Hazard Management for Blowout Control
Due Diligence. An operator must have a reasonable idea of basic blowout hazards associated with a given field or planned drilling activity, and likely consequences, where he operates. This hazard assessment is generally going to be subjective as industry statistics on blowout incidents are generally unreliable due to small sample size and the large number of independent variables associated with each. The assessment should be documented, with appropriate logic to back up the opinion.
Based on this initial judgment, an operator will decide whether additional detailed hazard assessment and control evaluation is warranted beyond acceptable standard operating/design practices. If justified, hazard analysis expansion should be continued until cost effectiveness based on total field investment and potential liability begins to diminish.
In general, areas that justify specific contingency plans have relatively high risk and associated high consequences. Areas that may justify specific contingency plans are those that have relatively low risk of occurrence but the consequences may be high if a blowout were to occur. The table below illustrates a simple impact/probability matrix. The column on the left indicates impact on the company if a blowout occurs. The right three columns indicate increasing probability of blowout occurrence. The intersection of the impact and probability matrix indicates the level of contingency plan that should be considered.
Impact on Company | Probability of Blowout Occurrence |
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Low |
Medium |
High |
|
Low | Minimal Contingency Plan |
Minimal Contingency Plan |
Modest Contingency Plan |
Medium | Minimal Contingency Plan |
Modest Contingency Plan |
Detailed Contingency Plan |
High | Modest Contingency Plan |
Detailed Contingency Plan |
Detailed Contingency Plan |
Simple Qualitative Impact Matrix
To determine the impact from a well control incident on your company you should consider the following individually: Human safety, environmental damage, asset damage, business disruptions, local public image and corporate public image. The impact should consider both the initial event (i.e., the blowout itself) and the impact on the safety and the length of time required for controlling the blowout.Example Situations of a Blowout having High Impact on an Operating Company
Example Situations with Higher Risk for Well Control Incidents
The matrix below illustrates an example evaluation of risk and impact for a Level 3 (blowout) well control incident.
BLOWOUT IMPACT MATRIX - Initial Event, Mitigation and Control | ||||||||||||||||||
Company: | Orogho |
State/County | Offshore |
Structure: | Jack-up | |||||||||||||
Country: | Nigeria |
Field/Block | 22/30 |
Slot/Well: | Well 4b - HPHT | |||||||||||||
Hazard Identification and Description: Loss of secondary well control. Underground blowout at shoe, casing evacuates, SIDP | ||||||||||||||||||
= 0 psi, SICP frac at shoe. Open hole collapses around BHA, full BHP up DP, pop-off valve on mud pumps exceeded, kelly | ||||||||||||||||||
valves fail, blowout through drillpipe into mud room, Shear DP, casing fails at cement top, ram body washes out, surface blowout. | ||||||||||||||||||
Initiating Factors: Loss of primary well control, insufficient shoe strength to hold pressure, rig crew not familiar with underground | ||||||||||||||||||
blowout signals and correct response, casing not in sufficient tension, casing wear, kelly valve failure | ||||||||||||||||||
Escalating Factors: gas has potential for explosion and fire, oil not burned for pollution, shallow underground blowout has | ||||||||||||||||||
potential for undermining and collapse of the rig, emergency procedures not in place, H2S present, ignition source near well. | ||||||||||||||||||
Date: June 1998 | Blowout Probability, Low <-- (A - E) --> High: | C |
Operations: Drilling | |||||||||||||||
Type of Response: Initial Response/Mitigation, Control | Initial Response |
Blowout Control |
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Internal Resources Rating, High <-- (1 - 5) --> Low: | 2 |
3 |
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External Resources Rating, High <-- (1 - 5) --> Low: | 3 |
2 |
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Risk Classification, Probability -Resource Rating (e.g. C5) | C3 |
C3 |
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Consequences of the Blowout Hazard |
|
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Rating |
Human |
Environment |
Assets |
Business |
Public Image |
Public Image |
A |
B | C |
D | E | |||||||
Range |
Range |
Range |
Range |
Range |
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Injury/Fatality |
Spill/Release |
Property Damage |
Disruptions |
Negative Reaction |
Negative Reaction |
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Event |
D5 |
C2 |
E4 |
C3 |
D4 |
C3 |
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Control |
C2 |
C4 |
B3 |
C3 |
C3 |
C2 |
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1 |
Slight Injury |
No Spill |
Slight Damage |
Slight |
Slight |
Slight |
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2 |
Minor Injury |
Slight Spill |
Minor Damage |
Minor |
Minor |
Minor |
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3 |
Major Injury |
Minor Spill |
Local Damage |
Major |
Major |
Major |
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4 |
Single Fatality |
Major Spill |
Major Damage |
Extensive |
Extensive |
Extensive |
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5 |
Multiply Fatality |
Massive Spill |
Massive Damage |
Massive |
Massive |
Massive |
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Total Impact Classification (Impact/6): Event = D4, Control = C3 |