Case Study: sCore Lithofacies Classification Reveals Barnett Shale Reservoir Quality

Litho Scanner service’s wellsite mineralogy and TOC outputs drive identification of optimal completion intervals

Challenge: Reliably identify intervals with superior reservoir and completion quality in the Barnett Shale.

Solution: Input accurate, quantified mineralogy from Litho Scanner high-definition spectroscopy service to the automated sCore lithofacies classification scheme to generate a log display of the classification and quality-indicator overlays on a ternary diagram.

Result: Identified the optimal intervals for completion from the sCore scheme’s reservoir and completion quality overlays.

Shale classification challenges

Key to successfully completing Barnett Shale reservoirs is targeting intervals with superior reservoir and completion quality. However, these so-called shales are more than just fine-grained sedimentary rocks with a high content of organic matter. Rather, these organic mudstones are typically a complex mineralogic assemblage that is heterogeneous at fine vertical scales. In addition to identifying optimal intervals in terms of reservoir and completion quality, operators need a mineralogy-based classification to better understand depositional conditions and correlate reservoirs across different fields and basins.

Optimal reservoir identification

Shale facies are readily and automatically identified using the sCore lithofacies classification scheme. The sCore classification is based on mineralogical relationships within a ternary diagram customized for organic mudstone lithologies to determine both lithofacies and reservoir and completion quality indicators.

The sCore scheme’s log display is generated with minimal processing and no interpretation input required. Descriptive parameters such as organic carbon, pyrite, and the presence of expandable clays are flagged. The log provides a consistent description of the organic mudstone section and the inputs necessary for effective decision making when selecting a landing points for well placement, tailoring completion designs, and planning a drilling development project. Quality indicator parameters such as porosity, total organic carbon (TOC), fracture density, and stress are also overlaid on a ternary diagram to relate the parameter quality to the sCore classification’s lithofacies types.

Accurate mineralogy input for the sCore classification comes from Litho Scanner high-definition spectroscopy service logging for carbonate, clay, QFM, and TOC in combination with additional inputs from basic triple-combo logs for porosity and resistivity. The mineralogy is provided at nearly immediate turnaround by Litho Scanner service, instead of having to wait for laboratory X-ray diffraction (XRD) analysis of core samples.

Lithofacies quality indicators

From the sCore classification log for the Barnett Shale well, reservoir quality and completion quality indicator overlays on the ternary diagram were generated. The color-coded points represent the different log depths for the indicator parameters that correlate with reservoir quality and completion quality.

Download: sCore Lithofacies Classification Reveals Barnett Shale Reservoir Quality (0.88 MB PDF)

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Quality Indicators Identified by sCore Classification

The sCore classificationsCore Barnett Shale LogReservoir Quality IndicatorCompletion Quality Indicator
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