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== Online multimedia ==
 
== Online multimedia ==
  
Hopmans, Paul. 2013. Journey of Well Integrity. https://webevents.spe.org/products/journey-of-well-integrity 
+
Hopmans, Paul. 2013. Journey of Well Integrity. [https://webevents.spe.org/products/journey-of-well-integrity&nbsp https://webevents.spe.org/products/journey-of-well-integrity]
  
 
Dethlefs, Jerry. Near Surface External Casing Corrosion; Cause, Remediation and Mitigation. [http://www.spe.org/dl/docs/2011/Dethlefs.pdf http://www.spe.org/dl/docs/2011/Dethlefs.pdf]
 
Dethlefs, Jerry. Near Surface External Casing Corrosion; Cause, Remediation and Mitigation. [http://www.spe.org/dl/docs/2011/Dethlefs.pdf http://www.spe.org/dl/docs/2011/Dethlefs.pdf]

Revision as of 08:38, 15 January 2018

There are different definitions of what is Well Integrity. The most widely accepted definition is given by NORSOK D-010: “Application of technical, operational and organizational solutions to reduce risk of uncontrolled release of formation fluids throughout the life cycle of a well.”[1]

Other accepted definition is given by ISO TS 16530-2 “Containment and the prevention of the escape of fluids (i.e. liquids or gases) to subterranean formations or surface.”

Well Integrity is a multidisciplinary approach. Therefore, well integrity engineers need to interact constantly with different disciplines to assess the status of well barriers and well barrier envelopes at all times.

Well Integrity operating philosophy

The well integrity operating philosophy is an important element that one should carefully consider with respect to how to manage the risk of loss of containment and overexpose oneself with additional risk by frequent well visits and interventions that brings exposure to the people and environment by doing these activities. The overall process should fit together. It is of little use to define a meantime to repair for failed barrier components and not have supporting critical spares or competent resources in place to able to respond to such an event. The philosophy should be aligned with risk exposure and be clearly under scribed by the process owner.

Roles and Responsibilities

Personnel competency and training

There are a number of competency assurance processes available. There are not many that are specific to well integrity, but the below example of a competence matrix (part 1&2) on how one may look, The assurance and training is similar to any other educational system in that there is a theoretical level and a practical level. Both are equally important. The verification process of the ability to perform a certain task is a must that one needs to consider and assure himself of.

The categories of people are subjective in example as each organization is different. This in itself is not an issue as one can adapt the matrix and make it suitable. The main issue is whatever task or activity is assigned in the well integrity process, one must assign the appropriate competencies for that task, assure that these competencies are in place, and that they are validated and maintained.

The above is applicable for operator staff or contractor staff. There may be some regulated standards available like Opito that is used in the North Sea.

Further, there are websites on well integrity that are a maintained by others such as http://www.wellintegrity.net/.

Standards and governances

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Well integrity management systems

A Well Integrity Management System (WIMS) is a meaningful solution to define the commitments, requirements and responsibilities of an organization to manage the risk of loss of well containment over the well lifecycle. The tasks necessary to deliver well integrity, and the roles accountable and responsible for delivery, are specified in a WIMS document. To operationalize the management system, software tools can be used. These have various forms from simple solutions managed with a spreadsheet to more complex systems managed using self-built or commercially available electronic management systems.

The objective of a WIMS is to specify requirements necessary for delivery of well integrity, including:

  • Well integrity refers to maintaining full control of fluids within a well at all times, in order to prevent unintended fluid movement or loss of containment to the environment.
  • Well integrity policy defines commitments and obligations to safeguard health, safety, environment, assets, and reputation.
  • WIMS is the system that assures that well integrity is maintained throughout the well life cycle by the application of a combination of technical, operational, and organizational processes.

Commercially available well integrity management systems software includes:

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Elements of the well integrity management system

  • Wells ownership over the lifecycle for wells that are:
    • Developed
    • Acquired
    • Divested
    • Suspended
    • Closed in
    • Operated
    • Exploration
    • Abandoned by company.
  • Organizational structure with roles:
    • Responsibilities
    • Competencies
  • Risk assessment with risk register that:
    • Defines the risk
    • Mitigations for the hazards that are to be managed
  • Well types with:
    • Well barriers
    • Well barrier envelopes that control hazards
  • Performance standards that:
    • Defines the requirements to maintain the well barriers within its operating limits.
  • Well barrier verification, or assurance processes that:
    • Assures the mechanical status of the well is maintained on a defined risk
  • Underlying processes like:
    • Reporting
    • Documentation
    • Management of change
    • Continuous improvement
    • Auditing processes.

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Objective of the well integrity management system

The overall objective is to give transparency on how risk is managed. One way to achieve this transparency is to benchmark other operators to verifing how effective the well integrity management system performs. Another way is to compare the system to industry standards (e.g. The NACE's Petroleum and natural gas industries--Well integrity--Part 1, ISO 16530-1).[2]

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An effective well integrity management system

An effective well integrity management system uses a risk based matrix that will demonstrate how to manage risk. This risk-based matrix is based on "as low as reasonably practical" ALARP . Well operating limits is a combination of the criteria established to ensure that the well remains within its design limits in order to maintain well integrity throughout the well life cycle. For each well type, it is normal when changes occur and the well operating limits should be checked.

To assure well operating limits, some parameters could be monitored over the well life cycle when the well is constructed, operated, shut-in or suspended;

  • requirements for any threshold settings for the well limits;
  • actions that should be taken in the event a well parameter is approaching its defined threshold;
  • actions, notifications and investigations required if well limit thresholds are exceeded;
  • safety systems that are necessary to ensure parameters stay

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Risk assessment

A Risk Assessment is a procedure to determine the quantitative or qualitative value of a risk or threat to a specific situation. Risk can be defined as a combination of both the severity of the consequences of an event and the likelihood or probability that the event will occur. Risk increases with increasing severity and/or likelihood. Risk tolerance and risk rank category definitions can vary by company and location. However, it is an industry-accepted practice to require prevention or mitigation for significant and/or high risk category wells.

One very general but accepted definition for a high risk well is: “A well in which that last barrier is under threat of being compromised.” Each company should create their own specific definitions for well risk based on operating area, well stock, and risk tolerance. There are numerous risk assessment methods available to facilitate the determination of well risk and a few of those methods are summarized below.

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Quantitative risk assessment (QRA)

Quantitative Risk Assessment (QRA) is a method of risk assessment based on numerical probability using historical data and reliability models. This method is commonly used for hydrocarbon processing facilities and oil pipeline systems. The challenge for using a QRA for well integrity is the availability and applicability of well failure and reliability data for use in a risk model. Even with a perfect model, initial conditions and boundary conditions must be correct or the prediction will be flawed.

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Qualitative risk assessment

A Qualitative Risk Assessment is a more conventional method for well integrity. It is primarily based on experience and the application of good engineering judgment. Qualitative Risk Assessments are easier to execute but are limited by the experience and knowledge of the people completing the assessment.

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QRA/Qualitative hybrid

Due to a lack of well integrity reliability data for QRAs, many well integrity risk assessments are QRA/Qualitative hybrids based on known failure data, rules, procedures, and risk matrices rather than using straight qualitative or QRA analyses. One such hybrid method documented in 142854-PA SPE Journal Paper – 2012 [3] is a hybrid risk assessment method that uses a qualitative, team-based brainstorming format following the “what if” methodology to identify hazards associated with known or predetermined well-barrier failure modes and likelihoods from a known well stock. This method uses a risk matrix with customized likelihood and consequences as shown in the sample below.

Considerations for Risk Assessments

Components that contribute to the risk profile of a well or number off wells that determine how the risk needs to be managed could be:

  • Outflow potential to surface or subsurface environments
  • Fluid types and composition, H2s, Co2, gas, oil, dehydration water etcetra’s
  • Location, subsea, offshore, swamp, land, urban, natural reserve etcetra’s
  • Earth model, subsidence, earth quakes, permafrost
  • Collision from vessels, fishing, trucks, landslides, intervention activities

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Well design, well construction, and barrier requirements

During well design and construction, the barrier requirements are driven by the input of the basis of design and the identified hazards. These hazards can change over the life cycle of the well or may actually be introduced during the construction of the well. The design and construction process is the main element that drives how the well needs to be operated, maintained, or abandoned. There is with each field or well development plan the element of economics, the time line to deliver, or earth model hazards that are encountered that may result in decisions that affect well integrity or well operating limits. From a well integrity management perspective, the relevancy is to understand the risk associated with exposure to certain hazards and that these are clearly defined in the well operating limits at well handover so that mitigating controls can be applied over the wells life.

Depending on the environment where the well is placed in and outflow potential of the well, with likelihood of failure and consequence of loss of containment, the well barrier requirements are defined. This is usually done in the field development stage by use of quantitative risk assessment. See below examples of various barrier designs whereby in a hydro static well, the liquid level is the primary barrier.

Some examples of elements that may have to be managed during the design construct of well barriers to assure them over the well lifecycle are:

  • Internal oxygen-related corrosion
    • CO2 corrosion
    • H2S corrosion
    • chloride stress cracking
    • stress cracking caused by bromide mud and thread compound
    • microbial-induced corrosion (MIC)
    • other chemical corrosion
    • acid corrosion (e.g. from stimulation fluids)
  • External corrosion as result of
    • aquifers
    • surface water
    • swamp or sea environments.
  • Sand/solids production
    • scale deposition
    • erosional velocities
    • formation of emulsion
    • scale
    • wax and hydrate deposits.
  • Compatibility between components, electrolytic corrosion.
  • Load cases as result of
    • thermal
    • fatigue
    • subsidence
    • stimulation
    • well kill
    • injection
    • production
    • evacuation
    • trapped pressures
    • casing wear.
  • Earth model fractures
    • pore pressures
    • permafrost movement
    • squeezing chalks
    • salts
    • earthquake
    • subsidence.
  • Zonal isolation placement and verification of isolation methods.

Typically well head valves and Xmas trees are single barrier elements as they use floating gates and seats that hold in one direction that results in valve bonnet , grease nipple, and stem packing to be under pressure at all times. See example of a typical gate valve below. When designing the well and its barriers, this needs to be taken into consideration.

The well barrier design and construction process objective should address the issues such that the barriers over the well life cycle assure containment that can effectively be managed and verified. This statement is a challenge in itself as many wells have issues over the life cycle as things were not clear from beginning or changes occurred or well was not designed and constructed as intended. The process of well integrity management is to understand the risks and address these by managing the well barriers within its operating limits to prevent loss of containment.

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Managing abnormal casing pressure and sustained casing pressure

Wells are designed and constructed to allow for operation with some pressure on the annuli. This pressure only becomes a problem when there is an indication of a well integrity issue or if the maximum allowable wellhead operating pressure (MAWOP) has been exceeded. Depending on the source of the pressure and applicable area regulations the appropriate operator response may differ. Therefor it is important to monitor annular pressure on a recurring basis and understand the source of the pressure.

There are three main sources for annulus pressure:

  1. Intentionally applied pressure – define as annulus pressure that is intentionally used by the operator for a specific purpose.
  2. Thermally induced pressure – define as pressure that results from thermal expansion of trapped fluid in the annulus.
  3. Sustained casing pressure - define as unintended pressure in an annulus that is not thermally induce nor intentionally applied. It pressure caused from communication to formation or another annulus through a defective or failed barrier.

The cause of annulus pressure can be evaluated by reviewing well records and temperature and pressure trends, relieving or bleeding the pressure, and then monitoring the build-up rate.

Barrier Verification/ Barrier Diagnostics

At various phases of a well’s life cycle, the integrity of the well barriers and/or well barrier elements should be verified. The verification may involve pressure measurement, tagging, pressure testing, leak testing, leak off testing, well logging or flow rate measurement. If anomalous behavior is observed then a diagnostic process is initiated, usually to determine the location and magnitude of the leak.

Typical key barrier verification steps and techniques during various well life cycle phases are as follows:

Life Cycle Phase

Well Barrier Element(s)

Barrier Verification Examples

Well Construction or Workover




Fluid column

Fluid density, fluid loss rate, fluid level


BOP

Pressure test, function test


FOSV or IBOP

Pressure test, function test


Casing and liner

Pressure test

Well logging - ultrasonic


Wellhead / casing hanger

Pressure test


Geological formation

Leak off test or formation integrity test

Well logging – ultrasonic or electromagnetic wall thickness, mechanical caliper


Liner hanger / liner

Pressure test

Negative (inflow) test


Annular Cement

Pressure measurements – calculated cement column height

Well logging – acoustic and ultrasonic tools


Tubing

Pressure test - internal or external


Production packer

Pressure test – from above or below packer element


Subsurface safety valve

Leak test, function test


Xmas tree

Pressure test, leak test, function test




Well Operations




Casing and liner

Annulus pressure monitoring

Annulus bleed down test

Annulus pressure test


Completion string

Annulus pressure monitoring

Pressure test – tubing or annulus

Leak off test (annulus bleed down)

Acoustic fluid level survey


Subsurface safety valve

Leak test, function test

Control line pressure test


Gas lift valve

Leak off test (annulus bleed down)

Acoustic fluid level survey


Wellhead / casing hanger

Pressure test, leak test, function test, visual inspection

Infrared thermal imaging, casing vent monitoring


Xmas tree

Pressure test, leak test, function test, visual inspection, ultrasonic wall thickness measurement

Infrared thermal imaging




Well Intervention (Rigless)




BOP

Pressure test, function test


Pressure control equipment

Pressure test


Completion string (including casing and liner below tubing tailpipe)

Well logging – mechanical caliper, ultrasonic and electromagnetic wall thickness, ultrasonic leak detection, pulsed neutron log, magnetic flux leakage, temperature, production log, video or acoustic tools, fiber optic distributed acoustic and temperature log

Pressure test - against downhole plug or straddle tool




Well Abandonment




Casing and liner

Pressure test

Well logging – mechanical caliper, ultrasonic and electromagnetic wall thickness


Annular Cement

Pressure measurements – calculated cement column height

Well logging – acoustic and ultrasonic tools


Cement plug

Tag top of cement



Pressure test



Negative (inflow) test

To determine whether the well barrier has an acceptable level of integrity, the barrier verification results are compared with the performance standards (or acceptance criteria) that apply to that well. Some oil and gas companies have their own in-house standards and some jurisdictions have regulatory regimes that prescribe the minimum verification requirements for certain well barrier elements, for example the length or height of cement plugs. Companies commonly adopt performance standards based on the following publically available reference documents.

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Since these documents are not consistent in all aspects, it is important for a company’s well engineering management system and/or well integrity management system to explicitly define the well barrier elements (and/or safety critical elements) and the performance standards that shall apply.

The performance standards need not be uniform across all wells operated by a company or within a region, and can vary after considerably based on the risk profiles for different well types and the specific regulatory regimes that apply. An example performance standard for well safety critical elements provided in ISO / TS 16530-2 [4] for the operational phase is reproduced below.


Description

Performance monitoring requirement

Units of Measure

Acceptance criteria example

Well Head/Tree Visual Inspection: There shall be no leaks/weeps of the well head/tree, valve and instrument connections. (Visual Inspection)

Acceptable visual inspection

No leaks

Zero

Wellhead/Tree valve operability: All wellhead/tree valves shall be operable in accordance with manufacturer defined specifications (number of turns).

Acceptable test / operate on demand as per manufacturer specification

Number of turns

18 3/4 turns

Wellhead/Tree valve Actuation : Actuated wellhead/tree valves shall close within the required time as defined by operator in the well hook up cause and effect requirements for shutdown based on API 14 B.

Acceptable response test

Time

30 seconds

Wellhead/Tree valve Leakage Rate: The valve leakage rate is not greater than the corresponding allowable leakage rate as specified by operator based on API 14 B

Acceptable test / leak rate

Ambient volume/ time

0,425M3/min

Annular Safety Valve integrity: The ASV performs within the parameters specified by the operator based on API 14 B

Acceptable test
Operates on demand records available

Pressure limit

xx MPa

Annulus Integrity Management (1): The annulus pressures are to be within specified values for Maximum Allowable Annulus Surface Pressure (MAASP)/Trigger and Minimum Values


Operates within MAASP records available

Pressure limit

xx MPa

Annulus Integrity Management (2): The annulus pressure monitoring equipment is calibrated correctly and alarms (where fitted) operate at the required set points or pressures are recorded manually on regular intervals.
Acceptable test
Operates on demand records available
Accuracy

Percentage

Annulus Integrity Management (3): The annulus pressures test is to be within the wells operating envelop as defined by Operator.

Acceptable test Operates on demand records available

Pressure test

xx MPa

Sub Surface Safety Valves (SSSVs) Integrity: The SSSV performs within the parameters specified by Operator.

Acceptable test
Operates on demand

Leak test

0,425M3/min

Well Plug(s) Integrity Test : The well plugs perform within the parameters specified by Operator.

Acceptable test
Operates on demand

Leak test

0,425M3/min

Gas Lift Valve (GLV) / Tubing Integrity Test : The GLVs and tubing perform within the parameters specified by Operator.

GLV Tubing to annulus test acceptable

Inflow test

0,425M3/min

Hanger neck seal, control line feed through, electrical feed through and DASF / adaptor spool seal area’s : The component pressures test is to be within the wells operating envelop as specified by Operator.

Acceptable test
Operates on demand

Pressure test

xx MPa

Shutdowns of artificial lift Pumps Electrical submersible pumps (ESP’s) / Beam pumps / Electrical Submersible Positive Cavity Pumps (ESPCP’s) / Positive Cavity Pumps (PCPS) /Jet pumps gas lift systems.

Artificial lift systems that have capability to overpressure flow line / wellheads or other well components, shutdown test is to be within defined cause and effect diagram parameters.

Acceptable test
Operates on demand

shutdown test

30 seconds

Location safety valve or production wing valve: Operates as defined in cause and effect s diagram as defined by well operator.

Acceptable test
Operates on demand

shutdown test

30 seconds

Operating envelop of Injection wells: Maximum allowable injecting pressure as defined by Operator.

Operating limit of pressure of injection pressure based on MAASP of well bore

Pressure limit

xx MPa

Steam wells
Maximum allowable pressure / temperature as defined by Operator.

Operating limit of pressure of injection pressure / temperature based on Maasp & temperature limitations of well bore

Pressure + Temperature limit

xx MPa / deg Celsius

Other useful reference documents include:

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References

  1. 1.0 1.1 D-010:2013. Well integrity in drilling and well operations. 2013. Lysaker, Norway: NORSOK. https://www.standard.no/en/sectors/energi-og-klima/petroleum/norsok-standard-categories/d-drilling/d-0104/
  2. ISO/DIS 16530-1. Petroleum and natural gas industries--Well integrity--Part 1: Life cycle governance Well Integrity Lifecycle. Houston: NACE. http://www.iso.org/iso/catalogue_detail.htm?csnumber=63192
  3. Dethlefs, J., & Chastain, B. (2012, June 1). Assessing Well-Integrity Risk: A Qualitative Model. Society of Petroleum Engineers. http://dx.doi.org/10.2118/142854-PA
  4. "ISO/TS 16530-2:2014 Well Integrity -- Part 2: Well Integrity for the Operational Phase." ISO. Web. http://www.iso.org/iso/catalogue_detail.htm?csnumber=57056.

Noteworthy papers in OnePetro

Dethlefs, J. and Chastain, B. 2012. Assessing Well-Integrity Risk: A Qualitative Model. SPE Drill & Compl 27 (02): 294-302. SPE-142854-PA. http://dx.doi.org/10.2118/142854-PA.

King, G.E. and Valencia, R.L. 2014. Environmental Risk and Well Integrity of Plugged and Abandoned Wells. Presented at the SPE Annual Technical Conference and Exhibition, Amsterdam, 27-29 October. SPE-170949-MS. http://dx.doi.org/10.2118/170949-MS.

Singh, S.K., Subekti, H., Al-Asmakh, M., et al. 2012. An Integrated Approach To Well Integrity Evaluation Via Reliability Assessment Of Well Integrity Tools And Methods: Results From Dukhan Field, Qatar. Presented at the SPE International Production and Operations Conference & Exhibition, Doha, Qatar, 14-16 May. SPE-156052-MS. http://dx.doi.org/10.2118/156052-MS.

Vignes, B., and Aadnøy, B.S. 2010. Well-Integrity Issues Offshore Norway. SPE Prod & Oper 25 (2): 145-150. SPE-112535-PA. http://dx.doi.org/10.2118/112535-PA.

Watson, V. 2010. A Quantitative Risk Assessment Approach. SPE International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production, Rio de Janeiro, 12-14 April. SPE-127213-MS. http://dx.doi.org/10.2118/127213-MS.

Wilson, V. A. 2014. HSE and Well Integrity: Friends or Foes? SPE International Conference on Health, Safety, and Environment, Long Beach, California, USA, 17-19 March. SPE-168407-MS. http://dx.doi.org/10.2118/168407-MS.

SPE papers grouped by conferences: https://www.onepetro.org/conferences/spe

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Online multimedia

Hopmans, Paul. 2013. Journey of Well Integrity. https://webevents.spe.org/products/journey-of-well-integrity

Dethlefs, Jerry. Near Surface External Casing Corrosion; Cause, Remediation and Mitigation. http://www.spe.org/dl/docs/2011/Dethlefs.pdf

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External links

SPE. Well Integrity Technical Section. http://connect.spe.org/WellIntegrity/home.

See also

Well integrity lifecycle

Well integrity onshore

Well integrity offshore

Well integrity sub sea

Well integrity thermal

Page champions

Federico Juarez - Well Integrity Engineer

MJ Loveland - Well Integrity Supervisor ConocoPhillips (retired)

Category