Azimuthal Attenuation Elastic Impedance Inversion for Fluid and Fracture Characterization Based on Modified Linear-Slip Theory

Xinpeng Pan,Yian Cui,Guangzhi Zhang

doi:10.1155/2019/4651020

Abstract

The seismic attenuation should be considered while accounting for the effect of anisotropy on the seismic wave propagating through a saturated fractured porous medium. Based on the modified linear-slip theory and anisotropic Gassmann’s equation, we derive an analytical expression for a linearized PP-wave reflection coefficient and an azimuthal attenuation elastic impedance (AAEI) equation in terms of fluid/porosity term, shear modulus, density, dry normal and tangential fracture weaknesses, and compressional (P-wave) and shear (S-wave) attenuation parameters in a weak-attenuation isotropic background rock containing one single set of vertical aligned fractures. We then propose an AAEI inversion method to characterize the characteristics of fluids and fractures using two kinds of constrained regularizations in such a fractured porous medium. The proposed approach is finally confirmed by both the synthetic and real data sets acquired over a saturated fractured porous reservoir.

Highlights

With the increasing demand for oil and gas around the world, fractured reservoirs have become the focus of the geophysical exploration of hydrocarbons [1]
Using the modified Schoenberg’s linear-slip model proposed by Chichinina et al [26, 27], we first derive the stiffness tensor of a fracture-induced equivalent horizontal transversely isotropic (HTI) attenuation medium, which relates to the elastic properties of isotropic background, porosity, matrix modulus, fluid modulus, fracture weaknesses, and attenuation parameters
Based on the modified Schoenberg’s linear-slip theory, we integrate the attenuation of background rock and fractureinduced attenuation in this paper and propose an attenuation elastic impedance (AAEI) inversion approach to characterize the saturated fractures in a fracture-induced equivalent HTI attenuation medium

Summary

Introduction

With the increasing demand for oil and gas around the world, fractured reservoirs have become the focus of the geophysical exploration of hydrocarbons [1]. To overcome the pennyshaped fracture model assumption, Gurevich [13] combined the anisotropic Gassmann’s [12] equation with the more generally linear-slip (LS) theory to propose a saturated fractured porous model, who derived the exact analytical expressions for the stiffness matrix of a fluid-saturated fractured porous rock, related to the dry elastic properties of isotropic background, matrix moduli, porosity, dry fracture compliances, and saturated fluid modulus. Using the modified Schoenberg’s linear-slip model proposed by Chichinina et al [26, 27], we first derive the stiffness tensor of a fracture-induced equivalent HTI attenuation medium, which relates to the elastic properties of isotropic background, porosity, matrix modulus, fluid modulus, fracture weaknesses, and attenuation parameters. We present the methodology, the synthetic tests, and applications of the proposed AAEI inversion approach on a real data set

Theory and Methods

Â χÀdbry

Examples

2.10 Well A

Discussion

Conclusions