DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS
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Borehole seismology is the highest resolution geophysical imaging technique available to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This proposal takes direct aim at this shortcoming. P/GSI is developing a 400 level 3C clamped downhole seismic receiver array for borehole seismic 3D imaging. This array will remove the acquisition barrier to record the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for economic use of 3D borehole seismic imaging for reservoir characterization and monitoring. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore facilitate 9C reservoir imaging. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the fluid types. The data quality and the data volumes from a 400 level 3C array will allow us to develop the data processing technology necessary for high resolution reservoir imaging.Keywords:
Geophysical Imaging
Vertical seismic profile
Summary A deep exploration well was drilled down to 5300 m on the top of a surface fold in the mountainous Zagros in order to encounter a deep anticline at the top of Permian reservoir formation expected in the area. Due to poor surface seismic, geological and practical considerations were used for locating the well. The structural interpretation was refined during the drilling operation, using: well logs, borehole resistivity imaging, geological data, a 2D surface seismic and an intermediate VSP recorded using a three component (3C) sensor tool implemented with a Relative Bearing / Roll angle sensor. The VSP data was processed before drilling the deep interval 5300m to 6130m Total Depth (TD), with the intention to predict any reflection below the intermediate 5300m drilled depth. Next, the whole borehole data was further analyzed after reaching TD. The main focus was on independent extraction of dip/azimuth information from oriented 3C VSP data and from borehole wall resistivity measurements. The highly folded structure encountered by the well and the absence of high energy seismic reflectors with substantial lateral extension detected by the VSP are coherent with the blurred results on the 2D surface seismic section in the well vicinity.
Vertical seismic profile
Anticline
Scientific drilling
Reflection
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This note describes a vertical borehole geophone array which can be used in slim boreholes. The array was designed as part of a research program in Sweden to study the potential of seismic crosshole techniques for mapping cracks and fracture zones in crystalline rock. The design meets not only the constraints imposed by the slim boreholes (diameter 56 mm) available in Sweden for crosshole surveys, but also the desire to make array recordings with three component locked geophones. The use of vertical arrays in boreholes has been discussed by Galperin (1974).
Geophone
Vertical seismic profile
Seismic array
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Borehole seismology is the highest resolution geophysical imaging technique available to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This proposal takes direct aim at this shortcoming. P/GSI is developing a 400 level 3C clamped downhole seismic receiver array for borehole seismic 3D imaging. This array will remove the acquisition barrier to record the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for economic use of 3D borehole seismic imaging for reservoir characterization and monitoring. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore facilitate 9C reservoir imaging. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the fluid types. The data quality and the data volumes from a 400 level 3C array will allow us to develop the data processing technology necessary for high resolution reservoir imaging.
Geophysical Imaging
Vertical seismic profile
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Borehole seismology is the highest resolution geophysical imaging technique available to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This proposal takes direct aim at this shortcoming. P/GSI is developing a 400 level 3C clamped downhole seismic receiver array for borehole seismic 3D imaging. This array will remove the acquisition barrier to record the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for economic use of 3D borehole seismic imaging for reservoir characterization and monitoring. By using 3C surface seismic or borehole seismic sources the 400 level receiver array will furthermore facilitate 9C reservoir imaging. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the fluid types. The data quality and the data volumes from a 400 level 3C array will allow us to develop the data processing technology necessary for high resolution reservoir imaging.
Geophysical Imaging
Vertical seismic profile
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This paper presents and analyzes results from a Finite Difference Modeling (FDM), processing, and imaging study of a Walkaway Vertical Seismic Profiling (WVSP) survey, and discusses how the images from WVSP enhance those from the surface seismic data. It is shown that the results from the WVSP integrate well with the image from the surface seismic performed in the same line. For the study, a seismic model with vertically and horizontally varying velocities was built and a WVSP data set was generated. The surface seismic had difficulty to show clear images from the layers with steep dips and near vertical displacements on the model due to the lack of ray coverage. The study demonstrates that the WVSP geometry can record reflections from near vertical layers facing the borehole, which help with imaging the parts of the subsurface structure which were missing in the surface seismic. With proper combination of the images from the WVSP and the surface seismic, a more complete image profile of the subsurface can be constructed around the borehole. However, while contributing to surface seismic, it is also seen that the WVSP introduces more migration artifacts related to source interval distance and interbed multiples than the surface seismic data.
Vertical seismic profile
Geophysical Imaging
Seismic survey
Seismic to simulation
Profiling (computer programming)
Seismic migration
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The U.S. Dept. of Energy funded Frio Brine Pilot provided an opportunity to test borehole seismic monitoring techniques in a saline formation in southeast Texas. A relatively small amount of CO{sub 2} was injected (about 1600 tons) into a thin injection interval (about 6 m thick at 1500 m depth). Designed tests included time-lapse vertical seismic profile (VSP) and crosswell surveys which investigated the detectability of CO{sub 2} with surface-to-borehole and borehole-to-borehole measurement.
Vertical seismic profile
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