Shale gas is natural gas that is tightly locked in very small spaces within the shale rock formation. To unlock it, CNOOC International uses technology to horizontally drill and stimulate (fracture) the gas-bearing zones. The creation of fractures within the shale releases the gas. Once released, shale gas is produced the same way as conventional natural gas.
Horizontal drilling enables CNOOC International to access the shale gas reservoir in a cost-effective and environmentally responsible way. The well is drilled for about 2,400 metres vertically, then the drill bit makes a gradual 90 degree turn and continues horizontally for up to 1,800 metres. This technology utilizes a flexible drilling pipe that ‘bends’ into a horizontal position that is parallel with the resource zone. Horizontal drilling reduces land disturbance allowing for multiple wells to be drilled from the same drilling pad and increases wellbore exposure to the shale rock. This increases the amount of natural gas that can be recovered from the shale formation.
Hydraulic fracturing, also known as fracing, is the process of high-pressure fluid injection (composed primarily of water and sand) into an oil or gas formation, which creates cracks, or fractures, that allow oil or gas contained in the formation to be released.
Precautions taken to ensure fracing does not interfere with ground water include: