Kicks in Offshore UK Wells

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 119942, ’Kicks in Offshore UK Wells - Where Are They Happening and Why?,’ by J.D. Dobson, SPE, Health and Safety Executive, originally prepared for the 2009 SPE/IADC Drilling Conference and Exhibition, Amsterdam, 17-19 March. The paper has not been peer reviewed. The first well on the UK continental shelf (UKCS) was spudded 44 years ago, and the area long has been considered a mature province. Despite this, kicks are still a frequent occurrence. Kicks occur in high-pressure/high-temperature (HP/HT) condensate exploration wells and in production wells in depleted subnormally pressured oil reservoirs. They occur during drilling operations and during workover operations. Analysis of data on well incidents has identified where, geographically, kicks occur most frequently. Introduction The Health and Safety Executive (HSE) is the regulator for oil and gas drilling on land in UK and on the UKCS. 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 sulfide (H2S), 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. The full-length paper focuses on kicks and their consequences, rather than on other incidents, but with the intention of sharing the overview more widely. Exploration on the UKCS began in the mid-1960s, with the first major discovery in December 1965. In a mature oil and gas province such as the North Sea, it might be assumed that the frequency of kicks during drilling or workover operations would be decreasing. This study indicates otherwise. Approach The study is based on a review of all kicks and blowouts reported for the area in the 10 years since 1999. The intent in reviewing the data is to consider which areas of the UKCS, and which type of operation, carry the greatest risk of kicks. A second, more detailed, review was carried out for incidents in the 3-year period 2006 to 2008, which examined each reported incident in more detail, reviewing the circumstances under which the kick occurred and, where possible, identifying the underlying cause. Areas of the UKCS Over the last 44 years, wells have been drilled in each of a variety of discrete geographical and geological areas off the coast of the UK (Fig. 1). Although wells have been drilled in all the basins shown, the vast majority of the drilling activity on the UKCS has been limited to six discrete geological areas—southern North Sea, central North Sea, Moray Firth, northern North Sea, West of Shetland, and Irish Sea. It is in these areas that the reported incidents considered in this study have occurred.