Ruhrgas, United Kingdom
Almost 20 years after its discovery, a Field Development Plan is being compiled to bring the Babbage gas field on stream.
Gas flow rates from the discovery well, 48/2-2, were disappointing at 3.8 mmscfgd due to occlusion of permeability by fibrous illite in the Leman Sandstone Formation. The widely held view was that, due to this poor reservoir performance and uncertainty of the size of the field, development would be uneconomic. Primary controls on the distribution of the authigenic illite are the burial and charge history, with facies distribution exerting a secondary control. The illite formed during Late Jurassic to Early Cretaceous times whilst the reservoir resided at its maximum palaeo-burial depth.
The appraisal well, 48/2a-4, drilled by E.ON Ruhrgas UK North Sea in 2006 successfully tested the Leman Sandstone Formation reservoir at 10.5 mmscfgd from a vertical well bore. The reservoir comprises an upper 80 ft thick interval with permeabilities locally in excess of 10 mD and a lower 200 ft thick interval with lower permeabilities. The structure is a NW-trending tilted fault block and the gas quality is good with low inert gas percentages and 93% methane. Gas volumes are sufficient to encourage development of the field.
Subsurface modelling indicates that the optimum development plan includes the drilling of three long, near horizontal wells in which multiple hydraulic fracturing of both reservoir intervals is planned. Flow rates from these wells are predicted to exceed the vertical appraisal well flow rates several fold and a field life of up to 20 years is predicted.
AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece