3-D, 4-D and Beyond

Abstract

Abstract Oil and gas exploration in the Gulf of Mexico (GOM) has benefited tremendously by the application of 3-D technology. By many measures --- CMP-km, sq., expenditures, number of multi-streamer vessels, to name a few --- 3-D coverage has increased dramatically over the past 15 years in the GOM. Today, in the GOM, 3-D seismic is the norn. There are two fundamental reasons for this, both related to technology. First, technical enhancements in acquisition, processing, and interpretation have reduced the costs of 3-Dseismic and second, technical advances have proven their worth in improved imaging, better delineating traps, and providing more reliable and higher resolution geologicmodels. This paper first examines the evolution of 3-D technology in the Gulf of Mexico and some of its ramifications. I will review several key technologies in the area of acquisition, processing, and interpretation that have evolved over the past decade. Secondly, I will address the current status and nearterm future of 3-D technology and other new technologies bylooking at such issues as turnaround time, cost, on-board processing, data compression and transmission, 3-D pre-stack depth migration, multi-streamer, multi-boat, and oceanbottom acquisition. Lastly, I will examine several new and forthcoming technologies and issues that will likely impactfuture exploration in the GOM, including sub-salt and deepwater exploration, reservoir monitoring, long-offsets, multiazimuth acquisition, and vertical-cable technology. Introduction The use of 3-D seismic data has received an extraordinary amount of attention in the recent years for its impact on hydrocarbon exploration and development in the Gulf of Mexico and elsewhere in the world. Indeed, it is hard to imagine the oil industry today without 3-D data. One indication of the dramatic growth of 3-D data is shown in Figure 1. This figures compares 3-D speculative and multiclient (Le. pre-funded non-exclusive) 3-D data coverage between 1990 and the beginning of 1996 in the GOM area south of Louisiana. It is easy to see that even in the past fiveyears alone, the amount of 3-D coverage in the Gulf of Mexico has increased many times over. In fact, much of the area shown has more than one 3-D survey covering it. The dramatic growth of exploration activity in the Gulf of Mexico over the past couple of years has been fueled by two main items:relatively stable and high oil and gas prices andtechnology advances that have contributed to lower costs and improve image quality and accuracy. It is this technology that I want to focus on in this paper. I will begin by examining some of the key technical advances in the areas of acquisition, processing, and interpretation that have led tothe current state of 3-D exploration. Next I will examine some of the recent technical developments and their impact on exploration and production. And finally, I will look at the longer tenn future and offer my speculations on what we might see in the next five to ten years. As oil and gas exploration continues to mature in the GOM, we as geophysicists, must continue to evolve in our role and the application of geophysical tools. To address this area, we can classify our current and future roles into three phases: exploration, reservoir characterization, and reservoir monitoring. Exploration is what most geophysicists know ow to do best and it includes the traditional steps of acquisition, processing, and interpretation. Reservoir characterization is taking the seismic information, and any other information, and inferring lithologic properties of the reservoir and leads to, among other things, reservoir modelssuitable for reservoir simulators. I include in this category such techn