Tight and shale gas technology
We are using advanced technology developed and refined over 60 years to safely unlock resources of natural gas trapped tightly inside dense rock in extremely fine pores. Today’s technology helps us reduce our environmental footprint, cut down the number of drilled wells, and lower costs.
In many conventional natural gas reservoirs, a few vertical wells every 2.5 square kilometres (around one square mile) are enough to produce the resources available. In contrast, tight and shale gas does not flow easily and resources are often spread over a much larger area, making it harder to access.
We drill wells in different directions from a central location that penetrate the reservoir vertically, often in an S-shape, or horizontally. This limits the number of drilling locations – known as well pads – and reduces our overall surface impact.
Well pads can be spaced up to five kilometres (three miles) apart. Some accommodate up to 50 wells or more. Mobile drilling rigs allow us to avoid dismantling and reassembling drilling equipment at each pad, making the process quicker and saving resources.
Wells can stretch several kilometres underground. For example, in Groundbirch, Canada, we drilled a well 6.3km (3.9 miles) long. In Changbei, China, we drilled an extensive network of wells up to two kilometres (1.2 miles) long to open up a much greater area for gas extraction. This increased potential production as much as ten times compared with conventional techniques.
Watch how we safely unlock tightly trapped gas and oil
Unlocking tightly trapped gas and oil
Natural gas, the cleanest-burning fossil fuel is vital to the world's energy future.
Hydraulic fracturing technology can safely unlock gas resources trapped tightly in tiny rock spaces.
When natural gas or crude oil is held tightly in rock pores engineers may release it into wells by means of a carefully controlled process called hydraulic fracturing, or "fracking".
Here's how it works.
In preparation, the rig crew first removes the drilling equipment, giving easy access to the well, a capped hole, lined with steel pipe and cement.
A crane holds an insertion device over the well's entrance.
Through it, the crew slips a flexible steel tube into the well.
The end of the tube hold a perforation tool.
It snakes down the well until it reaches the well's horizontal section.
That section lies thousands of metres below the surface, far below drinkable ground water.
Small charges on the tool make openings that expose the rock and the tool is withdrawn.
Steel pipes connect the well to powerful pumps that fill the well with a mixture of water, sand and chemicals.
First we test the well under pressure to make sure it is tightly sealed.
The mixture is pumped at high pressure to open up the exposed rock.
Temporary plugs divide the well into segments that are separately perforated and pressurized over the course of a few days.
The plugs are drilled out so that oil or gas with some of the hydraulic fracturing fluid, and salty water from prehistoric times, can flow from the open rock into the well.
At the surface, the water is separated from the oil or gas.
Sometimes it can be reused for hydraulically fracturing another well.
After all the wells at a site have been hydraulically fractured, the fieldworkers clear the site.
What remains is a small production facility.
Opening up rock
When we have completed a well we need to coax the gas from the very tight rock. We pump fluids into the well to make fractures in the rock that allow the gas to flow. This typically takes place a kilometre (several thousand feet) beneath supplies of drinking water, at pressures high enough to create fractures.
The fracturing fluids comprise around 99% water and sand (or ceramic particles), and 1% chemical additives. Sand and ceramic particles have large pores which keep the fractures open, allowing gas to flow. The chemical additives help to keep pipes cool and prevent scale build-up.
During this process, we sometimes place a string of sensors in a nearby well to pick up the popping and creaking of the controlled opening of the rock deep underground. The sounds help us to map out the contours of the cracked rock.
Temperature-sensitive fibre-optic strands help us monitor inside the wells. Cooler zones show us where gas is flowing freely into the wells so that we can adjust operations and improve efficiency. We use software to map out fields below the surface and better target fracturing.
At Shell, we believe we can explore, develop and produce these tight and shale resources safely and responsibly. Shell’s efforts are underpinned by the Shell Onshore Tight Sand or Shale Oil and Gas Operating Principles that we believe provide a framework for protecting water, air, wildlife and the communities in which we operate.
We line the wells with steel pipes and cement them in place from the surface to below the level of the drinking water. These barriers help to contain the fracturing fluid and, along with the depth at which we fracture, prevent the fluid from mingling with drinking water close to the surface.
During operations we monitor wells with pressure sensors to check they are firmly sealed. We also monitor the fractures and the fluids, which helps make production as efficient as possible and protects the environment.
The oil and gas industry has used hydraulic fracturing worldwide for more than 60 years in vertical wells and for almost 20 years in horizontal wells to recover natural gas (and oil). Globally, hydraulic fracturing has been used in more than two million oil and gas wells to date.
A 2012 study by the Royal Society and Royal Academy of Engineering for the UK government also concluded that hydraulic fracturing is safe “as long as operational best practices are implemented and robustly enforced through regulation”. A European Parliament report on the environmental impacts of shale gas and shale oil extraction, supports its findings.
More in natural gas
We are safely tapping into huge resources of natural gas, known as tight and shale gas, held deep inside rock.
We follow global operating principles focused on safety, environmental safeguards, and engagement with nearby communities to unlock resources safely and responsibly.