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Estimation of total organic carbon and brittleness volume

Sumit Verma, Tao Zhao, Kurt J. Marfurt and Deepak Devegowda
Estimation of total organic carbon and brittleness volume
Interpretation (Tulsa) (August 2016) 4 (3): T373-T385

Abstract

The Barnett Shale in the Fort Worth Basin is one of the most important resource plays in the USA. The total organic carbon (TOC) and brittleness can help to characterize a resource play to assist in the search for sweet spots. Higher TOC or organic content are generally associated with hydrocarbon storage and with rocks that are ductile in nature. However, brittle rocks are more amenable to fracturing with the fractures faces more resistant to proppant embedment. Productive intervals within a resource play should therefore contain a judicious mix of organics and mineralogy that lends to hydraulic fracturing. Identification of these intervals through core acquisition and laboratory-based petrophysical measurements can be accurate but expensive in comparison with wireline logging. We have estimated TOC from wireline logs using Passey's method and attained a correlation of 60%. However, errors in the baseline interpretation can lead to inaccurate TOC. Using nonlinear regression with Passey's TOC, normalized stratigraphic height, and acquired wireline logs, the correlation increased to 80%. This regression can be applied to uncored wells with logs to estimate TOC, and we used it as a ground truth in integrated analysis of seismic and well log data. The brittleness index (BI) is computed based on core Fourier transform infrared mineralogy using Wang and Gale's formula. The correlation between core BI and estimated BI using elastic logs (lambda (sub 2R) , mu (sub rho ) , V (sub P) /V (sub S) , Z (sub P) , and Z (sub S) ) combined with wireline logs was 78%. However, this correlation decreases to 66% if the BI is estimated using only wireline logs. Therefore, the later serves as a less reliable proxy. We have correlated production to volumetric estimate of TOC and brittleness by computing distance-weighted averages in 120 horizontal wells. We have obtained a production correlation of 38% on blind wells, which was encouraging, suggesting that the geologic component in completions provides an important contribution to well success.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 4
Serial Issue: 3
Title: Estimation of total organic carbon and brittleness volume
Affiliation: University of Wyoming, Department of Geology and Geophysics, Laramie, WY, United States
Pages: T373-T385
Published: 201608
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 27
Accession Number: 2017-002803
Categories: Economic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch map
N33°00'00" - N34°00'00", W99°00'00" - W97°00'00"
Secondary Affiliation: University of Oklahoma, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201703
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