Character of the Avalon Shale (Bone Spring Formation) of the Delaware Basin, West Texas and Southeast New Mexico: Effect of Carbonate-rich Sediment Gravity Flows

Stolz, Dustin J.; Franseen, Evan K.; Goldstein, Robert H.

doi:10.15530/urtec-2015-2154681

Cited by 4 publications

(2 citation statements)

References 46 publications

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“…Both the Top and Bottom units have high carbonate contents, 84.4 and 99.0 wt % calcium carbonate, respectively. Compared to other shale plays in the Permian Basin, these samples have unusually high carbonate contents. − Unlike the whole cores, the ground samples were chemically altered by HFF. After exposure to HFF, the dissolution of clays (specifically illite) is observable in the Top unit in the pressurized reactors but not the timed reactors, though the exact reasons for this difference are unknown.…”

Section: Resultsmentioning

confidence: 98%

Impact of Acid–Base Stimulation Sequence on Mineral Stability for Tight/Impermeable Unconventional Carbonate-Rich Rocks: A Delaware Basin Case Study

2022

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Mineral precipitation due to reactions with injected fluids during unconventional fracture stimulation is a well-recognized problem. The goal of this study is to evaluate secondary mineral precipitation and permeability attenuation under chemical injection scenarios specific to the Delaware basin. Whole cylindrical cores (2.54 cm diameter and 2.54 cm height) and ground shale (150−250 μm) from the carbonate-rich Bone Spring Formation, Delaware Basin TX (Leonardian), were reacted at 80 °C and 85 bar using a hydraulic fracturing fluid (HFF) recipe and an injection sequence typical of the Delaware Basin. The reacted shales and solutions were analyzed using a variety of laboratory-and synchrotron-based techniques to characterize both the chemical and spatial distributions of secondary mineral precipitation and identify changes in permeability and mineralogy. This carbonaterich shale (>84% calcite) rapidly neutralized the acidic HFF. Synchrotron-based X-ray fluorescence mapping coupled with X-ray absorption spectroscopy (both bulk and micro) showed that most of the iron was in an oxidized form prior to exposure to HFF and that almost all iron(II) became fully oxidized after the reaction. Scanning electron microscopy images of the ground shale samples primarily identified iron(oxyhydr)oxide microcrystals on grain surfaces. A few small isolated iron-rich areas also contained sulfur, suggesting that some pyrite was preserved when isolated within a calcite crystal but that most was oxidized. The rapid neutralization of the acid spearhead in these carbonate-rich samples demonstrates that the acid spearhead is useful for initiating fractures in extremely calcite-rich rocks but does little to enhance rock permeability. This suggests that the impact of the acid spearhead is significantly smaller for carbonate-rich shales compared to clay-rich shales, which has broad implications for acidizing in carbonate-rich shale formations and iron transformations within these shales.

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Section: Resultsmentioning

confidence: 98%

Impact of Acid–Base Stimulation Sequence on Mineral Stability for Tight/Impermeable Unconventional Carbonate-Rich Rocks: A Delaware Basin Case Study

2022

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“…Ultimately, if studies do not clearly explain characteristics that identify given facies, rigorous application of the work beyond the scope of the study is inappropriate. Stolz et al (2015) characterizes the Avalon Shale within the Bone Spring Formation as a mudrock that shares similar depositional facies as the mudrocks within the Wolfcamp Formation.…”

Section: Previous Workmentioning

confidence: 99%

Reservoir Characterization of the Bone Spring and Wolfcamp Formations, Delaware Basin, Ward County, West Texas

Bievenour¹,

Sonnenberg²

2019

Proceedings of the 7th Unconventional Resources Technology Conference

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The Bone Spring and Wolfcamp formations of the Delaware Basin consist of mixed sediment gravity flow and suspension sedimentation deposits. These deposits exhibit high levels of heterogeneity both at and below core and log scales. Conventional characterization efforts are too coarse to capture small-scale changes in lithology, rock properties, and reservoir quality observed in these unconventional deposits. A key goal of this work is to develop a framework to delineate complex heterogeneities at core and log scales. Due to the heterolithic nature of these strata, an integrated, multiscale approach to unconventional reservoir characterization is required to understand factors controlling reservoir quality. This study utilizes well logs and core data from two key wells, including high-resolution image data from thin sections and SEM, to (1) identify facies across multiple scales and (2) provide an in-depth characterization of reservoir properties in the Bone Spring and Wolfcamp formations along the eastern margin of the Delaware Basin. An integrated approach utilizing core (721 ft.), thin sections (70 samples), XRD analysis (64 samples), and high-resolution images (882 images) identified a total of nine facies. Each facies is comprised of different textures, mineralogy, and pore types. These differences and their effects on reservoir properties are illustrated in this research. Core-based measurements of source rock properties and reservoir properties were used to identify two primary reservoir facies, two secondary reservoir facies, two marginal reservoir facies and three non-reservoir facies. Within the study area, Ward County, the Bone Spring and Wolfcamp formations are in the early mature oil window, the preponderance of maturity data suggest a likely maturity of about 0.8% Ro, ranging 0.69%Ro-0.91%Ro. Four reservoir facies are organically rich with average wt.% TOC as follows; argillaceous-siliceous mudstone (3.1 wt.%, n=21), argillaceoussiliceous siltstone (2.0 wt.%, n=7), calcareous-siliceous mudstone (3.0 wt.%, n=15), and calcareous-siliceous siltstone (2.3 wt.%, n=7). The two primary reservoir facies are mudstones and contain comparable bulk mineralogy to the two secondary reservoir facies, which are siliceous siltstones. Secondary reservoir facies contain more detrital grains and less organic matter than their finer-grained mineralogically-equivalent primary reservoir facies. Lower organic content in secondary reservoir facies is related to dilution of organic matter via iv extrabasinal influx of detrital grains and possible consumption by benthic fauna in oxygenated conditions. These detrital grains are associated with higher sedimentation rates which effectively dilutes initial organic content, consequentially constraining present day total organic carbon values. Origin and type of silica is important for reservoir quality. Non-reservoir facies, biogenic siliceous mudstone, is similar in bulk mineralogy to primary reservoir facies, argillaceous siliceous mudstone. The former contains the least amount of...

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Sedimentologic and Stratigraphic Controls on Reservoir Sweet Spots in Wolfcamp ‘A,’ Howard County, Midland Basin

Flotron

Franseen

Goldstein

2019

Proceedings of the 7th Unconventional Resources Technology Conference

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Character of the Avalon Shale (Bone Spring Formation) of the Delaware Basin, West Texas and Southeast New Mexico: Effect of Carbonate-rich Sediment Gravity Flows

Cited by 4 publications

References 46 publications

Impact of Acid–Base Stimulation Sequence on Mineral Stability for Tight/Impermeable Unconventional Carbonate-Rich Rocks: A Delaware Basin Case Study

Impact of Acid–Base Stimulation Sequence on Mineral Stability for Tight/Impermeable Unconventional Carbonate-Rich Rocks: A Delaware Basin Case Study

Reservoir Characterization of the Bone Spring and Wolfcamp Formations, Delaware Basin, Ward County, West Texas

Sedimentologic and Stratigraphic Controls on Reservoir Sweet Spots in Wolfcamp ‘A,’ Howard County, Midland Basin

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