Challenges in Sea-Bottom Seismic

Abstract

Abstract Seismic technology, in the oil and gas industry, has been so far essentially limited to exploration applications. Recent developments in both acquisition and data processing have opened up new domains of application which now make it possible to use seismic methods in the context of reservoir characterization, development, and eventually management. This new capability will provide timely and adequate answers to asset managers when confronted with critical decisions to be made in terms of production optimization, additional drilling, fluid injection strategy and monitoring. This paper describes the recent developments in seismic technology that are particularly relevant in this context, and further focuses on the offshore and subsea applications of these methods where, given the tough economics of deep water production, they will significantly contribute to costs and risks reduction. Introduction Today, decision-making, in terms of reservoir management, is largely based on well data : logs, well testing, MWD, production data etc. The tool box is extensive, sophisticated, increasingly reliable and accurate. However the depth of investigation of these different techniques is limited to the immediate vicinity of the borehole, down to a few centimeters for log data. From these extremely discrete elements, a full reservoir image has to be drawn, in terms of size and geometry, fluid contents, static and dynamic rock properties. At the exploration and appraisal phases, seismic acquisition has already greatly contributed in bridging the inter well gaps and giving greater confidence as to the overall picture. 3D acquisition, now totally standard, has constituted a major step in this respect. Integration models have been developed which merge all the available data into a reasonably acceptable reservoir model. However, nasty surprises do still regularly occur, either at the development stage or during the field production life, and cast doubt on the validity of the models, leaving the asset manager with decisions to be made with more risks attached than ideally desirable. Recent developments in the seismic industry, both at acquisition and processing levels, including multi-component recording and time lapse acquisition, are likely to provide a vastly enhanced capability in the domain of reservoir characrterization both from a static and eventually dynamic point of view and therefore turn it into a very useful production tool. They should furthermore possibly revolutionize methodologies and work practices by bringing together people and disciplines. Multidisciplinarity is the key to this approach. These technologies will be applied both on land and offshore. However, for a number of reasons, offshore and particularly deep water environments present a number of specific difficulties as well as potential and opportunities that are intrinsic, and worth considering as such. Among others, in terms of potential and opportunities, the economic value of these innovations to the asset manager, will be measured against the risks and costs attached to deep water development and production. The reward in terms of drilling cost or barrels additionally recovered will dwarf the expense attached to the application of these new technologies.