Universal Curves Describing the Chemical and Physical Evolution of Type II Kerogen during Thermal Maturation

Abstract

This paper synthesizes and interprets literature data relating to the chemical and physical characteristics of kerogen (solid, insoluble sedimentary organic matter) representing more than a dozen petroliferous sedimentary basins across four continents, 400 million years of sedimentation, and burial histories ranging from thermally immature to overmature. The studied kerogen properties include chemical composition (elemental composition and carbon and heteroatom speciation), physical properties (skeletal density), nuclear responses (petrophysical properties), and microstructure (surface area). As occurs in the vast majority of economically significant conventional and unconventional petroliferous sedimentary basins, the kerogens are observed to be predominantly or entirely paleo-marine (derived from marine plankton and algae) and classified as so-called type II kerogen. The analysis described here reveals that that the wide range of chemical and physical properties of type II kerogen is explained nearly entirely by its extent of thermal maturation and is independent of basin location, age, and other basin-specific characteristics, such as formation lithology. The analysis results in a series of universal curves relating many type II kerogen properties to thermal maturity, with correlation coefficients typically of 0.85−0.90. The indistinguishable property−maturity relationships among type II kerogen in petroleum-bearing formations globally make it possible to infer its relevant chemical and physical characteristics only from knowledge of the thermal maturity of the organic matter. As shown by example, this presents substantial practical benefit for unconventional shale exploration and appraisal because chemical, physical, and petrophysical properties of kerogen are critical in such workflows but are nearly always unknown and otherwise impractical to measure in typical industrial projects.

Exploring Methane Behavior in Marcellus Shale Micropores via Contrast Matching Neutron Scattering

“…Samples were taken from a Middle Devonian Marcellus Shale core collected from an exploration well into the Marcellus Formation located in West Virginia, USA, as previously reported. , The samples, MAR2-TY and MAR3-TY, correspond to core depths of ∼2307 and 2310 m, respectively. Both samples contain thermally mature organic matter which is in the dry-gas window with H/C ratios of ∼0.45. , Each sample was cored perpendicular to bedding (note: these samples were incorrectly stated as cored parallel to bedding in our previous publication) and cylindrical pieces were cut from the samples, measuring 32 mm length and 4 mm (OD) in diameter, sized to fit tightly into custom-made null-scattering TiZr alloy pressure cells. Quantitative mineralogical, density, and total organic carbon (TOC) analyses were carried out on ground whole rock, taken from sample material directly adjacent to the subcores, by a commercial laboratory while the elemental (CHNOS) composition of the sample organic matter was carried out on kerogen isolates, also by a commercial laboratory (Table ).…”

Compositional Control on Shale Pore Structure Characteristics across a Maturation Gradient: Insights from the Devonian New Albany Shale and Marcellus Shale in the Eastern United States

“…The evolution of the BET SSA of isolated OM with increasing thermal maturity in this study is consistent with the previous studies of the evolution of BET SSA of isolated OM from black shales of varying ages and thermal maturities. 18,67 Interestingly, the mesopore and micropore volumes of OM do not show significant changes with increasing maturity (Table 3), which is likely because the rearrangement of the macromolecular structure of OM did not result in a significant loss of the pore volume but caused an increase in SSA through reducing the pore size.…”

Benthic Animals and Establishment of Biological Benchmarks Based on Phytoplankton Biological Index Method

“…Unlike the SSD method, which is derived by mapping, the TPR is calculated through empirical formulas to derive the benchmark, while abandoning the previous definition of a single value. The method is a comprehensive and advanced method for the derivation of water quality benchmarks through statistics by considering the two values separately [18][19]. Among them, the chronic value is expressed by the reference continuous concentration CCC.…”