Abstract: This invention relates to methods and apparatus for analyzing a multi-phase fluid flowing along a hydrocarbon well in order to determine, at each depth, the average static proportion of one of the phases by means of a local measurement. At each depth the local static proportion of the phase under investigation is determined at a point in the flow, which point is situated on a circle having a radius r in the transverse -section corresponding to the depth, where the radius r is substantially equal to 0.7 R, and R is equal to radius of the well. The local static proportion at this point is related to the average static proportion by a determined relationship.

Abstract: Logging equipment for use in a borehole has a sensor such as an ultrasonic sensor, oriented radially towards the wall of the borehole and rotatable in one direction during measurement about the longitudinal axis of the equipment. In order to allow the sensor to be recalibrated downhole, the equipment also includes a target which is automatically brought face to face with the sensor upon reversal of the direction of rotation of the sensor. The sensor can thus be calibrated under conditions which are as close as possible to the conditions of measurement.

Abstract: A method of establishing a stratigraphic model of the subsurface from an acoustic impedance profile A.sub.o ={a.sub.o (n),n=1,N} corresponding to a series of reflection coefficients R.sub.o ={r.sub.o (n),n=1,N}, where n is an index relating to the depth sampled in time t, and from a seismic section comprising a plurality of seismic traces T.sub.i (t),i=0,I recorded in response to the emission of a seismic wave of signature W(t), the method comprising the following steps:successively determining each series of coefficients R.sub.i ={r.sub.i (n),n=1,N} by minimizing a cross-entropy function H(R.sub.i /R.sub.i) between firstly a series R.sub.i obtained from the series R.sub.i-1 and a set of one or more seismic traces {T.sub.i-j,T.sub.i+j }, and secondly the looked-for series R.sub.i, said minimization being performed under pre-established constraints; anddetermining the acoustic impedance profiles A.sub.i ={a.sub.i (n)} corresponding to the series R.sub.i.

Abstract: Apparatus for shear wave borehole logging has a source section 30, a spacer section 32, a detector section 34 and a coupling section 36, adjacent sections being linked by isolation joints 38. The source section 30 has a slotted steel housing 48 containing a source 42 with two transducers 44a/44b and 44c/44d each arranged to produce acoustic radiation with a dipole radiation pattern. The transducers are oriented so that their radiation patterns are transverse to one another and to the borehole axis. The detector section 34 also has a slotted steel housing 80 and contains six detectors 82 each with two transducers 84a/84b and 84c/84d arranged similarly to the source transducers. The isolation joint 38 between adjacent sections comprises lengths of steel wire 76 secured at each end to one of the sonde sections and bridging a gap between the sections.

Abstract: The present invention is directed to filtering out unwanted components contained in acquired sonic well logging data, e.g., reflected wave components, converted wave components, casing arrivals, tool arrivals and/or noise. In the filtering method, the waveform components of each waveform are treated as vectors, each vector having n samples. The vectors, described in n-dimensional space, are rotated to a new coordinate system whose directions, characterized as eigenvectors, are aligned with the primary directions of the wave component vectors. The eigenvectors are ordered such that the first eigenvector represents the wave components' main direction, the second eigenvector represents the wave components' next main direction, et cetera. By projecting the waveform components onto the principal eigenvectors, the reflected wave components, converted wave components and/or noise component of each waveform is substantially eliminated. Methods are also disclosed for approximating the eigenvectors.

Abstract: The present invention is directed to a method of calculating the impedance of a material behind the section of a casing. An acoustic excitation pulse is directed towards a section of the casing, resulting in a return waveform having a reverberation segment and an initial reflection segment. The return waveform is analyzed to choose a resonance frequency indicative of the casing's nominal thickness. The return waveform is bandpass filtered about the chosen frequency. A time window of the reverberation segment is selected, and the energy content in the time window of the filtered reverberation segment is calculated. Both the bandpass filter and time windows are selected based on the chosen resonance frequency, thereby removing variations in the thickness of the casing. The energy content calculation produces a cementation signal indicative of the impedance of the cement behind the section of the casing. The impedance value is indicative of the cement quality.

Abstract: A method for the determination and deconvolution of the signature of an unknown, non-impulsive source signal. The method supposes that that an array of receivers is positioned at the earth's surface to detect and record the seismic signals resulting from the interaction of the source with the earth's subsurface. The traces of data recorded are time-shifted by an amount determined by a coherency analysis of the data. The signal is estimated from the time-shifted data with a weighting factor applied at each trace. A deconvolution filter is determined from the estimate and is weighted at each frequency according to the strength of the source at that frequency. The filter is then applied to the time-shifted data.

Abstract: The present invention relates to a device for placing a radioactive source into a formation through which a borehole passes. The device includes a gun barrel, a bullet containing a radioactive source and engaged in the barrel, and an explosive device for propelling the bullet towards the formation. The device further includes two items which reduce the speed at which the bullet, when fired, penetrates into the formation. These items are a spacer, placed in the barrel between the bullet and the explosive device, and a braking shield placed at the port end of the barrel. The spacer reduces the effect of the gases produced by the explosive device upon detonation. The braking shield is entrained with the fired bullet, the front end of the shield producing drag which also acts to retard the forward propulsion of the bullet. The shield is designed to break away from the bullet upon formation impact, further reducing the kinetic energy of the bullet. The invention is applicable to soft formations.

Abstract: Pressure and flow measurements made during extraction of fluid samples from a subsurface earth formation using a borehole logging tool having a single extraction probe are analyzed to derive separate values for both horizontal and vertical formation permeability. Build-up measurements are used to derive the slope of variation of formation pressure with respect to a spherical time function, and this value is incorporated in an expression for a dimensionless variable relating pressure, flowrate, porosity, compressibility and probe radius. The resulting value of the dimensionless constant provides an index into a look-up table obtained by a new analysis of the fluid dynamics in the immediate vicinity of the probe for an anisotropic formation. The table gives values for two or more dimensionless variables from which the permeability values are derived.

Abstract: A method for acoustically investigating characteristics of formations penetrated by a borehole such as fractures by taking differential Stoneley wave acoustic energy measurements between pairs of receivers of an array of receivers carried by a logging tool. The receivers of each pair all have the same spacing. The energy is that detected by the receivers in response to acoustic pulses generated by a transmitter spaced from the receivers on the tool. The differential energy measurements are stacked to obtain a stacked differential energy log.

Abstract: Apparatus and methods are described for detecting fractures in a wall of a borehole penetrating an earth formation. An acoustic transducer produces pulses of acoustic energy at beam forming frequencies with the direction of the beam being so oriented as to preferentially excite transverse waves in the wall of the borehole. Discontinuities such as fractures cause a reflection of the transverse waves and these in turn are detected so that a positive identification of fractures is obtained. Fractures having various inclination angles are detected by employing apparatus and methods for scanning the acoustic beam while maintaining its orientation which preferentially enhances transverse waves. In this manner the transverse waves may be directed perpendicular to the fractures to enhance detectable reflections. A transducer employing an array of individually excitable acoustic elements is described with associated controls.

Abstract: A method of processing seismic signals detected by at least one sensor disposed in a tool lowered down a borehole, the seismic signals Sj(t) being recorded at different depths j of the tool in response to the propagation of seismic waves through the formations surrounding the borehole, the method making use of the signals Shj(t) detected by the sensor at each depth j in response to excitation from a shaker disposed inside the tool, the method being characterized by the fact that it comprises the following operations: a reference signal Shref(t) is defined for the excitation response produced by the shaker; a deconvolution function Dj(t) is calculated for each signal Shj(t) picked up at depth j in response to the excitation produced by the shaker in such a manner that the signal Shj(t) picked up at this depth after being convoluted with said deconvolution function Dj(t) gives the reference signal Shref(t); and the deconvolution function Dj(t) corresponding to depth j is applied to each seismic signal Sj(t) pic

Abstract: A method and apparatus are described for generating a quick look display of an acoustic investigation of a borehole wherein a parameter of interest is derived from vertically spaced sonic receivers and displayed in a laterally continuous display log where the parameter values from respective receivers are recorded at preassigned positions. A fracture sensitive parameter is measured such as the energy in a low frequency Stoneley wave and when the parameter values are laterally recorded areas indicative of fractures become visually enhanced particularly with a laterally expanded display log. Techniques for the detection and evaluation of fractures are described.

Abstract: In order to increase the angular field of observation of a logging sonde usable, in particular for dip metering, the sonde is equipped with measuring pads each comprising two independent flaps. The flaps of the same pad are hinged to a central element which is held permanently parallel to the axis of the sonde body, and they are applied against the wall of a borehole by blade springs. Each of the flaps carries an array of electrodes. The flaps of each of the measuring pads are circumferentially offset relative to each other so that the angular field of observation is increased without increasing the diameter of the sonde, once the pads have been retracted.

Abstract: A method of velocity filtering seismic signals and an installation for implementing the method. A two-dimensional signal g(z,t) is available built up from a set of signals .sub.i (t) for I>i>n as produced by sound wave detectors located at different depths z.sub.1, . . . z.sub.n in a borehole in response to sound waves being emitted from a source as seismic waves, with said detected signals including upgoing waves and downgoing waves. In order to reinforce the upgoing waves (or conversely the downgoing waves) in the signal g(z,t), an operator A is applied recursively to said signal, where: A=1/2[Id+.epsilon..B.H.sub.t.D.sub.z ] where: Id is the identity operator; .epsilon.=+1(or -1); B is normalization factor whose value depends on the signal g(z,t) to which the operator A is applied; H.sub.t is the one-dimensional Hilbert operator relating to the variable t; and D.sub.z is a differentiation operator relating to the variable z.

Abstract: The invention is directed to a locking mechanism for locking a tool to an anchor seat located in the tubing of a well, the locking mechanism comprising keys which are radially movable relative to the axis of the tool, the keys emerging via apertures in the body of the tool to engage in a groove of an anchor seat located in the well conduit. The groove of the anchor seat has an internal diameter smaller than the internal diameter of the well conduit. Each key is axially movable within the aperture between a high position and a low position. Structure is provided for retaining the keys in the high position, positioning the keys in a radially retracted position, so that the keys do not cause the tool to be secured in the anchor seat. Structure is also provided for positioning the keys in a radially extended position, causing the keys to contact the groove of the anchor seat, thereby locking the tool to the anchor seat.

Abstract: The present invention is directed to a method of inverting seismic traces Sk by determining the series R={r.sub.i } representative of the seismic reflection coefficients from geological strata. The method includes the steps of determining an approximate solution to R.degree. by minimizing an entropy type function H(R)=.SIGMA.f(r.sub.i) under constraints related to the upgoing wavefield Uk and the downgoing wavefield Dk; determining a correction value .DELTA.R by minimizing a linear function J(.DELTA.R) under linear constraints related to the noise in the traces and to the time-depth curve extracted from the traces; and calculating R=R.degree.+.DELTA.R, representative of the reflection coefficients. In a variant, the selection of the approximate solution R.degree. is guided by taking into account information contained in one or more logs, and determining .DELTA.R so that the series R satisfies the stacking velocities which result from surface seismic processing.

Abstract: An automatic watering system for decorative plants which has adjustable timing capabilities for providing periodic, unattended watering of plants. It further includes tubing with branching capability so that complex distribution systems that are unobstrusive and concealable may be constructed. It may have check valves and T-sections with built-in valves to prevent flooding. It has a unique monitoring system that indicates an alarm indication in case of flooding or failure to provide water. The system may be constructed as a low pressure system for small installations or a high pressure system drawing water directly from the water mains.

Abstract: In a method for locating fractures in subsurface earth formations traversed by a borehole a first signal is generated representative of low frequency Stoneley waves (that is tube waves) propagating along the borehole from a source mounted in a logging tool. A second signal is generated by an array of detectors on the tool, representative of low frequency Stoneley waves propagating along the borehole and arising from reflection from fractures of the waves propagating from the source. An indication of the presence of fractures is derived by deconvolving the second signal with the first signal and identifying the time and magnitude of the peak value of the envelope of the deconvolved signal. The variation that would be expected in the presence of fracture and the actual variation are compared and a fracture detected when the actual and expected variations match. Alternatively the first and second signals can be cross-correlated and the time of the peak negative value of the cross-covariance determined.

Abstract: A method for determining the porosity of a subsurface geological formation traversed by a borehole is provided. The method generally comprises obtaining a means which relates ranges of apparent formation porosity (.phi..sub.a) as determined by a neutron-neutron log, formation fluid salinities, formation total capture cross sections (.SIGMA.), formation matrix and fluid constituents, and true formation porosity (.phi..sub.T) according to a predetermined equation. The predetermined equation relates the apparent porosity to a function of a modified migration length which is obtained in a semi-empirical manner (i.e. physics modifed by data). The modified migration length includes a slowing down length and a diffusion length, but causes at least the diffusion length to be a function of the slowing down length. The means which relates the apparent porosity to salinity, .SIGMA., matrix and fluid constituents, and .phi..sub.T solves a forward problem.