RIASSUNTO
Abstract
Ocean Bottom Cable (OBC) seismic survey has several technical advantages over conventional towed streamer technique. However, its usage is still limited as requirement of relatively large operational efforts likely results in more survey cost and duration. Moreover, OBC seismic operations could affect other field activities and multi-vessel operations required for OBC survey and longer survey duration potentially increase HSE risks in fields.
Consequently, enhancement and optimization of OBC survey productivity is essential particularly in specific situations such as shallow water, congested producing oil/ gas fields (e.g. Offshore Abu Dhabi) and in environmentally restricted areas.
Although several studies have been carried out to establish key parameters, designs and geometries for high OBC survey productivity, the current developments in the seismic industry technology and equipment are enabling to establish a variety of survey designs and geometries which were not feasible previously. Therefore, our study was conducted with the aim to analyze the impact of OBC Survey Designs / Geometries on productivity considering the current available equipment and technology and meeting the established geophysical survey objectives.
Applications of dual source operations were also discussed by using two cases: (1) Distanced Separated Simultaneous Shooting (DS3); and (2) Dual Source Vessel Flip-Flop Shooting (DSVFFS). Dual source operations for both marine streamer and land cases have been well described whereas few examples of its applicability to OBC survey have been presented. In this paper, we described the impact of dual source operations on OBC survey efficiency and technical challenges determined from the relationship between OBC Survey Geometries/Designs and interference noise wave fields which have to be considered as more complex scenario than other types of surveys.
We believe that the established new approach will assist to acquire future OBC survey with high productivity and in a very cost effective manner.
Introduction
Although significant, recent developments in marine towed streamer acquisition have occurred, OBC techniques still need to be considered as OBC surveys enables the acquisition of wide azimuth and high fold datasets having long offsets and less spatial discontinuities (Bouska, 2008 and Kim, 2011). OBC acquisition has been proven as an effective tool in shallow water environments and highly congested area, e.g., offshore Abu Dhabi. Inevitably, the business aspects of the acquisition; time and cost, are often regarded as the determining factor for the type of acquisition employed. In general and where applicable, the towed streamer technique is still the preferred business option. Therefore, further improvement of survey efficiency is crucial to narrow the business gap with towed streamer acquisition and enhance widespread applicability of OBC techniques. Additionally, since OBC surveys tend to take longer than towed streamer surveys, there is more exposure to in-field operations, such as drilling, production, and facilities maintenance. In some fields, seasonal biological activities need to be considered: migrations of whales, sea turtles, fish etc. Continued improvement in OBC surevy productivity leads to continued minimization of exposure to other in-field activites and HSE risks.