Step 1: Time series processing
Time series are analyzed. Frequency content is calculated through FFT. Resistivity’s estimates and other MT parameters are calculated through a series of robust calculations. One or more robust may be applied depending on signal over noise ratios
Cross-power (right panels) editing is an important step that can be used to reject outliers estimates that lays outside the main cluster of phase and resistivity estimates (upper right panel). This can dramatically improve overall data quality of measurements.
Step 2: Quality control
After time series processing and robust calculations, final MT curves are compiled in a processing package for further processing and interpretation.
Data quality is usually good, except when measurements get too close from major noise sources (High Voltages powerlines, major infrastructure etc…)
Data repeatability from site to site is excellent thanks to the density of measurements which makes data analysis easier. This can be seen on the following montage:
Group of resistivity curves on top of the known reservoir are compared to a group of resistivity curves away from the known reservoir. Within each group there is excellent repeatability although when compared between the two groups characteristics of the resistivity responses are very different: At high frequency (few hundred meters down) the group of curve above the reservoir shows a conductive feature that is not present for the group away from the reservoir. At mid-range (1Hz, 1kilometer and down), a resistive feature is visible only for the group of curves above the reservoir
Step 3: Skew
A map of Impedance skew at 1 Hz is calculated. Skew values less than 0.2 indicates an overall 1D response. Values higher than 0.2 are symptomatic of: 2D/3D Geology and/or high porosity / anisotropic formations.
1D inversions should not be carried on areas where skews are more than 0.2.
Note that the seismic anticline 3D structure is well recognized in the East Buzakhur.
Step 4: Polar diagram
A map of polar diagrams at 100 seconds (deep, many kilometers) confirms complicated events in the east Buzakhur. The “peanut shape” of these diagrams is symptomatic of porosity and/or 3D geology.
Note that the regional response of the polar diagram and the circular shape in the East Buzakhur area. The geometry of the anticline does not support such a response. This has been modeled and not supported by modeling (not presented here). Alterations, high temperature metamorphism and intrusions could generate such responses.
Step 5: TM phase pseudo section of the East West profile P52
The TM (bottom section) phase pseudo section of the East West profile P52 puts into evidence the fault the East Buzakhur – Karabay contact fault and reveals the possibility of a westward fault that needs to be tested through inversions.
Step 6: Resistivity pseudo section of the East West profile P52
Note the TM resistivity (bottom section). Again the evidence of the east trap is well presented. Note the large deep, arising anomaly in the central part of the deposit (well below the deposit)
