Seabed Seismic Techniques: QC and Data Processing Keys

By Mundy Obilor Jim

This book dwells on the fundamentals of seabed seismic in terms of data acquisition, QC and pre-processing. The focus is on receivers placed on the seabed— hydrophones to measure pressure in water (p-waves), geophones or accelerometers to measure vertical particle motion (p-waves) and horizontal particle motion (s-waves). The discussion is mainly on four components (4C) which more or less covers other multi-component seismic techniques. The first three chapters end with a set of exercises that will be of tremendous help within the educational environment.

• Language: English
• Publisher: BookBaby
• Release date: Feb 7, 2013
• ISBN: 9788299890670

Book preview

Environment

Chapter 1

General Perspective

The oil and gas exploration and production companies are continually seeking to recover reserves or hidden oil from areas that are difficult to access or from reservoirs that have proved more difficult to image, or even from areas that conventional seismic methods have been productively engaged. As these companies are mapping out strategies to tap more oil from existing fields, the technological methods involved are also changing and improving dramatically. Seabed seismic has seized the geophysical industry's fancy since its semi-commercial emergence in the North Sea in the autumn of 1996.[1].

Introduction

The objective of seabed seismic is to record both P-wave and PS converted wave data on the seabed. These mode converted records have proven to be very useful in seismic imaging. As an example, mode-converted shear-wave data and of course, better P-wave data acquired on the seabed allow for imaging where it is difficult in conventional seismic due to the presence of shallow gas and/or fluid in the pore spaces within rocks.

Notably, the ray path of mode-converted shear waves differ from the ray path of compressional waves. This provides a better imaging of the sub-surface target of interest; and since the P-wave and S-wave record independent measurements of the same subsurface, better images and rock properties can be uniquely ascertained. These often allow for improved reservoir characterization and lithology prediction. However, while seabed seismic data are generally of better quality than streamer data in the above regard, proper coupling of the sensors on the seabed and PS wave matching and separation, among other processes, are some of the challenging tasks during and after the data acquisition. Some of these tasks are treated in chapter 3.

How it all started

In the late 1980s, The SUMIC (SUbsea seismic) technique was developed by the Norwegian operator, Statoil. It is a method whereby both shear waves and pressure waves were recorded by sensors fitted in the seabed (Berg et al. 1994). A prototype SUMIC sensor array was developed in 1992 and quite a number of acquisition tests were carried out in the Norwegian North Sea sector a year later. The surveys were 2D tests with the objective of imaging subsurface structure through gas chimneys. Over three decades down the line, a lot of improvements have been recorded in seabed seismic. As at 2009, Statoil alone has performed 62 ocean-bottom seismic surveys, beginning with a Gullfaks trial in 1989 and the resulting data produced better imaging and feature resolution"(E&P,

Reviews for Seabed Seismic Techniques

[Edgar Manik · Rating: 5 out of 5 stars]

This is great introduction book for ocean bottom technology. Easy to read, and very informative.