Project Report             N° PR-GE-08.01              West Medvezhye 1                       Siberia                     ...
DISCLAIMERThe technical results, conclusions and recommendations contained in this report arebased on the Low Frequencies ...
Table of contents1.    Summary ..............................................................................................
1.     SummaryThis project report presents the results of the Geospectra IPDS® survey conducted in theWest Medvezhye area ...
2.    Data Acquisition2.1   Description of AcquisitionFrom the base camp at the border of the survey area tracked vehicles...
The third recorder and seismometer couple was used as a reference unit and measuredcontinuously on Well 103 throughout the...
Figure 4: Data point map             7/14
2.2    Field Acquisition and Quality CheckAfter each measurement, the recordings were checked directly in the field to con...
4.      First ResultsResult of the data processing is the creation of the RHI map (Reservoir HydrocarbonIndicator).Results...
All the Iso-Energy curves in the RHI map are created from the Low Frequencies Energy.The Iso-Energy map from the passive a...
Figure 6: Iso-Energy RHI map with measurement points. Values at the rim of    survey are the result of only one measuremen...
Figure 7: Iso-Energy Spectrographic map with measurement points.            Red Areas as potential exploration target     ...
Figure 8: 3D Iso-Energy Spectrographic map with measurement points.RHI values are on Z. Red Spot is the most interesting p...
•   The surrounding measurements play an important role to close the Iso-Energy curves    (Figure 7). Without additional m...
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West Med Seismic Survey Project Report - June 2009

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West Med Seismic Survey Project Report - June 2009

  1. 1. Project Report N° PR-GE-08.01 West Medvezhye 1 Siberia Russia Project N° PR-GE-08.01Operated by GeoDynamics Research S.r.l., Rovereto (TN) Italy June 2009 Abridged version for publication 1/14
  2. 2. DISCLAIMERThe technical results, conclusions and recommendations contained in this report arebased on the Low Frequencies Passive Seismic Spectroscopy Method provided byGeoDynamics Research IPDS® Technology with the objective to reveal prospective oil andgas areas and substantiate the results from a prior gas seismic tomography survey.The work was carried out according to the standard of skill and care that is expected ofprofessionally qualified and experienced consultants. However, GeoDynamics Researchdoes not warrant operational decisions based on any results, conclusions orrecommendations and accepts no liability for any loss, damage or costs that may beincurred or sustained through the use of results, conclusions or recommendations of thisreport. 2/14
  3. 3. Table of contents1. Summary ........................................................................................................ 42. Data Acquisition ............................................................................................... 52.1 Description of Acquisition .................................................................................. 52.2 Field Acquisition and Quality Check ..................................................................... 83. Processing Techniques ...................................................................................... 84. First Results..................................................................................................... 95. Discussion of Results ...................................................................................... 106. Conclusions and Recommendations................................................................... 13 3/14
  4. 4. 1. SummaryThis project report presents the results of the Geospectra IPDS® survey conducted in theWest Medvezhye area for “Victoria Oil and Gas” Plc, London.The survey area as a part of the West Siberian Plain is located in Siberia, Russia, 25 kmSouth-West of the Medvezhye gas field and 12 km to the North-East of the Nadym oiland condensate field.The main purpose of the Spectrometric IPDS® survey was to substantiate the resultsfrom a prior gas seismic tomography survey conducted in the West Medvezhye licensearea of the client. The survey area included Well 103 which was drilled in the center ofthe survey area in 2006 and revealed the presence of hydrocarbons.The acoustic recordings acquired in the field were processed at the Head Office ofGeoDynamics Research in Italy, allowing state-of-the-art quality control, signalprocessing and filtering.The processed results show two areas displaying relatively high Low Frequencies Energy(RHI = Reservoir Hydrocarbon Indicator) values which have been highlighted in Figurewith Well 103 being at the edge of one of the two areas.These two areas represent interesting exploration targets according to the GeoDynamicsSpectrometric IPDS® technique. The present survey therefore indicates areas with higherprospectivity and areas with lower prospectivity within the limits of the anomalymeasured during the geochemical survey completed in 2006. 4/14
  5. 5. 2. Data Acquisition2.1 Description of AcquisitionFrom the base camp at the border of the survey area tracked vehicles were used to reachthe measurement points due to the surface conditions.The measurements took place along profiles which were agreed with the client (Figure 4).Daylight lasted four hours a day. Therefore, in general, three setups per day wereachieved (6 data points).Each measurement setup consisted of three Recording Stations. Two of them wereKinemetrics Quanterra Q330 24 bit ADC and one station Kinemetrics K2 24 bit.All the Seismometers were GeoDynamics Seismometers SM-3Kv verticals withelectromagnetic sensor that measured simultaneously at 500 m from each other, aspresented on the Figure 1.Before the acquisition campaign started, all the Seismometers were tested in a lowtemperature laboratory at the Physics department of University of Trento to guaranteetheir functioning [as per internal report “GDR Report - Test at Low Temperature on GDRSeismometers SM-3kv”]. The working performance of the Seismometers at -37 °C wasflawless.All ADC converters have temperature limits down to -40 C°, so the acquisition team didnot have any particular technical problem with the GDR Equipment. Figure 1: Acquisition setupMobile and independent measurement units were used. These units are suited for theextreme weather conditions and working environment of this survey.Each measurement point was located with a Garmin GPS unit. Synchronization of themeasurements was also achieved by accurate GPS timing of each recorder in a continueloop modality. 5/14
  6. 6. The third recorder and seismometer couple was used as a reference unit and measuredcontinuously on Well 103 throughout the entire measurement day.To avoid additional unwanted artificial noise, measurements started after all crewmembers and vehicles had reached a distance of at least 500m from each measurementpoint.Figure 2: Seismometer placement Figure 3: Shows examples of the units used, with the Seismometer coupled to the frozen ground 6/14
  7. 7. Figure 4: Data point map 7/14
  8. 8. 2.2 Field Acquisition and Quality CheckAfter each measurement, the recordings were checked directly in the field to control thereliability and quality of the data.No significant artificial noise source was recorded in this remote area, as evidenced alsoby inspection of the spectrograms and PSDs of the measurements. As an example of thecalibration measurement points, at CAGE 12 and CAGE 13 no artificial noise wasrecorded and the PSD and Spectrogram were clean.At the beginning, in the middle and at the end of the survey calibration measurementswere performed to calibrate sensors and recorders.In general, calibration is also used to verify that the coupling with the ground wasoptimal and consistent. The analysis was made by using coherence methods, as it isnecessary that the Seismometers are equally calibrated, i.e. they produce the sameresponse when they are close to each other. The Seismometers are calibrated within 5%which is within our calibration limits.3. Processing TechniquesThe total number of measurements was 84.These included 38 calibrations and 4 reference measurements.The total number of useful data points measured was 42 (this number did not includecalibrations or reference measurements).The total number of measurements processed was 38.The survey was conducted in an area of the West Medvezhye license area where a priorgas seismic tomography exploration identified an anomaly.To better define and localize the measured anomaly, several data points (Figure 4) weremeasured outside the limits of the anomaly.The data received from the field crew was reviewed by staff at GeoDynamics Researchoffices in Rovereto, both in the time domain and in the frequency domain to ensure thatall recordings used were of acceptable quality.This was especially important because of the very low temperatures (-36°C to -8°C) atwhich the Seismometers and recorders were used. No significant problems wereencountered and no artificial noise had a negative impact on the data analysis.The objective of the Geospectra IPDS® approach is to process passive seismic data, usingdifferent types of signal analysis methodology, to identify and isolate particularities,related to hydrocarbon reservoirs.The objective of the passive seismic data pre-processing in the time and frequencydomain is to clean the signals from potential human noise, and then find out as clearly aspossible, using particular methodologies of analysis, the earth seismic background. Weinclude the Oceanic Peak at 0.25 Hz, as we use it as a reference during all the steps ofthe processing. 8/14
  9. 9. 4. First ResultsResult of the data processing is the creation of the RHI map (Reservoir HydrocarbonIndicator).Results are reviewed by reference to all the processing procedures adopted byGeoDynamics and applied to many fields in different parts of the world. The onlydifference is in the order of filtering and windowing of the signals to reflect thebackground noise of particular areas where the signals were acquired. Figure 5: Iso-Energy Spectrometric map measured in terms of RHI values. Values at the rim of survey are the result of only one measurement. 9/14
  10. 10. All the Iso-Energy curves in the RHI map are created from the Low Frequencies Energy.The Iso-Energy map from the passive acoustic spectroscopy shows then 3 types ofArea: • very low (Yellow), • low (Light Red) and • potential exploration targets (Red)5. Discussion of ResultsMost surveys conducted by GeoDynamics Research have revealed a positive correlationbetween hydrocarbon presence and the RHI values measured. The positive correlationappears to be linked to the cumulative thickness of hydrocarbons from all hydrocarbonbearing reservoirs. Red Areas thus contain potential exploration targets.Any parameter that influences hydrocarbon content and distribution will be expected toinfluence the RHI indicator. These parameters include structure, stratigraphy and as wellas porosity and permeability. The combination of these factors will determine thedistribution of hydrocarbons in the subsurface. The RHI map might reveal structuralelements, but only where these have a major influence on the distribution ofhydrocarbons in the subsurface.By analyzing the Spectrographic map and making a path between the measurementlocations we can analyze all the Power Spectral Densities (PSD) inside the Hydrocarbonpotential Areas. We can also see from the analysis that all the PSDs have similarcharacteristics.High RHI values in certain areas are related then to an increase in the Energy content ofthe measured signal with respect to the same frequency window from measurementsdisplaying lower RHI values.This means that RHI values are always relative to the local acquisition, and should notbe considered as an absolute indicator.The low number of data points collected in the West Medvezhye survey does not allow usto achieve the necessary resolution and, therefore, we have had to increase theuncertainty in some areas as shown in the yellow zones. The uncertainty could also beconnected with actual lower hydrocarbon potential.Values at the rim of the survey area which result from only one measurement should beconsidered less reliable, as the case for example of the acquisition point CAGE28A to thewest of the measured area, shown in the Figure 6.To have more resolution on the Spectrographic map and avoid systematic errors thatmay have occurred during the survey and to improve the processing in the border area ofthe survey, a greater number of data points could be collected on a subsequent surveyfor West Medvezhye. 10/14
  11. 11. Figure 6: Iso-Energy RHI map with measurement points. Values at the rim of survey are the result of only one measurement and thus less reliable. 11/14
  12. 12. Figure 7: Iso-Energy Spectrographic map with measurement points. Red Areas as potential exploration target 12/14
  13. 13. Figure 8: 3D Iso-Energy Spectrographic map with measurement points.RHI values are on Z. Red Spot is the most interesting potential exploration area6. Conclusions and RecommendationsThe Iso-Energy Spectrometric map (RHI map) is the final result of the Passive SeismicInterferometry Geospectra IPDS® processing technique.• Areas with higher values of RHI represent areas with higher likelihood of hydrocarbon accumulations.• Two areas have been highlighted in red in Figure 7 and they represent potential exploration targets.• The location of Well 103 is placed at the limits of one of these areas.• Only where there is consistent well control would it be possible to derive a direct correlation with hydrocarbon column thickness. One well is not sufficient to determine a reliable correlation. 13/14
  14. 14. • The surrounding measurements play an important role to close the Iso-Energy curves (Figure 7). Without additional measurements we are not able to close the Iso-Energy paths completely. Consequently, we have had to make extrapolations which may not always be consistent.• In order to improve the resolution, it would be advantageous to take additional measurements in our next survey campaign, and thus reduce the uncertainty which is always present.• The Iso-Energy map generally gives an estimation in terms of quantity, but in this case we are not able to provide a reliable estimation of the NPZ (Net Pay Zone), due to insufficient data to make a correlation.It is important to remark that any Passive Spectroscopy IPDS® survey should beused as a complementary approach to existing exploration methods and shouldnot be expected to produce 100% correlations with hydrocarbon accumulations. 14/14

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