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: 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 and system for computer programming provides a graphical editor function for creation and editing of a computer program by manipulation of graphical images on a high-resolution display. The program is specified in terms of a definition language which can be executed by a simulation function. This function simulates execution of the program on a different, target processor as if the program were expressed in a different language which can be executed by the target processor; in addition the simulation function incorporates a simulation of the external environment of the target processor and of the interaction of the program with that environment. The graphical display of the program is animated during execution so that the user can observe and check the program's operation. When the simulated execution is satisfactory the definition-language version of the program is tanslated into the language executable on the target processor.

Abstract: Waveform data obtained in a borehole by a tool having a sonic source and an array of sonic detectors is analyzed to obtain an image of formation features within several tens of feet of the borehole, such as fractures, bed boundaries and other boreholes. A value of background sonic slowness is derived from the data and used to determine the sonic energy transit time from the source to each detector via each point in a grid of points extending into the formation and along the borehole. The time for a particular detector/point pair is used to extract the amplitude of the waveform from that detector at that time relative to operation of the source. Such amplitudes for the same point and for different detectors and tool positions are cumulated. The final values for all points are plotted as a variable density display which provides the desired image.

Abstract: Methods and apparatus are disclosed for producing an indication of the partition between a borehole and a formation of the constituents identified by means of a nuclear investigation. A borehole logging sonde containing a pulsed neutron source and a gamma radiation detector traverses the borehole and resulting capture gamma rays are detected and counted according to energy in each of two time gates. The resulting energy spectra are analyzed to determine the type and relative gamma ray yield of each constituent of the borehole and formation. A characteristic neutron capture decay time constant for each constituent is derived from the yields and total gamma ray counts in the two time gates, and time constants for the borehole and formation overall are set equal to the derived time constants for constituents, such as iron and silicon, occurring predominantly in the borehole and formation respectively.

Abstract: Methods for determining the permeability of an earth formation traversed by a borehole are provided and comprise: logging the borehole to determine indications of at least a plurality of elements in the formation; determining the mineralogical content of the formation from the elemental indications; determining the porosity of the formation; and determining the permeability of the formation as a function of the determined mineralogical content and porosity. The mineralogical content of the formation is preferably determined according to a transform which relates elemental concentrations of the formation to mineral weight percentages.

Abstract: Methods are disclosed which provide for quantifying and characterizing the mineral content of a formation as a function of depth. Elemental data derived from logging tools are input into an element-mineral transform operation, to determine the quantity of at least one or more dominant minerals in the formation including minerals distinguishable by degree of crystallinity. From the mineral quantity information and the elemental log data, the formation minerals are further characterized. Information regarding the character and quantities of formation minerals is further used to obtain improved determinations of formation characteristics such as the cation exchange capacity and water saturation, and the grain density and formation porosity, as well as to obtain an increased understanding of the formation such as the depositional environment of the formation.

Abstract: Methods are disclosed which provide for quantifying and characterizing the mineral content of a formation as a function of depth. Elemental data derived from logging tools are input into an element-mineral transform operation, preferably a matrix which is constructed using multivariate statistical analysis on previously available data, to determine the quantity of at least one or more dominant minerals in the formation. From the mineral quantity information and the elemental log data, the formation minerals are further characterized. Information regarding the character and quantities of formation minerals is further used to obtain improved determinations of formation characteristics such as the cation exchange capacity and water saturation, and the grain density and formation porosity, as well as to obtain an increased understanding of the formation such as the depositional environment of the formation.

Abstract: The shear velocity of a formation traversed by a fluid-filled open or cased borehole is obtained directly. Waveforms are obtained from a dipole acoustic investigation of the formation relative to a common location in the borehole. In this investigation, the bandwidth of the waveforms is substantially bounded by an upper frequency f.sub.u at and below which energy traveling at the shear velocity is dominant. Moreover, the bandwidth of the waveforms is concentrated near the frequency f.sub.u. The shear velocity of said earth formation is determined from these waveforms. In one embodiment, the waveforms are obtained from a broadband dipole acoustic investigation. The waveforms are low-pass filtered, and an interim shear velocity v.sub.s is determined from the filtered waveforms. The filtering and determining of v.sub.s are done first for an initial f.sub.cut, and subsequently for additional decreasing values of f.sub.cut, until a preselected relationship between f.sub.cut and v.sub.s is satisfied.

Abstract: A method for evaluating the quality of the cement surrounding a borehole casing is provided. The method generally comprises obtaining signals which were recorded by a CET tool known in the art, and processing the signals by: dividing each signal into particularly defined time windows; determining absolute magnitudes for each signal which are functions of the energy of the signal in the respective windows; determining normalized magnitudes for each signal from the absolute magnitudes and normalization parameters; and evaluating the quality of cementation as a function of the fact that the normalized magnitudes for each signal obey a predetermined law, and as a function of the relationship between each normalized magnitude and a pair of threshold values respectively associated therewith.According to another aspect of the invention, information obtained from a CBL tool known in the art is compared to the information gained from the CET tool.

Abstract: A logging sonde for evaluating underground formations traversed by a borehole is disclosed. The sonde contains a frame which is free to rotate relative to the cylindrical body of the sonde. The frame supports a plurality of detector means including at least one detector which is free to rotate relative to the frame. Also attached to the frame are locking means including braking means and a solenoid for disengaging the braking means from their engaged surfaces. In a rest position, the braking means are arranged in such a manner as to lock the detector means relative to the cylindrical body. The invention is applicable, in particular, to geophones intended to detect seismic waves along three orthogonal axes, including a vertical axis, regardless of the tilt of the sonde.

Abstract: The shear velocity of a formation traversed by a fluid-filled borehole is determined in the presence of a significant flexural mode arrival. A plurality of waveforms are obtained from a dipole acoustic investigation of the formation relative to a common location in the borehole. The flexural mode phase velocity as a function of frequency is determined. If a low frequency asymptote is identifiable, it is reported as the shear velocity. If a low frequency asymptote is not identifiable, however, a plurality of additional curves of the flexural mode phase velocity as a function of frequency are theoretically determined, based on respective estimated shear velocities. These theoretically determined curves are respectively fitted to the curve determined from the waveforms, until a satisfactory least error fit is achieved. The last-estimated shear velocity is reported as the shear velocity of the formation.

Abstract: A method for determining in situ the carbon content of a source rock comprises determining the carbon/oxygen elemental ratio of the formation via inelastic gamma spectroscopy, determining the porosity of the formation, obtaining the oxygen contents and densities of the fluid and minerals in said formation, and determining the carbon content from said carbon/oxygen ratio, and said oxygen contents and densities of the fluid and minerals. The density of the fluid may be assumed, as may the oxygen content of both the formation fluid and minerals. The mineral density may also be assigned a constant value based on lithology. An alternative total carbon content determination is made by additionally determining the fractional volume, density, and oxygen content of the organic matter in the formation, and the combined mineral-organic matter density, and combining this additional information with the previously-listed determinations.

Abstract: A logging method and apparatus are provided for the acoustic inspection of a borehole fitted with a casing wherein obtained measurements which are representative respectively of one or more data items relating to the casing and to the material which surrounds it are corrected for the effects of the environment.

Abstract: In the apparatus and method of the invention, acoustic energy is propagated in two slightly differing, or offset, circumferential paths in such a way as to interact with the formation under investigation. The propagating energy is detected and the resulting waveforms are compared using semblance. The waveforms corresponding to the respective paths will be quite similar provided that the length of the paths are equal and that there are no fractures or other similar anomalies between the source and receiver. The waveforms for the respective paths will be quite dissimilar, however, if a fracture or similar anomaly does lie between the source and receiver for the respective paths. The semblance may be displayed in log format.

Abstract: Apparatus and methods for the flow analysis of multiphase fluids including a liquid phase in a tubular conduit use Stoneley waves by exciting and detecting sonic wave energy in the tubular conduit. Information about the Stoneley mode component is obtained in one approach by using techniques that excite only the Stoneley mode together with certain other well behaved wave types, and then compensating for the latter. Alternatively the Stoneley arrival is specifically identified in the detected waveforms. Embodiments are described for: determining the flow rate of a liquid; detecting the presence or absence of gas in a liquid; determining the composition by volume of the dispersed phases in a multiphase fluid; determining the size distribution of bubbles in a multiphase fluid; and determining the velocity of slugs in a multiphase fluid.

Abstract: Dip measurements and investigation of geological formations traversed by a deviated borehole is carried out by means of an apparatus comprising a measuring sonde and a cartridge connected to a cable. The sonde carries four measuring pads regularly distributed by means of articulated arms which keep the pads parallel to the axis of the sonde. The opposite arms are forced to stay symmetrical in relation to the sonde.The sonde is connected to the cartridge so that its axis can depart angularly from the axis of the cartridge, enabling the latter to rest on the borehole wall. The pads have a length smaller than twice the transverse dimension D of the sonde.

Abstract: Method and apparatus for distinguishing oil from fresh water in situ in a subsurface geological formation are proposed which utilize the anomalous response of a neutron porosity tool to some oils. Apparent porosity derived from a neutron porosity investigation tool which measures spatial neutron flux distribution is compared to the porosity derived from a second investigating tool whose response is not or at least is less sensitive to the hydrogen density of the formation fluid than is the neutron porosity tool. Where a real difference is evident, oil rather than fresh water is indicated.

Abstract: A seismic exploration method is disclosed for filtering the signals produced by a detector placed at different depths in a well in response to an emission of acoustic waves from a source on the surface: the signals comprising downgoing wave components and upgoing wave components.The filtering consists in sampling from among the N signals to be processed a group of n signals s.sub.1 . . . s.sub.n detected at respective levels x.sub.1 . . . x.sub.n, in determining the propagation time t.sub.k of the acoustic waves from the level x.sub.1 to each level x.sub.k, in both advancing and delaying the signals s.sub.k by the time t.sub.k in relation to s.sub.1, in adjusting the signals for the effects of the acoustic impedance of the formation, in combining s.sub.1 and the signals s.sub.k thus shifted and adjusted to obtain a sum z.sub.1 ', in calculating a sum y.sub.1 ' of s.sub.1 and of the thus delayed and adjusted signals s.sub.k, and in generating a signal u.sub.1.sup.