Introduction to the Seismic Exploration (original) (raw)

Land & Marine Seismic Data Acquisition from 2D to 3D

2013

The process of acquiring seismic data in the field, from my point of view, is the most important stage in the seismic work because the objective most common to all surveys is to obtain clean reflections free of interference from noise, other wave types and multiple events. Both processing and interpretation stages are very important and play a great role in the detection of subsurface structures but they depend on the quality of acquired data in the field and the observer report. This thesis is composed of two chapters that consist of many aspects of seismic data acquisition involving seismic survey designing and various seismic acquisition techniques. Starting from the introduction to the seismic reflection method (pre-acquisition) in chapter 1, in this chapter, I tried to give a brief introduction about the reflection method and some difficulties facing us in the field. Also, I preferred to discuss in semi-detail some important geologic risks followed by seismic risks and uncertainties which are considered the most important element in this chapter. In briefly, most of these geologic risks relate to petroleum system such as is there source rock or not? Migration path or not? Seal or fractured seal? So the recognition of the uncertainties in the estimation of geological risk; this is the concern of the geologist within us. But the concern of the geophysicist within us is the recognition of the seismic risk. Seismic risks are associated with many aspects such as cost, line spacing, location error, seismic noise, seismic velocity particularly with a salt swell, dipping structures, inadequate resolution,....etc. At the end of this chapter, I studied some important concepts such as reflection zone, reflection and transmission at normal incidence. The next chapter deals with modern seismic data acquisition. This chapter is classified into two parts; land Seismic data acquisition and marine seismic data acquisition. In the first part of land seismic data acquisition, It was necessary - at the discussion of seismic data acquisition - to refer to reflection field equipment where I described seismic sources, seismic receiver and recording systems. As well I have included the seismic array design and array geometries in this part. after that, I have given a detailed description of the various techniques of seismic acquisition that include 1D, 2D, 3D and 4D surveys designing. It was worth to study the importance of these various techniques and their applications, particularly with 2D and 3D. In the second part of marine seismic data acquisition, I focused on the types of marine seismic surveys that involve towed marine seismic methods (2D, 3D). As a result of insufficient data quality obtained from conventional towed streamer acquisition for cost-effective field development, it was necessary to discuss the advanced acquisition techniques that provide an improved signal-to-noise with the ratio of the resulting seismic data, and Ocean Bottom Techniques that generate areal array shots quite easily. With regard to recording data on the sea floor, autonomous nodes have recently been used commercially for performance this purpose. At the end of this report, I dealt with the most complex and challenging area of seismic acquisition that is known as Shallow water or transition zone (SW/TZ) acquisition and how to record data in these zones.