Current opinions on foam-based hydro-fracturing in deep geological reservoirs

Geomechanics and Geophysics for Geo-Energy and Geo-Resources, Dec 2015

Natural gas extraction is a greener solution to world energy resource depletion and water-based hydraulic fracturing is traditionally used to produce gas from deep and tight geological formations. However, since this practice fails to produce a commercially viable amount of gas and raises many environmental issues, better alternatives are being tested in the field, among which the usage of foam-based fluid is a comparatively novel but effective technique. The aim of this review is to understand the current opinion on foam-based fluid fracturing, its merits and demerits and the associated environmental footprint. Foams are made by mixing a gas phase with a liquid phase using a suitable surfactant, and the foam quality is composition-dependent, with high quality foams having higher percentages of gas. The properties of the injecting foam, including its rheology and viscosity, are important for the fracturing process. According to current studies, foams have two separate flow regimes (low and high quality) and a unique multiphase flow pattern. Foam viscosity should be low to enter the ends of the fracture and high to have a good proppant-carrying capacity. Greater proppant-carrying capacity, lower water consumption and chemical usage, quicker and easier fluid flowback and less environmental damage are the advantages of foam-based fracturing, and lack of knowledge, high capital cost, and potential damage to the environment from surfactants are the limitations. However, foam-based fracturing has been tested in very few locations to date.

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Current opinions on foam-based hydro-fracturing in deep geological reservoirs

Geomech. Geophys. Geo-energ. Geo-resour. Current opinions on foam-based hydro-fracturing in deep geological reservoirs W. A. M. Wanniarachchi . P. G. Ranjith . M. S. A. Perera . A. Lashin . N. Al Arifi . J. C. Li 0 1 2 3 4 0 A. Lashin Geology Department, Faculty of Science, Benha University , P.O. Box 13518, Benha , Egypt 1 A. Lashin Petroleum and Natural Gas Engineering Department, College of Engineering, King Saud University , P.O. Box 800, Riyadh 11421 , Saudi Arabia 2 W. A. M. Wanniarachchi P. G. Ranjith (&) M. S. A. Perera Deep Earth Energy Laboratory, Department of Civil Engineering, Monash University , Building 60, Melbourne, VIC 3800 , Australia 3 J. C. Li State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences , Wuhan 430071 , China 4 N. Al Arifi Geology and Geophysics Department, College of Science, King Saud University , P.O. Box 2455, Riyadh 11451 , Saudi Arabia Natural gas extraction is a greener solution to world energy resource depletion and water-based hydraulic fracturing is traditionally used to produce gas from deep and tight geological formations. However, since this practice fails to produce a commercially viable amount of gas and raises many environmental issues, better alternatives are being tested in the field, among which the usage of foambased fluid is a comparatively novel but effective technique. The aim of this review is to understand the current opinion on foam-based fluid fracturing, its merits and demerits and the associated environmental footprint. Foams are made by mixing a gas phase with a liquid phase using a suitable surfactant, and the foam quality is composition-dependent, with high quality foams having higher percentages of gas. The properties of the injecting foam, including its rheology and viscosity, are important for the fracturing process. According to current studies, foams have two separate flow regimes (low and high quality) and a unique multiphase flow pattern. Foam viscosity should be low to enter the ends of the fracture and high to have a good proppant-carrying capacity. Greater proppant-carrying capacity, lower water consumption and chemical usage, quicker and easier fluid flowback and less environmental damage are the advantages of foambased fracturing, and lack of knowledge, high capital cost, and potential damage to the environment from surfactants are the limitations. However, foam-based fracturing has been tested in very few locations to date. Unconventional reservoirs; Foam-based fracturing; Rheology and viscosity; Shale gas; Oil; Tight gas 1 Introduction Although the extraction of natural gas and oil from deep geological formations such as shale, tight gas and coal beds is a potential solution for the energy resource depletion crisis in the world (Xie et al. 2015) , the extraction of economically viable quantities of gas/oil from these formations has become a challenge due to their extremely low permeability. Therefore, research into advanced permeability enhancement techniques has become essential in the petroleum industry. Among the various possible permeability enhancement techniques, hydro-fracturing is the most common practice in the industry (Kinnaman 2011; Nehring 2010) . During the hydro-fracturing process high-pressure fluids are injected into deep rock formations to generate a network of fractures that enhance the reservoir permeability by making easy flow paths for fluid movement (Gu and Mohanty 2014), resulting in greater fuel extraction from the reservoir. In addition, the mixing of an appropriate propping agent with the fracturing fluid (proppant) is used in the hydro-fracturing process to keep the fractures open after releasing the fluid pressure (Liu et al. 2010) . These agents can be made using resincoated or uncoated sand, sintered bauxite, ceramic materials, and glass beads (Fink 2012) . For this reason, an appropriate proppant-carrying capacity is necessary for the fracturing fluid to prop open the fractures all around the wellbore, including the lower and upper surfaces of the wellbore. Currently, various types of hydraulic fracturing fluids are used in the petroleum industry, including water, foam, gas and hydrocarbons, and each has advantages and limitations. This paper reviews current findings on the usage of foam-based fluids for the fracturing process in deep geological formations. In general, foam can be made by mixing a gas with a liquid, and it therefore consists of gas bubbles inside a liquid phase, where the liquid act as the external phase for the gas. The two-phase fluid flow nature of foams leads to a high viscosity [up to about 150 mPa s (Ding et al. 2013) ] and low density (similar to air) fracturing fluid, both of which ensure a greater proppant-carrying capacity. The selection of the liquid phase depends on economic constraints and reservoir conditions (permeability, water availability, clay content and temperature etc (...truncated)


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W. A. M. Wanniarachchi, P. G. Ranjith, M. S. A. Perera, A. Lashin, N. Al Arifi, J. C. Li. Current opinions on foam-based hydro-fracturing in deep geological reservoirs, Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 2015, pp. 121-134, Volume 1, Issue 3-4, DOI: 10.1007/s40948-015-0015-x