Using Seismic Attributes for Data Alignment and Seismic Inversion In Joint PP/PS Seismic Analysis

Abstract

Method for aligning converted wave seismic reflection data (PS data) with conventional PP seismic reflection data so that both data types may be used to more accurately image the subsurface for hydrocarbon exploration or field development. Amplitude vs. angle (AVA) or amplitude vs. offset (AVO) attributes of PP and PS seismic data are identified and defined, which attributes are theoretically expected to be in phase and optimize seismic resolution in the data. In one embodiment of the invention, such attributes are calculated (310), then the same horizons are identified in a series of PP attributes and in a series of PS attributes, then the second series is aligned with the first at the horizon locations (316, 320), then a time transfer function is generated and applied to the PS mode data (322), and the aligned joint-mode data are inverted (326) using, for example, AVA attributes.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of both U.S. Provisional application 61 / 144,233 filed on 13 Jan. 2009 and U.S. Provisional application 61 / 166,531 filed on 3 Apr. 2009.FIELD OF THE INVENTION[0002]Exemplary embodiments of the present invention relate to methods for aligning compressional wave (PP) and converted shear wave (PS) reflection data and seismic inversion in joint PP / PS seismic analysis.BACKGROUND OF THE INVENTION[0003]This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.[0004]In the oil and gas industry, seismic prospecting techniques commonly are used to aid in t...

AI Technical Summary

Benefits of technology

The present invention provides a method for transforming seismic data to create a more enhanced data representation of a subsurface region. The method involves calculating a first series of seismic attributes describing the variation in PP mode data as associated with properties of the subsurface region, and a second series of seismic attributes describing the variation in PS mode data as associated with properties of the subsurface region. The two series are then refined aligned to create a time-transfer function, which can be applied to another portion of the seismic data to create an aligned data volume. The alignment process may be performed using a combination of the first and second series or other techniques such as cross-plotting or time-transfer function. The resulting data representation can be used for various applications such as oil and gas exploration.

Problems solved by technology

More specifically, adjacent layers in the subsurface have different physical properties due to changes in lithology and fluids, and thus may present different densities and velocities affecting the strength of the reflected elastic wave.

The accuracy of the image obtained by analyzing the seismic signals may be limited by the amount of data obtained for a specific site.

However, the difference in P-wave and S-wave propagation velocities, among others, necessitates aligning PP and PS mode reflection data and makes combining data collected in the different modes challenging in a joint PP / PS analysis.

However, because of the differences in phase and amplitude of PP and PS reflections, all forms (for example, near stack, full stack, angles stacks) of PP mode and PS mode data may not fulfill the assumption implicit in the alignment techniques.

Many alignment techniques may force a match the between PP mode and PS mode data even where such a match may not be theoretically justified.

This forced matching can lead to time alignment errors with serious effects in joint PP / PS inversion and geologic interpretation of PP / PS data.

To alleviate the phase problem, seismic envelope data is often used for alignment, but envelope data lack the seismic resolution critical for accurate registration of PP and PS data.

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