Monitoring shale gas resources in the Cooper Basin using magnetotellurics

Abstract

The magnetotelluric (MT) method is introduced as a geophysical tool to monitor hydraulic fracturing of shale gas reservoirs and to help constrain how injected fluids propagate. The MT method measures the electrical resistivity of earth, which is altered by the injection of fracturing fluids. The degree to which these changes are measurable at the surface is determined by several factors, such as the conductivity and quantity of the fluid injected, the depth of the target interval, the existing pore fluid salinity, and a range of formation properties, such as porosity and permeability. From an MT monitoring survey of a shale gas hydraulic fracture in the Cooper Basin, South Australia, we have found temporal and spatial changes in MT responses above measurement error. Smooth inversions are used to compare the resistivity structure before and during hydraulic fracturing, with results showing increases in bulk conductivity of 20%–40% at a depth range coinciding with the horizontal fracture. Comparisons with microseismic data lead to the conclusion that these increases in bulk conductivity are caused by a combination of the injected fluid permeability and an increase in wider scale in situ fluid permeability.

An Investigation of the Underlying Evolution of Shale Gas Research’s Domain Based on the Co-Word Network

“…Canada has also achieved a commercial development of SG and a number of countries and regions carried on the prospecting or developing work and related pilot test of SG [9][10][11][12]. Other countries, such as Poland [13,14], Australia [15,16], England [17][18][19], South Africa [20,21], Brazil [22], India [23], pay much attention to the search of SG.…”

Three‐dimensional resistor network modeling of the resistivity and permeability of fractured rocks

“…The magnetotelluric method is sensitive to changes in the subsurface resistivity both spatially and with orientation. It has been shown to have merit in detecting resistivity changes due to both addition of electrically conductive fluids in an enhanced geothermal system [e.g., Peacock et al , , ; Rosas‐Carbajal et al , ] and more recently, hydraulic stimulation of a shale gas prospect [e.g., Rees et al , , ]. In both examples, the addition of fluids was associated with increases in permeability along the fracture network.…”