CO2/Sand Fracturing in Devonian Shales

Abstract

A total of five carbon dioxide (CO2) /sand well stimulations were successfully executed with two Devonian shale operators in Perry and Pike Counties, Kentucky. This new stimulation method offers a minimum formation damage proppant stimulation approach for natural gas producers in the United States. Some operators have been concerned about the frac fluid formation damage associated with the water and chemicals used in conventional foam stimulations, whereas other operators have been concerned about the lack of proppant in straight nitrogen fracs used by service companies today. Two carefully screened geological areas of established Devonian shale production were selected based on active ongoing drilling and completion operations. One selected control area contained an existing set of wells with established production histories. More specifically, one operator furnished three offset wells which were stimulated with the carbon dioxide/sand frac method. The quantity of proppant and fluids pumped during each well stimulation ranged from 23,000 to 43,000 pounds of proppant and from 120 to 160 tons of liquid carbon dioxide. Another operator furnished two offset wells which were each stimulated with approximately 47,000 pounds of proppant and 120 tons of carbon dioxide. The logistics and field layout of a typical carbon dioxide/sand frac treatment has been described and highlighted. The importance and unique aspects of the closed system blender that is required for job execution is discussed. Five stimulation treatments have been reviewed, and stimulation and preliminary production data compared to offset wells stimulated with nitrogen, and explosives. Initial production results indicate more than a 50 percent increase in production rate compared to nitrogen fraced wells in the Pike County area. In addition, production is also 4.8 times better than conventional shot wells in the same area. These results are encouraging enough to formally combine existing pumping equipment, a closed system blender, and liquid carbon dioxide supplies to develop a new fracturing service in the eastern U.S. A total of 22 additional jobs are planned in the eastern U.S. in low permeability gas formations over the next year.

Environmental Life Cycle Analysis of Water and CO2-Based Fracturing Fluids Used in Unconventional Gas Production

“…A 100% increase in gas production over that baseline would consititute a PIF of 2. A limited number of industry and Department of Energy-sponsored pilot sites have explored the efficacy of CO 2 -based fracs to date across the U.S. and Canada, such as the Lewis Shale (NM), Devonian shale (KY), , Canyon Sands (TX), and scattered early vertical frac wells . For the base case, results compiled from a comprehensive literature review of actual CO 2 frac jobs were applied to project CO 2 performance.…”

“…In spite of the qualitative arguments for using CO 2 as a working fluid, few studies provide quantitative comparisons of the technical performance or the systems-level (e.g., logistics and life cycle) implications of using CO 2 instead of water for fracturing shale formations. Several studies have documented the efficacy of liquid-free CO 2 /sand stimulations in the U.S. and Canada, − but these did not provide clear comparisons between working fluids in the same formations. Heath et al summarize GHG life cycle assessments (LCA) for water-based fracs from multiple shale gas studies .…”

Promotion of CO2 fracturing for CCUS—the technical gap between theory and practice

“…Initial trials focused on using CO 2 as a miscible fluid to displace oil from reservoirs, with CO 2 being injected as a liquid from the wellhead. In order to enhance the performance of CO 2 fracturing and flooding, CO 2 was combined with foam-based fracturing techniques, leading to the development of CO 2 foam fracturing in the early 2000s (Martin and Taber, 1992;Yost et al, 1993). The use of foam in CO 2 fracturing offers several advantages over traditional hydraulic fracturing methods.…”

Supercritical Carbon Dioxide Utilization for Hydraulic Fracturing of Shale Reservoir, and Geo-Storage: A Review

“…Companies and researchers have been working hard to identify nonaqueous working fluids that offer an opportunity to enhance production, reduce water usage, and lessen environmental effects. − Moreover, studies have shown that Sc-CO 2 is a more efficient nonaqueous working fluid than water in extracting gas from shale gas reservoirs. − This can be explained by the unique physical and chemical properties of Sc-CO 2 . − In comparison to water-based fracturing fluids, Sc-CO 2 avoids huge flowback wastewater disposal and formation damage because of its water sensitivity, resulting in environmentally friendly performance. , Supercritical carbon dioxide (CO 2 ) exhibits properties that lie between those of a gas and a liquid, when it is under pressures and temperatures greater than 7.38 MPa and 31.1 °C, respectively. ,,− In laboratory experiments, researchers found that CO 2 in its supercritical state has strong rock-breaking capacity and can infiltrate any space larger than its kinetic diameter (0.330 nm) due to its strong permeability, low viscosity, and extremely low surface tension like gas. It can fracture rock at lower fracturing pressure and form multiple highly complex fracture networks, which enhance oil and gas recovery by displacing remaining hydrocarbon and create a great potential for CO 2 geo-storage. ,,,,,− …”