Abstract: Load cell having a body with a ball recess therein and a ball removably disposed in the recess above a strain gauge means disposed in the body centrally below the ball recess, the load cell useful in measuring samples of geologic materials, e.g., core samples and for methods and apparatuses for measuring ultrasonic velocities in materials, particularly in the triaxial testing of low permeability rock samples.

Abstract: A method for determining drilling fluid density for stabilizing a wellbore including obtaining shale cuttings from a wellbore. In one embodiment of a method according to this invention, shale cuttings are obtained from a wellbore and their index properties, including but not limited to surface area, is measured; mean effective stress around the wellbore is calculated using the geostatic overburden in situ stress, the field pore pressure, and the total stress around the wellbore; the in situ shale strength is determined using a correlation between surface area, mean effective stress and shale strength; and drilling fluid density is determined using the shale strength. Methods for determining in situ shale strengths, elastic properties, pore pressures, and formation stresses of low permeability rocks.

Abstract: Methods and apparatuses for measuring ultrasonic velocities in materials are disclosed which, in one embodiment, include such methods and apparatuses for triaxial tests of low permeability rock samples, the apparatus including top and bottom end caps for mounting to a sample to be tested, each end cap having an ultrasonic transducer mounted therein for disposition in contact with the material to be tested for measuring the velocities of ultrasonic waves through the material. In another embodiment, at least one end cap having channels and a sensor for sensing changes in sample pore pressure is disclosed. In another aspect, a pressure generator or microaccumulator for changing the amount of a pore pressure fluid in the channels, thereby changing sample water content and making possible an efficient multistage test is disclosed. In another embodiment an end cap for such measurements is disclosed.

Abstract: Methods are disclosed for multi-stage tests of material samples, including but not limited to rock and shale samples, the methods, in one aspect, including the steps of placing a load on the sample, while under a constant confining pressure the sample mounted in a triaxial test apparatus; measuring and recording sample pore pressure continuously during the test; removing the load on the sample; changing confining pressure on the sample; permitting the sample's pore pressure to equilibrate at a new pore pressure with the new confining pressure; permitting the sample to drain fluid to an equilibrium value and placing a new load on the sample measuring and recording resulting pressure and load. In one embodiment these steps are repeated a plurality of times and a plurality of pore pressure, confining pressure, and load readings are obtained.

Abstract: Methods and apparatuses are disclosed for determining a three factor envelope for the material of a preserved core sample. The three factors are ultrasonic velocity through the material, mean effective stress and an elastoplastic property of the material. Values are obtained, in one aspect of the invention, by applying a confining pressure to the material; measuring the material's pore pressure and the ultrasonic velocity therethrough; calculating the material's mean effective stress for that confining pressure; and then loading the sample to near shear failure to measure the value of the elastoplastic property. At different confining pressures the measurements are repeated on the same sample to obtain values for the mean effective stress and elastoplastic property at each level. The envelope is determined by graphically representing the data obtained.

Abstract: A method for determining drilling fluid density for stabilizing a wellbore including obtaining shale cuttings from a wellbore. In one embodiment of a method according to this invention, shale cuttings are obtained from a wellbore and their index properties, including but not limited to surface area, is measured; mean effective stress around the wellbore is calculated using the geostatic overburden in situ stress, the field pore pressure, and the total stress around the wellbore; the in situ shale strength is determined using a correlation between surface area, mean effective stress and shale strength; and drilling fluid density is determined using the shale strength. Methods for determining in situ shale strengths, elastic properties, pore pressures, and formation stresses of low permeability rocks.

Abstract: A microaccumulator for receiving and holding fluid under pressure, and for measuring fluid volume changes in one aspect in very small amounts, and for indicating the amount, the microaccumulator having a body with an interior cavity for receiving the fluid and a piston movably disposed therein which moves in response to a change in fluid amount, the piston having a sensor interconnectible with a monitor and/or system control (e.g. a computer) which can control monitor and/or record changes in the amount of fluid. A triaxial test apparatus for low permeability rock (e.g. shales) using such a microaccumulator. Methods for triaxial tests and for the use of such devices.

Abstract: A method for determining at wellsites the swelling-clay content of cement mixtures by high-frequency dielectric measurements including: grinding a cement mix sample to a size suitable for testing; washing the cement mix sample with a fluid having a water activity substantially less than water, which may contain a soluble cation; packing the washed cement mix sample into a sample cell suitable for dielectric measurement; measuring the dielectric constant at a preselected frequency; and comparing the measured dielectric constant of the cement mix sample to calibration curves.

Abstract: A method for determining at wellsites the solids content of drilling fluids by high-frequency dielectric measurements including: preparing samples of the drilling fluid, of the drill cuttings from the formation, and of each solids-additives type added to the drilling fluid for uniform dielectric constant measurements at preselected frequencies and obtaining the solids content in accordance with the relationship between the dielectric constant measurements of the drilling fluid-solids, drill cuttings, and each of the solids-additives type. In accordance with the method of the invention two levels of determination are possible. These levels of determination depend upon whether the quantities of solids-additives type added to the drilling fluid are known.

Abstract: A method for determining at wellsites the swelling-clay content of shales and shaly sandstones earth formations whereby a sample of the formation is washed with a fluid having a water activity substantially less than that of water, which fluid may contain a soluble cation, and measurements of the sample's dielectric constant are made at a preselected frequency for subsequent comparison to calibration curves, thereby obtaining a measurement of the welling-clay content of the formation. The determinations of the swelling-clay content may be performed at different levels depending on the nature of the samples.