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What happened?
Gas from well entered surface lines and flowed back to mud pit room due to incorrect line up.
During a well plug and abandon operation on a platform, prior to injectivity test for subsequent well kill operations, a line up plan was agreed for the injectivity test using a rig mud pump.
The well was known to be live with gas at surface prior to beginning operations.
Without additional team communication a decision was made to change the line up configuration. As a result of this and while performing the altered line up, there was a lower explosive limit (LEL) alarm originating from pit room.
The team reverted to the initially planned line up, suspended simultaneous operations (SIMOPS), shut in, and secured the wells on platform.
Investigation determined that when the well's master valve was opened, gas from the well was introduced into the standpipe manifold and flowed to the pit room through the mud pump suction line. Pressure recorded on the standpipe after securing the well was 1800psi.
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Why did it happen?
The Christmas tree master valve was opened for injectivity test without equalising system pressure with the well prior to opening, leading to gas evacuation into the standpipe manifold lines and to the pit room.
Communication breakdown: Inadequate handover at crew change between crew members.
Pump line up was changed unknowingly to others involved in the operations.
Poor planning/Risk assessment/Procedure normalisation of deviance.
Poor operational supervision to ensure procedures were followed.
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What did they learn?
Install a check valve on the kill line to the production tree swab valve to ensure wellbore fluid does not flow back to the rig manifolds.
Review and improve details in the Platform handover SIMOPs matrix and other processes such as Permit to work, Risk assessment and Tool box risk assessment, as well as leadership involvement.
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Ask yourself or your crew
How can something like this happen here (e.g. on our site)?
What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
How do we know the risk controls/barriers are working?
What improvements or changes should we make to the procedures, controls/barriers, or the way we work?
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What happened?
Gas from well entered surface lines and flowed back to mud pit room due to incorrect line up.
During a well plug and abandon operation on a platform, prior to injectivity test for subsequent well kill operations, a line up plan was agreed for the injectivity test using a rig mud pump.
The well was known to be live with gas at surface prior to beginning operations.
Without additional team communication a decision was made to change the line up configuration. As a result of this and while performing the altered line up, there was a lower explosive limit (LEL) alarm originating from pit room.
The team reverted to the initially planned line up, suspended simultaneous operations (SIMOPS), shut in, and secured the wells on platform.
Investigation determined that when the well's master valve was opened, gas from the well was introduced into the standpipe manifold and flowed to the pit room through the mud pump suction line. Pressure recorded on the standpipe after securing the well was 1800psi.
Why did it happen?
The Christmas tree master valve was opened for injectivity test without equalising system pressure with the well prior to opening, leading to gas evacuation into the standpipe manifold lines and to the pit room.
Communication breakdown: Inadequate handover at crew change between crew members.
Pump line up was changed unknowingly to others involved in the operations.
Poor planning/Risk assessment/Procedure normalisation of deviance.
Poor operational supervision to ensure procedures were followed.
What did they learn?
Install a check valve on the kill line to the production tree swab valve to ensure wellbore fluid does not flow back to the rig manifolds.
Review and improve details in the Platform handover SIMOPs matrix and other processes such as Permit to work, Risk assessment and Tool box risk assessment, as well as leadership involvement.
Ask yourself or your crew
How can something like this happen here (e.g. on our site)?
What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
How do we know the risk controls/barriers are working?
What improvements or changes should we make to the procedures, controls/barriers, or the way we work?
During the rig up of a well plug and abandon operation, the initial line up and procedure for an injectivity test was modified without proper risk assessment, resulting in an unintentional gas release to a mud pit room. An LEL alarm was activated, prompting the crew to shut the well and platform in. The team reverted to the original line up and installed a check valve where needed to prevent reoccurrence.
Original material courtesy of the International Association of Oil & Gas Producers (IOGP)
