Gassy Water Research Articles

Spontaneous potential: Key to understanding continuous and conventional gas in Upper Cretaceous sandstones, deep eastern Greater Green River Basin, southwest Wyoming

Spontaneous-potential (SP) log data from wells in the deep eastern Greater Green River Basin (GGRB) suggest that what appears to be overpressured pervasive gas at high saturation in Upper Cretaceous sandstones outside conventional fields is gassy water with gas present at uneconomically low saturation. Sandstones of the Lewis Shale and Mesaverde Group within conventional-trap fields in the deep eastern GGRB exhibit normal-SP deflections, indicating saline formation water with low formation-water resistivity () that yields calculated water saturations less than 50%. However, in deep-basin areas outside conventional traps, these Upper Cretaceous sandstones generally exhibit reversed-SP signatures reflecting anomalously low-salinity formation water with anomalously high that yields calculated greater than 60%. Uneconomically low gas saturations are corroborated by lack of commercial gas production from reversed-SP sandstones despite (1) prominent gas shows during drilling, (2) significant overpressure, and (3) log-measured porosity and resistivity that often are indistinguishable from those observed with commercially productive normal-SP sandstones within conventional traps. Anomalously low-salinity water in deep-basin sandstones outside conventional traps is proposed to result from dilution of original saline formation water by fresh water expelled during smectite-clay conversion to illite with increasing temperature (burial depth). Low permeability of deep-basin sandstones retards escape of the added fresh water, which contributes to overpressure and to deceptively high formation resistivity. Although the upward transition to more saline formation water is gradational, mapped top of reversed SP cuts across stratigraphic boundaries, with relief exceeding 2000 ft (610 m). It is unclear whether regional continuous gas in reversed-SP sandstones has been at low saturation since the onset of gas migration or whether saturations were higher prior to the influx of fresh water. What is reasonably certain is that subsequent to gas migration, fresh-water influx in the deep basin regionally diluted original saline formation water outside conventional traps. Similar formation-water salinity of normal-SP sandstones of the Lewis Shale and Mesaverde Group within deep-basin conventional traps suggests that high-saturation gas and associated irreducible saline formation water in these fields are locked-in accumulations unaffected by subsequent fresh-water influx.

Radial response of individual bubbles subjected to shock wave lithotripsy pulses in vitro

Direct measurements of individual bubble oscillations in lithotripsy fields have been performed using light-scattering techniques. Studies were performed with bubble clouds in gassy water as well as single levitated bubbles in degassed water. There is direct evidence that the bubble survives the inertial collapse, rebounding several times before breaking up. Bubble dynamics calculations agree well with the observations, provided that vapor trapping (a reduction in condensation during bubble collapse) is included. Furthermore, the afterbounces are dominated by vapor diffusion, not gas diffusion. Vapor trapping is important in limiting the collapse strength of bubbles, and in sonochemical activity.

The search for electrical discharges from single- and multi-bubble sonoluminescence

Previous research supported the notion that electrical discharges resulted from the collapse of bubbles in cavitation fields [G. Giminez and F. Goby, in Cavitation and Inhomogeneities in Underwater Acoustics, edited by W. Lauterborn (Springer-Verlag, New York, 1980), pp. 101–107]. Further research was performed in a cavitation field, as well as with a single cavitating bubble. The cavitation field was generated in a standing wave-field using gassy water, resulting in a small confined region of cavitation. Single-bubble cavitation was also performed in this system, but with degassed water. Two methods were used to detect electrical pulses. In one case a small probe consisting of two fine wires coupled to a low-current differential amplifier was placed near the cavitation bubble(s). Signals were only observed when the probe was in contact with the cavitation field (no signals were observed in the single-bubble system). The second method utilized a coiled loop of wire surrounding the levitation cell, connected to a high-bandwidth lock-in amplifier. In this case, the reference frequency was scanned from about 25 kHz to more than 20 MHz. Signals were observed at harmonics of the drive frequency. [This research supported by DOE-EM.]

Acoustical resonator frequency shift due to the migration of particles and bubbles

A change of the resonant frequency of an acoustic chamber can arise due to the presence and migration of objects inside the chamber. In the investigations of collinear four-wave mixing mediated by a suspension, it was noticed that for sufficiently high particle concentrations, the resonant frequency of the chamber shifted as the particles formed periodically spaced bands, due to the induced radiation pressure from two counter-propagating pump waves. This frequency shift, which also affects the Q factor of the cavity, is another manifestation of the interaction of sound with sound. A transfer-matrix approach was developed which uses a continuum approximation for the particle suspension, and is in good agreement with previous theory and experiment. By using sufficiently gassy water, pump pressures of large enough amplitude led to the measurement of the response of the system to cavitation bubbles. By proper tuning, the frequency shift of higher azimuthal modes of the cylindrical cavity were probed, with experimental results showing both stable and unstable modes. [Work was supported by the Office of Naval Research.]

A study of the timing of sonoluminescence flashes from stable cavitation

In a previous paper [J. Acoust. Soc. Am. Suppl. 1 80, S24 (1986)], experimental measurements of the timing of sonoluminescence (SL) flashes from stable cavitation in gassy water were described. The theory has been extended to examine larger acoustic pressure amplitudes and excellent agreement has been found between the measured and predicted phase angles of the emitted flashes. Since this phase angle is sensitive to the explicit formulation of the equations for bubble dynamics, these data can be used to examine the applicability of various theoretical models. The results of this comparison will be presented and reasons for the inapplicability of certain formulations will be given. [Work supported in part by the NIH and the ONR.]

A comparison of the thresholds for free‐radical generation and transient cavitation activity induced by short pulses of ultrasound

Insonification of relatively dirty water with short pulses (order 10 μs) of high‐frequency (1‐MHz) focused ultrasound can lead to acoustic cavitation. If the bubble activity is sufficiently energetic, free radicals are produced that can be detected as sono‐or chemiluminescence in the fluid. The question remains as to how the thresholds for light production compare to measured thresholds for transient bubble activity. The threshold for chemiluminescence in gassy water doped with luminol using photon counting techniques was measured. In addition, thresholds were simultaneously monitored for bubble activity using a high‐frequency (30‐MHz) acoustic backscattering technique. All measurements were carried out for various combinations of acoustic pulse length and repetition frequency, and were compared with previous investigations as well as theoretical predictions. [Work supported in part by ONR and NIH.]

Acoustics of gas-bearing sediments I. Background

Acoustical properties of water saturated and gassy sediments are observed to be significantly different. The present state of knowledge of the acoustical properties of saturated sediments, gassy water, and gassy sediments is reviewed. The dynamics of bubbles in water and in various solid materials, including sediments, are experimentally examined in a companion paper. Pulsation resonance is exhibited by the bubbles in all materials examined. Predictions of bubble resonance frequency and damping are shown to agree with the measurements. Equations for sound speed and attenuation, based on the model of resonating gas bubbles, are shown to agree with published measurements in gassy sediments. Parameters required for predicting gassy sediment acoustical properties are identified. Ranges of values of these parameters for various sediments are discussed.

Acoustics of gas-bearing sediments. II. Measurements and models

Acoustical properties of water saturated and gassy sediments are observed to be significantly different. The present state of knowledge of the acoustical properties of saturated sediments, gassy water, and gassy sediments is reviewed in a companion paper. The dynamics of bubbles in water and in various solid materials, including sediments, are experimentally examined here. Pulsation resonance is exhibited by the bubbles in all materials examined. Predictions of bubble resonance frequency and damping are shown to agree with the measurements. Equations for sound speed and attenuation, based on the model of resonating gas bubbles, are shown to agree with published measurements in gassy sediments. Parameters required for predicting gassy sediment acoustical properties are identified. Ranges of values of these parameters for various sediments are discussed.

Stable and Transient Acoustical Cavitation in Water and in Liquid Helium

The occurrence of stable and transient acoustical cavitation in liquid helium has been reported recently by Finch et al. and by Jarman and Taylor. It appears to be similar to acoustical cavitation in unfiltered gassy water. Solutions to the non-dissipative incompressible differential equations for the motion of gaseous and/or vaporous cavities in water and liquid helium have been obtained on an analog computer, and these will be related to experimental data. [Work supported by a research grant from The University of Western Australia and by the U. S. Office of Naval Research.]

Ultrasonic Cavitation Thresholds in Water

The temperature dependence of the minimum sound pressure needed to produce cavitation in gassy water has been measured over a range of 0 to 30°C. Both plane progressive and focused waves of frequency one megacycle per second were used. The cavitation pressure threshold Pc is not a linear function of temperature, and increases by a factor of 2.5 between 30 and 0°C. About 50 percent higher sound-pressure amplitude is needed to initiate cavitation than to maintain it. The relation of Pc to the reciprocal temperature, to viscosity, and to the degree of undersaturation is discussed.

A Simple Calibration Technique for Low Sensitivity Transducers

Increased interest in studies of high amplitude acoustic waves has made practical the use of small probe mounted transducers having extremely low sensitivities (i.e., −130 to −150 db re 1 volt/dyne/cm2). These low sensitivities make calibration by standard techniques, such as reciprocity methods, difficult to perform. In the course of some cavitation studies the radially symmetric standing wave pattern obtainable in a spherical resonator is utilized to obtain a high pressure variation. It was observed that in gassy water, under one atmosphere hydrostatic pressure, that a distinct distortion of the output wave form of the probe transducer, used to measure the sound pressure variation in the standing wave pattern, was observed at the instant the peak sound pressure exceeded one atmosphere. At the suggestion of Dr. R. W. Leonard, a careful investigation of the exact pressure at the time at which distortion occurs was made, with the possibility in mind of using this property of the medium as a means for pressure calibration of transducers. This paper shows that the accuracy and reproducibility of this phenomenon is limited only by the limits of ability to read the output voltmeter. A simple apparatus and technique for performing the measurements is described.