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Abstract
Non-Integral Wells are common in every aged field and managing their integrity
is becoming a challenging issue, particularly in large fields and for complex
dual completions such as the case in ZADCO operated fields. As part of the Well
Integrity Management System (WIMS), integrity concerns are identified,
investigated and subsequently mitigation measures are recommended to restore
the well integrity, all in a systematic approach. Well barrier integrity is
given the highest priority; therefore a comprehensive Risk Register and Risk
Ranking process is implemented by ZADCO Well Integrity Team.
The Risk Register process utilizes every related data and integrity
investigation results to evaluate the integrity of the well primary &
secondary barriers for every flow path. An individual integrity assessment is
performed on the different containment sections in a well such as wellhead,
inner and outer annuli and zonal isolation. Based on the severity, consequences
and likelihood of a barrier failure the individual containment is given a risk
rank according to ADNOC/ZADCO risk matrix. The overall risk ranking of a well
reflects the highest risk rank of any of its containments. To complete the risk
register, existing safeguards are addressed
and appropriate short and long term mitigation actions are recommended to keep
the risk at ALARP.
Key Words: Well Integrity Management System, Well Barriers,
Wellhead Equipment, Sub-surface Equipment, Risk Management, Risk Matrix.
Introduction:
ZADCO owns a huge inventory of around ~500 wells, mostly completed with dual
string to produce from or inject into two different reservoirs. In order to
provide standard guidelines to ensure that technical integrity of all these
wells is maintained throughout their life cycle, a comprehensive Well Integrity
Management System (WIMS) has been developed and put in place. The WIMS
recognizes following three types of wells based on their integrity status but
irrespective of their service status (i.e. producer, water injector, gas
injector, gas lift, observer etc.)
1. Integral Well
2. Abnormal Well
3. Non-Integral Well
Integral Well: A wells that operates within design envelope and its integrity
is assured.
Abnormal Well: A well that has no safety issue (i.e. two barriers are intact)
but it may have potential threats to integrity and/or operating conditions,
e.g. scale prone, corrosion potential, thermal annulus pressure, injection gas
breakthrough, poor cement integrity / zonal isolation etc.
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