An Experimental Study of Open-Hole Hydraulic Fracturing as a Stress Measurement Method with Particular Emphasis on Field Tests

摘要

The process of hydraulic fracturing has found a variety of applications in areas outside the Petroleum Industry. One of these areas, for which open hole fracturing shows great potential, is the field of in-situ stress measurement. Special equipment suitable for fracturing in 2-1/4 inch diameter boreholes was developed. The bottom hole pressure was recorded with the aid of a pressure transducer, and the fracture orientation determined by means of an impression packer. The tests were carried out close to the surface in a quarry as well as in three locations, 1100, 1000 and 500 feet underground. The rock in which the tests were performed had negligible permeability when tested in the standard manner. At each location several boreholes 2-1/4 inches in diameter and up to 60 feet long were drilled. Wherever possible, the holes were oriented in mutually perpendicular directions. Far-field stresses were calculated from the breakdown pressure obtained in the fracturing tests and the rupture strength of the rock taking into account the influence of the underground excavations. The latter was determined in separate tests. (Author)