Jack H. Cole

Electro‐hydraulic dipole vibrator

A downhole seismic shear wave source is used to generate seismic shear waves a downhole environment. At least one double headed piston rod with a third piston on the center of the rod slides laterally in the downhole tool. Each end piston head is connected to a rolling diaphragm that is secured at its edges around the periphery of the piston receiving cavity. The cavity is filled with a low viscosity non-conducting oil. A servovalve is connected to opposite sides of the center piston head to produce low frequency vibration of the source generator. A veed target rod extends between the end piston heads, past a pair of eddy current transducers (ECTs) to monitor movement of the generator and provide feedback control to the servovalve. A second downhole seismic shear wave source contains a continuous vibrator ring replaces the diaphragm/oil system and a linear variable differential transformer (LVDT) replaces the eddy current transducers as the feedback signal generator.

Hydraulic vibrator with wide dynamic range

Vibrator apparatus having adjustable cylinder volume by means of a continuously adjustable end sleeve that varies the axial limit of the cylinder. A reaction mass with an axial cylinder bore reciprocates on a double rod piston. Frist and second end sleeves define the cylinder volume and one end sleeve is threaded and axially translatable relative to the piston to vary volume while a position sensing device continually maintains centering of the piston in the cylinder.

Seismic shear wave vibrator with telescoping blade

This invention is an improved type of shear wave vibrator are carried by a support vehicle and utilizing telescoping tubes for energy engagement within an underlying earth medium. A shear wave vibrator so constructed is particularly desirable for use over marshy or soft surface earth areas. The device consists of a jack assembly supporting a shear wave vibrator relative to a suitable carrier vehicle in vibrationally isolated manner. The vibrator structure consists of a pair of parallel, elongatable telescoping blades for earth penetration and engagement with a passive reaction mass pivotally secured across the top portion of the telescoping blades and an active mass/vibrator system pivotally secured across the lower portion of the telescoping blades adjacent the earth surface.

Frequency shift of a rotating‐imbalance vibration source caused by radiative damping in the surrounding medium

The motion of vibrating bodies in a surrounding fluid is often used to infer the transport properties of the fluid. A new sensor configuration is presented that consists of a rotating imbalance source radiating into an unbounded fluid medium. Under these circumstances, the reaction of the fluid medium onto the vibration source includes a steady state torque that opposes the applied torque required to sustain the rotating imbalance. This reaction torque causes a shift in frequency of the vibration source. The frequency shift is related to the density of the surrounding fluid medium and vibration source characteristics. A description of measurements taken with a rotating‐imbalance source located in unbounded water and air is provided. The total mass, eccentricity, and length of the source were 4.1 kg, 3.28(10−4) kg m, and 0.432 m, respectively. Motive torque to drive the imbalance was provided by a permanent‐magnet dc motor. For an applied dc voltage that caused the source to operate at a nominal frequen...

Amplitude and frequency experimental field measurements of a rotating‐imbalance seismic source associated with changes in lithology surrounding a borehole

Field measurements of the vibration amplitude of a rotating‐imbalance seismic source in a liquid‐filled borehole are described. The borehole was a cased oil well that had been characterized by gamma‐ray cement bond and compensated neutron litho‐density/gamma‐ray logs. The well logs indicated an abrupt transition from shale to limestone at a depth of 2638 ft. The vibration amplitude and frequency of a rotating‐imbalance seismic source was measured versus applied voltage as the source was raised from 2654 to 2618 ft through the shale–limestone transition. It was observed that the vibration amplitude changed by approximately 10% in magnitude and the frequency changed approximately 15% as the source passed the shale–limestone transition. The measurements were compared to predictions provided by a two‐dimensional analytical model of a rotating‐imbalance source located in a liquid‐filled bore hole. It was observed that the sensitivity of the experimentally measured vibration amplitude of the seismic source to t...

Transmission of turbulent boundary layer pressures through thin and thick shells

Turbulent flow along a structural boundary acts as a source of noise to the interior space. Characteristics of the transmitted noise are determined not only by the turbulent flow field but also by the transmission characteristics of the bounding structure. In low‐speed flow applications, the spatial scale of the turbulence can be smaller than the structural wall thickness. Under this circumstance, thickness effects are important in modeling the wall transmissibility. These effects are examined using the elasticity solution for the axisymmetric response of cylindrical shells. Results are presented for steel‐like and rubber‐like wall materials and compared with results from thin shell theory.