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38 Maritime Reporter & Engineering News Offshore Technology Annual The search for oil and gas is a challenge that carries a high financial risk. Wells may cost more than $50-70 million each and be drilled to nearly six miles below the ocean's surface. In the early days of energy explo- ration, discoveries were often a matter of luck. Even today, the U.S. Energy Information Administration estimates 13% of all holes drilled in the U.S. do not find commercial quantities of oil and gas (down from 37% in 1973). Advanced geophysical and geological tools such as three-dimensional seismic imaging, sophisticated well-logging tools and techniques, com- puter-based petrophysical analysis, and paleontology reduce the risk associated with locating oil and gas reserves. In the past, geoscientists had to rely on two-dimen- sional seismic data interpretation to define potential hydrocarbon prospects. The images scientists assem- bled were useful, but less than complete. Today, how- ever, advanced three-dimensional seismic data are pro- viding a more detailed understanding of a prospect. Seismic data are obtained by using hydrophone or geo- phone receivers. These receivers record the time it takes for a signal or sound wave (caused by an air pulse) to travel from the source to the receiver. As the signal or wave travels, it reflects off the layered sedi- ments it encounters and returns to the receiver. The source and receiver are then moved in a grid pattern across an area as the process is repeated. The data generated through this method are then processed to yield a three-dimensional image or "pic- ture" that represents the subsurface strata and geologic features (faults, salt domes, etc.) in the area of investi- gation. By estimating the velocity of sound through the various subsurface strata and the travel time of the sig- nal from the source to the receiver, the depth to a par- ticular reflector can be estimated. Geoscientists then translate the seismic data into maps, cross-sections, and three-dimensional models of potential hydrocar- bon accumulations or prospects. In the evaluation of a new lease block, exploratory wells may be drilled to test subsurface strata and struc- tures for potential hydrocarbon accumulations. Logs obtained from these exploration wells (see figure on page 3) provide information that can enhance the three-dimensional seismic picture of the area. Well logs are continuous recordings of specific physical properties of the subsurface strata encountered during drilling of an exploratory well. Such logs may be obtained by wireline logging, which consists of lower- ing a logging tool into a well and recording data as the tool is raised from the bottom of the well. Logs can Searching for Oil and Gas Prospecting With New Tools CONFERENCE PARTNERS: Conference Program leading voices of the maritime industry LEADING VOICES Nor-Shipping has introduced an innovative new conference concept for the 2005 exhibition. Developed in cooperation with key partners to help strengthen the exhibition’s role as one of the world’s essential maritime events, the Nor-Shipping exhibition will feature the industry’s most dynamic and comprehensive conference programme in 2005. In addition to a broad range of seminars hosted by influential maritime publications and maritime organisations, Nor-Shipping is pleased to announce the participation of some of shipping’s leading voices to address key issues facing the industry today. For more details, please visit www.nor-shipping.com OF THE MARITIME INDUSTRY - OSLO, NORWAY 7-10 JUNE 2005 Andreas Sohmen-Pao Managing Director of World-Wide Shipping. Deputy Chairman of Bergersen D.Y ASA Børge Brende The Norwegian Minister of Trade and Industry Mrs Lim Hwee Hua Singapore´s Minister of State for Finance and Transport Bjørn Møller Director, President and CEO of Teekay Shipping Wilhelm Wilhelmsen Chairman of Wilh Wilhelmsen ASA Michael Savory Lord Mayor of London Circle 272 on Reader Service Card MR APRIL 2005 #5 (33-40).qxd 4/1/2005 4:27 PM Page 6
