Multicomponent seismic data bring unique advantages to geophysical reservoir characterization in settings with fracturing or stratigraphic complexity. Their use allows much better estimation of elastic attributes such as shear-wave impedance and Poisson's ratio than is possible with conventional seismic alone. Also, because of their great sensitivity to the anisotropy parameters diagnostic of fracturing, multicomponent techniques are the tools of choice for characterizing natural fracture networks geophysically. The use of recently developed joint inversion methodologies for deriving elastic parameters is the most straightforward way to take advantage of the extra information multicomponent seismic data provide.

Geologic CO2 sequestration (GCS) has received high-level attention from the global scientific community as a response to climate change due to higher concentrations of CO2 in the atmosphere. However, GCS in saline aquifers poses certain risks including CO2/brine leakage through wells or non-sealing faults into groundwater or to the earth's surface. Understanding crucial reservoir parameters and other geologic features affecting the likelihood of these leakage occurrences will aid the decision-making process regarding GCS operations. In this study, we develop a science-based methodology for quantifying risk profiles at geologic CO2 sequestration sites as part of US DOE's National Risk Assessment Partnership (NRAP). We apply NRAP tools to a field scale project in a fractured saline aquifer located at Kevin Dome, Montana, which is part of DOE's Big Sky Carbon Sequestration Partnership project. Risks associated with GCS injection and monitoring are difficult to quantify due to a dearth of data and uncertainties. One solution is running a large number of numerical simulations of the primary CO2 injection reservoir, shallow reservoirs/aquifers, faults, and wells to address leakage risks and uncertainties. However, a full-physics simulation is not computationally feasible because the model is too large and requires fine spatial and temporal discretization to accurately reproduce complex multiphase flow processes. We employ the NRAP Integrated Assessment Model (NRAPIAM), a hybrid system model developed by the US-DOE for use in performance and quantitative risk assessment of CO2 sequestration. The IAM model requires reduced order models (ROMs) developed from numerical reservoir simulations of a primary CO2 injection reservoir. The ROMs are linked with discrete components of the NRAP-IAM including shallow reservoirs/aquifers and the atmosphere through potential leakage pathways. A powerful stochastic framework allows NRAP-IAM to be used to explore complex interactions among a large number of uncertain variables and to help evaluate the likely performance of potential sequestration sites. Using the NRAP-IAM, we find that the potential amount of CO2 leakage is most sensitive to values of permeability, end-point CO2 relative permeability, hysteresis of CO2 relative permeability, capillary pressure, and permeability of confining rocks. In addition to demonstrating the application of the NRAP risk assessment tools, this work shows that GCS in the Kevin Dome has a higher probability of encountering injectivity limitations during injection of CO2 into the Middle Duperow formation than previous studies have calculated. Finally, we estimate very low risk of CO2 leakage to the atmosphere unless the quality of the legacy well completions is extremely poor.

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.

The Big Sky Carbon Sequestration Partnership is a US CO2 storage project in the Duperow formation from the Kevin Dome structure located in Montana. The goal of the study is to characterize the Duperow interval as a potential long-term storage zone for injected CO2. During the years 2013-2015, a North American company, Vecta Oil & Gas operated a multi-component seismic survey on behalf of the Partnership over Kevin Dome, using P- and S-wave sources. After processing of 3D-9C seismic data, pre-stack PP, PS, SH and SV datasets were generated and migrated in their corresponding time domains. We evaluate from the real case study the benefits of inverting jointly PP, PS, SH and SV prestack seismic data. We developed registration laws using inverted shear impedances from sequential inversions as the input to the registration process. This parameter choice represents a significant improvement over methods which rely on attempting to match trace waveforms which may have different phase, frequency content, and polarity. This real case study of multi-component pre-stack stratigraphic inversion is an elegant way of employing all modes of a multi-component acquisition to generate an optimal estimate of P-, S-wave impedances and density to determine lithology and fluid contents used by quantitative reservoir characterization. Presentation Date: Wednesday, September 27, 2017 Start Time: 11:25 AM Location: Exhibit Hall C/D Presentation Type: POSTER

The exploitation of unconventional hydrocarbons requires innovative skills to allow better characterization of brittle reservoir zone. The Young's modulus is a measure of their brittleness and requires an accurate determination of the rock density which is well known only at the well locations. The multi-component inversion is a process that holds a great potential but requires a specific seismic survey using P- and S-wave sources to generate mode-converted waves. During the years 2013-2015, a North American company, Vecta Oil & Gas operated a multi-component seismic survey on behalf of the Big Sky Carbon Sequestration Partnership over Kevin Dome. Within this context, we apply a model-based prestack inversion of mode-converted wave including four kinds of wave fields PP, PS, SV and SH. Then we evaluate from the real case study the benefits of inverting jointly PP, PS, SH and SV prestack seismic data in recovering the elastic rock property, we focus especially on the inverted density parameter from Bakken target area. Presentation Date: Tuesday, September 26, 2017 Start Time: 8:55 AM Location: 370A Presentation Type: ORAL

We compared results of different methods of multicomponent receiver orientation analysis using data from the Big Sky 9C-3D survey, including polarization analysis, polarity flip mapping, and sensor null mapping. Polarization analysis and polarity flip mapping provided inconclusive or non-physical results. We found the most consistent results by mapping nulls in the H1 and H2 sensitivity patterns using trial rotations to radial/transverse coordinates and computing semblance over a window containing the first arrivals. We use the ratio of maximum to minimum semblance energy of all trials to quantify the null depth as a quality control factor. For receiver gathers with a large null depth, the computed orientation angles better fit data than nominal field orientations. By comparing semblance calculations over different offset ranges, we can determine the optimal offset range for orientation analyses through spatial maps of the null depths after analysis rather than attempting to pre-select the optimal range. Presentation Date: Wednesday, October 19, 2016 Start Time: 1:30:00 PM Location: 166 Presentation Type: ORAL

Exploration for oil-bearing Morrow sandstones using conventional seismic data/methods has a startlingly low success rate of only 3%. The S-wave velocity contrast between the Morrow shale and A sandstone is strong compared with the P-wave velocity contrast, and, therefore, multicomponent seismic data could help to characterize these reservoirs. The SV and SH data used in this study are generated using S-wave data from horizontal source and horizontal receiver recording. Prestack P- and S-wave inversions, and joint P- and S-wave inversions, provide estimates of P- and S-wave impedances, and density for characterization of the Morrow A sandstone. Due to the weak P-wave amplitude-versus-angle response at the Morrow A sandstone top, the density and S-wave impedance estimated from joint P- and S-wave inversions were inferior to the prestack S-wave inversion. The inversion results were compared with the Morrow A sandstone thickness and density maps obtained from well logs to select the final impedance and density volume for interpretation. The P-wave impedance estimated from prestack P-wave data, as well as density and S-wave impedance estimated from prestack SV‐wave data were used to identify the distribution, thickness, quality, and porosity of the Morrow A sandstone. The stratal slicing method was used to get the P- and S-wave impedances and density maps. The S-wave impedance characterizes the Morrow A sandstone distribution better than the P-wave impedance throughout the study area. Density estimation from prestack inversion of SV data was able to distinguish between low- and high-quality reservoirs. The porosity volume was estimated from the density obtained from prestack SV-wave inversion. We found some possible well locations based on the interpretation.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2007Prestack 9‐C joint inversion for stratigraphic prediction in the Williston BasinAuthors: Bryan DeVaultThierry TonellotDanièle MacéStéphan KerMorgane PichardBryan DeVaultVecta Oil & Gas, Ltd.IFPSearch for more papers by this author, Thierry TonellotVecta Oil & Gas, Ltd.IFPSearch for more papers by this author, Danièle MacéVecta Oil & Gas, Ltd.IFPSearch for more papers by this author, Stéphan KerVecta Oil & Gas, Ltd.IFPSearch for more papers by this author, and Morgane PichardVecta Oil & Gas, Ltd.IFPSearch for more papers by this authorhttps://doi.org/10.1190/1.2792581 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract We have successfully applied the multicomponent prestack elastic waveform inversion methodology proposed by Agullo et al (2004) to 9‐C 3D data from North Dakota. The objective of the survey was to image grainstone shoals which form stratigraphic traps for oil using the P and shear modes. The shoals are a difficult exploration target as they are characterized by a subtle, nonunique P‐wave seismic response. Prestack joint elastic inversion of the P and SH modes delineates both the shoal itself and the updip seal facies that act as the trap in this part of the play. Elastic attributes were particularly successful at characterizing the dolomite fraction at the reservoir, which allowed mapping of trap geometries.Permalink: https://doi.org/10.1190/1.2792581FiguresReferencesRelatedDetailsCited ByMulticomponent Seismic Data and Joint Inversion11 March 2022Quadri-joint inversion: Method and application to the Big Sky 9C 3D data set in northern MontanaVincent Clochard, Bryan C. DeVault, David Bowen, Nicolas Delépine, and Kanokkarn Wangkawong30 October 2018 | Interpretation, Vol. 6, No. 4Brittleness issues with geomechanical attributes from quadri-joint multicomponent inversion: Application to a real case, the Kevin Dome (Montana, US)Vincent Clochard, Nicolas Delépine, Bryan C. Devault, and Kanokkarn Wangkawong17 August 2017Warping of 9C seismic data and its application to 9C stratigraphic prestack inversion: A real case study from the Big Sky CO2 Project (Montana, US)Vincent Clochard, Nicolas Delépine, Bryan C. Devault, and Kanokkarn Wangkawong17 August 2017Poststack, prestack, and joint inversion of P- and S-wave data for Morrow A sandstone characterizationParitosh Singh, Thomas L. Davis, and Bryan DeVault17 July 2015 | Interpretation, Vol. 3, No. 3Improved unconventional reservoir characterization using multi-azimuth stratigraphic inversion, case study on the Fort Worth BasinJournal of Unconventional Oil and Gas Resources, Vol. 3-4 SEG Technical Program Expanded Abstracts 2007ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2007 Pages: 3124 publication data© 2007 Copyright © 2007 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished: 14 Sep 2007 CITATION INFORMATION Bryan DeVault, Thierry Tonellot, Danièle Macé, Stéphan Ker, and Morgane Pichard, (2007), "Prestack 9‐C joint inversion for stratigraphic prediction in the Williston Basin," SEG Technical Program Expanded Abstracts : 1039-1043. https://doi.org/10.1190/1.2792581 Plain-Language Summary PDF DownloadLoading ...

We have observed significant azimuthal variation in shearwave stacking velocities in a recently-acquired 9-C 3-D survey in the Williston Basin of North Dakota. While not uncommon for P-wave data, we are unaware of any previous observations of this phenomenon on shear-wave 3-D data. The amount of azimuthal anisotropy (not to be confused with the difference in vertical shear-wave velocities that gives rise to shear-wave splitting) observed in the stacking velocities of the slow shear mode (>10% in the deep subsurface) is somewhat larger than for the fast mode. Interestingly, no measurable azimuthal P-wave velocity anisotropy is present, and the total amount of shear-wave splitting from the surface to the target reservoir is less than 1%. Inconsistencies between the values of measured from splitting and inferred from azimuthal variation in the moveout lead us to conclude that the subsurface here displays weak orthorhombic symmetry.

The Nieuwerkerk Formation is a major Lower Cretaceous synrift and postrift fluvial unit in the West Netherlands Basin (southwest Netherlands) that attains thicknesses in excess of 1 km in places. A strong tectonic overprint on its deposition and a large degree of facies heterogeneity have complicated correlation and greatly hampered understanding reservoir and seal distribution within the unit. The integrated application of fluvial sequence stratigraphic concepts with biostratigraphic dating and the correlation of cycles of changing accommodation to sediment supply ratio (A/S cycles) on three-dimensional (3-D) seismic, well-log, and core data have allowed a much improved understanding of reservoir facies distribution within the Nieuwerkerk Formation. A major intraformational unconformity divides the Nieuwerkerk Formation into two members. The lower of these, the Alblasserdam Member, is predominantly nonmarine and has a significant tectonic depositional overprint. Correlation within this member is dependent on the identification of base-level transit cycles probably induced by pulses of tectonism. The inclusion of 3-D seismic isopach data facilitates mapping thicknesses and reservoir properties of the Alblasserdam Member in areas with no well control. The upper member, the Rodenrijs Claystone Member, was deposited during the postrift stage and is predominantly a coastal-plain succession. Biostratigraphic correlation proved useful in subdividing this unit and correlating key seismostratigraphic markers. Use of biostratigraphic and cyclostratigraphic correlation techniques allowed chronostratigraphically consistent reservoir maps to be made of the constituent members of the Nieuwerkerk Formation. These maps exhibit localized nonmarine syndepositional basins (Alblasserdam Member sand depocenters), followed by gradual southward, landward stepping of facies tracts of the Rodenrijs Claystone Member above the intraformational unconformity. The Rodenrijs Claystone Member is capped by a marine transgression that terminated fluvial deposition in this part of the basin. Interestingly, no major lacustrine facies have been identified in the fluvial units in the West Netherlands Basin, rendering it somewhat anomalous among rift basins.

Shear‐wave amplitude variation with offset (AVO) analysis can be used to map changes in density, shear‐wave velocity, and fracturing at reservoir scale by allowing the influence of each factor to be separately extracted from the observed seismic response. Weighted least‐squares inversion of the anisotropic reflection coefficients was implemented to find the shear‐wave splitting coefficient and velocity‐contrast parameters. A time‐lapse nine‐component, 4‐D seismic survey acquired over Vacuum field in Lea County, New Mexico, was used to test our methodology of shear‐wave AVO analysis and to compare the results with well production and azimuthal P‐wave AVO analysis.Weighted least‐squares shear‐wave AVO stacks of the splitting parameter were found to be excellent predictors of well fluid‐production performance, implying a strong link between seismically inferred fracturing and reservoir‐scale permeability of the San Andres dolomites at Vacuum field. Analysis of the shear‐wave velocity contrast indicated the presence of a second set of open fractures to the south of a carbon dioxide injector well where a 4‐D anomaly associated with injection had been observed.

Summary Shear-wave AVO analysis is a powerful tool for separating the contributions of changes in density, velocity, and fracturing to the observed seismic amplitude response. Shear-wave AVO analysis can be used to map variations in each of these quantities and to thereby characterize both fracturing and porosity in hydrocarbon reservoirs. Weighted least squares solution of linearized anisotropic plane-wave reflection coefficient equations for the fracture density and shear-wave velocity contrast parameters has been used to analyze lateral variations in fracture density in San Andres carbonates in the Central Vacuum Unit using a multicomponent 3-D seismic survey. The use of weighted least squares techniques also allows computation of standard deviations for each of the AVO attributes and, therefore, estimation of the reliability of the resulting interpretations.

Abstract In the (W of Mexico, many gas-saturated sands are not Bright Spots and thus arc difficult m dewct on conventional 31) seismic data. These small amplitude reelections occur frequently in pliocene-Miocene exploration plays when the acoustic impedances of the gas-saturated sands id shales are approximately the same. In these areas, geophysicists have had limited success using AV() to reduce the exploration risk. That interpretation of the conventional AV() attributes is often difficult and contains questionable relationships to the physical properties of the media. A 31) AV() study was conducted utilizing numerous well-log suites, core analyses, and production histories to help calibrate the seismic response to the pctrophysical properties. This study resulted in an extension of the AV() method to a technique that now displays Bright Spots when very clean sands and gas saturated sands occur. These Iitho-stratigraphic reflections on the new AV() technique are related to Poisson's ratio, il petrophysicid property that is normally mixed with the acoustic impedance on conventional 3D migrated data. Introduction During the last five years, the significance of 3D seismic data in reducing the risks of oil/gas exploration has ham well documented.however, (here still exists areas, especially in over pressured zones, where conventionally process 3D seismic data exhibits poor data quality making it difficult 10 map structure and stratigraphy. in fact. the amplitude variations on the conventional seismic bear no relationship to the known geology. Thus, it is not surprising that in Ume areas, 1i) synthetic seismograms show a very poor t]e to the seismic data. While 3D stacking has received much acclaim, Tucker: warned that stacking enhances continuity and parallelism ofthe reflection. ... but overstocking can destroy the geology. ... Stacking can also distort the stratigraphy ... thus playing havoc with successful stratigraphic mapping. These astute observations were made (in 1982) before the advent 01 AV()' and before the information content of (he reflection stack was fully understood.' 1(is primarily the mixing of' two pctrx)physical properties, acoustic impedance and Poisson's ratio, that leads to the distortion of the, geology and stratigraphy. In this study. d robust method of, separating the effects of acoustic impedance from Poisson's ratio was developed and applied to a GOM offshore area. Numerous wells, some dating to the late 60s, arc scattered throughout the 3D AV() study area. The exploration play is P1ioccne-Mioctnw, imd is Iocated in the shallow-water transition mm! of Texas and I.ouisiana. Borehole information was utilized for both calibration and verification of the reservoir characterization from the 3D seismic data.