Sensitivity Analysis and Imaging Technique of the 3D Crosswell Electromagnetic Measurements
Wang Xindong Shen Jinsong.
Resistivity is one of the most important parameters in evaluating the water saturation among many petrophysical parameters. Because 3D crosswell electromagnetic measurement can provide the interwell resistivity between two boreholes, its importance in evaluating formation hydrocarbon was regarded more and more highly. However, because of complexity of the 3D crosswell electromagnetic responses, up to now, the study has been mainly focused on the two dimensional or 2.5D model which can only simulate formation approximately in some special cases and their applicability in practice has been largely limitted. In this paper, the method of the sensitivity equation was adopted to derive the sensitivity of the magnetic and electric fields to the conductivity. Analysis of spatial distribution of the sensitivity was carried out in 3D space. The regularized least square iterative inversion was carried out to produce 3D resistivity image. In the inversion process, the implementation of constraints of the model parameters was addressed. Through numerical simulation, it is indicated that the horizontal and vertical components of the magnetic field present different sensitivity distributions both in vertical and radial directions, the higher sensitivity occurs on the area nearby the transmitter and receiver, whereas the low sensitivity exists on the middle part between the two wells?The validity of the imaging technique was checked by the stable imaging result of the 3D numerical data.
【CateGory Index】： P631.3