Back to the Future in Depth Imaging, One Company's Perspective
Authors: McElroy M.N. , Wyatt K.D. 
Published: October 2008

Abstract
By the mid 1980's it was very clear to the petroleum industry that most of the "easy to find" oil had disappeared. The industry was increasingly investing it's resource into oil exploration in more demanding and complex geological areas. At the same time, the industry was anxiously anticipating rapid increases in computing power. Those in the industry that had the foresight to begin developing the seismic 3D, prestack depth (PSDM) imaging technology that could be realized with this new power were able to kick-start their ability to explore in these complex geological areas. One of the first areas where this technology was successfully applied was in the Gulf of Mexico subsalt play. In retrospect, the press related to this activity may have been a bit overdone;. nevertheless, the improvements in the seismic images were indeed remarkable in many cases. But it should always be remembered that the results of all of this high technology only allows interpreters to ‘build prospects’ which contain the same inherent risks associated with ‘traditional’ prospects. Our maturity in the ability to effectively apply this technology has grown appreciably in the past few years and its usefulness has extended to many other significant exploration plays such as in the North Sea, offshore West Africa, and others. So too, however, has our understanding of the limitations of this technology. It is well recognized that much work has yet to be done, such as proper handling of amplitudes and anisotropy and improvements in how we build our velocity models. The future holds exciting promises, too, in going beyond our current PSDM technology to being able to image with the full wave equation, and the ability to image with converted shear waves. We anticipate that the computing power, new acquisition technologies, and improved visualization hardware and software will help lead us towards success in realizing many of our most ambitious dreams in advanced seismic imaging of the geology in the next ten years.

INTRODUCTION
In September of 1993, Phillips, Anadarko Petroleum Corp., and Amoco Production Corp, announced discovery of the Mahogany Field, the world's first commercial subsalt play. Seismic depth imaging technology was cited as a major factor in the success of this find. Imaging the earth beneath the large salt sheets in the Gulf of Mexico was extremely difficult due to the distortion of the seismic waves as they pass through the salt. With the advent of advanced seismic imaging technology such as 3D prestack depth migration, geoscientists were able to take their first peek at potential hydrocarbon traps beneath the salt. Though the press related to this activity may have been a bit overdone, the improvements in the seismic process are remarkable and have most certainly contributed to successful exploration in complex areas. Nearly five years later, we have an opportunity to reflect (no pun intended) on this technology and examine where we are today, what lessons we have learned, what challenges remain, and perhaps to predict where the future will take us.