Kicks in Offshore UK Wells - Where Are They Happening, And Why?
- James Donald Dobson (Health & Safety Executive)
- Document ID
- Society of Petroleum Engineers
- SPE/IADC Drilling Conference and Exhibition, 17-19 March, Amsterdam, The Netherlands
- Publication Date
- Document Type
- Conference Paper
- 2009. British Crown Copyright
- 5.1.2 Faults and Fracture Characterisation, 4.5 Offshore Facilities and Subsea Systems, 1.6 Drilling Operations, 2.4.3 Sand/Solids Control, 5.2.1 Phase Behavior and PVT Measurements, 1.14 Casing and Cementing, 1.11 Drilling Fluids and Materials, 3 Production and Well Operations, 1.7.5 Well Control, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 5.2 Reservoir Fluid Dynamics, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.7 Pressure Management, 6.5.2 Water use, produced water discharge and disposal
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The first well on the UK Continental Shelf was spudded 44 years ago and the area has long been considered a mature province. Despite this, kicks are still a frequent occurrence.
Kicks occur across the entire UKCS area from the Atlantic margins, west of the Shetland Islands to the mature gas fields of the southern North Sea, where the first significant discovery was made in December 1965. Kicks occur in high pressure high temperature condensate exploration wells and in production wells in depleted, sub-normally pressured oil reservoirs. They occur during drilling operations and during work-over operations.
Analysis of data on well incidents held by HSE, the UK regulator, has identified where, geographically, kicks occur most frequently. Analysis also identifies the type of operation being carried out at the time and some of the more significant factors behind the influxes.
The purpose of this paper is to share the regulator's observations with industry. While well operators and drilling contractors hold in-depth information on individual incidents, it is the regulator that is often best placed to observe the wider picture.
The Health and Safety Executive (HSE) is the regulator for oil and gas drilling on land in Great Britain and on the UK Continental Shelf. As such our inspectors are in a unique position by having access to information on all the well incidents that are reported for the area.
UK Health and Safety Regulations specify which well incidents must be reported by well operators. These reportable incidents are kicks, blowouts both underground and at surface, the unanticipated presence of hydrogen sulphide, unplanned intersections and near misses and serious failure of a safety-critical element including the primary pressure containment envelope of the well.
The purpose of the regulation is not merely to inform HSE of the incident, but also to allow the regulator to spot trends in the industry that may not be noticeable to individual well operators and drilling contractors. This paper focuses on kicks and their consequences, rather than other incidents, but with the intention of sharing the overview more widely.
Exploration on the UK Continental Shelf began in the mid 1960s with the first major discovery, BP's West Sole gas field in block 48/6, in December 1965. Exploration moved northwards with Amoco's Arbroath field in block 22/18 in the Central North Sea being discovered in December 1969 and Shell's Brent (211/29) East of Shetland in July 1971. In a mature oil and gas province such as the North Sea it might be assumed the frequency of kicks during drilling or work-over operations would be decreasing. This study indicates otherwise.
The study is based on a review of all kicks and blowouts reported for the area in the ten years from 1999. The intent in reviewing the data is to consider which areas of the UKCS and which type of operation carry the most risk of kicks. A second, more detailed, review was carried out for incidents in the three-year period 2006 to 2008. This looked at each reported incident in more detail, reviewing the circumstances under which the kick occurred and, where possible, identifying the underlying cause.
Data held by HSE on each kick is as reported by the well operator, except for the small proportion of incidents that have been investigated in depth by inspectors. Significant information may not have been included in the report, for example on kick size, and thus missed from the study.
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