Pressure buildup halts Stebbing well offshore the Falklands

Offshore staff

LONDON – Borders & Southern will P&A its second exploration well offshore the Falkland Islands following insurmountable technical issues.

Well 61/25-1 was drilled to a MD of 3,060 m (10,039 ft), and a TVD of 3,011 m (9,878 ft). It penetrated the upper Tertiary target on prognosis but could not reach the lower targets due to anomalous pressure conditions. These targets remain unevaluated.

The well encountered very strong gas shows in the Tertiary section. Petrophysical analysis of wireline logs suggests an interval at a depth of 2,500-2,651 m (8,202-8,697 ft) of thin bedded siltstones and claystones with a net to gross of 36% and average porosity of 19%.

Due to the thin-bed character of this sequence, a clear indication of the fluid type or saturation could not be obtained.

Borders & Southern says the geophysical anomalies identified on seismic are coincident with this zone containing hydrocarbons. It appears unlikely that this upper target is commercial; further technical evaluation is needed.

Strong gas shows continued below the upper target, but drilling progress was slow due to lost circulation and well flows in consecutive hole sections. Several of these flows contained gas.

On each occasion, the well was controlled, but additional casing strings had to be set, using the contingency casing considered in the well design. In the final 6-in. hole section, rising fluid pressures generated further well flows making it impossible to continue drilling while maintaining well integrity.

The company will review all geological and engineering data in an attempt to understand the complexities of this prospect.

Samples from this year’s Darwin gas/condensate discovery are undergoing laboratory analysis.


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