Natural gas is a fossil fuel. Natural gas consists for the most part of methane.
Natural gas originated from plants that died hundreds of millions of years ago. This created layers of earth with organic components, which are buried very deep under our earth’s surface and form a huge stock of carbons. This stock sank deeper and deeper and became more and more concentrated. It became coal. In the seas, much the same thing happened to dead sea creatures and plants. This is where petroleum was born. Due to the heat and the pressure at that depth, methane was released. That’s natural gas. Because natural gas is lighter than water, it seeped up. Eventually it was stopped by impenetrable layers (clay or salt). It stayed in the porous layers below. These layers are located at a depth of 2 to 4 kilometres. The natural gas is, under high pressure, in the pores (which are tiny holes) of this sand or limestone layer.
Vermilion extracts approximately 713 million cubic meters (m3) of natural gas per year in the Netherlands. This is equivalent to the gas consumption of approximately 500,000 Dutch households. There are almost 8 million households in the Netherlands, so that amounts to the consumption of more than 6% of all Dutch households.
First, we take measurements in deep layers of the earth and analyse them. If we think natural gas is in the ground, we drill a well. Then we can extract the gas from the deep subsurface. Depending on the gas field, this can take decades. When a gas field is empty, we clean everything up again. Gas production can therefore be subdivided into the following phases:
In the first phase, we investigate whether natural gas may be present in an area. We do this with seismic research. Sound waves are sent into the ground to gather information. We analyse the signals from this research in detail with advanced software. After this, our geologists determine whether natural gas may be present somewhere.
In the second phase, we use a borehole to see how much natural gas is really in the gas field. Such a drilling usually takes about four weeks and continues 24 hours a day. This is the phase that the environment notices the most. For example, it concerns sound or light in the evening hours. As a local resident, we always inform you in advance if you notice something of our activities.
From a drilling rig at the location, we go further and further into the ground. The diameter of the hole we drill in the ground is not large, often only one meter. But the deeper we go, the smaller it gets. At the location of the gas field – at a depth of more than two kilometres – the drill head is often only tens of centimetres in size. The drill head is sent to the spot designated by the geologists. That is really precision work and only real specialists can do that.
In the third phase, we produce the gas, which usually comes up on its own. The gas then goes via underground pipes to a gas treatment station, after which it finds its way to Dutch households and businesses. During gas production, there is virtually no nuisance. However, maintenance work is sometimes required. Then our technical people are present at the location. In case of maintenance work that can cause nuisance, we always inform the environment well in advance.
In the final phase, we are going to clean up. If a location is no longer used for gas production and we are sure that this will remain the case, we clean it up neatly. We bring the location back to its original state.
Hydraulic stimulation (also called fracking) is a technique to increase the permeability of the rock. This makes it easier to extract natural gas. Through the borehole we then pump water with small grains into the gas-carrying rock in a short time – usually for a few hours – under high pressure. This creates small cracks in the layer in which the gas is located. The cracks are kept open by the small grains. This makes it easier for natural gas to flow to the well. Hydraulic stimulation usually only needs to be performed once.
Outside the Netherlands, natural gas is also extracted by fracking shale rock to extract shale gas. Extracting shale gas requires large quantities of wells and fracks. The extraction of shale gas is not permitted in the Netherlands. This does not happen here.
With gas production on land, water rises with it. This is water with a very high salinity. In our gas treatment stations, we separate the natural gas from the water. The natural gas goes to Dutch households and businesses. We bring the production water back to where it came from: in the deep subsurface, at a depth of more than two kilometres. We call this water injection.