Shale gas operators discuss fracing procedures at Nexen's Dilly Creek operations in northeastern British Columbia.
Understanding the Resource
What is shale gas?
Shale gas is natural gas that is tightly locked in very small spaces within the shale rock formation. To unlock it, Nexen 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.
What is horizontal drilling?
Horizontal drilling enables Nexen 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.
The horizontal well is drilled into a rock formation containing gas (typically tens to hundreds of metres thick, extending several hundred metres in every direction). The fractures extend in the shale gas formation providing a pathway for the natural gas to flow.
What is fracing?
Hydraulic fracturing 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:
- Adhering to government regulations on the minimum depth for fracing
- Using multiple layers of steel and cement throughout the wells to prevent fracing fluids from escaping and to protect water aquifers
- Monitoring and controlling fracture pressure to manage fracture length
- Fracing in formations that are contained by barriers of dense rock layers to prevent fractures from spreading outside of the target formation, and keep fluid from moving to another formation
- Supporting transparency of frac fluid and participating in fracfocus.ca – a website project of the British Columbia Oil and Gas Commission, designed to provide objective information on hydraulic fracturing