Skip to Main Content
GEOREF RECORD

A diagenetic study of the Woodford Shale in the southeastern Anadarko Basin, Oklahoma, USA; evidence for hydrothermal alteration in mineralized fractures

Jennifer M. Roberts and Richard Douglas Elmore
A diagenetic study of the Woodford Shale in the southeastern Anadarko Basin, Oklahoma, USA; evidence for hydrothermal alteration in mineralized fractures
Interpretation (Tulsa) (February 2018) 6 (1): SC1-SC13

Abstract

The objective of this study is to test if external fluids (e.g., hydrothermal) altered the Woodford Shale in the southeast Anadarko Basin and how the diagenesis caused by such fluids, particularly in mineralized fractures, has affected the reservoir quality and mechanical behavior of the Woodford Shale. Two Woodford Shale cores from the Anadarko Basin were sampled to identify diagenetic events, interpret their origin, and determine the diagenetic history of the shale. Thin sections for both cores were analyzed using reflected and transmitted light, cathodoluminescence (CL), and scanning electron microscopy to identify minerals and cross-cutting and textural relationships. X-ray computed tomography was conducted to further characterize fracture networks seen on the petrographic scale. Early diagenesis is dominated by events in the matrix and allochems, with later diagenesis dominated by events associated within fracturing and brecciation. The mineralized fractures and brecciated intervals contain complex mineralogies. Multiple minerals, interpreted to be hydrothermal in origin, are present, including magnesite, norsethite, witherite, gorceixite, potassium feldspar, sphalerite, chalcopyrite, and saddle dolomite. CL in minerals within fractures reveals evidence of evolving fluids and multiple fluid-flow events. Although porosity is present within pyrite framboids, between clay sheets, and as dissolution vugs within fractures and allochems, fracture porosity was destroyed by mineralization that filled the fractures and permeated into the matrix. Vitrinite reflectance data from both cores indicate a correlation between thermal maturity and level of hydrothermal alteration, with core A (0.80% VR (sub o) [approximately 125 degrees C]) displaying a lower amount of alteration and core C (approximately 1.5% VR (sub o) [approximately 210 degrees C]) displaying a higher amount of alteration. The extensive faulting present in the southeastern Anadarko Basin likely facilitated the movement of the hydrothermal fluids through the unit. The presence of hydrothermal minerals not only has implications for the thermal maturity and reservoir quality of the Woodford Shale, but it also contributes to the discussion of whether or not shales behave as open or closed systems.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 6
Serial Issue: 1
Title: A diagenetic study of the Woodford Shale in the southeastern Anadarko Basin, Oklahoma, USA; evidence for hydrothermal alteration in mineralized fractures
Affiliation: Chesapeake Energy Corporation, Oklahoma City, OK, United States
Pages: SC1-SC13
Published: 201802
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 60
Accession Number: 2019-006688
Categories: Economic geology, geology of energy sourcesSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Special section; Characterization of the Woodford Shale, latest concepts and techniques
Illustration Description: illus. incl. geol. sketch map
N34°15'00" - N35°00'00", W98°00'00" - W97°00'00"
Secondary Affiliation: University of Oklahoma, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201906
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal