Media publications

New Product S-Wave Pulse Source

by Alena Lipyavko | Oct 03, 2013

Oil and Gas Vertical, No.22 November 2012

  NEW PRODUCT

S-WAVE PULSE SOURCE

  S.M. ZARIPOV

Vice President, Operations

CJSC GEOTECH Holding

V.A. DETKOV

Managing Director

LLC Evenkiyageofizika

(subsidiary of CJSC GEOTECH Holding)

M.A. KOPYLOV

Director of Minusinsk

Branch

LLC Evenkiyageofizika

(subsidiary of CJSC GEOTECH Holding)

V.V. KARSTEN

Research Associate

Institute of Petroleum Geology and Geophysics SB RAS

The challenging geological conditions of Eastern Siberia require new methods and completely new equipment. • Methodology CDP- 2D3C and CDP-3D3C for recording elastic waves • monotype S-wave sources for emission. To resolve these problems, at the Minusinsk Branch of LLC Evenkiyageofizika CJSC GEOTECH Holding two S-wave source mockups were developed and brought to production. This article covers the progress achieved and the results of field trials of the equipment. Field trials of S-wave mockup sources were conducted to evaluate their functionality in December 2011 at the geophysical test facility of the Minusinsk Branch of LLC Evenkiyageofizika. Fig. 1, 2 show Enisey IPV S-wave sources. The source is designed as a two-sledge skid. The sledges are linked by a frame. An electrical room is mounted on the frame. The source is used with a tractor. The sledge, with power electric magnets inside, is an impact module. The design of this impact module, IPV-50S.02, is shown on Fig.3. Observations were conducted in wells 1 and 2 with different arrangements of directional and nondirectional sources. Single three-component seismic receivers, GS-3C, were used on the surface. A AMTs-3-48 recorder was used to record the signals in the well with 4 recording modules spaced at 20 meters. The signals were recorded in the well at a depth of 0-80 meters with a 5-meter stepout. Testing consisted of several stages: Recording in an open-hole well 1 - S-wave sources are positioned on PV-7. The SEM-100P source and horizontal module mounted on a 2-meter frame make an impact. Impact is also made on the end of the sleeper that is positioned at the wellhead in PV-6. The long reach (40 meters) of the S-wave sources is explained by the risk of failure of uncased well. Well 1 is located on the edge of a 10x5 water pool with concrete walls, and the direction of the impact of all S-wave sources is parallel to the side of the water pool. SEM-20 shoots from PV-3 and KEM-4 shoots from PV 4 to check the orientation of downhole devices. Signals are recorded at surface stakes 1-21. S-wave sources are positioned on PV-5. SEM-100P and the horizontal module mounted on the 2-meter frame shoot. Impact is made at the end of the sleeper located also on PV-5. The shots are made in a direction perpendicular to the setup (Y-impact). Shots are made from PV1 and PV2 to check the polarity and orientation of three-component seismic receivers using a KEM-4 source. Ten concentrations of each impact were made. Separate impacts were also recorded. Each horizontal impact was made in two opposite directions. It allows to obtain a sum and difference of opposite impacts and to separate P-waves and S-waves according to polarization in the source. Preliminary processing of the results of test results was performed in the processing system VSPLab (developed by the Institute of Petroleum Geology and Geophysics SB RAS) and included entering momentary statistics, summation of concentrations, calculation of difference, and stacked traces and multichannel amplitude adjustments that preserved the ratio of amplitude between selected traces. Processing results are provided on Figures 5-12. Figure 5 presents a comparison of the impacts of different poles of  source SEM100P on the surface on three components. Three-component rating is applied. It preserves the ratio of component amplitudes. A significant similarity of the record is clear in the case of a positive or negative impact, especially in the initial phases. However, some discrepancies are seen in the subsequent part of the record. Figure 6 shows the same comparison of the impacts of different poles of the horizontal module with three components on the surface. Three-component rating is also applied. It preserves the ratio of component amplitudes. Almost complete reversal of the shape of the record is apparent especially on horizontal components. The same reversal also characterizes the impact on the sleeper end. It demonstrates the significant prevalence of S-wave emissions over P-wave emissions. Figures 7 and 8 show the sum and differential of differently directed impacts of source SEM100P. The ratio of amplitudes was preserved between the differential and sum. It is clear that the sum of the impacts is significantly more intensive than the differential. The sum on the z-component in the first onsets shows direct and head P-waves. Subsequent time periods show intensive S-waves which ar possibly interfere with converted waves. The x-component also shows P-waves: there are converted waves. The y-component before the onset of the S-wave does not show a regular signal. S-waves are recorded over a lengthy time. Their intensity and regularity increases at distance. It is possible that the observed wave pattern is caused by the anisotropy of the upper part of the section. The signal is not observed on all components on the differential of impacts (Fig.8) at the period of first onsets. The pure direct and head S-wave is recorded on the y-component. It allows with high accuracy to determine its onset. Waves with high apparent velocities are found on the x and z components in the interval between onsets of P-waves and S-waves. Probably, these are SP-type converted waves. Figures 9 and 10 show the sum and differential of differently directed impacts of the horizontal module with a preserved amplitude ratio. Here, on the opposite, the differential is significantly more intense than the sum. It is possible to trace a P-wave on the sum on the z-component. It is lost in the noise at larger distance. S-waves and possibly converted waves are also observed in the subsequent x- and z-components. A regular signal is not found on the y-component both before the onset of the S–wave and at a significant distance after. A pure S-wave is recorded on the impact differential (Fig. 10). It is more intensive than the P-wave. It is also possible to see a signal on the x and z components before the onset of the S-wave. The differential of impact on the sleeper has the same character. It is provided here for comparison (Fig. 11). The S-wave is clear on the y-component. Its onset coincides with the pattern generated by the tested sources. Regular signals on the x and z components are weak and are lost in the noise. Figure 12 shows a comparison of the differential of the positive and negative impacts by different sources on the vertical profile on the y-component. The ratio of amplitudes is preserved for all three sources at each depth. It is clear that all sources allow to record the pure S-wave and to determine its parameters. The increase in the intensity of the signal in case of sleeper impact is explained by the fact that the sleeper at this stage of testing was positioned at the wellhead, while the sources were located at a distance of up to 40 meters. Despite the significant total intensity of the impact of source SEM100P, the emitted S-wave energy of all sources is comparable. Thus, preliminary results of the processing of the data of completed tests demonstrate the functionality of both presented S-wave source mockups. Both sources allow to have a rather clean S-wave by a deduction of differently directed impacts. Based on the obtained results, GEOTECH Holding will continue to work on these products. Production of a test model of a non-explosive pulse source of monotype S-waves is scheduled for March 2013.