The USGS Nebraska Water Science Center is conducting a pilot study to determine whether sand from the Lewis and Clark Reservoir delta has the desired properties to be used as a proppant in unconventional oil and gas wells that receive hydraulic fracturing (fracking) treatment. Proppants are small particles that are part of the fracking fluid mixture injected into a well to hold open the fractures created during the hydraulic fracturing process.
Why Frac Sand?
Issue 1: Sediment Management
Six large reservoirs along the mainstem of the Missouri River are managed by the USACE. USACE is considering several sediment management options for these and other reservoirs in the Midwest. Management options include hydraulic dredging, reservoir flushing, sediment by-pass, and use for habitat construction. All options would be expensive to implement.
Issue 2: Proppant Sources
Successful use of hydraulic fracturing to stimulate production from oil and gas wells resulted in unprecedented demand for natural proppants such as sand. Proppants increase and prolong hydrocarbon recovery in unconventional oil and gas (UOG) wells. Such treatment requires large quantities of frac sand for each well—the average 3,048-m (10,000-ft) horizontal well may use as much as 2,268 Mg (2,500 tons) of proppant. Proppants presently include three chief types: sand (frac sand) from either sandstone bedrock or unconsolidated deposits, resin-coated sand, and manufactured ceramic spheres. Ideal properties of a frac sand include: size distribution enriched in size ranges specified by the American Petroleum Institute (API), particle shape that is well rounded and approximately spherical, hardness and crush resistance (usually correlated with high content of quartz mineral), minimal overburden, and proximity to a terminal for bulk transport.
Surface Geophysical Reconnaissance
Subsurface texture was characterized at four sandbar complexes in the lake delta using continuous resistivity profiling. Resistivity profiles were collected using the Geometrics OhmMapper™. The OhmMapper™ is a capacitively coupled resistivity system which can can collect continuous resistivity data along 5 depth levels. For this study, the array was pulled behind a tracked ATV.
The OhmMapper™ data have been processed, modeled, and interpreted in partnership with the USGS Crustal Geophysics team in Colorado. The results from the surface geophysical reconnaissance guided site selection. Twenty-eight sites on delta sandbars were targeted for coring.
Lake Delta Sampling
Direct-push sediment cores were collected using a tractor-mounted Geoprobe™ at 24 sites. Duplicate cores were collected at each site to ensure enough sample was collected for core description, laboratory analyses, and archival. Target depth was 12 feet, which is considered the pre-impoundment surface.
Upstream Sources
Deltaic sediments generally are deposited episodically during periods of high transport from incoming sources, and these sources may carry sediment mixtures of differing composition and physical character. For this study, all sampling sites used to characterize potential upstream sources were located along the lower Niobrara River valley, consistent with indications1 that it is the source of nearly three-fourths of the sand load entering the Missouri River delta.
Sampling sites:
- 6 sites in the pond upstream from Spencer Dam
- 17 channel sandbar sites along the lower Niobrara River
- 3 sites on sandbars in tributaries to the lower Niobrara River
Sampling Methods:
- Push cores (3-inch dia.)
- Short cores (Universal push- core sampler; 2.625-in. dia.)
- Sandbar edge "bank scrape" with scoop/trowel
Sample Analysis
Cores were split, logged, photographed, and subsampled. Subsamples targeted the sand of apparent best-quality for proppant. Samples were analyzed by the Montana Tech Proppant Research Group. Montana Tech Proppant Research Group evaluated particle-size distribution, bulk density, sphericity, roundness, and crush resistance at a single stress level of 5,000 lbs./sq.in. (psi).
1Coker, E.H., Hotchkiss, R.H., and Johnson, D.A., 2009, Conversion of a Missouri River dam and reservoir to a sustainable system—Sediment management: J. American Water Resources Assoc., v. 45, p. 815-827, DOI: 10.1111/j.1752-1688.2009.00324.x
- Overview
The USGS Nebraska Water Science Center is conducting a pilot study to determine whether sand from the Lewis and Clark Reservoir delta has the desired properties to be used as a proppant in unconventional oil and gas wells that receive hydraulic fracturing (fracking) treatment. Proppants are small particles that are part of the fracking fluid mixture injected into a well to hold open the fractures created during the hydraulic fracturing process.
Why Frac Sand?
Issue 1: Sediment Management
Six large reservoirs along the mainstem of the Missouri River are managed by the USACE. USACE is considering several sediment management options for these and other reservoirs in the Midwest. Management options include hydraulic dredging, reservoir flushing, sediment by-pass, and use for habitat construction. All options would be expensive to implement.
Issue 2: Proppant Sources
Successful use of hydraulic fracturing to stimulate production from oil and gas wells resulted in unprecedented demand for natural proppants such as sand. Proppants increase and prolong hydrocarbon recovery in unconventional oil and gas (UOG) wells. Such treatment requires large quantities of frac sand for each well—the average 3,048-m (10,000-ft) horizontal well may use as much as 2,268 Mg (2,500 tons) of proppant. Proppants presently include three chief types: sand (frac sand) from either sandstone bedrock or unconsolidated deposits, resin-coated sand, and manufactured ceramic spheres. Ideal properties of a frac sand include: size distribution enriched in size ranges specified by the American Petroleum Institute (API), particle shape that is well rounded and approximately spherical, hardness and crush resistance (usually correlated with high content of quartz mineral), minimal overburden, and proximity to a terminal for bulk transport.
OhmMapper™,an array of capacitively coupled resistivity meters, pulled behind a tracked ATV. (Public domain.) Surface Geophysical Reconnaissance
Subsurface texture was characterized at four sandbar complexes in the lake delta using continuous resistivity profiling. Resistivity profiles were collected using the Geometrics OhmMapper™. The OhmMapper™ is a capacitively coupled resistivity system which can can collect continuous resistivity data along 5 depth levels. For this study, the array was pulled behind a tracked ATV.
The OhmMapper™ data have been processed, modeled, and interpreted in partnership with the USGS Crustal Geophysics team in Colorado. The results from the surface geophysical reconnaissance guided site selection. Twenty-eight sites on delta sandbars were targeted for coring.
Sample log from the OhmMapper™. (Public domain.) Lake Delta Sampling
Direct-push sediment cores were collected using a tractor-mounted Geoprobe™ at 24 sites. Duplicate cores were collected at each site to ensure enough sample was collected for core description, laboratory analyses, and archival. Target depth was 12 feet, which is considered the pre-impoundment surface.
Upstream Sources
Deltaic sediments generally are deposited episodically during periods of high transport from incoming sources, and these sources may carry sediment mixtures of differing composition and physical character. For this study, all sampling sites used to characterize potential upstream sources were located along the lower Niobrara River valley, consistent with indications1 that it is the source of nearly three-fourths of the sand load entering the Missouri River delta.
Sampling locations. (Public domain.) Sampling sites:
- 6 sites in the pond upstream from Spencer Dam
- 17 channel sandbar sites along the lower Niobrara River
- 3 sites on sandbars in tributaries to the lower Niobrara River
Sampling Methods:
- Push cores (3-inch dia.)
- Short cores (Universal push- core sampler; 2.625-in. dia.)
- Sandbar edge "bank scrape" with scoop/trowel
Sample Analysis
Cores were split, logged, photographed, and subsampled. Subsamples targeted the sand of apparent best-quality for proppant. Samples were analyzed by the Montana Tech Proppant Research Group. Montana Tech Proppant Research Group evaluated particle-size distribution, bulk density, sphericity, roundness, and crush resistance at a single stress level of 5,000 lbs./sq.in. (psi).
Example output from optical particle-size analyzer used by Proppant Research Group to characterize size distribution for the API 40/70 size fraction of Niobrara River sample NR-09, from one of 18 sampled sand deposits along the river. Listed characteristics of the size distribution for sample NR-09 include percentiles (10th, 50th, and 90th), mean size (326.1 microns) and arithmetic standard deviation (63.2 microns). 1Coker, E.H., Hotchkiss, R.H., and Johnson, D.A., 2009, Conversion of a Missouri River dam and reservoir to a sustainable system—Sediment management: J. American Water Resources Assoc., v. 45, p. 815-827, DOI: 10.1111/j.1752-1688.2009.00324.x
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