A New System for Three-Dimensional High-Resolution Geophysical Surveys

Abstract

High-resolution geophysical surveys have been used for some time to reduce risk from the installation of fixed platforms offshore. They have been used primarily in relatively shallow water for the placement of fixed, freestanding oil and gas platforms. However, their relevance has changed with the advent of offshore wind farms and the need to understand the underlying geology. Furthermore, the Deepwater Horizon accident has shown that these data are essential to any structure attached to the seabed, not just those that are rigidly fixed. The development of accurate acquisition techniques reduces the uncertainty and increases the effectiveness of these surveys (RenewableUK, 2011). Adapting conventional exploration survey acquisition techniques to high-resolution surveys allows the use of precise positioning systems and robust operational equipment. The result is a three-dimensional (3D) high-resolution (HR3D) survey similar in the visualization offered by conventional seismic surveys but with much higher spatial resolution. The HR3D technique presents some physical challenges in the design of the acquisition system. However, the same technique offers some advantages that simplify engineering. Engineering and adaptation of larger-scale geophysical equipment is straightforward. Furthermore, some methods not viable for use in the exploration survey industry have a use in this application. A series of trials in late 2010 and early 2011 allowed the development of the system with individual focuses on the physical, navigation, and geophysical aspects of the system. A production survey was acquired in June 2011. Results from this survey show the advantages of this technique.