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The AAPG/Datapages Combined Publications Database

Southeast Asia Petroleum Exploration Society (SEAPEX)

Abstract


Offshore South East Asia Conference, 1996
Pages 145-153

Shallow Gas Problem at Duyong B Offshore Malaysia

Tom Lunne, Omar Md. Isa, Melvyn Tan

Abstract

Leakage along gas wells caused gas charging of sand layers at 60 and 90 m below seabed at the Duyong field offshore Malaysia. This was discovered during drilling of a soil investigation borehole for a new platform when a blow out occurred. This evidence of shallow gas caused concern related to the safety of three existing and one planned new platform. A study was carried out in order to reliably assess the effect of the shallow gas on the safety of the platforms. An important part of the study was a soil investigation with several new techniques including profiling of in situ gas-water saturation by the BAT probe. The soil investigation and subsequent analyses showed that the main effect of the shallow gas was to build up pore water pressure in the clay layers which reduces with time the bearing capacity of the foundation piles. By terminating the soil borings as relief wells, this progressive detrimental development could be reduced and the integrity of the foundations could be maintained. By installing production wells to the deep gas source the problem was finally solved. Recommendations are given for investigations to solve similar shallow gas problems at other sites.


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