The new quality of the geophysical forecast: adaptive multi-offset TEM survey (M-TEM) based on correction for edge effects of inhomogeneities and traps in “vertical” EM soundings. Technique of volume geoelectrical reconstruction of geologic media is used.
(Patents: Russia No. 2411549, Australia No. 2010303966)
Solvable tasks: forecast of productivity for oil and gas collectors in conditions of inhomogeneous overburden and complexly structured host media.
- decreasing of amount of “dry” wells;
- validity of prediction of sites not suitable for drilling – 80%;
- validity of forecast of high-permeability collectors – over 70%.
Observation system: provides necessary spatial density of measurements and practically leads to a small grow in cost of works but provides additional important informaton about peripheral parameters of a media for more precise forecast of a reservoir productivity.
Observation system provides accounting of mostly large lateral inhomogeneities by progressive step between receiver points:
On seismic profiles it is usual to use orthogonal offsets.
- Based on division of EM-field components into a normal component – host medium influence, and anomalous component – influence from 3D inhomogeneities.
- Simultaneous fitting of objects and EM-signals within all spatial and time areas of source influence allows to consider the features of upper part of section, eliminates edge affections of inhomogeneities of geologic media not linked with targets of interest; eliminates distortions of reconstruction of deep part of section, sufficiently reduces areas of equivalence of the solution of the inverse task and increases reliability of the forecast.
Evidential base: The technology of adaptive TEM electromagnetic survey has passed wide industrial approbation and meets declared requirements. Geologic section forecast has been proved by following drilling.
High precision of determination of electrophysical parameters of a section is shown (evaluating of accuracy of a binding by depth of target objects – 2.5%).