Two primary methods are used to locate, explore, and develop natural gas deposits: seismic reflection imaging and drilling.

SEISMIC WAVES

Seismic imaging involves technicians sending seismic waves into underground geological structures; these waves are reflected back by the boundary layers between different layers of rock. The reflected signals are received above the surface by geophones and are processed at a measuring station to produce a direct map of what is beneath the surface. The seismic waves are created either by vibrating plates mounted on the underside of lorries or by small explosions in flat boreholes.

 

The results of seismic imaging can now almost always able to be displayed three-dimensionally, allowing for the geological structure of the deposits to be modelled and viewed from all sides. This enables drilling to be conducted to a high degree of accuracy.

DRILLING

After seismic mapping and geological surveying of potential natural gas deposits is complete, the drilling rigs start their work. Exploratory drilling establishes direct proof of the rock formation and whether or not it contains gas. 

 

Depending on the size of the deposit, it may be necessary to drill several exploration wells to prove beyond doubt that the deposit is technically suitable for production. Advancements in deep-drilling technology now enable horizontal drilling across several hundred metres between gas-bearing strata. The exploration wells usually reach the natural gas deposits at depths of between 2,000 and 4,000 metres – and, sometimes, up to 5,000 metres. 

PRODUCTION

Natural gas wells are drilled in vertical sections, and each section secured immediately after drilling with tapered pipes that line the inside of the well. The pipes used are slightly smaller than the holes drilled, which allows for the pipes to be securely and impermeably cemented to the surrounding rock. The deepest section of this pipe is perforated so that the natural gas can enter the well in a controlled manner.