An integrated study of a Mississippian tripolitic chert reservoir – Osage County, Oklahoma, USA

Dowdell, Benjamin L.; Roy, Arpita; Marfurt, Kurt J.

doi:10.1190/segam2012-1563.1

Cited by 6 publications

(3 citation statements)

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“…Using wells A and B, a poststack P-impedance inversion ( Figure 14) was done (Dowdell et al, 2012), and the results compared with the multiattribute unsupervised seismic facies analysis. High impedance (purple) corresponds to regions interpreted in the facies volumes as either high-density chert (Osage B) or St. Joe limestone.…”

Section: Discussionmentioning

confidence: 99%

“…Figure 3a and 3b (modified from Rogers, 2001) show the two schematic depositional models for the chert and the formation of high-porosity and low-density chert. (Dowdell et al, 2012). The logs include GR (gamma ray), NPOR (neutron porosity), RHOB (density), V P , V S , PHIT (calculated total porosity), and RHOMAA (calculated density of the apparent matrix).…”

Section: Applicationmentioning

confidence: 99%

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Characterizing a Mississippian tripolitic chert reservoir using 3D unsupervised and supervised multiattribute seismic facies analysis: An example from Osage County, Oklahoma

2013

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Seismic interpretation is based on the identification of reflector configuration and continuity, with coherent reflectors having a distinct amplitude, frequency, and phase. Skilled interpreters may classify reflector configurations as parallel, converging, truncated, or hummocky, and use their expertise to identify stratigraphic packages and unconformities. In principal, a given pattern can be explicitly defined as a combination of waveform and reflector configuration properties, although such “clustering” is often done subconsciously. Computer-assisted classification of seismic attribute volumes builds on the same concepts. Seismic attributes not only quantify characteristics of the seismic reflection events, but also measure aspects of reflector configurations. The Mississippi Lime resource play of northern Oklahoma and southern Kansas provides a particularly challenging problem. Instead of defining the facies stratigraphically, we need to define them either diagenetically (tight limestone, stratified limestone and nonporous chert, and highly porous tripolitic chert) or structurally (fractured versus unfractured chert and limestone). Using a 3D seismic survey acquired in Osage County Oklahoma, we use Kohonen self-organizing maps to classify different diagenetically altered facies of the Mississippi Lime play. The 256 prototype vectors (potential clusters) reduce to only three or four distinct “natural” clusters. We use ground truth of seismic facies seen on horizontal image logs to fix three average attribute data vectors near the well locations, resulting in three “known” facies, and do a minimum Euclidean distance supervised classification. The predicted clusters correlate well to the poststack impedance inversion result.

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Section: Discussionmentioning

confidence: 99%

Section: Applicationmentioning

confidence: 99%

Characterizing a Mississippian tripolitic chert reservoir using 3D unsupervised and supervised multiattribute seismic facies analysis: An example from Osage County, Oklahoma

2013

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“…Angelo (2010), Yenugu et al (2010, Matos et al (2011), and Roy et al (2012) use gray level co-occurrence matrix (GLCM) seismic texture attributes, selforganizing maps (SOM), and unsupervised 3D seismic facies analysis to identify petrofacies within the Mississippi Lime. Finally, work by Dowdell et al (2012) and Dowdell (2013) show the use of poststack and simulta-neous prestack seismic inversion to predict zones of tripolitic chert using petrophysical properties measured on well logs. Generalized stratigraphic column for Osage County.…”

Section: Introductionmentioning

confidence: 99%

Seismic characterization of a Mississippi Lime resource play in Osage County, Oklahoma, USA

2013

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With the advent of horizontal drilling and hydraulic fracturing in the Midcontinent, USA, fields once thought to be exhausted are now experiencing renewed exploitation. However, traditional Midcontinent seismic analysis techniques no longer provide satisfactory reservoir characterization for these unconventional plays; new seismic analysis methods are needed to properly characterize these radically innovative play concepts. Time processing and filtering is applied to a raw 3D seismic data set from Osage County, Oklahoma, paying careful attention to velocity analysis, residual statics, and coherent noise filtering. The use of a robust prestack structure-oriented filter and spectral whitening greatly enhances the results. After prestack time migrating the data using a Kirchhoff algorithm, new velocities are picked. A final normal moveout correction is applied using the new velocities, followed by a final prestack structure-oriented filter and spectral whitening. Simultaneous prestack inversion uses the reprocessed and time-migrated seismic data as input, along with a well from within the bounds of the survey. With offsets out to 3048 m and a target depth of approximately 880 m, we can invert for density in addition to P-and Simpedance. Prestack inversion attributes are sensitive to lithology and porosity while surface seismic attributes such as coherence and curvature are sensitive to lateral changes in waveform and structure. We use these attributes in conjunction with interpreted horizontal image logs to identify zones of high porosity and high fracture density.

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Mississippian chat and tripolite zones in Osage County, Oklahoma: Paleokarst interpretation based on 3D seismic and well logs

Aboaba

Liner

2021

Interpretation

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Mississippian paleokarst Chat and tripolitic chert (tripolite) zones associated with the Mississippian Lime have been hydrocarbon exploration targets in Osage County for many decades. Chat is residual chert, either in place or transported, weathered out of chert-bearing Mississippian Limestone that was eroded at the Mississippian-Pennsylvanian unconformity. Thus, the formation of Chat is an epigene paleokarst process. Tripolite occurs as a highly porous, silica-rich interval within the Mississippi Lime. It is formed by in-place alteration of limestone by silica-rich surface waters or deep-seated hydrothermal fluids, making tripolite formation a mixed or hypogene paleokarst process. Here, we have studied Chat and tripolite by seismic analysis calibrated by well control with full-wave sonic and density log data. We identify that Chat and tripolite show clear separation from Mississippian Lime log-based acoustic impedance and VP/ VS, but there is no meaningful separation of Chat from tripolite, and they both exhibit total porosities greater than 20% with evidence of fracture porosity. We find that the sonic-based normal incidence wedge model for Chat bounded above by the Pennsylvanian Shale and below by the Mississippian Lime indicate that two seismic expressions are plausible: first, a strong negative amplitude when the Chat thickness is above the tuning thickness (for this survey it is 56 ft) and, second, a weak positive or negative amplitude associated with the small impedance contrast between Chat and overlying Pennsylvanian Shale. Our analysis suggests that the traditional Chat “strong response” and a new “dim-out” exploration strategy may be usefully applied in Osage County. We show that the tripolite response is consistently a negative amplitude event that strengthens with increasing tripolite thickness. We provide an interpretive framework for characterizing Chat and tripolite zones associated with the Mississippian Lime in the US Midcontinent, which may apply to regions around the world.

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An integrated study of a Mississippian tripolitic chert reservoir – Osage County, Oklahoma, USA

Cited by 6 publications

References 3 publications

Characterizing a Mississippian tripolitic chert reservoir using 3D unsupervised and supervised multiattribute seismic facies analysis: An example from Osage County, Oklahoma

Characterizing a Mississippian tripolitic chert reservoir using 3D unsupervised and supervised multiattribute seismic facies analysis: An example from Osage County, Oklahoma

Seismic characterization of a Mississippi Lime resource play in Osage County, Oklahoma, USA

Mississippian chat and tripolite zones in Osage County, Oklahoma: Paleokarst interpretation based on 3D seismic and well logs

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