Abstract: A method for monitoring a formation property includes determining at least two slowness values from at least two datasets each characterizing an acoustic wave having a different frequency traversing a formation; and deriving an indicator based on the at least two slowness values. A system for monitoring a formation property includes a process and a memory, wherein the memory stores a program having instructions for: determining at least two slowness values from at least two datasets each characterizing an acoustic wave having a different frequency traversing a formation; and deriving an indicator based on the at least two slowness values.

Abstract: Techniques for detecting a kick in a borehole include acquiring a set of measurements with a sonic tool in the borehole; determining borehole mud slowness from the set of measurements; and comparing the mud slowness with a selected criterion, wherein the determining the mud slowness includes determining fluid mode slowness as a function of frequency for at least one fluid mode, and determining the mud slowness from the fluid mode slowness.

Abstract: A method for obtaining high-quality well logging data acquired during a drilling operation includes acquiring well logging data during a pump-off period when a mud pump is turned off; and extracting a subset of data from the acquired well logging data, wherein the subset of data corresponds to a quiet period within the pump-off period, wherein the quiet period is substantially free of interference from turning the mud pump on or off.

Abstract: A method for determining mud slowness of a mud in a borehole includes determining slowness as a function of frequency for at least one fluid mode from a set of measurements acquired with a sonic tool in the borehole; and determining the mud slowness from the slowness as a function of frequency for the at least one fluid mode. A downhole sonic tool includes a transmitter capable of generating signals covering a frequency range, a high end of which is more than 30 KHz; and a receiver array comprising a plurality of receivers, which are responsive to the frequency range of the transmitter, wherein the transmitter and the receiver array are spaced apart on a tool body at a selected TR spacing.

Abstract: A method for identifying environmental effects in well log data includes selecting a plurality of models, each of the plurality of models including at least one parameter to be optimized; fitting the models to the well log data by optimizing the at least one parameter, the fitting producing a plurality of optimized models; determining an indicator of goodness of fit for each of the plurality of optimized models; and selecting a model representing a best fit of the well log data based on the indicator.

Abstract: A method for identifying environmental effects in well log data includes selecting a plurality of models, each of the plurality of models including at least one parameter to be optimized; fitting the models to the well log data by optimizing the at least one parameter, the fitting producing a plurality of optimized models; determining an indicator of goodness of fit for each of the plurality of optimized models; and selecting a model representing a best fit of the well log data based on the indicator.

Abstract: A method and apparatus is disclosed for determining the properties of formations surrounding an earth borehole that have been invaded by borehole fluid to form an invaded zone.

Abstract: A well logging method and apparatus are disclosed for determining borehole corrected formation resistivity, borehole diameter, and downhole borehole fluid (mud) resistivity with improved accuracy. A logging device in the borehole transmits electromagnetic energy from a transmitter, which energy is received at receivers on the logging device. The phase and amplitude of the received energy are measured at the receivers and a phase shift, phase average, and attenuation are associated with the transmitter-to-receivers spacing. The process is then repeated for a plurality of further transmitters having different spacings from the receivers. A formation and borehole model having model values of borehole corrected formation resistivity, borehole diameter, and borehole fluid resistivity is generated.

Abstract: A method is disclosed for determining the horizontal resistivity, vertical resistivity, and dip of formations surrounding a borehole, comprising the following steps: (a) suspending a logging device in the borehole; (b) transmitting electromagnetic energy from a transmitter location on the logging device, and receiving the transmitted electromagnetic energy at receiver locations on the logging device for a first transmitter-to-receivers spacing associated with the transmitter and receiver locations; (c) determining, from the received electromagnetic energy, measurement characteristics associated with the first transmitter-to-receivers spacing; (d) repeating steps (b) and (c) for a plurality of further transmitter-to-receivers spacings to obtain measurement characteristics for the plurality of further transmitter-to-receivers spacings; (e) generating a model of anisotropic formations that has horizontal resistivity Rh, vertical resistivity Rv, and a Dip angle with respect to a borehole reference; (f) selecting

Abstract: An apparatus for determining a property of earth formations surrounding a borehole is presented. In accordance with a particular embodiment, an elongated logging device movable through a borehole is provided with a transmitter array consisting of only first, third, and second transmitting antennas longitudinally spaced on the device. A pair of longitudinally spaced receiving antennas are also provided and are located between the second transmitting antenna and one of the first and third transmitting antennas. In particular, the first, third, and second transmitting antennas are spaced from the midpoint between the receiver pair by first, third, and second distances, respectively, where the first and second distances are substantially the same while being different from the third distance. This antenna arrangement is possible while still providing a borehole compensated output.

Abstract: A borehole correction software of a multipole sonic well tool adapted to be disposed in a borehole determines a true, corrected value of shear wave slowness from a measured uncorrected shear wave slowness value by first building a look up table comprising hole diameter, measured synthetic shear wave slowness and correction factor, and using the table in a system including the look up table and a multiplier to determine a bias, which bias is subtracted from the measured uncorrected shear wave slowness to produce an output medium reflecting a true, corrected value of shear wave slowness. The measured uncorrected shear wave slowness values are input to the look up table. For a given hole diameter, the measured uncorrected shear wave slowness is matched to a measured synthetic shear wave slowness, and a value of correction factor is determined from the table. The correction factor is multiplied by the measured uncorrected shear wave slowness, via the multiplier, and a bias figure is determined.

Abstract: Undesirable internal changes in a running turbine are diagnosed by monitoring the dynamic pressure of the stream of fluid and the structure-borne vibration of the stationary shell. Incipient erosion of blades, material deposit buildup, and other abnormalities are detected by analyzing the dynamic pressure and vibration signal utilizing several signal processing techniques. A better maintenance schedule can be derived, this also serves as a turbine efficiency monitor.