GERMAN DEEP TEST RUNS LONG STRING OF 16 IN.

The German research project to investigate the earth's crust with a 10,000 m (32,800 ft) hole has employed advanced drilling technology to reach a major first stage in the program. Project operator for the Kontinentales Tiefborhrprogram Der Bundesrepublik Deutschland (KTB), or Continental Deep Drilling Program of the Federal Republic of Germany, said 3,000 m (9,840 ft) of 16 in. casing weighing about 360 metric tons has been run to 3,003 m. The borehole is at Windischeschenbach, Germany,

July 8, 1991

2 min read

The German research project to investigate the earth's crust with a 10,000 m (32,800 ft) hole has employed advanced drilling technology to reach a major first stage in the program.

Project operator for the Kontinentales Tiefborhrprogram Der Bundesrepublik Deutschland (KTB), or Continental Deep Drilling Program of the Federal Republic of Germany, said 3,000 m (9,840 ft) of 16 in. casing weighing about 360 metric tons has been run to 3,003 m. The borehole is at Windischeschenbach, Germany, near the Czechoslovakian border (OGJ, Feb. 27, 1989,p. 64).

The first stage was drilled with slim hole clearance and automatic downhole steering systems. Inclination averaged only 0.5 in the first 3,000 m of hole.

Outside diameter of the Hydril connectors on the 16 in. casing is 413 mm, or 161/4 in., while the hole size is 4441/2 mm, or 171/2 in., leaving a clearance of only 5/8 in.

The KTB operator said bonding the casing to the surrounding rock by filling the annular volume plus out of gauge hole from the bottom to the top with cement and with only a nominal 16 mm clearance represents a technological success of international importance. Halliburton Co. completed the cementing May 30.

Extra large spiders used in setting the casing were rented from Austria's state owned oil company, OMV, which has done some of the deepest drilling in Europe.

The next step is to drill to 6,000 m with a 143/4 in. bit and set 133/8 in. casing. The entire project is to be complete by the end of 1994.

KTB drilling began Oct. 6, 1991, and is scheduled to go to 10,000 m-possibly 12,000 m unless temperature exceeds 300 C. (572 F.) at the 10 km mark.

The temperature gradient has been higher than predicted. However, the Germans point out that the objective is not to drill the deepest but the most interesting hole.

The drillsite was selected because it is in a geologically interesting region where tectonic plates thrust over each other. The subsurface is mainly crystalline rock.