The U.S. Geological Survey (USGS) published a recent study suggesting that sediment from the Missouri River Basin could be used a proppant in hydraulic fracturing. The researchers took samples of sediment from the Missouri River and analyzed them using protocols from the American Petroleum Institute (API). They found that sand coming from the Nebraska Sand Hills and flowing into the Missouri River could potentially be used as suitable proppant or “frac sand.” The use of river sediment for hydraulic fracturing could help mitigate the cost of removing excess sediment from river basins.
The beneficial uses of reservoirs on our large rivers are affected by the amount of sediment collected. Options for reservoir managers to manage sediment are dredging, hydraulic flushing, sediment bypass and habitat construction. Removal of the sediment where it can be economically or ecologically used helps to defray cost of its removal. The USGS study looked at large river delta deposits of the Missouri River sub-basins that receive sand loads from the Nebraska sand Hills as potential sources of proppant sand. The research also looked to identify and test methodologies for similar work in other reservoirs.
Fracture sand, or ‘frac sand’ is a specialized sand that is added to fluids injected into unconventional oil and gas (UOG) wells during the hydraulic fracturing process. This process enhances the extraction of oil and gas from low-permeable reservoirs by creating fractures, in which the frac sand or proppant helps to ‘hold open’ the fractures, allowing the hydrocarbons to be released. The proppant makes up about 4.5% of the hydraulic fracturing fluid. As technology and science have allowed more efficient hydraulic fracturing techniques to be used, more proppant is required. In 2014, the average UOG well used 4,100 to 5,000 tons of proppant. While there are also treated sand and man-made ceramic materials used as proppants, a 2015 study indicated that 78-93% of estimated national consumption of proppant consisted of processed frac sand.
Proppants may be customized for the different hydrocarbon reservoirs, but API has specific physical properties for frac sand based on geology, grain size, crush resistance, solubility, and sphericity and roundness. USGS looked at the direct comparisons for the dominant-size fraction of each sample; distribution within each sample of the physical properties of particle-size distribution (PSD), roundness/sphericity, crush resistance, and stratigraphy; and estimation of the volume and spatial extent of evaluated sand bodies in the river delta.
USGS scientists collected and analyzed 71 sediment samples at various depths from 25 locations, and found that 48 percent of the samples were the adequate size, shape and strength to be used as frac sand.
“Information from the new study could shift how deposited reservoir sediment is mitigated, and how recovered sediments potentially could be viable to various industries,” said Ron Zelt, a USGS scientist and the lead author of the study.
The study “Suitability of River Delta Sediment as Proppant, Missouri and Nibrara Rivers, Nebraska and South Dakota”, can be found on the USGS website.