DRILLING PROGRESSES ON GERMAN DEEP TEST

Drilling was under way below 1,700 m in a 17 1/2 in. hole early this month on an ultradeep well in Germany, part of a 500 million deutschemarks geoscientific research program. The project is funded by the German Ministry for Research and Technology. Drilling, which began last Oct. 6, is slated to go to at least 10,000 m. If bottom hole temperatures don't exceed 300 C. at the 10 km mark, drilling may continue to as deep as 12,000 m, said Klaus Spannbrucker, spokesman for the project in

March 25, 1991

3 min read

Drilling was under way below 1,700 m in a 17 1/2 in. hole early this month on an ultradeep well in Germany, part of a 500 million deutschemarks geoscientific research program.

The project is funded by the German Ministry for Research and Technology.

Drilling, which began last Oct. 6, is slated to go to at least 10,000 m. If bottom hole temperatures don't exceed 300 C. at the 10 km mark, drilling may continue to as deep as 12,000 m, said Klaus Spannbrucker, spokesman for the project in Hannover.

Early planning called for drilling to 14,000 m (OGJ, Feb. 27, 1989, p. 64). But information gained from a pilot hole caused planners to revise the depth target.

Planned casing program includes 16 in. at 3,000 m, 133/8 in. to 6,000 m, a 9 5/8 in. liner tied back to surface, and an optional 7 5/8 in. liner.

Technical Director Heinrich Rischmuller said a key concern was maintaining a vertical hole to minimize drillstring torque and drag. Two active vertical drilling systems developed especially for the project are being used.

The special rig built for the project has 12,900 hp and a depth rating of more than 12,000 m. Features include fully electric drive, sound-proofing, and on-site emission conditioning facilities. Layout and design of the rig were developed by German drilling contractors Deutag, DST, and ITAG.

Drilling is to be completed by the time funding for the project expires Dec. 31, 1994. The well is being drilled 200 m from the pilot hole completed in 1989.

PILOT HOLE RESULTS

The idea for the German Continental Deep Drilling project (KTB) was first discussed in the late 1970s. Then 40 proposed sites for the project were screened in the early 1980s, and a site was selected in 1986 southeast of Bayreuth near the village of Windischeschenbach.

The first step in the drilling phase was a pilot hole begun in 1987 and completed early in 1989. The pilot hole, among other advantages, provided information at a lower cost that could be used to plan the ultradeep hole.

About 90% of the 4,000 m pilot hole was cored, and 15-20% of the ultradeep hole will be cored.

A temperature profile about one-third higher than expected was one of the key pieces of data revealed by the pilot hole. At 4,000 m, temperature was 118 C., indicating temperature at 10,000 m will be about 290 C.

Final decision on total depth will be made when the hole reaches about 8,000 m. Although the option remains to go to 12,000 m, technical planning and funding is based on a total depth of 10,000 m. More than 80% of the major geoscientific objectives can be met at 10,000 m depth.

The project has a wide range of objectives. New drilling systems have been developed for the project, and operating data will be obtained on drilling equipment, systems, and methods.

A report on the project by Rischmuller said the "KTB ... has encouraged and developed cooperation with a number of nations and institutions..." including the U.S., France, Sweden, Canada, U.K., Czechoslovakia, Japan, China, Germany, and U.S.S.R.