+ What is hydraulic fracturing (fracking)?
Hydraulic fracturing is the process of injecting water, sand and additives into hydrocarbon bearing rocks. This injection creates tiny fissures along the rock which release the natural gas. Additives (representing less than 1 per cent of the fluid injected) are used for several purposes, mostly to increase the viscosity of the injected fluid, optimise post-fracturing water recovery or protect the production pipe casing from corrosion.
+ What is horizontal drilling?
A well is first drilled vertical to a depth suitable for hydrocarbon recovery. Then the drill is redirected horizontally to increase the contact with the hydrocarbon reservoir. Horizontal wells can continue for thousands of metres, allowing the operators to concentrate on a single rock unity and increase the volume of fractured material along the well bore. After the hydraulic fracturing, the horizontal and vertical sections of the well bore act as a drain for the gas.
+ What is a seismic survey?
A seismic (geophysical) survey is used to map layers of rock in a chosen region. This improves the knowledge of subsurface geology, and much like a submarine’s use of sonar, advancing mapping technology generates an image of the rock beneath the surface.
The first stage of a survey involves laying a temporary network of “geophones” (similar to sensitive microphones) across the survey area at ground-level to record energy signals. This equipment is temporary and will be removed after the survey is completed.
The survey crew then generates energy signals to map the subsurface geology.
This process involves using tractor-like vehicles with “vibrating plates”. The vehicles can travel both on and off road, regularly lowering their vibrating plates to the ground in order to send signals down into the rock layers. Typically, a survey will use up to four trucks and the process can take anywhere from two to eight weeks, depending on the size of the survey area.
The energy signals generated by the vibroseis process travel down into the rock formations, returning in varied strength and speed, and are recorded by the network of geophones (see figures 1A and 1B below). Using computer technology to process this information, we are able to create an image of the rock formation.