Abstract: Resistivity data acquired at two different epochs using different types of tools are jointly inverted. For example, a multiple propagation resistivity (MPR) tool is run first, preferably at several frequencies and several transmitter-receiver spacings. At a later epoch, an induction tool may be run, preferably on a wireline. The joint inversion process identifies bed boundaries based on inflection points in the propagation resistivity and induction logging raw data. An initial guess for an uninvaded earth model is generated using the selected bed boundaries and the apparent raw resistivity values. An inversion run using shallow measurements of propagation resistivity logging data is performed to estimate a resistivity structure representative of the near borehole zone resistivity (invaded zone). The bed boundary positions of the layers are also updated as part of the inversion process. Synthetic data for both the shallow and deep measurements are generated to delineate the invasion zones.

Abstract: A method for determining the permeability of earth formations penetrated by a wellbore from acoustic signals measured by an acoustic wellbore logging instrument. The method includes separating components from the measured acoustic signals which represent Stoneley waves propagating through the earth formations. Signals representing Stoneley waves propagating through the same earth formations are synthesized. The separated acoustic signal components and the synthesized Stoneley wave signals are compared. The permeability is determined from differences between the synthesized Stoneley wave signals and the separated acoustic signal components. In a preferred embodiment, the step of calculating the permeability includes inversion processing a wave center frequency shift and a wave travel time delay with respect to the permeability of the earth formations.

Abstract: A method of determining the acoustic propagation velocities of earth formations using signals generated by an acoustic array well logging instrument. The method includes generating a model of the acoustic velocities including a value of velocity for each propagation mode for which the velocity is to be determined Acoustic waveforms are synthesized for a plurality of receiver locations on the acoustic logging instrument by using the values of the acoustic velocities in the model. A difference is determined between the synthesized waveforms and measured waveforms generated by acoustic energy detected at corresponding receiver locations on the acoustic logging instrument. The model is adjusted and the waveforms are resynthesized until the difference is determined to be at a minimum. The step of adjusting the model is performed by very fast simulated annealing.

Abstract: A method for determining orientations and velocities of slow and fast waves in an anisotropic earth formation. Signals are used from an acoustic logging tool including dipole transmitters and receiver arrays. An initial value of angle subtended between orientation of the fast wave and one of the transmitters is selected. A waveform of a fast principal wave and slow principal wave at first and second selected receiver positions are calculated from received signals at each of these positions and the selected subtended angle. A derivative waveform with respect to subtended angle is calculated for both fast and slow principal waves. An initial velocity of slow waves is selected and the calculated waveforms of the slow principal wave and its derivative waveform at the first position are time shifted by a time corresponding to distance between first and second receiver positions and the selected value of velocity.