Multicomponent Seismic Survey Research Articles

Multidisciplinary analysis of hydraulic stimulation and production effects within the Niobrara and Codell reservoirs, Wattenberg Field, Colorado — Part 1: Baseline reservoir conditions

In the Wattenberg Field, the Reservoir Characterization Project at the Colorado School of Mines and Occidental Petroleum Corporation (Oxy) (formerly the Anadarko Petroleum Corporation) collected time-lapse seismic data for characterization of changes in the reservoir caused by hydraulic fracturing and production in the Niobrara Formation and Codell Sandstone member of the Carlile Formation. We have acquired three multicomponent seismic surveys to understand the dynamic reservoir changes caused by hydraulic fracturing and production of 11 horizontal wells within a 1 mi2section (the Wishbone Section). The time-lapse seismic survey acquisition occurred immediately after the wells were drilled, another survey after stimulation, and a third survey after two years of production. In addition, we integrate core, petrophysical properties, fault and fracture characteristics, as well as P-wave seismic data to illustrate reservoir properties prior to simulation and production. Core analysis indicates extensive amounts of bioturbation in zones of high total organic content (TOC). Petrophysical analysis of logs and core samples indicates that chalk intervals have high amounts of TOC (>2%) and the lowest amount of clay in the reservoir interval. Core petrophysical characterization included X-ray diffraction analysis, mercury intrusion capillary pressure, N2gas adsorption, and field emission scanning electron microscopy. Reservoir fractures follow four regional orientations, and chalk facies contain higher fracture density than marl facies. Integration of these data assist in enhanced well targeting and reservoir simulation.

Quadri-joint inversion: Method and application to the Big Sky 9C 3D data set in northern Montana

The Kevin Dome [Formula: see text] storage project, located in northern Montana, attempted to characterize the Duperow Formation as a potential long-term storage zone for injected [Formula: see text]. A multicomponent (9C) seismic survey was acquired for the Big Sky Carbon Sequestration Partnership over a portion of the Kevin Dome using P- and S-wave sources. Prestack migrated PP, PS, SH, and SV data sets were generated. We then applied several stratigraphic inversion workflows using one or several kinds of seismic wavefield at the same time resulting in joint inversions of each data set. The aim of our study is to demonstrate the benefits of doing quadri-joint inversion of PP-, PS-, SH-, and SV-wavefields for the recovery of the elastic earth parameters, especially the S-wave impedance and density. These are crucial parameters because they can help determine lithology and porefill in the reservoir characterization workflow. Because the inversion workflow always uses the original seismic data recorded in its own time domain, it is necessary to compute registration laws between PP-PS-, PP-SH-, and PP-SV-wavefields using a time shift computation procedure (warping) based on inverted S-wave impedances from inversion of a single wavefield. This generated a significant improvement over methods that rely on attempting to match trace waveforms that may have a different phase, frequency content, and polarity. Finally, we wanted to investigate the reliability of the quadri-joint inversion results in the Bakken/Banff Formations, which have less lateral geologic variation than the underlying Duperow target. This interval shares many of the geophysical characterization challenges common to shale reservoirs in other North American basins. We computed geomechanical parameters, such as Poisson’s ratio and Young’s modulus, which are a proxy for brittleness. Comparison of these results with independent laboratory measurements in the Bakken interval demonstrates the superiority of the quadri-joint inversion method to the traditional inversion using P-wave data only.

Integrated shale-gas reservoir characterization: A case study incorporating multicomponent seismic data

The objective of this case study is to predict geologic properties of a shale reservoir interval to guide production and completion planning for successful development of the reservoir. The conditioning, analysis, and blending of the converted-wave (PS) seismic data into a quantitative interpretation (QI) workflow are described in detail, illustrating the successful integration of geologic information and multiple seismic attributes. A multicomponent 3D seismic survey, several wells with dipole sonic logs, and a multicomponent (3C) 3D vertical seismic profile are available for the study. For comparisons of the incremental value of PS data, the QI workflow is completed entirely using only PP data and then modified and redone to incorporate information from the PS data. Predictions of the geologic properties for both workflows are assessed for accuracy against the existing well log and core evidence. Determining reservoir properties of the shale units of interest is important to the successful placement of horizontal wells for efficient multistage hydraulic fracturing and maximum gas production. Although conventional interpretation of conventional seismic data can only provide reservoir geometry, the quantitative analysis of prestack multicomponent data in this study reveals detailed distinctions between reservoir units and relative measures of porosity and brittleness bulk properties within each unit. Using all of the elastic properties derived from the seismic data analysis allowed for the classification of lithological units, which were, in turn, subclassified based on unit-specific reservoir properties. The upper reservoir units (Muskwa and Otter Park) were shown to have more variability in brittleness than the lower reservoir unit (Evie). Validation at a reliable well control confirmed these distinctive units and properties to be very high resolution and accurate, particularly when the PS data were incorporated into the workflow. The results of this method of analysis provided significantly more useful information for appraisal and development decisions than conventional seismic data interpretation alone.

Pre-stack separation of PP and split PS waves in HTI media

Separation of PP and split PS waves in transversely isotropic media with a horizontal axis of symmetry is crucial for imaging subsurface targets and for fracture prediction in a multicomponent seismic survey using P-wave sources. In conventional multicomponent processing, when a low velocity zone is present near the surface, it is often assumed that the vertical Z-component mainly records P modes and that the horizontal X- and Y-components record S modes, including split PS waves. However, this assumption does not hold when the ubiquitous presence of azimuthal anisotropy makes near surface velocity structures more complicated. Seismic wavefields recorded in each component therefore generally represent a complex waveform formed by PP and split PS waves, seriously distorting velocity analysis and seismic imaging. Most previous studies on wave separation have tended to separate P and S modes using pre-stack data and to separate split S modes using post-stack sections, under the assumption of orthogonal polarization. However, split S modes can hardly maintain their original orthogonal polarizations during propagation to the surface due to stratigraphic heterogeneity. Here, without assuming orthogonal polarization, we present a method for pre-stack separation of PP, PS1 and PS2 waves using all three components. The core of our method is the rotation of wave vectors from the Cartesian coordinate system established by Z-, R- and T-axes to a coordinate system established by the true PP-, PS1- and PS2-wave vector directions. Further, we propose a three-component superposition approach to obtain base wave vectors for the coordinate system transformation. Synthetic data testing results confirm that the performance of our wave separation method is stable under different noise levels. Application to field data from Southwest China reveals the potential of our proposed method.

Full Waveform Modelling for Subsurface Characterization with Converted-Wave Seismic Reflection

While a large number of reservoirs have been explored using P-waves seismic data, P-wave seismic survey ceases to provide adequate result in seismically and geologically challenging areas, like gas cloud, shallow drilling hazards, strong multiples, highly fractured, anisotropy. Most of these reservoir problems can be addressed using P and PS seismic data combination. Multicomponent seismic survey records both P-wave and S-wave unlike conventional survey that only records compressional P-wave. Under certain conditions, conventional energy source can be used to record P and PS data using the fact that compressional wave energy partly converts into shear waves at the reflector. Shear component can be recorded using down going P-wave and upcoming S-wave by placing a horizontal component geophone on the ocean floor. A synthetic model is created based on real data to analyze the effect of gas cloud existence to PP and PS wave reflections which has a similar characteristic to Sub-Volcanic imaging. The challenge within the multicomponent seismic is the different travel time between P-wave and S-wave, therefore the converted-wave seismic data should be processed with different approach. This research will provide a method to determine an optimum converted point known as Common Conversion Point (CCP) that can solve the Asymmetrical Conversion Point of PS data. The value of γ (Vp/Vs) is essential to estimate the right CCP that will be used in converted-wave seismic processing. This research will also continue to the advanced processing method of converted-wave seismic by applying Joint Inversion to PP&PS seismic. Joint Inversion is a simultaneous model-based inversion that estimates the P&S-wave impedance which are consistent with the PP&PS amplitude data. The result reveals a more complex structure mirrored in PS data below the gas cloud area. Through estimated γ section resulted from Joint Inversion, we receive a better imaging improvement below gas cloud area tribute to the converted-wave seismic as additional constrain.

高密度速度解析手法，マルチコンポーネント反射法地震探査および深海曳航方式反射法地震探査を用いたメタンハイドレート賦存状況把握の試み

In the methane hydrate research project by METI/MH21 consortium, some unconventional data analysis techniques are developed and various types of geophysical surveys have been carried out to estimate the distribution and characteristics of methane hydrate. In this paper, we describe the continuous velocity analysis technique, 2D multi-component seismic survey and 2D deep-towed seismic survey which could give promising results not only for methane hydrates but for conventional oil and gas exploration.The continuous velocity analysis is applied to PSTM gather of 2D/3D seismic data in order to estimate the detailed velocity structure around methane hydrate bearing layer. Especially the high velocity anomaly above BSR is recognized as one of the indication which implies existence of methane hydrate concentrated zone. This velocity analysis technique has been applied for monitoring the oil-sand production with SAGD and it gave the successful results.A 2D multi-component seismic survey was carried out using the RSCS in 2006. It is an ocean bottom cable system employing a series of 3-component geophones connected with submarine optical cable. The resulting PP reflection PSTM sections with the vertical component showed excellent agreement with the 3D survey migrated volume. The PS-converted wave sections with inline horizontal component showed amplitude anomalies around BSR. This fact indicates S-wave velocity anomaly and gives information to estimate the rock physics model.A 2D deep-towed seismic survey was carried out in 1996. Both the source and the hydrophone cable are towed close to the seabed to obtain higher resolution section and velocity profiles compared with 3D marine seismic in the very shallow part. But, we can not recognize BSR clearly on the section because of its insufficient source energy. The high resolution section of the survey has great potential for finding active faults or hydrothermal deposits.

Delineating oil-sand reservoirs with high-resolution PP/PS processing and joint inversion in the Junggar Basin, Northwest China

Dramatic lateral lithological variations in the fluvial sediments in Chepaizi, in the Junggar Basin of Northwest China, have posed challenges in distinguishing true and false “bright spots” in oil-bearing sand reservoirs. A high-resolution multicomponent seismic survey and joint prestack PP and PS inversion conducted recently provided an effective technique for solving the problem and successfully delineating the characteristics of the reservoir. This is due to the different reflection response of shear waves to the lithology and fluid content, and their ability to resolve thin layers. Surface-consistent amplitude- and resolution-preserving pro-cessing produced high-quality prestack PP and PS migrated gathers and stacks for extracting seismic attributes. Application of joint prestack PP and PS inversion resulted in higher fluid factors and lower [Formula: see text] in oil-bearing sands compared with dry sands. The correlation between the inversion and the existing well data suggests that high-resolution multicomponent AVO can reduce drilling risks and provide more accurate reservoir characterization.

Tight-gas seismic monitoring, Rulison Field, Colorado

Time-lapse multicomponent seismic monitoring of pressure depletion in tight-gas development can be used to increase recovery efficiency. Tight-gas plays require technology to enhance the economic viability of resource development. Our study at Rulison Field, Colorado, confirms that time-lapse, multicomponent seismic surveys can monitor tight-gas depletion and be used for well planning and completion design.

Let's get cracking

The Reservoir Characterization Project at the Colorado School of Mines acquired three time-lapse multicomponent seismic surveys at Rulison Field, Piceance Basin, Colorado, to identify fracture zones in the tight gas sand reservoir (Figure 1). The purpose of the time-lapse study is to delineate fractures and to use this knowledge to aid in the exploration and development of this tight gas sand field. Tight gas is an important resource, and natural fractures play a significant part in enhancing permeability and controlling production.

Data Processing of Marine Multicomponent Seismic-A Case Study of 4-Component 2D OBC data, Offshore Norway-

Multicomponent seismic technology has been improved significantly with higher fidelity acquisition systems and more advanced data analysis methods. Especially in marine seismic, 4-Component Ocean Bottom Cable (OBC) is practically applied for reservoir characterization and exploration at the water depth of more than 1000m. Converted wave processing and interpretation is a fairly new topic and there is a lack of data and expertise around the world. Until now, the most common converted wave data has been essentially 1-D, VSP and OBS (Ocean Bottom Seismometer) records. Recently there is an increasing use of multi-component OBC 2-D and 3-D surveys. They are especially applied to evaluate reservoirs, because it has been revealed that P-S converted waves can give valuable additional lithological information. They also give clear reflections where the P-wave reflections are poor due to a very small acoustic impedance contrast. It is worthwhile that we introduce the actual processing of the 4-C line to discuss on P-S converted wave processing and later to develop new tools and techniques in this rapidly evolving field. Since marine multicomponent seismic survey has not been carried out yet in Japan, we use a 4-Component OBC (4C OBC) 2-D line, acquired by PGS Norway in 1998. The data was purchased by JNOC/TRC in 2002, as a part of the methane hydrate research program, to evaluate the use of P-S converted wave data in determining the properties of the hydrate layer and the BSR. The 4C line was acquired along the track of a previous conventional streamer line which showed a BSR. The location is in the Norwegian Sea, just up-dip of a major sedimentary slide, known as the 'Storegga Slide'. The results of the first investigation of the 4C data were published by Andreassen et al (2001). They presented a very significant difference between the P-wave and the PS converted wave sections in the hydrate layer and around the BSR. In fact, the BSR was not visible on the PS-wave section. The result shows that a lot of additional information is contained in the converted waves. We reprocessed the 4C data and discussed the specific problems.

Scott explores multi-component business with rxt

Abstract Former key man in PGS and GECO, Mike Scott, has launched a multicomponent seismic survey company. He talks to Andrew McBarnet about his plans for rxt.

Processing the Hod 3D multicomponent OBS survey, comparing parallel and orthogonal acquisition geometries

The Hod 3D multicomponent ocean-bottom seismic (OBS) survey was acquired to image the reservoir through a gas cloud. Data were acquired with shot lines both along the receiver cables (in-line or parallel shooting) and orthogonal to the receiver cables (cross-line shooting).

P- and SV-wave separation by polarization-dependent velocity filtering: application to vertical seismic profiles from Kola superdeep borehole, Russia

In multicomponent seismic surveys, separation of interfering compressional (P) and shear-wave (S) energy provides valuable information for the interpretation of mode conversions and seismic anisotropy. We present a technique for such a separation using a polarization-dependent velocity filtering. At the first step of the procedure, a linear two-channel filter is designed in the frequency-wavenumber domain, with filter coefficients determined by the angles of incidence of respective seismic waves. Due to several physical reasons, the filter is unstable near the high end of the P-wave spectrum. We stabilize the filter with the use of S-wave spectrum balancing. This operation results in a robust decomposition into P- and SV-responses, while retaining the full energy of the vector wavefield. We implement this method in a module of our seismic processing system. The module employs a versatile parametrization scheme, as well as structured data input/output. It is able to process VSP or surface data, with velocities varying by either depth or offset. Application of the module to the processing of an offset VSP from the Kola Superdeep Borehole demonstrates that the program successfully separates P- and S-wave phases in crustal VSP data.

3-D AVO analysis and modeling applied to fracture detection in coalbed methane reservoirs

Over the years, amplitude variation with‐offset (AVO) analysis has been used successfully to predict reservoir properties and fluid contents, in some cases allowing the spatial location of gas‐water and gas‐oil contacts. In this paper, we show that a 3-D AVO technique also can be used to characterize fractured reservoirs, allowing spatial location of crack density variations. The Cedar Hill Field in the San Juan Basin, New Mexico, produces methane from the fractured coalbeds of the Fruitland Formation. The presence of fracturing is critical to methane production because of the absence of matrix permeability in the coals. To help characterize this coalbed reservoir, a 3-D, multicomponent seismic survey was acquired in this field. In this study, prestack P‐wave amplitude data from the multicomponent data set are used to delineate zones of large Poisson's ratio contrasts (or high crack densities) in the coalbed methane reservoir, while source‐receiver azimuth sorting is used to detect preferential directions of azimuthal anisotropy caused by the fracturing system of coal. Two modeling techniques (using ray tracing and reflectivity methods) predict the effects of fractured coal‐seam zones on angle‐dependent P‐wave reflectivity. Synthetic common‐midpoint (CMP) gathers are generated for a horizontally layered earth model that uses elastic parameters derived from sonic and density log measurements. Fracture density variations in coalbeds are simulated by anisotropic modeling. The large acoustic impedance contrasts associated with the sandstone‐coal interfaces dominate the P‐wave reflectivity response. They far outweigh the effects of contrasts in anisotropic parameters for the computed models. Seismic AVO analysis of nine macrobins obtained from the 3-D volume confirms model predictions. Areas with large AVO intercepts indicate low‐velocity coals, possibly related to zones of stress relief. Areas with large AVO gradients identify coal zones of large Poisson's ratio contrasts and therefore high fracture densities in the coalbed methane reservoir. The 3-D AVO product and Poisson's variation maps combine these responses, producing a picture of the reservoir that includes its degree of fracturing and its possible stress condition. Source‐receiver azimuth sorting is used to detect preferential directions of azimuthal anisotropy caused by the fracturing system of coal.

Inversion of 4-C borehole flexural waves to determine anisotropy in a fractured carbonate reservoir

Observations of anisotropy in fractured carbonate reservoirs can yield important information such as the orientation of aligned crack systems and crack density. A new generation of borehole acoustic tools provides the data necessary to observe anisotropy around the borehole. The flexural waves, excited by two dipole sources operating perpendicularly to each other in these tools, are recorded in two perpendicular directions, resulting in four‐component flexural wave recordings, Superposition of sources and rotation of receivers are the basic elements for the inversion of the waveforms to determine fast or slow mode orientations. Since the two sources are not necessarily of the same strength, a reciprocity‐based source equalization is carried out as part of the inversion. We have inverted four‐component borehole flexural waves, recorded in a vertical well, penetrating three lithologic units of a fractured carbonate reservoir in northern Oman. For the lower unit, a northeast‐southwest azimuth of flexural wave anisotropy is well resolved, which is parallel to the strike of open fractures observed in the borehole, preferential flow directions, and to the regional present‐day in‐situ maximum horizontal stress. Furthermore, the northeast‐southwest direction corresponds with polarization directions of the fast shear wave observed in a multicomponent surface seismic survey over the reservoir. The middle unit is most likely isotropic, except for a depth interval of low gamma readings, where a northeast‐southwest orientation is found for the fast mode. For the upper unit, a north‐south fast mode orientation is found, which does not correspond to the expected northeast‐southwest direction. Borehole geometry data indicate that the shape of the hole is circular for the middle unit but elongated for the upper and lower unit. Caliper orientations track the flexural wave anisotropy azimuths in these two units. Because of the elongation of the borehole, the observed flexural mode orientations, as well as the magnitude of flexural wave anisotropy, cannot be related to formation anisotropy directly, which obscures the determination of fracture orientation and fracture density from four‐component borehole flexural waves.

95/01951 1993 carbon dioxide fact sheet (notebook)

In multicomponent seismic surveys, separation of interfering compressional (P) and shear-wave (S) energy provides valuable information for the interpretation of mode conversions and seismic anisotropy. We present a technique for such a separation using a polarization-dependent velocity filtering. At the first step of the procedure, a linear two-channel filter is designed in the frequency-wavenumber domain, with filter coefficients determined by the angles of incidence of respective seismic waves. Due to several physical reasons, the filter is unstable near the high end of the P-wave spectrum. We stabilize the filter with the use of S-wave spectrum balancing. This operation results in a robust decomposition into P- and SV-responses, while retaining the full energy of the vector wavefield. We implement this method in a module of our seismic processing system. The module employs a versatile parametrization scheme, as well as structured data input/output. It is able to process VSP or surface data, with velocities varying by either depth or offset. Application of the module to the processing of an offset VSP from the Kola Superdeep Borehole demonstrates that the program successfully separates P- and S-wave phases in crustal VSP data.

95/01955 Climate alteration. A global issue for the electric power industry in the 21st century

In multicomponent seismic surveys, separation of interfering compressional (P) and shear-wave (S) energy provides valuable information for the interpretation of mode conversions and seismic anisotropy. We present a technique for such a separation using a polarization-dependent velocity filtering. At the first step of the procedure, a linear two-channel filter is designed in the frequency-wavenumber domain, with filter coefficients determined by the angles of incidence of respective seismic waves. Due to several physical reasons, the filter is unstable near the high end of the P-wave spectrum. We stabilize the filter with the use of S-wave spectrum balancing. This operation results in a robust decomposition into P- and SV-responses, while retaining the full energy of the vector wavefield. We implement this method in a module of our seismic processing system. The module employs a versatile parametrization scheme, as well as structured data input/output. It is able to process VSP or surface data, with velocities varying by either depth or offset. Application of the module to the processing of an offset VSP from the Kola Superdeep Borehole demonstrates that the program successfully separates P- and S-wave phases in crustal VSP data.

95/01950 Canadian tribes consider waste store - Canada

In multicomponent seismic surveys, separation of interfering compressional (P) and shear-wave (S) energy provides valuable information for the interpretation of mode conversions and seismic anisotropy. We present a technique for such a separation using a polarization-dependent velocity filtering. At the first step of the procedure, a linear two-channel filter is designed in the frequency-wavenumber domain, with filter coefficients determined by the angles of incidence of respective seismic waves. Due to several physical reasons, the filter is unstable near the high end of the P-wave spectrum. We stabilize the filter with the use of S-wave spectrum balancing. This operation results in a robust decomposition into P- and SV-responses, while retaining the full energy of the vector wavefield. We implement this method in a module of our seismic processing system. The module employs a versatile parametrization scheme, as well as structured data input/output. It is able to process VSP or surface data, with velocities varying by either depth or offset. Application of the module to the processing of an offset VSP from the Kola Superdeep Borehole demonstrates that the program successfully separates P- and S-wave phases in crustal VSP data.

Azimuthal responses of some three‐component geophones

A significant and often overlooked aspect of seismic surveys is the importance of data fidelity. Geophone fidelity is particularly critical for multicomponent seismic surveys in which the full vector wavefield is sampled by geophones which house multiple elements. Traditionally, geophones are tested on “shake tables” in the laboratory (with field testing equipment) or evaluated on the basis of simulation or equivalent circuits. There appear, however, to be few studies which evaluate geophone performance in the field.

Estimation of near‐surface elastic parameters using multicomponent seismic data

In multicomponent seismic reflection surveys, surface and near‐surface effects can severely deteriorate the quality of reflection data. Such effects are more pronounced on shear‐wave than on compressional‐wave profiles. Amplitude anomalies, statics, and strong coherent source‐generated noise (i.e., surface waves) are often associated with inhomogeneous, poorly compacted near‐surface sediments of the weathering layer. The magnitude of such effects increases when sources and receivers are deployed at or near the surface in proximity to such inhomogeneities. Near‐surface effects can be investigated with respect to their depth of occurrence by burying seismic sources and/or receivers at various depths below the inhomogeneous weathering layer. In this context, an experiment was conducted to collect multicomponent seismic field data on a borehole‐controlled test site in east Texas. Data were recorded on three‐component surface and buried receivers using a full‐vector wavefield surface source. Although the geology appears simple, results of modeling one or two components of the field data with synthetics yields nonunique estimates of elastic parameters. Effects of anisotropy and heterogeneities are better identified and estimated with full‐wavefield surface and buried receiver observations. Single fold data from buried receivers yield reflection events with higher signal‐to‐noise ratio than 30‐fold CDP surface data previously acquired in the same area.