Abstract: Systems and methods which provide modeling or simulation of gamma ray (GR) tool response using a hybrid analytical and numerical technique are shown. Embodiments employ a GR tool simulation technique which provides gamma ray information simulated as a function of only the gamma particles which reach the detector without scattering. Embodiments utilize a discretization function to determine the gamma particles which would reach a point detector from each unit volume source of an investigation domain without scattering. Embodiments further utilize the foregoing discretization function with respect to a plurality of point detectors, wherein the particular number and configuration of point detectors are selected to relatively accurately simulate the results of a particular GR detector configuration, such as line detector or volume detector configurations.

Abstract: Systems and methods which provide accurate formation information regardless of formation and borehole geometry, including those associated with high angle and horizontal wells, are shown. In providing processing of logging or image data, such as may be provided by a density tool or other tool, according to embodiments, formation attributes or features (e.g., density and dip angle) are estimated using raw data provided by a the tool. The foregoing estimations may thereafter be iteratively refined using effective volume of interest (EVOI) information. According to embodiments, depth boundaries of formation information provided by the tool are shifted as a function of azimuth for correct spatial positioning of formation features using EVOI information. Processing of formation attribute or feature data provided by embodiments may be used with respect to various tool configurations, including configurations with and without borehole standoff.

Abstract: The invention is a method for inverting reservoir bi-axial anisotropy and identifying complicated fracture/cross-bedding system (104) by using tri-axial induction logs and wellbore survey/image log data. An inversion method is disclosed that uses all nine components that can be measured by tri-axial induction tools (101), plus borehole azimuth and deviation data, to solve for the tri-axial induction response in an arbitrary anisotropic formation due to the non-orthogonal bedding plane and fracture plane (or cross bedding plane). A mathematical formula is provided relating the conductivity tensor in the tool's reference frame to the conductivity tensor in a reference plane associated with the fracture/cross bedding planes (102). This equation is inverted (103) to yield the conductivity tensor components in the fracture/cross bedding coordinate system, along with dip and azimuth angles for both the fracture/cross bedding planes and the tool.

Abstract: Method for determining reservoir permeability from Stoneley wave attenuation extracted from conventional sonic logs by inversion of the full Biot wave equations for a porous medium. Frequency-dependent Stoneley-wave attenuation is extracted by analyzing array sonic measurements. Then, based on Biot's full theory applied to a borehole model and the standard logs (gamma ray, caliper, density, neutron, resistivity, sonic, etc.), a simulation model with the same parameters as the Stoneley-wave measurements is built. Next, a theoretical Stoneley-wave attenuation is computed for a given permeability. Finally, reservoir permeability is determined by comparing the modeled Stoneley-wave attenuation with the measured Stoneley-wave attenuation by an iterative inversion process.

Abstract: The invention is a method for inverting reservoir bi-axial anisotropy and identifying complicated fracture/cross-bedding system (104) by using tri-axial induction logs and wellbore survey/image log data. An inversion method is disclosed that uses all nine components that can be measured by tri-axial induction tools (101), plus borehole azimuth and deviation data, to solve for the tri-axial induction response in an arbitrary anisotropic formation due to the non-orthogonal bedding plane and fracture plane (or cross bedding plane). A mathematical formula is provided relating the conductivity tensor in the tool's reference frame to the conductivity tensor in a reference plane associated with the fracture/cross bedding planes (102). This equation is inverted (103) to yield the conductivity tensor components in the fracture/cross bedding coordinate system, along with dip and azimuth angles for both the fracture/cross bedding planes and the tool.

Abstract: Systems and methods which provide accurate formation information regardless of formation and borehole geometry, including those associated with high angle and horizontal wells, are shown. In providing processing of logging or image data, such as may be provided by a density tool or other tool, according to embodiments, formation attributes or features (e.g., density and dip angle) are estimated using raw data provided by a the tool. The foregoing estimations may thereafter be iteratively refined using effective volume of interest (EVOI) information. According to embodiments, depth boundaries of formation information provided by the tool are shifted as a function of azimuth for correct spatial positioning of formation features using EVOI information. Processing of formation attribute or feature data provided by embodiments may be used with respect to various tool configurations, including configurations with and without borehole standoff.

Abstract: Systems and methods which provide modeling or simulation of gamma ray (GR) tool response using a hybrid analytical and numerical technique are shown. Embodiments employ a GR tool simulation technique which provides gamma ray information simulated as a function of only the gamma particles which reach the detector without scattering. Embodiments utilize a discretization function to determine the gamma particles which would reach a point detector from each unit volume source of an investigation domain without scattering. Embodiments further utilize the foregoing discretization function with respect to a plurality of point detectors, wherein the particular number and configuration of point detectors are selected to relatively accurately simulate the results of a particular GR detector configuration, such as line detector or volume detector configurations.

Abstract: A method and apparatus for estimating the slowness of a geological formation using waveforms recorded by an acoustic borehole logging tool. Phase slowness coherence is extracted from the recorded waveforms after transformation to the frequency domain (804) at various frequencies (806), and this is converted into a formation slowness curve (808) which can be used as an objective function from which an anomaly, such as a local maximum or minimum (810), can be identified as representative of an estimate of the formation slowness.

Abstract: Method for determining reservoir permeability from Stoneley wave attenuation extracted from conventional sonic logs by inversion of the full Biot wave equations for a porous medium. Frequency-dependent Stoneley-wave attenuation is extracted by analyzing array sonic measurements. Then, based on Biot's full theory applied to a borehole model and the standard logs (gamma ray, caliper, density, neutron, resistivity, sonic, etc.), a simulation model with the same parameters as the Stoneley-wave measurements is built. Next, a theoretical Stoneley-wave attenuation is computed for a given permeability. Finally, reservoir permeability is determined by comparing the modeled Stoneley-wave attenuation with the measured Stoneley-wave attenuation by an iterative inversion process.

Abstract: A method and apparatus for estimating the slowness of a geological formation using waveforms recorded by an acoustic borehole logging tool. Phase slowness coherence is extracted from the recorded waveforms after transformation to the frequency domain (804) at various frequencies (806), and this is converted into a formation slowness curve (808) which can be used as an objective function from which an anomaly, such as a local maximum or minimum (810), can be identified as representative of an estimate of the formation slowness.

Abstract: A method to convert seismic traces to petrophysical properties is disclosed. One embodiment of the method comprises (a) deriving a combined log seismic response from at least one petrophysical log from a well and at least one seismic trace substantially near the well, (b) convolving the combined log seismic response filter with each seismic trace to convert the seismic traces to logs of petrophysical properties, (c) outputting the petrophysical properties. Equations to derive the combined log seismic response and to convolve the combined seismic response filter are disclosed. The method may be used to output the petrophysical data as a two-dimensional cross-section or as a three-dimensional volume cube.

Abstract: A method to convert seismic traces to petrophysical properties is disclosed. One embodiment of the method comprises (a) deriving a combined log seismic response from at least one petrophysical log from a well and at least one seismic trace substantially near the well, (b) convolving the combined log seismic response filter with each seismic trace to convert the seismic traces to logs of petrophysical properties, (c) outputting the petrophysical properties. Equations to derive the combined log seismic response and to convolve the combined seismic response filter are disclosed. The method may be used to output the petrophysical data as a two-dimensional cross-section or as a three-dimensional volume cube.

Abstract: A 2D inversion of true formation resistivity from dual laterolog tool measurements is accomplished using a pre-calculated look-up table. An initial earth model is derived and divided into intervals. A 2D tool response is calculated in each interval using the earth model. Matching is checked between the calculated 2D tool response and the tool measurements. The following steps are iterated until the match is satisfactory. A 1D radial tool response is derived in each interval using the pre-calculated look-up table. Shoulder bed effects are approximated in each interval by subtracting the 1D radial tool response from the 2D tool response. A non-linear least square optimization is applied at boundaries of the intervals and local maximum and minimum values in the intervals to update the earth model.

Abstract: A 2D inversion of true formation resistivity from dual laterolog tool measurements is accomplished using a pre-calculated look-up table. An initial earth model is derived and divided into intervals. A 2D tool response is calculated in each interval using the earth model. Matching is checked between the calculated 2D tool response and the tool measurements. The following steps are iterated until the match is satisfactory. A 1D radial tool response is derived in each interval using the pre-calculated look-up table. Shoulder bed effects are approximated in each interval by subtracting the 1D radial tool response from the 2D tool response. A non-linear least square optimization is applied at boundaries of the intervals and local maximum and minimum values in the intervals to update the earth model.

Abstract: A low impedance acoustic source suitable for used in down-hole well logging includes a mechanical transformer for impedance matching of the source to the surrounding environment. Elliptically shaped flexible beams are positioned along the long axis of an ellipse, and a pump is oriented along the long axis of the ellipse for driving the flexible beams. In a preferred embodiment the pump comprises first and second stacks of transducers which engage the flexible beams at opposing ends with the two stacks of transducers operating in a push-pull mode of operation. Rigid extension at opposing ends of the flexible beams function as levers in translating the motion of the transducers to the flexible beams. A rigid support rod is positioned along the long axis of the ellipse in engagement with the rigid extensions at fulcrum points, and an adapter associated with each stack of ceramic transducers engages and drives the rigid members about the fulcrum point.