Method and testing device for determining the minimum rock stress

摘要

The invention relates to a method and a testing device for determining the minimum rock stress of underground geological formations. Hitherto known methods are relatively costly and time-consuming and require a high investment in equipment. The invention makes it possible reliably to determine and evaluate the stress condition of a geological formation in-situ within a test interval using a further-developed testing device. Testing is performed directly and involves a low outlay on equipment, being carried out by means of on-line depth manometers and the results being evaluated in an above-ground PC station. In the method a significant proportion of the test-gas volume is prepressurised, introduced up to the test interval and compressed there until crack formation occurs. A pressure balance takes place between the foot and the head of the testing device such that axial anchoring of the testing device in the bore hole is not necessary. The fluid which arises in the test interval is passed into a fluid take-up tube which has been used to hold the prepressurized test-gas volume.