ABSTRACT:

In recent years, rock physical interpretation of seismic data has been aggressively used in oil and gas industry for characterizing and monitoring oil and gas reservoirs. In this field, only sedimentary rocks such as sandstone have been modeled using mainly P-wave seismic data. In rock engineering applications, rock physical interpretation of geophysical data has also become more important to obtain mechanical and hydrogeological subsurface models. In those applications, not only sedimentary rocks but also volcanic and crystalline rocks must be characterized and modeled for further analysis. More geophysical data other than P-wave seismic data are potentially available for rock physics modeling in this field. However there are not so many rock physics models for those types of rocks with many geophysical data. We have, therefore, collected geophysical properties of those types of rocks obtained in laboratory tests and well loggings. Then we have tried to apply the existing rock physics models to soft sedimentary and crystalline rocks which are very commonly characterized in rock engineering applications in Japan. The weathered rocks were also studied in modeling. These trial applications have clarified the applicability of the existing rock physics models and the problems to be addressed in the future study on rock physics modeling of various types of rocks to be characterized in rock engineering applications.

1. INTRODUCTION

In recent years, rock physical interpretation of seismic data has been aggressively used in oil and gas industry for characterizing and monitoring oil and gas reservoirs [1]. Rock physics models have been so far developed mainly for sedimentary rocks such as sandstone because many reservoirs are composed of sandstone or shaly sandstone. In addition, only seismic data have been used to study rock physics models because their resolution, quality and reliability are superior to other geophysical data in deep oil and gas exploration. In applications to rock engineering, rock physical interpretation of geophysical data has become more important to obtain quantitative mechanical and hydrogeological subsurface models. In rock engineering applications, not only sedimentary rocks, but also crystalline rocks such as granite must be characterized and modeled for further analysis. More geophysical data other than P-wave seismic data are also potentially available for rock physics modeling in this field. However there are not so many rock physics models for those types of rocks with many geophysical data. We have therefore started studying rock physics modeling of a variety of rocks using many geophysical data for rock engineering applications. We have first collected geophysical and rock engineering properties of various types of rocks obtained in laboratory tests and well loggings in Japan. Then we have tried to apply existing rock physics models to soft sedimentary and crystalline rocks which are very commonly encountered in rock engineering applications in Japan, in order to evaluate their applicability. In this paper we describe these trial applications and their evaluations to clarify the problems to be addressed in the future study.

2. ROCK PHYSICS

Rock physics is the science that addresses the relationship between physical properties of rocks and geophysical data [2].

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