exemption of sc-sssv in mature onshore gas wells in the netherlands...

Exemption of SC-SSSV in mature onshore gas wells in the Netherlands

A different approach to produce more gas from liquid loading wells

European Gas Well Deliquification Conference 2014

Groningen (NL), 22. – 24. September, 2014

Koos Ham and Ingrid Raben (TNO)

•September 23., 2014•Koos Ham•Exemption of SC-SSSV

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The challenge

A surface-controlled subsurface safety valve (SC-SSSV) is required by law in the Netherlands in all naturally flowing wells.

The SC-SSSV results in technical and economical complications for application of some deliquificationtechniques.

An exemption of the SC-SSSV obligation can be obtained if can be demonstrated that at least the same level of safety is achieved in another manner.

Dutch mining authorities (SodM) have defined a (minimum) set of conditions and criteria to be fulfilled for consideration of an exemption request, based on a specific exemption case of one of the operators.


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Goals of the project

To determine the criteria for a viable request for SC-SSSV exemption:

Identify cases (well properties) where SC-SSSV can be removed without increasing:

safety risks to the public, caused by initial blowdownadverse consequences to the environment and/or to government’s or operator’s reputation, caused by the long term effects.

Assess or quantify the safety risks and environmental impact of a well blowout, for situations with and without SC-SSSV.

Identify what is necessary to ensure the original safety level and to mitigate and limit the duration of a well blowout.

Formulate the criteria and the format for a viable exemption request.


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Project set up

Initiated by a consortium of Dutch onshore gas production operators

Close cooperation with participating operators and advisors

In interaction with authorities


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Role of TNO

Project management, coordination and communication.

Execution of the technical studies in the project, in interaction with

partners; TNO has

expertise in consequence modelling and QRA;

expertise in gas well deliquification modeling,

experiments and mitigation.


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Objectives of work packages

WP2: Benefits SC-SSSV removal

WP3: Requirements / other countries

WP4: Risk history & blowout statistics

WP5: How to meet the criteria

WP6: Minimizing effects

WP7: Framework exemption request

WP8: Pilot(s) exemption request


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WP2: What are the benefits of SC-SSSV removal?Scope

1. Evaluation of pros and cons of different GWD techniques and

compatibility with SC-SSSV [literature study and operator interviews]

Lowering THP

Velocity string

Foam assisted lift

Intermittent production

Plunger lift

Gas lift

Pump

2. Impact on operational risk of SC-SSSV in combination with GWD.

3. Estimation of costs with and without SC-SSSV.


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WP2: What are the benefits of SC-SSSV removal?Data


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WP2: Opportunities for GWD techniquesConclusions

Several options of deliquification are currently only possible when SC-

SSSV is removed.

Absence of SC-SSSV reduces frequency of well intervention; related

risks of installation and repair of GWD will be less.

Removal of the SC-SSSV leads to significant cost reductions of

deliquification, thus making continued production from mature fields

economically viable.


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WP3: Regulation on SC-SSSVScope

What exactly are the requirements in different countries?

How do the regulations in other countries / areas compare to the

Dutch situation?


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WP3: RegulationRequirements in the Netherlands

Dutch Mining regulations, Article 8.4.1:

Clause 1: A self-producing well shall be equipped with a safety

protection installation, installed at a depth of at least 50 meters below

the earth’s surface or the bottom of surface water to prevent

uncontrolled flow from the well. This protection facility shall be operable

from above the earth’s surface or surface water.

Clause 5: The Minister can grant exemption from Article 8.4.1.1

provided that it has been demonstrated that at least the same level of

safety is achieved in another manner.


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WP3: RegulationApproach

Survey by questionnaires among 19 countries (facilitated by SSM)

9 responses

More detailed investigation of legislation in 5 countries (Germany,

USA, Canada, United Kingdom, Poland).


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WP3: RegulationConclusion

Regulations vary widely for onshore gas wells:

Some countries do not explicitly require SC-SSSV: UK, EI, NZ, CND

(Newfoundland, Labrador), US, RO, AU. Installation of (SC-)SSSV is

responsibility of the operator, based on safety evaluation or ALARP.

In other countries, SC-SSSV requirement is related to specific

conditions, e.g. production rates or presence of H2S: CND (Alberta),

DE, AT, PL.

In a few cases, SC-SSSV is required in all situations: NL, FR, PT.


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WP3: RegulationConclusion, specified properties onshore gas wells

Country/ State H2S (vol%) Flow rate (m3/day)

UK, Ireland, USA, Australia, New Zealand, Canada (Newfoundland and Labrador)

Not specified

The Netherlands, France, Portugal > 0

Germany, Niedersachsen, Bremen > 1 > 400,000 technical open flow

Germany, Schleswig-Holstein, Hamburg >1 high

Canada (Alberta) > 5 > 140,000 and not on pump

Poland flow H2S > 25920 m3/ day

Austria (company policy) ?? (> 400,000)

Romania (company policy) (> 0.001)


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WP4: Risk history & blow out statisticsApproachAnalysis of data from:

Sintef Offshore Blowout Database: offshore wells equiped with SC-

SSSV and production packer.

Railroad Commission of Texas: onshore wells not equiped with SC-

SSSV and production packer.

Alberta Energy Regulator, of ERCB: onshore wells not equiped with

SC-SSSV and production packer.

.


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WP4: Risk history & blow out statisticsConclusions

70 - 90% of all blowouts occur during activities other than production.

In 30% of offshore blowouts flow path occurs outside tubing; for onshore production blowouts this contribution is 60%.

Of production blowouts offshore over 90% have external causes, e.g. extreme weather, ship collision, etc. These are causes that are hardly relevant in onshore situations. Of production blowouts onshore, only 10% have an external cause.

Detailed data about the nature of internal causes is scarce. The more frequent (and more complicated) well interventions for maintenance and repair of SC-SSSV and the risks associated with these well entries is of interest in this project. It will need further consideration in assessing its contribution to the total blowout risk during production.


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WP5: Arguments for exemption requestObjectives and conditionsOperator’s objectives:

Continue economically viable production from liquid-loaded wellsWithout compromising safety.

Authorities objectives:Maintain existing safety levelsMinimize consequences of well incidentsOperators are encouraged to apply state-of-art technologies in GWD; no limitative set of conditions for SC-SSSV exemption will be issued.


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WP5: Arguments for exemption requestCriteria for risk and environmental impactsSituation without SC-SSSV:

Must comply to legal requirements for urban planning (Bevi) (determined by blowdown phase);Should have limited risks to personnel, public, assets, reputation (mainly determined by long term steady state release).

Environmental aspects considered:Heat radiation (torch fire)NoiseOdourPollution, etc.


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WP5: Arguments for exemption requestCriteria for risk and environmental impacts

New guideline on QRA for Mining installations (Bevi) issued: risk assessment methodology, generic failure scenarios, frequencies and modeling tools.

Immediate risks to personnel and public according to QRA guideline: determined (mainly) by initial depressurization (blow-down)

duration: seconds – minutes

automatic closure of SC-SSSV not within 20 s, unless for full rupture of well head.

Long lasting effects and reputation damage, due to heat radiation (torch fire), noise, odour, pollution, etc.

determined (mainly) by production capacity (open flow potential)

duration: hours – days – weeks, depending on mitigation options.


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WP5: Arguments for exemption requestCriteria for mitigation

Mitigation strategies: bullhead kill with own resources (~days); expected feasible for leaks

cap and kill with external intervention team (~weeks); expected feasible for

ruptures

drilling relief well (~months); not expected necessary for any scenario for

candidate mature wells.

Determination of ranges of own mitigation capacity / capability:effects and impact for representative scenarios, over range of well

dimensions and properties → which can be managed?

conduct full analysis for study case (existing liquid-loaded well)

capacity and resources will be evaluated against international experiences.


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Example of modeling resultsBlowout release rate and distance to heat radiation


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Conditions: • well diameter 3”• tubing depth 2,000 m

Example of modeling resultsIndividual risk contours for a gas field


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Risk contours: • left well with SC-SSSV • right well without SC-SSSV

Next steps

Finalize WP5: set up exemption criteria

WP6: how can we deal with the effects (blowout mitigation)

WP7: format for exemption request

WP8: pilot exemption request for 3 - 4 cases

And (outside the scope of the current project):

How can we use QRA to discuss and investigate alternative

engineering solutions while maintaining safety standards, e.g.

evaluation of the risk profile of alternative technologies for well

abandonment?


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Thanks for your attention

Questions?

[email protected]; [email protected]


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exemption of sc-sssv in mature onshore gas wells in the netherlands...

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