Developing Tight Gas in a Mature Basin - United Kingdom North Sea

Abstract

Numerous undeveloped gas discoveries remain undeveloped in the UK Southern North Sea despite their common proximity to production infrastructure. The UK Oil and Gas Authority estimates 3.8 TCF of gas is currently stranded in the basin, mostly in discoveries in low permeability sandstones each with less than 100bcf of potential recoverable resource and is implementing a strategy to ‘Maximise Economic Recovery’. However, technical advances in well productivity, combined with the point in the economic cycle are driving development plans. Significant ullage in a nearby late-life pipeline (LAPS) will not be available beyond 2023 without developing additional gas, so time is of the essence. One such development project is outlined in this paper which is projected to produce up to 400bcf in conjunction with 1GW of wind-hybrid electricity. Production would amount to 2% of the UK’s power needs and 4% of its indigenous gas production by 2022. In the central part of the Southern Gas Basin in the UK is a major inverted basin where the primary reservoir, the Early Permian Rotliegendes aeolian-dominated sandstone, has been deeply buried and uplifted during the Tertiary inversion of the Sole Pit Basin. This has led to significant burial diagenesis, including illitisation, that has reduced unstimulated well productivity to sub-economic levels. Recent use of horizontal multi-frac wells in the Clipper South Field has demonstrated the commerciality of developing these tight reservoirs. Horizontal fracced wells testing dry gas at over 20mmscpfd compare well to unstimulated wells testing at less than 1mmscfpd. OK Energy has built a portfolio of tight gas assets in neighbouring acreage and is proposing a development of a hub and up to 4 satellites. The development of these reserves depends on several factors all aligning at the same time in order to create a good economic outcome: proven tools to overcome low permeability issues, low cost drilling and other capex, industry synergies, access to under-utilised infrastructure and strengthening gas prices.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018