Accessibility of Pores to Methane in New Albany Shale Samples of Varying Maturity Determined Using SANS and USANS

The accessibility of pores to methane has been investigated in Devonian New Albany Shale Formation early-mature (Ro = 0.50%) to post-mature (Ro = 1.40%) samples. A Marcellus Shale Formation sample was included to expand the maturation range to Ro 2.50%. These are organic matter-rich rocks with total organic carbon (TOC) values of 3.4 to 14.4% and porosity values of 2.19 to 6.88%. Contrast matching small-angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) techniques were used to generate porosity-related data before and after pressure cycling under hydrostatic (in a vacuum and at 500 bar of deuterated methane) and uniaxial stress (0 to ca. 350 bar) conditions. Our results showed that the accessible porosity was small for the samples studied, ranging from zero to 2.9%. No correlation between the accessible porosity and TOC or mineralogical composition was revealed, and the most likely explanation for porosity variation was related to the thermal transformation of organic matter and hydrocarbon generation. Pressure caused improvements in accessible porosity for most samples, except the oil window sample (Ro = 0.84%). Our data show that densification of methane occurs in nanopores, generally starting at diameters smaller than 20 nm, and that the distribution of methane density is affected by pressure cycling.

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Porosity of the Marcellus Shale: A contrast matching small-angle neutron scattering study

International Journal of Coal Geology ◽

10.1016/j.coal.2018.02.002 ◽

2018 ◽

Vol 188 ◽

pp. 156-164 ◽

Cited By ~ 26

Author(s):

Jitendra Bahadur ◽

Leslie F. Ruppert ◽

Vitaliy Pipich ◽

Richard Sakurovs ◽

Yuri B. Melnichenko

Keyword(s):

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Marcellus Shale ◽

Scattering Study ◽

Neutron Scattering Study ◽

Contrast Matching

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HYDROCARBON GENERATION AND EXPULSION FROM EARLY CRETACEOUS SOURCE ROCKS IN THE BROWSE BASIN, NORTH WEST SHELF, AUSTRALIA: A SMALL ANGLE NEUTRON SCATTERING STUDY

The APPEA Journal ◽

10.1071/aj03005 ◽

2004 ◽

Vol 44 (1) ◽

pp. 151 ◽

Cited By ~ 6

Author(s):

A.P. Radlinski ◽

J.M. Kennard ◽

D.S. Edwards ◽

A.L. Hinde ◽

R. Davenport

Keyword(s):

Neutron Scattering ◽

Pore Size ◽

Source Rock ◽

Early Cretaceous ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Source Rocks ◽

Geochemical Data ◽

Hydrocarbon Generation ◽

North West

Small Angle Neutron Scattering (SANS) analyses were carried out on 165 potential source rocks of Late Jurassic–Early Cretaceous age from nine wells in the Browse Basin (Adele–1, Argus–1, Brecknock South–1, Brewster–1A, Carbine–1, Crux–1, Dinichthys–1, Gorgonichthys–1 and Titanichthys–1). Samples from Brewster–1A and Dinichthys–1 were also analysed using the Ultra Small Angle Neutron Scattering (USANS) technique.The SANS/USANS data detect the presence of generated bitumen and mobile hydrocarbons in pores and are pore-size specific. As the pore-size range in mudstones extends from about 0.001–30 μm, the presence of bitumen in the small pores detected by SANS indicates the depth of onset of hydrocarbon generation, whereas the presence of bitumen and mobile hydrocarbons in the largest pores detected by USANS indicates a significant saturation and the onset of expulsion.Although geochemical data imply the existence of a potential gas and oil source rock in the Lower Cretaceous section (Echuca Shoals and Jamieson Formations), the SANS/USANS data indicate significant generation but little or no expulsion. This source limitation may explain poor exploration success for liquid hydrocarbons in the area. The SANS/USANS data provide evidence of intra- and inter-formational hydrocarbon migration or kerogen kinetics barriers. There is no evidence of an oil charge to the Berriasian Brewster Sandstone from the Echuca Shoals Formation, although some gas charge in Brewster–1A is possible. This novel microstructural technique can be used to independently calibrate and refine source rock generation/expulsion scenarios derived from geochemistry modelling.

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