Our core regions
We take you on a discovery tour of Wintershall's world of exploration and production.
Dates
- 20.05.2012Kassel MarathonKassel, Germany
- 04.06.201225th World Gas Conference Kuala Lumpur
- 09.06.2012Documenta 13Kassel, Germany
OnshoreHow do the valuable sources of energy get to the surface?
Crude oil and natural gas are located in the pores of deep layers of rock, rather like water in a sponge – which means that there are no underground "oil lakes" or "gas bubbles" from which these sources of energy could simply be extracted. In most cases, the oil is "trapped" under a dome of impermeable rock, such as slate: Oil and gas had been traveling from where they originated toward the surface for millions of years, until their progress was halted by this anticlinal trap. Oil and gas can also be held in other geological formations – for example faults and the area around salt domes.
Oil and gas under high pressure
Oil and gas are often under great pressure below the surface, which increases by approximately one bar for every ten meters of depth. If such a reservoir has been tapped into by drilling a well, the raw materials usually gush from the ground unaided. To prevent their uncontrolled release, a "Christmas tree" with valves and pressure gauges is installed above the well. For as long as there is sufficient pressure in the reservoir, oil and gas stream to the surface completely unaided.
When the pressure drops too low, the oil has to be brought to the surface with the help of technology. With the gas lift process, for example, natural gas is pumped back into the well; this reduces the weight of the oil column in the well, allowing the valuable resource to rise further. Once this ceases to produce results, the time has come for well pumps. In most cases, the characteristic horsehead pumps are used to transport the oil: These pumps go up and down at a rate of between two and twelve strokes a minute, and each time a piston at the end of the well pushes the oil column a step closer to the surface.
To increase the yield from a reservoir, water is often forced into holes distributed around the actual oil well. The pressure this generates drives the oil to the well. The flow of the viscous oil can also be improved by forcing surfactants or water vapor into the ground, for example. All these processes are aimed at recovering as much oil as possible from the deposit. But in spite of all the efforts, in most cases only 30 percent of the raw material can be produced economically. With the help of state-of-the-art technology and improved exploration procedures, Wintershall can today move beyond this threshold. Examples include the steam flood technology used in Emlichheim in Lower Saxony or the biopolymer schizophyllan.
Hydraulic fracturing produces more natural gas
In some natural gas fields – for example in Northern Germany, Argentina, or Russia – the gas (usually in what are known as tight gas deposits) is trapped in very small pores, so that it can hardly flow of its own accord. As a result, only a tiny fraction of a deposit can be produced unaided. Through hydraulic fracturing (or "fracking" for short), water pressure creates fine cracks, only millimeters wide, in predefined places in the hard layers of the rock. These fractures are propped open by sand (proppants) added to the water to keep the cracks open for longer. This facilitates the flow of the gas in the rock into the well and makes it easier to produce. The fluid used in fracking is a slurry of water and sand (99%) and a small amount of other additives (around 1%).
To establish whether this technique, which has been in use for several decades, is also suitable for possible unconventional natural gas deposits in North Rhine-Westphalia (shale gas), preliminary geological surveys are to be conducted in the next few years, initially without the use of fracking and deep wells.
To establish whether this technique, which has been in use for several decades, is also suitable for possible unconventional natural gas deposits in North Rhine-Westphalia (shale gas), preliminary geological surveys are to be conducted in the next few years, initially without the use of fracking and deep wells.
