Trail of Exploration - Crude oil, natural gas and geothermal energy

Into the depth with hi-tech from Celle

Celle is the European centre for the crude oil, natural gas and geothermal heat industry. More than 50 companies, some of them international, employ approx. 4,500 people and cover all elements of value creation. This includes but is not limited to research and development, education, training and qualification, product development and plant engineering for surface and underground equipment as well as logistics and appurtenant services.

Have a look at the exhibits along this trail of exploration and discover the opportunities for geothermal heat utilization in the exhibition area of Bohrmeisterschule Celle (Drilling School Celle).

The trail of exploration for crude oil, natural gas and geothermal heat has been set up by the City of Celle, the GeoEnergy Celle e.V. association, Bohrmeisterschule Celle, and by Deutsches Erdöl- und Erdgasmuseum (German Crude Oil and Natural Gas Museum) in Wietze. The exhibits have been made available by companies from Celle.

Well head

This product is used to close the wellbore and the casing string suspended in the well. The flanges on the sides are the inlets and outlets of the various annular spaces which have different functions.

Depending on the type of borehole, a well head sustains various amounts of pressure, temperatures and fluids. The tightness of this product must be guaranteed under every load condition and this must be continuously demonstrated by performing extensive pressure tests to international standards. High-value materials, precise machining and the strict observance of all EU and API regulations are the standard for every approved manufacturer.

Drilling Bit

For exploration of reservoirs of crude oil and natural gas or for the production of geothermal energy from warm water in deep rock layers, deep drilling of often several kilometres into the depth is necessary. The reservoirs are deep in the ground and access goes through hard rock formations. For thi, drilling rods in a rig are put into rotation by means of an electric or diesel motor. The most important tool is the drill bit, which is screwed at the lower bottom of the drilling rods. By this rotation and the enormous weight of the drilling rods the drill bit removes the rock inch by inch.

There are different types of drilling bits: rolling tools ( roller bits ) and shaving tools ( PDC bits – Polycrystalline Diamond Compact, synthetic diamonds ).They differ in the structure and the way they destroy the rock. Roller bits make a crack in the rock and small pieces of rock are broken off whereas with the PDC bit the rock is removed by scraping/shaving.

Roller bits have two or three rolls that rotate on the bore hole bottom around their own axes. The cutting structure is either milled from metal, a so called tooth bit suitable for soft rock formations, or otherwise it is equipped with hard metal inserts ( TCI Tungsten Carbide Inserts ), a so called insert bit which can drill through hardest rock layers. The rolls are on ball bearings and are protected from fluids with seals. Due to the many movable parts roller bits can be damaged in difficult formations so the drilling bit may have to be exchanged after some hundreds of metres.

Nowadays more and more PDC bits are used. They have no movable parts but consist of a basis from steel or a matrix with webs at the drill top. There are inserts in these webs with artificial diamond discs, which shave the rock. PDC bits have the great advantage that they have a considerably longer life-time on the one hand, and on the other hand they can drill more metres per hour, i.e. they can reach a much higher drilling speed in comparison to roller bits.

Drill string

Deep wells are sunk in suitable geological formations in order to develop oil and natural gas deposits or use deep geothermics.

Apart from a deep drilling rig, a drill string is one of the key technical components for ensuring the success of a well. A drill string basically consists of a drilling tool, i.e., a drill bit, a meas-uring and control unit, drill collars and drill pipes. The exhibit presented here is composed of a 8 ½" PDC drill bit with poly-crystalline inserts, a 6 ¾" control system of the Autotrak type, an 8 ½" stabilizer, a 6 ½" spiral drill collar and a 5" API drill pipe.

This drill string allows to sink boreholes more than 5,000 metres deep and also drill over a horizontal distance of several hundred metres in a geological formation.

Drill cores

When drilling for near-surface geothermal energy, a difference is made between various drilling sections or work phases.

A three-column model has been created to make it easier to explain these different work phases.

This presentation is limited to the running-in phase as well as to the subsequent grouting and backfilling sections.

The first column of the model shows the geothermal probe bot-tom to present the installation at the bottom hole.

The second model column represents the geothermal probe in-cluding the grouting process in a sectional model. This sectional view is used for training purposes. So the probe foot is shown without grouting.

The third model column shows a geothermal probe which is backfilled completely and integrated into the rock, showing the probe ends which stand out over the top level of ground prior to their connection to the overall system.