Analysis of systems for diverting shallow gas

Journal Article · Wed Sep 01 04:00:00 EDT 1993 · Drilling Contractor; (United States)

OSTI ID:5960766

Roche, J R; Fowler, J H

When drilling an offshore well, penetrating pressurized shallow-gas sands presents the hazard of large gas-volume blowouts. The drive pipe or surface conductor typically lacks the pressure-containing capability necessary to permit shutting in the well to implement well-control measures. Diverter systems have evolved to re-route gas/sand flow away from the rig floor to an overboard discharge. It has been well-document that fragile and complex diverter systems have led to frequent inability to endure a shallow-gas event. It follows that simplified and strengthened diverter systems should improve safety. Studies in Europe and the US have shown that diverter systems do not successfully execute their mission roughly 50% of the time when used to divert a kick. The purpose of this paper is to document results of a reliability analysis of two common, but configurationally different diverter-system types: An integral-vent diverter system that uses an annular packing element, has automatic simultaneous vent opening and flowline closing with port/starboard discharge selection by an always-open flow sector. This was shown to be the higher-reliability system. A sequenced-apparatus diverter system using a bladder-type packer requiring a bushing insert and using valves for flow-line shut off and vent-line opening. This was shown to be a lower-reliability system. The calculated reliabilities for both types for a typical 150-hour mission are summarized.

• OSTI ID: 5960766
• Journal Information: Drilling Contractor; (United States), Journal Name: Drilling Contractor; (United States) Vol. 49:5; ISSN 0046-0702; ISSN DRCOA2
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030300* -- Natural Gas-- Drilling
Production
& Processing
030500 -- Natural Gas-- Health & Safety
ACCIDENTS
BLOWOUT PREVENTERS
BLOWOUTS
DESIGN
DRILLING
DRILLING EQUIPMENT
ENERGY SOURCES
EQUIPMENT
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
HAZARDS
NATURAL GAS
NATURAL GAS WELLS
OFFSHORE DRILLING
OFFSHORE SITES
RELIABILITY
WELLS