Improving Efficiency Tight Gas

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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 todevelop single and multiple well gas fields. However, this method has high cost implicationsfor 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 fieldsin the SNS is becoming more important.

Improving the economic viability of tight, low reserve gas fields in the SNS may be achievedusing 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 thedesign of this subsea unit. This presents an opportunity to develop a simple and economicalsolution 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’sunique Clever Thinking ® methodology. This approach ensured that the most suitable sandremoval 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 wellproduction, umbilical systems, control systems and the export pipeline system. For theseparator a single cyclonic unit was selected from the number of possible solutions. The keybenefit of using this subsea separation technology is that it is a simple construction with nomoving 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 theunit to avoid any possible dead spaces which cause difficulties in solids removal from thecontainer. 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 allowpressure 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 safemanner.

The success of this undertaking was greatly influenced by the close partnership with anoperating company whilst carrying out this conceptual study. The collaboration meant thatthe overall team, made up of both OSL and operational personnel were able to combineknowledge and experience whilst investigating solutions for recovering gas from strandedoffshore 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 creativethought process and break-away from established thought patterns, this method is proven torelease potential from the team with a wealth of untapped ideas.

The proposed solution satisfies the defined design aspects and has overcome the potentialoperational difficulties, providing strong financial benefits for single well tight gas marginalfield development. The proposed solution has proven to be attractive as it is technicallyfeasible, 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 gassecurity of supply. Developing new reserves has become one of the key issues in recentyears, especially the exploration of stranded gas reserves as more conventional fields becomedepleted. A number of technologies have been studied in order to create economic viabilityfor future exploration.

It is estimated that there are more than 100 assets in the Southern North Sea (SNS) that arelabelled as stranded fields. These are a collection of tight reservoirs with distantinfrastructure, possibly with small volumes, and inconsistent gas qualities. The main reasonswhy these resources have not yet been developed are related to cost and technology, thoughsome 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 developmentsand 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 beexported to a nearby offshore platform through a subsea pipeline for further production. Thisprocess 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 thissubsea unit. Solid particles may cause clogging and erosion in pipelines, pipework and

rotating machinery which threaten pipeline and system operations. This study will propose asolution to this problem, which complements the selected separation process.

OSL Consulting (OSL) and its partner operating company recognise an opportunity to developa 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 proppantsreleased as part of hydraulic fracturing (fracking) activities.


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3. REDUCING COSTS WHILST TARGETING TIGHTGAS

3.1.

Tight Gas FieldsNatural 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 ofless than 0.1 millidarcy (mD) [Ref. 1], however recently the German Society for Petroleumand Coal Science and Technology (DGMK) announced a new definition for tight gas

reservoirs elaborated by the German petroleum industry, which includes reservoirs with anaverage effective gas permeability less than 0.6 mD. This gas source mainly produces drygas 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 manygas 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 isexpected 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 servicecompanies implementing and offering skid based or otherwise portable fracturing spreadsfor deployment on to temporary platforms or suitable temporary boats.

Developments in horizontal drilling have made the development of tight gas reservoirs morepromising. The bores can intersect natural fissures and fractures that are present in theformation 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 toaccelerate production. Significant stimulation of the well hydraulic fracturing (fracking) isrequired to ensure commercial flows. Because of this the solids handling of the returningproppant 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 aresignificant and often uncertain development costs involved with the drilling. The cost ofdrilling is particularly high when drilled horizontally for long distances before initiating thefracking process.

3.3. Problem HistoryThere are many low-reserve, tight gas fields, which are currently disregarded due to theiruneconomic 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 suitableproduction flow rate of gas from the field. The proppants used in the fracturing processreturn to the surface with the gas and flowback liquids. There are many options that havebeen 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 todevelop such fields, at the normal costs associated with the installation of the requiredinfrastructure.

This issue has affected the development of low-reserve tight gas fields as the costs ofsupplying suitable processing equipment. OSL Consulting Engineers (OSL) have partneredwith 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 solidsremoval,

3.4.

The Tight Gas ChallengeExploration of stranded tight gas reserves has become a challenging topic in recent years. Anumber of technologies have been studied in order to create economic viability for futureexploration. Directional drilling from a platform is used to develop single and multiple well gasfields.. However, this method has high cost implications for single well and dual welldevelopments and may not be economically viable for low reserve fields.

Solids removal will represent the main challenge in designing this package. Except in cases ofrecovering 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 inoperation, 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 assetinoperable. Generally, the production facilities experience a maximum solids production rateduring 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 toremove 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 besimple and have a small footprint, but economically favourable and must require minimum

maintenance and intervention.


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3.5. IdeaThe project partners have discussed ways of improving the economic viability of tight, lowreserve gas fields in the Southern North Sea. The partners see an opportunity to provide asimple 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 acyclone unit modified for subsea use to segregate sand and proppants particles used as partof or as a result of well fracturing. Well fluids will then be exported to a nearby offshoreplatform 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 andstructures.

Solids handling and disposal management is a significant issue for the design of this subseaunit. 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 topropose a solid management solution to this problem which complements the selectedseparation 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 configurationschemes suitable for subsea separation.

An important feature of the study involved the research and development work OSL carriedout 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 andoptimised to meet the set project criteria.

3.6. ApproachThe objective of the study was to:

Identify a suitable solid particle separation technology and investigate the technicalfeasibility of the selected separation technology using CFD

Develop an outline overall process scheme and determine the suitable size of keyprocess 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 andproppant 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 incollaboration with a local research institute. Thorough assessment and verification of theprocess mechanics, carrying out solids/liquids separation performance of the process usingComputational Fluid Dynamics (CFD), ensured that the final solution of the cyclone

performance was verified. Assessing sensitivity analysis on process parameters and inletparticle distribution, the model was used to optimise the solution using various numericalmethods 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 optionincluding pipeline costs and solids removal costs. This was then further developed into a highlevel economic assessment of the overall project. This economic assessment consisted of ahigh 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 andgas 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 toconduct 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 losingsight of the goal.

The Clever Thinking ® strategy encourages and facilitates the thought processes that we, asprofessional 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 mayresolve them, without compromising safety.

Clever Thinking ®

allows OSL to provide custom fit solutions for every problem, providingmaximum 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 efficientand 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 atOSL. This cultural philosophy benefits the working environment and improves the quality ofthe 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 ® isabout 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 ofconflicts 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 strongmotivators for a team to work harder and aim higher. By celebrating team members’ achievements in front of colleagues, it stimulates all concerned. By recognising individualsinput 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 takeresponsibility, to be more productive, to influence their environment, and to increase theirown capabilities.

Finally, Clever Thinking ® techniques will not suit all situations and all people. It cannot beforced, so encouragement of the concept should be ingrained into the fabric of the companyculture

4.3. The Clever Thinking® Methodology

4.3.1. Defining the Problem

The leader or team members should generate an appropriate problem statement whichsummarises 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 duringthe meeting.

This statement should contain details of the problem that needs solving (i.e., Pipeworkrequires replacement or Investigate the feasibility of offshore compression). The elements ofthe statement should only state facts and not mention or intimate at any possible solutions soas 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 thebackground 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 befollowed by a discussion of the problem to set the boundaries for generation of possibledesign 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 getinto the correct frame of mind to generate the most creative solutions. It is useful to changethe environment (i.e. a particular room), the change in scenery will help alter the pattern ofthinking from the daily norm. Minimising the formality of the session makes a break from therigid 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 andunrushed 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 beon post-it notes, written on a whiteboard or on a laptop

The meeting attendees should use ‘Provocation Operation’ [Ref. 1] and make a bold orcreative statement about the problem to move the thinking forward so that new ideas orsolutions may be found. Also consider using ‘Random Stimulation’ techniques in which teammembers use creative and/or random words to promote creativity and ideas. Both of thesetechniques 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 themchance 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 anassessment 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 inthe appropriate manner. These then undergo a screening exercise to remove those that areconsidered 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 forthe project to be completed.

4.4. TeamworkIndividuals 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 andconsidering 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 andpossible 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 ofcreativity 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 whereeveryone in the group is thinking in the same direction, from the same perspective, at thesame 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 morecollaborative 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 andadding 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 theteam members. The leader should encourage involvement from all team members by sharingparticipation, also recognising the importance of individual contribution to the discussions.Recognition of efforts is a way to encourage input and reduce disengagement. The leadershould 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 andwhen the field has become more mature and its pressure has depleted. These solids canthreaten the mechanical integrity of the choke valves and the downstream system, due toerosion 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 damaginghydrocarbon spills would be excessively high. Pipeline leaks would be detrimental to thecompany’s finances and reputation. Therefore, separation equipment that can achievesatisfactory efficiency to reduce the risk of mechanical failure due to erosion issues is requiredalong with a removed solids accumulator.

5.1. Technology Selection

As part of the technology selection process, suitable criteria were defined. Suitable separationtechnology must offer a wide range of operating conditions, process operations flexibility forcommissioning, 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 appraisalof trade-offs between separation efficiency and associated replacement costs of equipmentand eroded pipelines, along with an option to improve erosional resistance for pipelineinternals, e.g. protective coating and/or wall thickness increase.

An investigation of alternative novel technologies such as inline axial cyclone was a keyelement of the decision along with potential concepts to satisfy solids disposal management.Solids disposal options included the installation of a Solids Accumulator and the requirementfor the vessel to be depressurised prior to initiating solid removal activities. Solids removaloptions 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 thesesolid 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 needfor 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 toallow relocation as and when a new low reserve gas field needs to be decommissioned.

The package includes the wellhead, cyclonic separator, solids accumulator, flow meteringstation and umbilical installations [Ref. 4]. Figure 5-1 depicts a simplified block diagramshowing 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 theshape of the cyclone enables solid particles to be suspended in the swirling gas stream insidethe cyclone. This causes solid particles, which are denser than the well fluids, to be collectedon the cyclone wall and to travel downwards towards the bottom of the cyclone as shown inFigure 5-2.

The particles therefore can be collected in an appropriate container and leave the cleanedwell fluids in in a reverse-flow direction through the gas outlet, commonly at the top of thecyclone. 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 thatit is a simple construction with no moving parts, which makes it the most common technologyusing 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 capitalinvestment 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 usesexisting topsides technology redeployed with some design modifications.


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5.3. Tight Gas SolutionThe subsea production system typically consists of subsea wellhead systems with Christmastrees, process equipment, subsea manifolds, tie-in and flowline systems for multiple wellproduction, 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 solidsaccumulator vessel. The accumulator will be situated underneath the cyclone collectingseparated 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 anypossible 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 locatedwithin the storage vessel.

A fiscal flow meter will measure the flowrate of the export gas from the separator, prior tobeing 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 besegregated from the production stream and collected in the solid accumulator. The solid freegas will be exported to end users through the pipeline. The production piping is fitted with aseries of actuated valves to control the flow of gas coming from the wellhead. Piping will besupported 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 ManagementOnce 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 thecyclone to allow pressure reduction. In order to empty the solids accumulator, the solids willneed 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 waterenters the solids accumulator. The injection pump has a sufficient pressure to allow slurryfluid to be transferred via a temporary hose to a container on the ROV vessel. The slurry willbe 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 deephorizontal drilling. These fields cannot be produced at economic flows without assistance fromstimulation treatments, i.e. fracking. This imparts the continual problem of solids handlingdue to the release of sand and the fracturing proppants used to stimulate the well. Thesesolids 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. Thismethod has high cost implications for single well and dual well developments and may not beeconomically 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. Anapproach to find new ways of doing things, or reapply current methods in a new way isrequired, so as to improve efficiency of the recovery system and reduce costs to ensure theviability 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 workin 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 personnelwere able to combine knowledge and experience whilst investigating solutions for recoveringgas from stranded offshore gas fields and transporting it using subsea pipelines to anadjacent 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, sharingknow-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. Thephilosophy aims to utilise creative thinking techniques to improve the value of the solutionsthat are provided. The approach provides the ability to think creatively, unimpeded byorthodox constraints, without losing sight of the goal.

Clever Thinking ® sessions where a team is formed of personnel directly involved in the issueat hand and also people independent from the project team to give as wide a range ofexperience and opinions as possible. A facilitator guides the team through the process of firstidentifying ideas, then reviewing and developing these, with the ultimate goal to produce alist 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


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This practise employs techniques that are designed to drive the creative thought process andbreak-away from established thought patterns. One approach is used but this method isproven 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 demandson the gas market are bringing this to the fore. Tight gas is becoming an industry priority andthe development of these reserves in the SNS is starting to take off. In the overview ofactivities from September 2015, the UK Oil and Gas Authority (OGA) focus on prioritiesplanning 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 gasindustry.

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 driverin the economics of unconventional gas. If the costs of well exploitation are reduced, thenthis makes tight gas a very viable prospect. The solution developed by this process for thesubsea extraction method and processing unit is poised to become an integral part ofreducing 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 andprovides 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.


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7. REFERENCES

1. Law, B. E., and J. B. Curtis, 2002, Introduction to unconventional petroleum systems:

AAPG Bulletin, v. 862.

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 andCompany, 8th Edition (2004)

Improving Efficiency Tight Gas

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