Shale gas reserve evaluation by laboratory pyrolysis and gas holding capacity consistent with field data

Abstract

Exploration for shale gas occurs in onshore basins, with two approaches used to predict the maximum gas in place (GIP) in the absence of production data. The first estimates adsorbed plus free gas held within pore space, and the second measures gas yields from laboratory pyrolysis experiments on core samples. Here we show the use of sequential high-pressure water pyrolysis (HPWP) to replicate petroleum generation and expulsion in uplifted onshore basins. Compared to anhydrous pyrolysis where oil expulsion is limited, gas yields are much lower, and the gas at high maturity is dry, consistent with actual shales. Gas yields from HPWP of UK Bowland Shales are comparable with those from degassed cores, with the ca. 1% porosity sufficient to accommodate the gas generated. Extrapolating our findings to the whole Bowland Shale, the maximum GIP equate to potentially economically recoverable reserves of less than 10 years of current UK gas consumption.

Direct gas-in-place measurements prove much higher production potential than expected for shale formations

“…For example, in the United Kingdom, the gas in place within the Bowland–Hodder shale formation was initially estimated as 1300 trillion cubic feet (TCF) 6 , 7 . However, subsequent studies resulted in much lower estimates for the volumes of gas in place, up to 6–7 times lower compared to former estimates 8 . In Poland, early-stage estimations indicated gas in place of 187 TCF 9 whereas, recent figures suggest ~ 70 TCF 10 .…”

“…Indeed, two laboratory methods are widely practiced: canister desorption tests and separate measurements of porosity and adsorption Langmuir capacities 7 . However, both approaches are known to produce notable degrees of error 8 , as reflected in the ~ sevenfold variability in range from 1300 to 185 TCF for UK shale gas resources. The complexity in estimation of the gas in place can be attributed to complex processes taking place during core lifting, which impact the adsorption characteristics of hydrocarbon gas components such as methane and ethane, where pressure and temperature conditions can have opposing impacts on adsorption behavior.…”

Socio-technical transitions in UK electricity: part 2 – technologies and sustainability

“…The most controversial of these studies was arguably that concerning the benefits and 'costs' of shale gas fracking in Britain (Hammond and O'Grady, 2014;Parker et al, 2014). Exploratory drilling in the UK is at an early stage, with great uncertainty over the scale of the potential shale gas resource (Hammond and O'Grady, 2014;Whitelaw et al, 2019). However, such activities are already meeting fierce community resistance.…”

Determining reservoir intervals in the Bowland Shale using petrophysics and rock physics models

“…The Mississippian Bowland Shale Formation of north England is considered the best candidate for shale gas extraction in the United Kingdom (Smith et al 2010), though the size of the potential resource is disputed (Andrews 2013;Whitelaw et al 2019). Exploration thus far has focused within the Craven Basin of NW England, where the Bowland Shale exhibits excellent shale reservoir properties (Clarke et al 2014a(Clarke et al , 2018 and has been subject to several sedimentological and microstructural studies (Fauchille et al 2017;Newport et al 2018;Emmings et al 2019Emmings et al , 2020a.…”