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)