Abstract

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.

URTeC 1576906

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