OFFSHORE PIPELINE DECOMMISSIONING GUIDELINE
1. SCOPE OF GUIDANCE
This guidance covers the offshore oil and gas pipeline network and all associated sub-sea structures in
the Kingdom of Thailand governed by the Petroleum Act B.E. 2514. This guidance does not include the
PTT pipelines.
2. REGULATORY AND INTERNATIONAL FRAMEWORK
Thailand is a signatory to the present 1982 United Nations Convention on the Law of the Sea
(UNCLOS) but has yet to ratify. The 1972 London Convention and its 1996 protocol have also been
adopted for the purpose of these guidelines.
The provisions in Article 60 (3) of the 1982 Convention on the Law of the Sea (UNCLOS) can be
interpreted that the pipelines should be decommissioned by ensuring safety of navigation with due
regard to fishing, the protection of the marine environment and the rights and duties of other users of
the sea.
The 1972 London Convention and its 1996 protocol prohibit certain materials for dumping at sea.
However, some materials can be considered for disposal at sea if the land based disposal methods are
limited. A waste assessment framework (WAF) is provided to assess if the material can be disposed at
sea.
3. DECOMMISSIONING TIMING AND DEFERRAL
When a pipeline becomes due for decommissioning under the criteria stated in Section xxx (Legal
Section) and due to technical and/or economical reasons it is desired to defer the decommissioning,
then a Suspension Application Form (Form xxx) must be completed stating reasons for deferral.
Guidance for suspension is included in Section 3.7.2.4 of this guidance.
If the pipeline is not due for decommissioning, under the criteria stated in Section xxx, but due to
operational and/or technical reasons the pipeline is required to be put out of service, appropriate
measures should be taken to ensure that the final decommissioning method is not compromised.
4. IMPLICATIONS FROM AGREED ENVIRONMENTAL POLICIES AND PRINCIPLES
The environmental policies and principles stated in Section xxx (Environmental Policies and
Management) shall have the following implications with regards to pipeline decommissioning:
•
In the event of uncertainty, with regards to decontamination of pipelines, the
decommissioning option will err on the side of caution by including a comprehensive and
extended monitoring plan.
•
The environmental responsibilities normally lies with the concessionaire but may also rest
with the contractor and relevant authorities, as determined under the mechanism stated in
the Section xxx (Legal Section, Release of Liability).
•
At the time of drafting this guideline, the methods for pipeline decontamination is still under
research. Development of any such environmental technologies should be performed in a
process to ensure diffusion of knowledge and development of practical techniques and
procedures for the benefit of protecting the environment in a cost effective manner.
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•
All available environmental data should be made available to stakeholders upon request
through the relevant government authorities. Stakeholders will have the right to comment on
the comparative Best Practical Environmental Option (BPEO) assessment and have their
comments integrated into the final report to ensure public acceptability is addressed as part
of the decision-making criteria. The comments should be addressed to the extent that they
are relevant, valid and factually accurate.
5. OBJECTIVES, GENERAL APPROACH AND PLANNING
The objective of this guidance is to ensure that pipelines will be decommissioned with due regards to
the environment, navigation, fisheries and other users of the sea.
•
The decision criteria specified in these guidelines will enable concessionaires to determine
the likelihood of the approved recommended decommissioning method;
•
All generic options, as described in Section 3.7, should be considered. However, if initial
studies indicate one or more of the options are not feasible, or there is an additional option
not included, prior consultation with the relevant authorities should be performed in
accordance with the decommissioning process in Section xxx (Legal Section) to gain
approval (case-by-case);
•
A comparative assessment shall be performed following BPEO process as prescribed in
Annex xxx to determine the preferred decommissioning option;
•
Once the preferred option has been determined using the BPEO assessment, the
implementation of the preferred option shall be made in accordance to the flow chart in
Figure xxx.
•
The planning schedule must give the opportunity to ensure all aspects of the assessment
and implementation are considered in accordance with the decommissioning process in
Section xxx (Legal Section).
•
Cumulative impacts from the concessionaire’s total pipeline network should be considered
when assessing the significance of any potential impacts.
6. PIPELINE INFORMATION REQUIREMENTS
Concessionaires should submit pipeline information as specified in the following sub-sections (using the
forms in Annex xx) to support the assessment and recommended decommissioning method. The
information is also necessary to ensure records of any pipelines left in-situ can be updated into marine
navigation and fishing charts.
If sufficient historical data is not available then the concessionaire will be required to obtain the missing
information by performing the relevant surveys.
Technical Specifications:
Inventory information describing: length; water depth; diameter and wall thickness; material; type of
service (oil, gas, multi-phase); fluid composition (recent representative samples); weight coating;
corrosion coating; remaining life of cathodic protection; original state (on seafloor or trenched); design
structural life; as-built pipeline route; associated sub-sea structures and/or valve assemblies.
a) Historical Data:
A summary of the records on: installation date; inspection records (corrosion, free span, etc.); recent
gas composition; damage and repairs during pipeline life.
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b) Surveying Requirements (if not available in historical data):
Scouring / deposition rates, current state (exposed, buried, partially buried etc.), pipeline corrosion
results.
7. DECOMMISSIONING OPTIONS
All the following options need to be considered for the BPEO assessment. Any deviation from these
options will require consultation in advance with the relevant authorities, as previously mentioned.
7.1 Reuse
If an opportunity for reuse can be identified, such as future developments, re-injection or CO2
sequestration plans, a preliminary assessment should be performed to evaluate its technical feasibility.
7.2 In Situ
On condition that there is no significant impact to the environment and other users of the sea, it is
envisaged that most of the pipelines will be left in place due to technical issues, safety implications and
land based disposal limitations.
7.2.1
Leave in Place (seafloor)
Pipelines left in place should ensure the following:
•
•
•
•
7.2.2
The pipeline has been cleaned and decontaminated to the specified level stated in Section
3.8.1 and 3.8.2, confirmed by the verification process (Section 3.8.3) and the postmonitoring process is followed per Section 3.10.2;
It is accepted by the specified key stakeholders, as listed in the Section xx (Legal Section);
The pipeline is stabilized using the most appropriate method, such as burying the ends or
by placing grout bags;
Notification to the designated authorities must be given with regards to depth, position, size,
and condition of any pipelines left in place to ensure the pipelines do not become an
obstruction or hindrance to navigation and fishing.
Burial or Trenching
If one or more of the above criteria cannot be achieved the pipeline should be considered for burial.
Pipelines should be buried if the following conditions exist:
•
If determined by the designated authority in the anticipation of it being an obstruction to
fishing and/or shipping;
• It can be demonstrated that the sediment quality in the vicinity of the pipeline is not
contaminated;
• Verification that the pipeline has been sufficiently cleaned and decontaminated (as
specified in Section 3.8.3) and the burial depth, as demonstrated by research, field trials
and monitoring, is sufficient to prevent any future harmful effects on marine life.
• The buried pipeline is monitored, as agreed with the designated authorities. The length of
monitoring should be of a period sufficient for the verification purposes and/or future
pipeline exposure.
7.2.3
Removal and Onshore Disposal
The following items should be removed and disposed of onshore:
1. Sub-sea structures protruding above the seafloor in such a way that they pose a hazard to
fishing, navigation or other users of the sea;
2. Pipeline sections that could be a hindrance to fishing/shipping, or cannot be properly
decontaminated at offshore locations to the acceptable standards.
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Any such items should be cleaned and decontaminated to a level which is safe for handling and
transportation.
Removal of any pipeline sections or associated structures should be supported by the proposed
mitigation measures to minimize potential impacts on the environment at each phase of the removal
process from removal, transportation to shore, onshore handling and through to final disposal.
The treatment and final destination of any pipeline, associated structures and residual wastes removed
to shore should be carried out in accordance with the Onshore Dismantling and Disposal Criteria
specified in Section xxx.
7.2.4
Suspension
If the pipeline is to be suspended for deferral or further future use it should be appropriately protected
against corrosion both internally and externally using environmentally friendly methods.
Suspended pipelines should be isolated from the remaining network and sufficient provisions should be
made for future cleaning and/or decontamination, if required. An appropriate maintenance and survey
regime should be implemented to ensure the minimum risk to environment, marine life and other users
of the sea.
Suspended pipeline should be assessed to determine the preferred option prior to decommissioning.
The suspension method should not compromise the final decommissioning option.
8. PIPELINE CLEANING AND DECONTAMINATION REQUIREMENTS
All pipelines should be cleaned and will also require decontamination if unacceptable levels of
contaminants are found by the presence of impurities in the fluid properties and/or the presence of
contaminants in the hydrocarbon cleaning residue. A Cleaning and Decontamination Notification Form
(Form xxx) should be submitted to the relevant authorities as specified in Annex xxx.
8.1 Cleaning Requirements
All pipelines should be pigged and purged to flush residual fluids using the most appropriate methods
and suitable chemical additives to ensure effective cleaning. The historical information of the pipeline
should be considered in preparing specific cleaning procedures.
8.1 Decontamination Requirements
Although the chemical technology to leach out or encapsulate contaminants is available there are no
definitive field studies to prove the practicality of any of the methods. Research projects have been
initiated to evaluate these and other developing technologies. This section of the guidelines will be
updated when the results of these research projects and field trials are concluded.
Any decommissioning application with regards to contaminated pipelines, prior to the update of this
section, should include a proposed decontamination method. This will be assessed on a case-by-case
basis considering the results of any field trials or other supporting evidence to prove the effectiveness of
the proposed method.
8.2 Verification
Cleaning and/or decontamination of pipelines should be verified by using a qualified third party, as
specified in Section xxx.
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To verify the cleaning process, the concentration of Total Petroleum Hydrocarbons in final flushed water
discharged from the pipeline should be below or equal to 40ppm.
The verification process for the decontamination of pipelines will require the pipeline to be left in a
condition that will allow sampling and monitoring of internal fluids. Monitoring frequency should be once
every three years for the total of four cycles. Future justification can be made, based on the results
obtained from future pilot project to monitor internal fluid of abandoned sub-sea pipeline.
The allowable concentrations of eight (8) heavy metals monitored in the internal fluid should be below or
equal to Soluble Threshold Limit Concentration (STLC) as shown in the Appendix A of this Guideline.
This STLC and standard test method are referred to in Annex II of Notification of Ministry of Industry
B.E. 2548 (2005) regarding Waste Disposal.
9. KEY ENVIRONMENTAL ISSUES
The eventual deterioration of the pipeline (if left in-situ) together with the release of any residual
contaminants should be considered when assessing the possible future effects on the marine
environment, marine life and other users of the sea. The evaluation of any likely effects on marine life
should consider the final fate of any possible contaminants by assessing the toxicity; persistence,
accumulation and biotransformation; and the probability of tainting fishing resources.
Other environmental aspects with regards to pipelines should refer to the Environmental Policies and
Management (Section xx) and the BPEO in Annex xxx.
10. MONITORING AND AUDIT PLAN
A two phase monitoring program should be applied as followed: pre-decommissioning and postdecommissioning monitoring.
10.1
Pre-decommissioning Monitoring
Historical data accumulated during production monitoring should be analyzed and summarized to
highlight the pipeline condition and other environmental trends for the key environmental components,
as specified in Section xxx (Monitoring Requirements). If historical data, as specified in Section 2 and
Section xxx, is not available for the pipeline, environmental surveys will be required to establish the
required baseline data.
10.2
Post-decommissioning Monitoring
The aim of the post-decommissioning monitoring is to verify the effectiveness of the decontamination
procedures and other mitigation measures adopted to ensure no harm to the environment or other users
of the sea.
On the completion of pipeline decommissioning a post-monitoring suite shall be performed. The scope
and duration of the post-decommissioning monitoring will be determined by the specific condition of the
pipeline and in consultation with the relevant government authorities.
Initially, extensive monitoring will be required for contaminated pipelines due to present uncertainty in
the effectiveness of decontamination methods. As proven decontamination methods become available
the guidelines will be updated to reduce the monitoring requirements.
Monitoring for in situ pipelines will generally require a longer duration and specific parameters. Suitable
environmental components, parameters, duration, frequency and schedule should be proposed along
with the appropriate surveying methods as specified in the Monitoring Requirements (Section xxx). It is
however expected that for pipelines left on the seafloor marine surveys shall be performed at least
every three years for a recommended minimum of nine years.
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An environmental audit will be required using a qualified third party, as specified in Section xxx and
included in Final State Report.
11. CONSULTATION REQUIREMENTS
All consultation requirements will be determined as specified in the Decommissioning Process, Section
xxx.
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Pipeline due for
decommissioning
Apply for deferal
No
Decommission
Follow deferral or
suspension requirements
Yes
No
Obtain stakeholders
requirements through
designated authorities
Approved by
designed authority
Yes
Perform BPEO assessment
and determine preferred
option
End of suspension period
Obtain consent from
designated authorities
Revise and resubmit
No
Consent obtained
Yes
Submit the pipeline
decommissioning program
Revise and resubmit
No
Approved by
designed authority
Yes
Implement the program
Hydrocarbon cleaning
Verification achieved
No
Yes
No
Decontamination
required
Yes
No
Leaving in place
acceptable
Yes
Perform decontamination
Burial
environmental
acceptable
Monitoring
No
Yes
No
Verification achieved
Yes
Leave in place
Burial
Recover
Figure xxx Pipeline Decommissioning Guideline Flowchart
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Appendix A: List of heavy metals required by decontamination verification
Substances
Arsenic and/or arsenic compounds
Barium and or barium compounds (excluding barite and barium sulfate)
Cadmium and/or cadmium compounds
Chromium (VI) compounds
Copper and/or copper compounds
Lead and/or lead compounds
Mercury and/or mercury compounds
Nickel and/or nickel compounds
Offshore Pipeline Decommissioning Guideline
STLC(mg/l)
5.0
100
1.0
5
25
5.0
0.2
20
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