Organic matter characterization in mixed hydrocarbon producing areas within the Duvernay Formation, Western Canada Sedimentary Basin, Alberta

Akai

et al. 2020

Sci Rep

Self Cite

core samples from petroleum wells are costly to obtain, hence drill cuttings are commonly used as an alternative source of rock measurements for reservoir, basin modelling, and sedimentology studies. However, serious issues such as contamination from drilling mud, geological representativeness, and physical alteration can cast uncertainty on the results of studies based on cuttings samples. this paper provides a unique comparative study of core and cuttings samples obtained from both vertical and horizontal sections of a petroleum well drilled in the canadian Montney tight gas siltstone reservoir to investigate the suitability of cuttings for a wide range of geochemical and petrophysical analyses. the results show that, on average, the bulk quantity of kerogen or solid bitumen measured in cuttings is comparable to that of the core samples. However, total organic carbon (toc) measurements are influenced by oil-based drilling mud (OBM) contamination. Solvent-cleaning of cuttings has been shown to effectively remove OBM contamination in light, medium, and heavy range hydrocarbons and to produce similar kerogen/solid bitumen measurements to that of core samples. Similarly, pyrolysis methods provide an alternative to the solvent-cleaning procedure for analysis of kerogen/solid bitumen in as-received cuttings. Microscopic study substantiates the presence of significant contamination by OBM and caved organic and inorganic matter in the cuttings, which potentially influence the bulk geochemistry of the samples. Furthermore, minerals in the cuttings display induced micro-fractures due to physical impacts of the drilling process. These drilling-induced micro-fractures affect petrophysical properties by artificially enhancing the measured porosity and permeability. Recent advances in horizontal drilling and hydraulic fracturing provide the opportunity for economic hydrocarbon extraction from the tight rocks such as organic-rich mudrock and fine-grained siltstone. The reservoir quality of unconventional tight mudrocks is highly influenced by the deposited minerals and organic matter (OM) macerals present as well as their alteration by diagenetic and thermal maturity processes 1-4. Reservoir and source quality characterization of unconventional tight mudrocks is often conducted on readily available drill cuttings samples using various organic geochemical, petrographic, and petrophysical techniques. However, analytical results of cuttings are often compromised by the use of oil-based drilling mud (OBM), caved fragments from shallower strata, and physical impacts of the drilling process. While drill-core samples are preferred for rock analysis, obtaining such samples from the horizontal section of wells is difficult, and routinely collected cuttings samples 5 are alternatively used for conducting geochemical and petrophysical analyses. The objective of this study is to compare the organic geochemistry, petrology, and petrophysics results of core samples versus drill cuttings obtained from closely correlated depth intervals in a...

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Core versus cuttings samples for geochemical and petrophysical analysis of unconventional reservoir rocks

Sanei

Akai

et al. 2020

Sci Rep

Self Cite

“…The dominant OM in the immature Duvernay samples (Fig. 3 ) are bituminite (as in-situ bituminized algae), alginite, minor inertinite and chitinozoan fragments, and pore-filling solid bitumen 28 , 43 . Alginite exhibits green to yellow fluorescence color, which indicates low thermal maturity (Fig.…”

Section: Resultsmentioning

confidence: 99%

Early porosity generation in organic-sulfur-rich mudstones

Knapp

Reyes

et al. 2023

Sci Rep

High total organic sulfur (TOS) content (i.e., Type IIS kerogen) is well known to significantly influence kerogen transformation but the effect of TOS content on the evolution of organic porosity has only rarely and indirectly been investigated. This study demonstrates that organic porosity is generated at lower thermal maturity in mudstones containing Type IIS kerogen relative to those with Type II kerogen. To our knowledge this phenomenon has not been previously demonstrated. The implications are relevant for the characterization of organic-rich mudstones as cap rocks, hydrocarbon reservoirs, and disposal reservoirs for CO2 or nuclear waste because pore systems control storage volumes and matrix fluid flow. Five thermally immature core samples were selected from three organic-rich mudstone units with low to high TOS content: the late Devonian Duvernay Formation (Canada), middle late Miocene Onnagawa Formation (Japan), and early Jurassic Gordondale member of the Fernie Formation (Canada). Hydrous pyrolysis was used to artificially mature splits of the immature samples to four maturity stages, upon which petrophysical and organic geochemical properties were measured and compared to baseline immature samples. Most porosity growth in Type IIS samples occurred below 0.70% VRoeqv, but in Type II samples was broader and robust until 1.1% VRoeqv.

“…The data set we used in this study consists of four 3D blocks of organic-rich shale samples from the Western Canadian Sedimentary Basin. The shale samples are from the Duverney formation, a self-sourced shale oil and gas reservoir in Alberta, Canada. , The 3D images were obtained using the focused ion beam scanning electron microscopy (FIB-SEM) method at JOGMEC’s Technology Research Center in Chiba, Japan. The resolution of the FIB-SEM cubes is 10 nm 3 /voxel, which translates into a minimum resolvable pore diameter of 12.4 nm.…”

Section: Samples and Methodsmentioning

confidence: 99%

Pore Characterization of Organic-Rich Shales through Application of Topological Data Analysis and Persistent Homology

Bizhani

2021

Energy Fuels

This paper discusses pore characterization of organic-rich shales using 3D high-resolution imaging and a topological data analysis (TDA) framework. In particular, our focus is on persistent homology. Our data set contains four organic-rich shale samples (imaged at 10 nm3/voxel) and a Bentheimer sandstone as the anchor point for comparison. The analysis shows that pores larger than 12.4 nm have poor connectivity, and there is no evidence of a percolating path through any of the shale samples. In contrast, the Bentheimer sandstone shows remarkable differences from the shales in terms of pore connectivity. In terms of geometry, pores and grains in shale are shown to be highly nonconvex, while sandstone exhibits a more uniform and convex distribution of pore and grain size. Euler characteristics of the samples are also computed and discussed along with the pore network extracted on the segmented images. The results show all three methods have an agreement in the overall description of the pore space. However, persistent homology data reveal more information on the pore and grain phase as compared to the other methods. In the last section of the paper, we present an investigation of topological changes in the pore space as a function of pore radius. The analysis indicates most pores must be enlarged by ∼70–80 nm for the pore space to span into a connected network. The implication is that flow mainly occurs through independent channels in shales, as opposed to sandstone where many redundant flow pathways exist.