Borehole
How is a natural gas well drilled?
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After the natural gas reservoir has been mapped using seismic measurements, a well can be planned to test for the presence of gas and to produce the gas. Before drilling can begin, a suitable drilling site must be selected and a detailed drilling programme for drilling, including well site construction, must be prepared. An operating plan is drawn up for the detailed drilling planning and submitted to the LBGR for approval.
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This operational plan will also include analyses of all impacts of the activities on the environment and a full waste management plan. Waste will be avoided where possible and otherwise safely and responsibly managed and disposed of in cooperation with and with the consent of the German authorities.
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A drilling site is usually the size of two football fields and is selected at some distance from settlements to cause as little disturbance as possible. The drilling can be controlled so that there is flexibility in the selection of the drilling site on the surface. Once selected and all approvals have been obtained, the site is prepared. This includes removing the top overburden and laying out a watertight membrane to ensure that no fluids from the drilling site can enter the groundwater. A gravel layer is placed on top of the membrane to create a working base. Water and electricity supplies and a good access road can also be established before the site is ready for the drilling rig.
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The natural gas in the Zehdenick area is at a depth of about 4,000 metres. A drilling rig capable of drilling a well to a depth of more than 4,000 metres is about 35-50 metres high, or about half the height of a wind turbine or less. Drilling a well to over 4,000 m would take 2 to 4 months.Once the well is completed, the derrick is removed.
How to drill?
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The drilling rigs used for gas drilling work in rotation. This means that the entire drill pipe or tube is rotated from the drilling rig at the surface to the drill bit. The drill bit at the end of the pipe acts like a chisel, breaking through the rock to deepen the borehole as it is rotated. Drilling fluid is pumped into the borehole inside the drill pipe to remove the rock broken off by the bit, and returns to the surface outside the drill pipe. There, the fluid is separated from the broken rock and then pumped back into the borehole again. The drillinjg fluid is not only used to remove the drilled rock, but also to cool the drill bit and equalise the pressure in the borehole. At a depth of 4,000 metres, temperatures of 120-150°C and pressure of 400 bar are expected (car tyres have about 3.5 bar pressure). The drilling fluid therefore has a precisely adjusted density that creates a pressure at the drill bit that is higher than the pressure in the environment.
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To protect the groundwater and other water-bearing strata, as well as for safety during drilling and production, various pipe strings, known as casing, are inserted into the borehole and cemented in place (picture below).
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This ensures that liquids or gas from inside the well cannot mix with liquids in layers outside the well. However, the many pipes not only serve to protect the groundwater or other water layers between the surface and the gas reservoir, but are also necessary for safe and controlled pumping of the gas to the surface. The pipes cemented into the ground are not visible at the surface, but are connected to the safety valve, which is located at the surface and remains in the borehole even after the drilling rig has been withdrawn. The safety valve is usually 2 to 4 metres high.
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After drilling and testing the well, the drilling rig is dismantled and removed. If the well is used as a gas production site, an area of up to 10 by 10 metres remains with some 1-3 m high pipes and safety valves, a so-called Christmas tree installed above the gas well and a pipeline buried in the ground to transpot the gas way from the well to a processing plant.
How will the removal of the rig and well site be paid for if the well is unsuccessful?
Prior to the commencement of drilling operations, Jasper Resources will provide LBGR with a security deposit in accordance with Section 56 (2) BBergG to ensure that the dismantling and reclamation work can be carried out in any event.
