The ConocoPhillips Norway, Reservoir Characterization section performed a 2D OBC seismic test over the Ekofisk field in September, 2002. This test involved using Input/Output’s recently developed VectorSeis® system based on their proprietary MEMS (Micro-Electro- Mechanical Systems) accelerometer technology. A single 2km prototype cable was developed for this test, resulting in the first deployment of the VectorSeis sensor in a marine field environment. The objective of this test was to evaluate the feasibility of using these new sensors to improve imaging in future OBC work at Ekofisk.
Previous OBC surveys in the Ekofisk area demonstrated poor vector fidelity of the three vector component geophones, yielding an inaccurate representation of the recorded vector wave field.
We examine the differences and similarities between the two common categories of wave-equation migration by looking at their mathematical formulations and examining their imaging results. We compare different implementations of shot profile and double square root downward continuation imaging in the context of the overall imaging challenge, including image accuracy, velocity model building, and the ability to generate prestack gathers. We examine the strengths and advantages of the methods by considering the approximations that go into them, the resulting images, and the relative costs of the methods.
The challenges of exploration in increasingly complex geological areas has led to increased industry interest in wave-equation depth migration methods (Bevc and Biondi, 2002; Ritchie, 2003).