No shale gas in UK's Weald basin, & little recoverable oil, survey concludes.

Guardian: “Government hopes that Britain can emulate the US by starting a shale-gas revolution have been knocked back after a long-awaited report unexpectedly concluded there was no potential in fracking for gas in the Weald region of southern England.”
“Michael Fallon, the energy minister, insisted he was neither “disappointed nor happy” at the findings from the British Geological Survey and denied the government had hyped the potential for extracting shale gas in Britain.
He preferred to focus on more positive BGS findings that there could be 4.4bn barrels of oil in the shale rocks of the area, which stretches from Salisbury to Tunbridge Wells – although in practice recoverable reserves are likely to be a fraction of this.
….The government has started a 12-week consultation on new legislation that would bypass the law of trespass for underground work that is 300 metres or more below the surface and for voluntary community payments of £20,000 for each lateral well drilled.
….But the BGS conclusion that “there is unlikely to be any shale-gas potential” in the Weald area is a major blow to ministers’ wider hopes that shale could be found throughout the country.
The use of new technology such as fracking could mean extra volumes, but the BGS said more drilling and testing was needed to “narrow down that [4.4bn barrels] figure”. Even then, the amount of shale oil brought to the surface may be only “a few percent” of any recoverable reserves.”
BGS Report: “Following the publication of shale gas resource estimates for the Carboniferous Bowland-Hodder shales (Andrews 2013), this report is the second to address the potential distribution and in-place resources of unconventional oil and gas contained in shales beneath the UK. It summarises the background geological knowledge and methodology that have enabled a preliminary in-place oil resource calculation to be undertaken for the Weald Basin and adjacent areas in southern Britain (Figure 1). No significant shale gas resource is recognised in the Jurassic of the Weald Basin.
Marine shales were deposited in the Weald Basin at several intervals during the Jurassic (c.145-200 Ma). The basin is composed of several fault-controlled sub-basins, which form part of a wider basin that extended into northern France. It is geologically distinct from the Wessex Basin which lies to the south-west, outside the study area.
Five units within the Jurassic of the Weald Basin contain organic-rich, marine shale: the Mid and Upper Lias Clays (Lower Jurassic) and the Oxford Clay, Corallian Clay and Kimmeridge Clay (Upper Jurassic). These attain gross shale thicknesses of up to 300 ft (90 m), 220 ft (67 m), 500 ft (150 m), 260 ft (80 m) and 1,800 ft (550 m) respectively in the Weald Basin depocentre, and they contain varying amounts of organic matter. Conventional oil and gas fields in the basin attest to the capability of some of these units to produce hydrocarbons. It is possible that oil could have been generated from any or all of the five shales, but in the current model even the deepest Jurassic unit is not considered to have been sufficiently deeply buried to have generated significant amounts of gas. Some gas has been generated in association with oil and shallow biogenic gas may also be present.
....None of the Jurassic shales analysed by Rock-Eval methodology in the Weald Basin has an ‘oil saturation index’ (S1*100/TOC) of greater than 50, i.e. much of the ‘oil’ may be physically associated with kerogen, rather than present in pore space. This is low in comparison to shale oil producing areas in North America, so it may be that only limited amounts of shale within the Jurassic of the Weald Basin have any potential to produce oil in commercial quantities. However, after correcting for the evaporation of light hydrocarbons since the sample was taken, it may be that some horizons within the Mid and Upper Lias, lower Oxford Clay and Kimmeridge Clay exceed the 100 required for the oil to be ‘producible.’ Also, the fact that oil has migrated into conventional reservoirs suggests that optimum conditions are reached at least locally within the basin. Interpreting the presence of producible oil in the organic-rich shales allows for an in-place resource volume to be calculated with a broad range of probabilities.
The maturity of the shales is a function of burial depth, heat flow and time. In this study, the Jurassic shales are considered mature for oil generation (vitrinite reflectance, Ro, values between 0.6% and 1.1%) at depths between approximately 7,000-8,000 ft (2,130-2,440 m) and 12,000-13,000 ft (3,660- 3,960 m) (where there has been minimal uplift). However, southern Britain experienced a phase of significant uplift in Cenozoic times, due to basin inversion, that has raised the mature shales by up to 6,750 ft (2,060 m) to shallower present-day depths than would otherwise be expected. However, even the Lias shales are unlikely to have attained sufficient maturity to allow for significant gas generation.
Where they have been buried to a sufficient depth for the organic material to generate oil, all five prospective shales are considered to have some potential to form a shale oil resource analogous, but on a smaller scale, to the producing shale oil provinces of North America (e.g. Barnett, Woodford and Tuscaloosa).
….This study offers a range of total in-place oil resource estimates for the various Jurassic shales of the Weald Basin of 2.2 – 4.4 – 8.6 billion bbl (0.29 – 0.59 – 1.14 billion tonnes) (P90 – P50 – P10) (Table 1). It should be emphasised that these ‘oil-in-place’ figures refer to an estimate for the entire volume of oil contained in the rock formation, not how much can be recovered. It is still too early to use a more refined methodology, like the USGS’s Technically Recoverable Resource “top-down” estimates, which require production data from wells. In time, the drilling and testing of new wells will give an understanding of achievable, sustained production rates. These, combined with other non-geological factors such as oil price, operating costs and the scale of development agreed by the local planning system, will allow estimates of the UK’s producible shale oil reserves to be made.
There is a high degree of uncertainty in these figures. Indeed, there is a chance that there may be little or no ‘free oil’, given that the ‘oil saturation index’ is considerably less than 100 (see Jarvie 2012b) and what oil there is could be located entirely within the kerogen particles and would thus require heating/retorting to extract it. In these circumstances, the resource could no longer be categorised in terms of ‘shale oil’. The potential for hybrid plays in which oil might have migrated into tight reservoirs adjacent to mature shale is acknowledged, but the potential volumes of oil trapped in such plays is not addressed in this report.
Other areas in the UK have shale gas and shale oil potential, and later in 2014 the Carboniferous shales of the Midland Valley of Scotland will be the subject of a further BGS/DECC report.