields
in the SNS is becoming more important.
Improving the economic viability of tight, low reserve gas fields in the SNS may be achieved
using seabed separation technology so that the well fluid can then be exported to a nearby
offshore platform. Sand handling and disposal management is a significant challenge for the
design of this subsea unit. This presents an opportunity to develop a simple and economical
solution for such a subsea unit in the SNS, possibly using cyclonic processing techniques.
A study was initiated to propose a suitable separation system and a solid management
solution. The objective of the study was to:
 Identify a suitable solid particle separation technology and investigate using CFD
 Develop an outline process scheme and size the key process equipment
 Investigate a suitable solids removal and disposal system
 Develop a design of a proposed subsea separation skid
 Perform an economic evaluation to assess the commercial feasibility of the project.
All possible options for the challenge, including cyclonic technology was assessed using OSL’s
unique Clever Thinking®
methodology. This approach ensured that the most suitable sand
removal solution was identified for further development.
The subsea production system typically consists of subsea wellhead systems with Christmas
trees, process equipment, subsea manifolds, tie-in and flowline systems for multiple well
production, umbilical systems, control systems and the export pipeline system. For the
separator a single cyclonic unit was selected from the number of possible solutions. The key
benefit of using this subsea separation technology is that it is a simple construction with no
moving parts. An accumulator will be situated underneath the cyclone collecting separated
solid particles from the well stream. A spherical design was implemented in the design of the
unit to avoid any possible dead spaces which cause difficulties in solids removal from the
container. A fiscal flow meter will measure the flowrate of the export gas from the separator,
prior to being transferred to the host platform through the subsea pipeline.
The accumulator will be emptied using an ROV. Whilst isolated from the cyclone, to allow
pressure reduction, the solids will be fluidised with water to allow slurry fluid to be transferred
to a container on the ROV vessel. The slurry will be treated and disposed of onshore in a safe
manner.
The success of this undertaking was greatly influenced by the close partnership with an
operating company whilst carrying out this conceptual study. The collaboration meant that
the overall team, made up of both OSL and operational personnel were able to combine
knowledge and experience whilst investigating solutions for recovering gas from stranded
offshore gas fields before transporting it using subsea pipelines to an adjacent platform.

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The Clever Thinking®
practise employs techniques that are designed to drive the creative
thought process and break-away from established thought patterns, this method is proven to
release potential from the team with a wealth of untapped ideas.
The proposed solution satisfies the defined design aspects and has overcome the potential
operational difficulties, providing strong financial benefits for single well tight gas marginal
field development. The proposed solution has proven to be attractive as it is technically
feasible, constructible, maintainable and economic.

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2. INTRODUCTION
There are currently many challenges in the gas production and supply markets such as gas
price, ageing assets, shareholders’ expectations, maintaining safe operations, UK oil and gas
security of supply. Developing new reserves has become one of the key issues in recent
years, especially the exploration of stranded gas reserves as more conventional fields become
depleted. A number of technologies have been studied in order to create economic viability
for future exploration.
It is estimated that there are more than 100 assets in the Southern North Sea (SNS) that are
labelled as stranded fields. These are a collection of tight reservoirs with distant
infrastructure, possibly with small volumes, and inconsistent gas qualities. The main reasons
why these resources have not yet been developed are related to cost and technology, though
some of these stranded tight gas fields may be successfully developed with the use of a
subsea well, horizontal drilling, and fracturing.
Directional drilling from a platform is used to develop single and multiple well gas fields.
However, this method has high cost implications for single well and dual well developments
and may not be economically viable for low reserve fields. Finding ways of improving the
economic viability of tight, low reserve gas fields in the SNS is becoming more important.
This may be achieved using seabed separation technology so that the well fluid can then be
exported to a nearby offshore platform through a subsea pipeline for further production. This
process will reduce the total cost of such projects due to the reduction of drilling distance,
and negating the requirement for a costly topside production platform and associated
structure.
Solids handling and disposal management is a significant challenge for the design of this
subsea unit. Solid particles may cause clogging and erosion in pipelines, pipework and
rotating machinery which threaten pipeline and system operations. This study will propose a
solution to this problem, which complements the selected separation process.
OSL Consulting (OSL) and its partner operating company recognise an opportunity to develop
a simple and economical solution for such a subsea unit in the SNS, possibly using cyclonic
processing techniques. The seabed unit is intended to segregate sand particles and proppants
released as part of hydraulic fracturing (fracking) activities.

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3. REDUCING COSTS WHILST TARGETING TIGHT
GAS
3.1. Tight Gas Fields
Natural gas present in low permeability geological formations is referred to as Tight Gas.
Tight Gas is defined as natural gas from reservoirs with an average matrix permeability of
less than 0.1 millidarcy (mD) [Ref. 1], however recently the German Society for Petroleum
and Coal Science and Technology (DGMK) announced a new definition for tight gas
reservoirs elaborated by the German petroleum industry, which includes reservoirs with an
average effective gas permeability less than 0.6 mD. This gas source mainly produces dry
gas due to the tight porosity of the reservoir formations.
The exploration and exploitation of this ‘Unconventional’ source of natural gas has up until
recent years been avoided due to prohibitive field development costs. Because of this many
gas discoveries and fields have been left undeveloped. In the UK Continental Shelf (UKCS)
the opportunity size is estimated at approximately 4TCF for new field developments and it is
expected that the figure is greater than this for further developments of existing fields.
3.2. Barriers to Targeting Offshore Tight Gas
3.2.1. Technology
Execution thus far has been complicated by the lack of available stimulation equipment for
the SNS. Recently this appears to have become less of an issue, with several service
companies implementing and offering skid based or otherwise portable fracturing spreads
for deployment on to temporary platforms or suitable temporary boats.
Developments in horizontal drilling have made the development of tight gas reservoirs more
promising. The bores can intersect natural fissures and fractures that are present in the
formation and improve the production from these reservoirs significantly.
Progress in hydraulic fracturing (fracking) techniques in recent years, due to the US Shale
Gas boom have also made vast improvements in the possible recovery rates of these fields.
3.2.2. Fracking
The main purpose and value of hydraulic fracturing in a low permeability formation is to
accelerate production. Significant stimulation of the well hydraulic fracturing (fracking) is
required to ensure commercial flows. Because of this the solids handling of the returning
proppant material (sand or aluminium oxide) is required.
3.2.3. Economics
Currently challenging economics hinder the development of the Tight gas fields. With the high
costs associated with well development and well stimulation costs there is a concern that
much of the unconventional gas resource such as tight gas is uneconomic to exploit.

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Distinct from the costs of designing and building a suitable topside platform, there are
significant and often uncertain development costs involved with the drilling. The cost of
drilling is particularly high when drilled horizontally for long distances before initiating the
fracking process.
3.3. Problem History
There are many low-reserve, tight gas fields, which are currently disregarded due to their
uneconomic nature.
Solids production is part and parcel of gas exploration and extraction. With tight gas fields
this is more of an issue due to the hydraulic fracturing that is required to obtain a suitable
production flow rate of gas from the field. The proppants used in the fracturing process
return to the surface with the gas and flowback liquids. There are many options that have
been developed to remove the associated solids in the gas streams. Generally, this separation
takes place on a platform. However, it is not economically feasible at lower reserves to
develop such fields, at the normal costs associated with the installation of the required
infrastructure.
This issue has affected the development of low-reserve tight gas fields as the costs of
supplying suitable processing equipment. OSL Consulting Engineers (OSL) have partnered
with a large European gas supply operator to undertake a conceptual study in collaboration to
find the most efficient and economical solution for subsea separation, including solids
removal,
3.4. The Tight Gas Challenge
Exploration of stranded tight gas reserves has become a challenging topic in recent years. A
number of technologies have been studied in order to create economic viability for future
exploration. Directional drilling from a platform is used to develop single and multiple well gas
fields.. However, this method has high cost implications for single well and dual well
developments and may not be economically viable for low reserve fields.
Solids removal will represent the main challenge in designing this package. Except in cases of
recovering solids caused by drilling, it is anticipated that at the beginning of the extraction,
solids presence will be relatively small. However, it may be the case, that after some time in
operation, the well may start producing solids at a high rate. If not managed and treated
properly, this will give rise to potential pipeline erosion issues, which will make the asset
inoperable. Generally, the production facilities experience a maximum solids production rate
during early production phase. When the well is established, solid production will decrease
and stay constant at a low rate, and may finally increase again when the well is depleting.
The amount and timing of the solids arrival is not predictable so a system must be installed to
remove any solids from the gas stream throughout its lifetime.
The solution to this issue must be able to operate on one or two wells at a time. It must be
simple and have a small footprint, but economically favourable and must require minimum
maintenance and intervention.

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3.5. Idea
The project partners have discussed ways of improving the economic viability of tight, low
reserve gas fields in the Southern North Sea. The partners see an opportunity to provide a
simple and economical solution using cyclonic processing techniques for separation of the well
fluids, using conventional technology but applied in a new environment.
This can be achieved via the installation of a skid located on the seabed which will utilise a
cyclone unit modified for subsea use to segregate sand and proppants particles used as part
of or as a result of well fracturing. Well fluids will then be exported to a nearby offshore
platform via a subsea pipeline for further processing as normal. This scheme aims to reduce
the total cost of such projects due to lower associated costs of drilling, equipment and
structures.
Solids handling and disposal management is a significant issue for the design of this subsea
unit. Solid particles may cause clogging and erosion in pipelines, pipework and rotating
machinery (installed on downstream platform) which threaten pipeline and system operations.
This can potentially lead to requiring additional pigging. The intention of the study was to
propose a solid management solution to this problem which complements the selected
separation process.
As part of the study the partners firstly confirmed whether cyclone technology is the best
option and examine all possible modifications of cyclonic technology and cyclone configuration
schemes suitable for subsea separation.
An important feature of the study involved the research and development work OSL carried
out in collaboration with a local research partner. Use of Computational Fluid Dynamics (CFD),
would ensure that the final solution of the cyclone performance was suitably verified and
optimised to meet the set project criteria.
3.6. Approach
The objective of the study was to:
 Identify a suitable solid particle separation technology and investigate the technical
feasibility of the selected separation technology using CFD
 Develop an outline overall process scheme and determine the suitable size of key
process equipment items and the main piping systems
 Investigate a suitable solids disposal and handling management system for the safe
disposal of the separated solids from the produced well fluids
 Develop a design of a proposed subsea separation skid and determine mechanical and
structural requirements to satisfy the constructability of the package
 Perform an economic evaluation to assess the commercial feasibility of the project
considering direct costs, indirect costs and sale revenues.
All possible options for the challenge, including cyclonic technology was assessed using OSL’s
unique Clever Thinking®
methodology. This approach ensures that the most suitable sand and
proppant removal solution is identified for further development.
Following on from the assessment the process design was progressed with a basis of design,
process drawings, a solids disposal and handling study and preliminary process design,
including equipment sizing and line sizing.

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An important feature of this work is the research and development work OSL carried out in
collaboration with a local research institute. Thorough assessment and verification of the
process mechanics, carrying out solids/liquids separation performance of the process using
Computational Fluid Dynamics (CFD), ensured that the final solution of the cyclone
performance was verified. Assessing sensitivity analysis on process parameters and inlet
particle distribution, the model was used to optimise the solution using various numerical
methods and algorithms, highlighting any further developments to improve the performance.
Further design development followed on with the team generating 3-D models of wellhead,
separation equipment and controls with a standard frame size.
A cost estimate followed on from the design estimating the total cost of the selected option
including pipeline costs and solids removal costs. This was then further developed into a high
level economic assessment of the overall project. This economic assessment consisted of a
high level cost analysis which incorporates drilling costs, gas reserves value, capital
expenditure (capex) and operational expenditure (opex)
This problem solving approach is a template deployable to other similar projects in the oil and
gas industries:
 Assess the problem
 Clever Thinking®
 Proposed list of possible solutions
 Identify best solution
 Develop design
 Verify design
 Further design development
 Cost and economic assessment.

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4. THE CLEVER THINKING ® APPROACH
4.1. What is Clever Thinking®
?
Clever Thinking®
is a unique method of addressing technical challenges. The Clever Thinking®
philosophy has been developed to describe the distinctive way in which OSL strives to
conduct business. It aims to provide a structured way of delivering maximum quality to our
customers. The ability to think creatively, unimpeded by orthodox constraints, without losing
sight of the goal.
The Clever Thinking®
strategy encourages and facilitates the thought processes that we, as
professional Engineers, undertake on a daily basis when faced with a technical challenge. It
encompasses the definition of problems and the generation and assessment of ideas that may
resolve them, without compromising safety.
Clever Thinking®
allows OSL to provide custom fit solutions for every problem, providing
maximum quality and adding value to our customers. The process is carried out during the
different design stages and at various project phases. Use of this practise ensures efficient
and focussed project solutions, Figure 4-1 illustrates the general work flow of the process.
Figure 4-1 - Clever Thinking® Process Flowchart
4.2. A Clever Thinking®
Culture
The culture of creating solutions by sharing ideas is an integral part of the working life at
OSL. This cultural philosophy benefits the working environment and improves the quality of
the solutions OSL produce.
Everyone’s ideas are of equal value, requires respect for each other’s views and ideas.
Support and encouragement will be required to help people engage in the Clever Thinking®
process
Define the
problem
Collate the
team
Communicate
the problem
Divergent
thinking
Convergent
thinking
Selecting
solutions
Close out and
actions

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There is strength in different perspectives, experiences and viewpoints. Clever Thinking®
is
about collaboration, not competition. The philosophy of the best idea may be someone else’s
is good way to promote teamwork. Conflicts may arise from time to time; the avoidance of
conflicts is not recommended, as the team may be able to capitalise on such conflicts as
conflicting views can create a productive environment for the team.
It is well documented that appreciation, acknowledgement and recognition are strong
motivators for a team to work harder and aim higher. By celebrating team members’
achievements in front of colleagues, it stimulates all concerned. By recognising individuals
input and effectiveness, you tap into the best way to motivate them and bring out their
hidden talents.
Attentive listening is empowering for all involved. Listening empowers people to take
responsibility, to be more productive, to influence their environment, and to increase their
own capabilities.
Finally, Clever Thinking®
techniques will not suit all situations and all people. It cannot be
forced, so encouragement of the concept should be ingrained into the fabric of the company
culture
4.3. The Clever Thinking® Methodology
4.3.1. Defining the Problem
The leader or team members should generate an appropriate problem statement which
summarises the work to be completed as concisely as is possible (i.e., in a paragraph). This
statement is to be recorded as the basis for the discussions and displayed prominently during
the meeting.
This statement should contain details of the problem that needs solving (i.e., Pipework
requires replacement or Investigate the feasibility of offshore compression). The elements of
the statement should only state facts and not mention or intimate at any possible solutions so
as to keep the team members’ minds free from any influences or clear of any contaminating
ideas. The statement should contain any relevant background information and will not pre-
judge the problem or infer any preconceived solution.
An engineer who either prepared the problem statement or someone who understands the
background to the challenge should introduce the problem to the team to fully ensure that
there is complete understanding of the issues involved and the background. This is to then be
followed by a discussion of the problem to set the boundaries for generation of possible
design solutions.
4.3.2. Generation of Ideas and Solutions
Essential to the success of the Clever Thinking®
philosophy is the ability of the user to get
into the correct frame of mind to generate the most creative solutions. It is useful to change
the environment (i.e. a particular room), the change in scenery will help alter the pattern of
thinking from the daily norm. Minimising the formality of the session makes a break from the
rigid structure of a normal meeting (i.e. strict agendas, formal meeting protocol, etc.), this
helps encourage creativity from the team members. Clever Thinking®
requires a positive and
unrushed environment.

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Along with the problem statement, the team should be given suitable questioning and idea-
steering guidewords, such as:
 What? (In the simplest terms, what is the purpose of the work?)
 Why? (What requirements are driving this work?)
 Boundaries (Boundaries of the problem)
 Information (What information is needed to solve the problem?)
 Assumptions (What assumptions are we to make in the generation of solutions?).
For these guidewords the team will provide short statements for discussion. These could be
on post-it notes, written on a whiteboard or on a laptop
The meeting attendees should use ‘Provocation Operation’ [Ref. 1] and make a bold or
creative statement about the problem to move the thinking forward so that new ideas or
solutions may be found. Also consider using ‘Random Stimulation’ techniques in which team
members use creative and/or random words to promote creativity and ideas. Both of these
techniques are designed to drive the creative thought process and break-away from
established thought patterns.
It may be necessary to not pursue answers wholly within the set time-frame of the meeting,
but allow the team to generate the list of ideas over a reasonable longer period giving them
chance to ‘sleep on it’. Possibly make space on the whiteboard or post-it notes available for
people to write down ideas when they arise.
4.3.3. Assessing suitable solutions
Following the initial definition of the problem and the generation of possible solution ideas an
assessment of the feasible actions and areas for further investigation are proposed by the
team. It should be emphasised that all solutions and areas for investigation are recorded in
the appropriate manner. These then undergo a screening exercise to remove those that are
considered technically infeasible, not economically viable or not possible due to any other
reason. The reasons for not taking them forward are to be recorded to ensure full visibility.
The remaining areas for investigation are then to be agreed by the team as a set of
recommendations. The team should also consider what additional information is necessary for
the project to be completed.
4.4. Teamwork
Individuals have different viewpoints and ways of thinking, but to achieve the goals of the
exercise and identify solutions the group need to work and think as a team. Thinking up and
considering new ideas requires a change in cognitive reasoning. If you appraise the problem
from a range of viewpoints the team will have a more holistic perspective on the problem and
possible solutions.
One method of achieving cooperative group thought is to use the Six Thinking Hats®
[Ref. 3].
This is a simple, but powerful tool conceived by one of the foremost experts in the fields of
creativity and Lateral thinking, Edward De Bono, that defines a teamwork thinking tool

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involving six coloured hats. OSL have added a further coloured hat and thought process,
which is our seventh hat – connectivity. It is based on his principle of parallel thinking where
everyone in the group is thinking in the same direction, from the same perspective, at the
same time. It guides team members away from the confines of everyday inflexible viewpoints
and one-way thinking. This tool enables a group of individuals to look at things in a more
collaborative way, outside of normal perspectives.
Colour Direction Notes
White hat Facts information / data needs - what information is available?
what are the facts?
Red hat Feelings emotional / gut feeling - intuitive gut reaction or
statements of emotional feeling (without justification)
Yellow hat Benefits positives - identify advantages
Black hat Cautions negatives / risk - identifying reasons to be wary
Blue hat Process managing the thinking process - what is the subject?
what are we thinking about? what is the goal?
Green hat Creative ideas – though provocation and inquiry, following a train
of thought
Purple hat Connectivity OSL added the connection of all the other thoughts and
adding extra value to the process
Table 4-1 OSL’s Seven Thinking Hats
Managing group thinking requires a skilful facilitator to lead the proceedings. A strong and
independent temperament is important as well as being open to ideas and criticism from the
team members. The leader should encourage involvement from all team members by sharing
participation, also recognising the importance of individual contribution to the discussions.
Recognition of efforts is a way to encourage input and reduce disengagement. The leader
should also ensure regular summarising, keeping everyone informed of the thought processes
and helping to keep the group members committed to the task.

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5. THE SOLUTION
The production of solids containing sand and proppants following the fracking procedures can
happen at any stage of the field life, however it is most likely to occur at the beginning and
when the field has become more mature and its pressure has depleted. These solids can
threaten the mechanical integrity of the choke valves and the downstream system, due to
erosion and deposition, including the subsea export pipelines.
It is considered that the cost implications associated with eroded pipeline decommissioning,
new pipeline installation, periodic pipeline inspections and a risk of environmentally damaging
hydrocarbon spills would be excessively high. Pipeline leaks would be detrimental to the
company’s finances and reputation. Therefore, separation equipment that can achieve
satisfactory efficiency to reduce the risk of mechanical failure due to erosion issues is required
along with a removed solids accumulator.
5.1. Technology Selection
As part of the technology selection process, suitable criteria were defined. Suitable separation
technology must offer a wide range of operating conditions, process operations flexibility for
commissioning, start-up and shutdown, a minimal footprint and a light load for jack up
deployment and to eliminate the requirement for piling. The assessment included an appraisal
of trade-offs between separation efficiency and associated replacement costs of equipment
and eroded pipelines, along with an option to improve erosional resistance for pipeline
internals, e.g. protective coating and/or wall thickness increase.
An investigation of alternative novel technologies such as inline axial cyclone was a key
element of the decision along with potential concepts to satisfy solids disposal management.
Solids disposal options included the installation of a Solids Accumulator and the requirement
for the vessel to be depressurised prior to initiating solid removal activities. Solids removal
options involved either intervention using a remotely operated underwater vehicle (ROV) or
by diver intervention.
5.2. Subsea Cyclone System
A separation unit is required to be situated close to the wellhead, designed to remove these
solid particles from well fluids from early life to late life production. A self-contained subsea
separation unit is proposed to be installed by the rig on the well conductor without the need
for piling. The unit should also be capable of being handled and installed by a standard jack-
up rig and have a standard subsea tree guide frame. Moreover, the unit must be designed to
allow relocation as and when a new low reserve gas field needs to be decommissioned.
The package includes the wellhead, cyclonic separator, solids accumulator, flow metering
station and umbilical installations [Ref. 4]. Figure 5-1 depicts a simplified block diagram
showing the processes of the unit and their interactions.

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Figure 5-1 - Subsea Separation Block Diagram
For the separator a single cyclonic unit was selected from the number of possible solutions.
For the operation of this unit centrifugal force generated by the flow of the fluids and the
shape of the cyclone enables solid particles to be suspended in the swirling gas stream inside
the cyclone. This causes solid particles, which are denser than the well fluids, to be collected
on the cyclone wall and to travel downwards towards the bottom of the cyclone as shown in
Figure 5-2.
The particles therefore can be collected in an appropriate container and leave the cleaned
well fluids in in a reverse-flow direction through the gas outlet, commonly at the top of the
cyclone. Therefore, the single cyclone separator is typically called a reverse flow cyclone.
Figure 5-2 - Single Cyclone Mechanism [Ref. 5]
The benefits of using this subsea separation cyclone technology rather than any other is that
it is a simple construction with no moving parts, which makes it the most common technology
using centrifugal forces to separate solids particles from fluids. The equipment is made of few
parts so has small footprint and as it is easy to assemble a relatively low level of capital
investment is required. The single cyclone unit also has a relatively low operating pressure
drop compared with multiple cyclone units. A key advantage of this solution is that it uses
existing topsides technology redeployed with some design modifications.

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5.3. Tight Gas Solution
The subsea production system typically consists of subsea wellhead systems with Christmas
trees, process equipment, subsea manifolds, tie-in and flowline systems for multiple well
production, umbilical systems, control systems and the export pipeline system. The process
flow diagram (PFD) shown in Figure 5-3 depicts the equipment set up.
Figure 5-3 – Process Flow Diagram
5.3.1. The Process Equipment
The main process equipment consists of the cyclone (discussed in section 5.2) and a solids
accumulator vessel. The accumulator will be situated underneath the cyclone collecting
separated solid particles (such as sand and proppant), from the produced well stream. A
spherical design was implemented in the design of the separation package to avoid any
possible dead spaces which could result in difficulties in solids removal from the container.
The accumulator will be filled up with water and a suitable hydrate inhibitor. The quantity of
produced solids can then be monitored by a rise in liquid level using a level indicator located
within the storage vessel.
A fiscal flow meter will measure the flowrate of the export gas from the separator, prior to
being transferred to the host platform by way of the subsea pipeline.
Figure 5-4 shows the compact skid design of the subsea unit. Production piping connects the
wellhead tree directly to the cyclone separator, where the sand and proppants will be
segregated from the production stream and collected in the solid accumulator. The solid free
gas will be exported to end users through the pipeline. The production piping is fitted with a
series of actuated valves to control the flow of gas coming from the wellhead. Piping will be
supported within the framework to ensure operational stability. The steel superstructure of
the unit will provide adequate support for equipment items and suitable subsea protection.

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Figure 5-4 – Subsea Separation Unit
5.3.2. Solids Disposal Management
Once a suitable level is reached, the solids in the accumulator will be emptied using an ROV.
Prior to removing solids from the container, the Solids Accumulator shall be isolated from the
cyclone to allow pressure reduction. In order to empty the solids accumulator, the solids will
need to be fluidised with water through a water injection pump. Water distribution nozzles
may be required to aid this process to enable solids suspension as the replacement water
enters the solids accumulator. The injection pump has a sufficient pressure to allow slurry
fluid to be transferred via a temporary hose to a container on the ROV vessel. The slurry will
be treated and disposed of onshore in a safe manner.

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6. CONCLUSION
6.1. Contemporary Approach
The contemporary approach to the development of tight gas accumulations involves deep
horizontal drilling. These fields cannot be produced at economic flows without assistance from
stimulation treatments, i.e. fracking. This imparts the continual problem of solids handling
due to the release of sand and the fracturing proppants used to stimulate the well. These
solids then create downstream difficulties with erosion of equipment, especially choke valves,
and pipework along with the significant maintenance cost associated with this.
Directional drilling from a platform is used to develop single and multiple well gas fields. This
method has high cost implications for single well and dual well developments and may not be
economically viable for low reserve fields. Finding ways of improving the economic viability of
tight, low reserve gas fields in the SNS is becoming more important.
There is a growing industry approach to examine this issue from alternative perspectives. An
approach to find new ways of doing things, or reapply current methods in a new way is
required, so as to improve efficiency of the recovery system and reduce costs to ensure the
viability of these assets.
6.2. Collaboration: Client and Partners
The success of this undertaking was greatly influenced by the fact that OSL was able to work
in close partnership with an operating company to undertake this conceptual study. The
collaboration meant that the overall team, made up of both OSL and operational personnel
were able to combine knowledge and experience whilst investigating solutions for recovering
gas from stranded offshore gas fields and transporting it using subsea pipelines to an
adjacent offshore platform.
During the experience of the cooperation it became evident that working together generates
much more than working in isolation. The partner teams were able to pool resources, sharing
know-how and expertise such that the ideas and solutions output from the Clever Thinking®
meeting was more creative giving rise to comprehensive, practical and constructive results.
6.3. Clever Thinking®
: Solution Generation
OSL define Clever Thinking®
as the culture of creating solutions by sharing ideas. The
philosophy aims to utilise creative thinking techniques to improve the value of the solutions
that are provided. The approach provides the ability to think creatively, unimpeded by
orthodox constraints, without losing sight of the goal.
Clever Thinking®
sessions where a team is formed of personnel directly involved in the issue
at hand and also people independent from the project team to give as wide a range of
experience and opinions as possible. A facilitator guides the team through the process of first
identifying ideas, then reviewing and developing these, with the ultimate goal to produce a
list of possible solutions to the issue along with assigned actions for follow up work. During
the sessions the creative thinking toolbox may be employed as necessary

Date: 27 Nov 2015
Page 19 of 20
This practise employs techniques that are designed to drive the creative thought process and
break-away from established thought patterns. One approach is used but this method is
proven to release potential from the team with a wealth of untapped ideas.
6.4. Tight Gas Development
Tight gas is a prospect which currently remains underexploited outside the US, but demands
on the gas market are bringing this to the fore. Tight gas is becoming an industry priority and
the development of these reserves in the SNS is starting to take off. In the overview of
activities from September 2015, the UK Oil and Gas Authority (OGA) focus on priorities
planning has SNS tight gas regional developments intended for the latter half of 2016. Tight
gas has the potential to facilitate and maximise the current upsurge of growth in the gas
industry.
Extracting value from tight gas reservoirs represents a challenge for the industry as it
necessitates the use of advanced technologies. Well costs are the most significant cost driver
in the economics of unconventional gas. If the costs of well exploitation are reduced, then
this makes tight gas a very viable prospect. The solution developed by this process for the
subsea extraction method and processing unit is poised to become an integral part of
reducing the costs and making tight gas recovery economically practicable.
The proposed solution for solids separation and solid removal approach will satisfy the
defined design aspects. It also has overcome the potential operational difficulties and
provides a strong financial benefit for single or dual well tight gas marginal field development.
The proposed solution has proven attractive for SNS operators as it is technically feasible,
constructible, maintainable and economic. This innovative technology has the potential to
become the leading solution in the production of marginal gas fields.

Date: 27 Nov 2015
Page 20 of 20
7. REFERENCES
1. Law, B. E., and J. B. Curtis, 2002, Introduction to unconventional petroleum systems:
AAPG Bulletin, v. 86
2. The Mechanism of Mind (1969)
3. Six Thinking Hats - Edward de Bono (1985)
4. OS-0483-BAY-PRP-0006 - Conceptual Study for Subsea Separation: Summary Report,
Rev. A00 (April 2015)
5. Gas Condition and Processing Volume 2: The Equipment Modules, J.M. Campbell and
Company, 8th
Edition (2004)

Improve Efficiency Tight Gas Fields

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