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A common question asked by Geologist, Engineers and Geophysicists involved in unconventional resource plays is "can multi-component 3D seismic help in my onshore exploration effort??. The question has been answered in offshore exploration with numerous examples of reservoir improvements associated with gas clouds and low P-wave impedance contrasts. This paper answers this question for onshore unconventional plays using the Marcellus Shale as an example. It shows that using shear-wave measurements recorded from multi-component 3D seismic, provides better characterization enabling improved vertical resolution and lateral continuity of the Marcellus formation members, superior determination of geomechanical properties such as brittleness, and, good differentiation of density and Total Organic Content (TOC).
This example uses a recent proprietary multi-component 3D recorded simultaneously with a large conventional 3D covering the thickest and highest TOC area in Bedford County, Pennsylvania, where Marcellus drilling activity is highest.The paper shows a comparison of the results obtained from a conventional elastic inversion for two cases, one using the conventional P-wave data, where the shear component is estimated, and the second using the multi-component shear data, where it is measured. It is observed that the second case using the measured shear provides improved vertical resolution and lateral continuity of the Marcellus formation members providing potential new insights for Marcellus exploration. Geometric attributes are shown which detail the complex structural framework which can be used to assist in any structural association relating to the attributes derived from elastic inversion.
The inversion results are used to calculate geomechanical and rock properties of the Marcellus interval. Comparisons are shown for the two inversion cases for the Upper and Lower Marcellus Intervals. Crossplots of Young's Modulus and Poisson's Ratio (Brittleness based on Rickman et al - SPE paper)) are compared showing that in general the Lower Marcellus exhibits a lower brittleness than the Upper Marcellus which is better defined in case 2.
The depositional presence of high TOC content in the Lower Marcellus shown on gamma ray logs is reflected in low values on density logs. This indicates that it is possible to find these high TOC sweet- spots on seismic data under the right conditions. Crossplots of rock properties show that these sweet- spots can be detected, where case 2, with improved density estimates, is interpreted as showing better differentiation.
Brown, Morgan P. (Wave Imaging Technology Inc.) | Higginbotham, Joseph H. (Wave Imaging Technology Inc.) | Macesanu, Cosmin (Wave Imaging Technology Inc.) | Ramirez, Oscar E. (Wave Imaging Technology Inc.) | List, Dave (Fidelity E&P Company) | Lang, Chris (Fidelity E&P Company)
Unconventional resource plays currently absorb a significant proportion of onshore U.S. E&P budgets. The perceived simplicity and homogeneity of unconventional reservoirs explained their initial appeal to firms seeking to reduce "dry hole risk??. However, as inconsistent drilling results from many resource plays highlight, shale reservoirs are neither simple nor homogeneous. Used infrequently 5-10 years ago, drillers today commonly employ 3D seismic to improve horizontal well "geosteering??. Looking ahead, there is great interest in exploiting 3D seismic to delineate productive "sweet spots??. In particular, differential horizontal stress (from azimuthal anisotropy analysis) and elastic inversion for "brittleness?? are paired to find optimal drill locations and wellbore orientation (Sena et al., 2011).
While prestack depth migration (PSDM) is commonly applied in "complex?? plays such as the sub-salt Gulf of Mexico, it has been adopted in resource plays at a slow (but accelerating) pace. PSDM promises two major "structural?? benefits over conventional time imaging:
Additionally, in areas that exhibit velocity complexity, seismic anisotropy, and dipping beds, PSDM can provide more accurate input for most attribute technologies.
We present a case study from a wide-azimuth 50 mi2 (140 km2) survey acquired in the Niobrara Shale (see Figure 1). While the study area exhibits mildly dipping beds, a significant shallow lateral velocity variation motivates the use of PSDM to correct event dips and improve the focusing of faults. Vertical mistie correction predicted the top Niobrara to within 4 feet on a new well, but we show enough variation in Thomsen ??? to justify anisotropic PSDM.
Azimuthal velocity analysis using Wave Equation PSDM (WEM) azimuth angle gathers indicates a very weak level of overburden azimuthal anisotropy. However, we show that amplitude versus azimuth (AVAZ) may better measure differential horizontal stress in the target interval. Sonic scanner data from a recent well broadly confirms the magnitude of AVAZ response observed in the data.
Brown, Morgan P. (Wave Imaging Technology Incorporated) | Higginbotham, Joseph H. (Wave Imaging Technology Incorporated) | Macesanu, Cosmin M. (Wave Imaging Technology Incorporated) | Ramirez, Oscar E. (Wave Imaging Technology Incorporated) | List, Dave (Fidelity E&P Company) | Lang, Chris (Fidelity E&P Company)
DESCRIPTION : Shale gas production in the Lower Haynesville is the main target for this study, located in Northwest Louisiana. Production from wells has been highly variable, leading to the use of 3D seismic for sweet spotting, well placement and to a lesser extent completion strategies. This abstract describes and shows results of a workflow integrating reservoir and geomechanical properties from pre-stack seismic inversion, as well as stress and fracture information, by applying a novel global azimuthal seismic inversion. The final key aspect of this flow is the quantitative validation of those attributes by the integration of other data types and sources: such as microseismic and mineralogy from x-ray scanning of cuttings. APPLICATIONS : Sweet Spot mapping, well location planning, frac planning, stress field analysis, well economics optimization. RESULTS AND CONCLUSIONS: Correlations between the size of the microseismic-based stimulated area and key properties such as Young's modulus and Differential Horizontal Stress Ratio exist. Correlations between Young's modulus and brittleness/ductility estimates derived from cuttings-based mineralogy are apparent. This is important along long laterals where only limited well log data is available. TECHNICAL CONTRIBUTIONS: To finalize the workflow, mineralogical and elemental data together with microseismic data have been integrated and used to validate the results of the seismically-derived properties. Interesting and perhaps significant correlations between the size of stimulated area and key properties such as Young's modulus and DHSR exist. Low DHSR and high Young's Modulus, taken together, correlate with wide zones of microseismic activity. Technology is continually being enhanced to improve exploitation of shale plays, in part by quantitatively integrating and interpreting data from wells, surface seismic, and microseismic. Integration of disciplines and data types and sources (including at different scales) is a key element in efforts to improve drilling and completion strategies, by examining how these relate to well production. No single attribute by itself is conclusive; multi-attribute analysis is required to derive physically meaningful correlations.
Summary An integrated study of the well Zhao-104 and surrounding wide-azimuth 3D seismic volume within the shale gas reservoir in South China has been conducted with the objective of generating shale formation properties related to fracture orientation and intensity in the area and deriving such reservoir rock properties as data quality allows. The inversion for P and S impedance and derivative attributes produced volumes that relate to rock properties such as brittleness and rigidity that are likely to impact fracturing. Seismic attribute analysis of anisotropy from elliptical velocity inversion indicates that anisotropy varies horizontally and vertically, and that it is dominantly controlled by stress azimuth, which conforms to the current day stress field as independently determined from borehole breakouts. Introduction An integrated study of the well Zhao-104 and surrounding wide-azimuth 3D seismic data volume within the shale gas reservoir in South China has been conducted with the objective of generating shale formation properties related to fracture orientation and intensity in the area and deriving such reservoir rock properties as data quality allows. Well data, structural seismic information and prestack inversion products were combined in an integrated interpretation. Seismic gather conditioning improved seismic data quality prior to prestack inversion by improving signal/noise ratio, removing NMO stretch and aligning reflection events. Velocities from residual moveout (RMO) analysis on individual sectors were used as input to detection of fracture orientation and anisotropy. Fracture strike and P wave anisotropy were calculated using the RMO updated sector velocity fields in elliptical velocity inversion, while inversion for P and S impedance and derivative attributes produced volumes that relate to rock properties such as brittleness and rigidity that are likely to impact fracturing. Inversion of seismic data During the prestack inversion process, the velocity field was updated after residual moveout analysis for each sector and used in elliptical velocity inversion to determine degree and direction of anisotropy.