Abstract: A method of maintaining the integrity of a sheath, in particular a cementing sheath in a well consists in calculating or estimating variations in well pressure and/or in well temperature and/or in the variations in in-situ stresses, which may occur during the lifetime of the well, evaluating the stresses in the sheath as a function of the above variations, determining the nature of the stress likely to be first in causing deterioration of the sheath, and the risk thereof, and evaluating the influence of the elastic properties of the sheath, of the rock and/or of the casing on this stress, in order to select a sheath which is capable of attenuating this deterioration. The method is of particular application to oil, water, gas, and geothermal wells.

Abstract: A method of maintaining the integrity of a sheath, in particular a cementing sheath in a well consists in calculating or estimating variations in well pressure and/or in well temperature and/or in the variations in in-situ stresses, which may occur during the lifetime of the well, evaluating the stresses in the sheath as a function of the above variations, determining the nature of the stress likely to be first in causing deterioration of the sheath, and the risk thereof, and evaluating the influence of the elastic properties of the sheath, of the rock and/or of the casing on this stress, in order to select a sheath which is capable of attenuating this deterioration. The method is of particular application to oil, water, gas, and geothermal wells.

Abstract: A method of fracturing an underground formation traversed by a borehole comprising: a) placing an inflatable member inside the borehole in the formation to be fractured, b) inflating the member so as to exert stress on the formation while monitoring the pressure of a fluid used to inflate the member so as to determine the pressure at which fracture initiates; c) isolating the portion of the borehole containing the fracture; d) propagating the fracture by pressurizing the interval with fluid; and e) monitoring the pressure of the fluid in the interval during propagation.

Abstract: A downhole penetrometer comprising a body which can be lowered into a borehole and including a tooth and an associated actuator for moving the tooth radially outwardly from the body so as to penetrate the wall of the borehole, a sensing arrangement being provided for determining the force applied to the tooth and the extent of penetration of the tooth into the borehole wall. A motor and pump arrangement is included to power the actuator, power typically being provided by a wireline which can also be used to communicate readings to the surface. A pair of inflatable packer modules are situated above and below the tooth to isolate an interval of the borehole in which a measurement is being made.

Abstract: A method of performing small scale micro hydraulic fracturing in which fluid is pumped into the test interval until the initiation of a fracture is indicated, immediately after which fluid is pumped out of the interval so as to prevent propagation of the fracture and allow closure thereof, the portion then being repressurized by pumping fluid back in. By pumping out when the fracture is initiated, propagation is substantially prevented allowing estimation of the fracture length and toughness to be obtained and the time taken for the measurement reduced.