In geophysical exploration different types of measurements are used to probe the same subsurface region. In this paper we show that the wavelet transform can aid the process of linking different data types. The continuous wavelet transform, and in particular the analysis of amplitudes along wavelet transform modulus maxima lines, is a powerful tool to analyze the characteristic properties of local variations in a signal. The amplitude-versus-scale curve of a particular transition in a signal can be seen as its fingerprint. Hence, local variations in different data types can be linked by comparing their fingerprints in the wavelet transform domain. Insight in the physics underlying the different types of measurements is required to 'tune' the different wavelet transforms in such a way that a particular geological transition in the Earth's subsurface leaves the same fingerprint in the wavelet transform of each data type. We discuss the wavelet transform as a tool for geophysical data integration for three situations. First we discuss how one can link the scale-dependent properties of outliers in borehole data to those of reflection events in surface seismic data. We use wave theory to derive relations between the two data types in the wavelet transform domain. Next we analyze the relation between the wavelet transforms of detailed geological models and (simulated) migrated seismic data, with the aim of improving the geological interpretation. A spatial resolution function provides the link between the wavelet transforms of the geological model and the migrated seismic data. Finally we consider the integration of geotechnical (cone penetration test) data with shallow shear wave seismic data. We illustrate with a real data example that specific geological features of the shallow subsurface can be identified in the wavelet transforms of both data types. We conclude that the wavelet transform can be used as a tool that aids the integration of different types of data.

Ultrasonic experiments carried out on Rotliegend reservoir sandstone samples have shown a specific stress-dependent behaviour of the transmission response. Apart from the well-known velocity increase as ambient stress increases, the amplitude and the time are scaled when the stress is changed from one value to another. Our hypothesis is that when stress changes, some mineralogical constituents of the rock may change their acoustic properties differently from other constituents. As a consequence, different scattering attenuation effects take place within the rock. The observed stress-dependent scaling behaviour can be a consequence of the latter phenomenon.In order to quantify the scaling behaviour, two approaches are used. First, a heuristically derived model from the experimental data is tested on numerically simulated data. Next, an analytically derived model from a modified version of the O'Doherty-Anstey expression for the transmission response through finely layered media is also analyzed and tested both on numerically simulated and experimental data. Both scaling models present two scalar parameters that relate a wavelet recorded at a high ambient stress with another recorded at a relatively low stress. Estimating these parameters from measurements for a range of different ambient stresses gives valuable information about the stress-dependent behaviour of the reservoir rock.

In this paper the nonlinear iterative algorithm, the so-called Extended Contrast Source Inversion is applied to subsurface sensing problem where the number of measured data are very limited and the unknown objects/layers are illuminated from only one side. Some numerical results obtained from synthetic and real data are presented to illustrate the strengths and the weakness of the method.

In this paper the nonlinear iterative algorithm, the so-called Extended Contrast Source Inversion is applied to subsurface sensing problem where the number of measured data are very limited and the unknown objects/layers are illuminated from only one side. Some numerical results obtained from synthetic and real data are presented to illustrate the strengths and the weakness of the method.

We formulate reciprocity theorems for time-lapse seismic methods, based on the full and the one-way wave equations. The latter form allows a straightforward physical interpretation of the various contributing terms. Unlike difference data taken at the acquisition surface, the boundary integral in the one-way reciprocity theorem represents the true time-lapse changes of the reflectivity of the top reflector of a reservoir below the boundary at which this integral is evaluated. Evaluation of the boundary integral yields therefore suited input for time-lapse AVO analysis.

In the following analysis we consider the action of a point source of the injection type in an acoustic medium. The seismic medium response is recorded with a set of point receivers.