First Break - Volume 27, Issue 6, 2009

In the United States, European Union, and Asia fears about dependence on oil and gas imports from unstable regions have become a major theme of political debate. Daniel Litvin* argues that current policy responses to this challenge are focused on broad-brush measures such as reducing energy demand and strengthening military or diplomatic alliances with oil-producing regions. Comparatively little attention is devoted to the ‘self-fuelling fire’ that underlies the problem.

Ruud Weijermars introduces the concept of a clockspeed accelerator* as an analysis tool for optimizing the development of global oil and gas resources in a market currently characterized by intense competition between various ‘Oils’ and in the longer term threatened by growth of alternative energy sources.

Jim Hannon, managing director of UK based industry consultants, Hannon Westwood, was invited by the Geological Society recently to argue against the motion that the UK North Sea was finished as an exploration province. This is an abridged version of his robust defence of the North Sea’s remaining potential.

To anyone wondering how service companies are managing the current oil and gas industry downturn, Andrew Gould, chairman and CEO of Schlumberger, speaking at the 37th Annual Howard Weil Energy Conference in March provided a template, first outlining the global energy outlook, and then describing his company’s strategy.

In his year as president and CEO of Petroleum Geo-Services (PGS), Jon Erik Reinhardsen has been presented with the challenge of keeping a notable success story going in increasingly difficult economic circumstances. Andrew McBarnet reports on a recent conversation.

David Eyton, BP’s group head of research and technology (R&T), last month was speaking at Cambridge University, UK and provided these ‘snapshots’ of how the company has harnessed technology to remain one of the world’s largest energy providers.

J. De Wildt, R.K. Oldfield and R. Silva illustrate the use of an Eigenimage filter to attenuate different types of multiples arising from land seismic data acquired in Texas.

A. Barkov, I. Yakovlev, Y. Stein, T. Grechishnikova and B. Webb, discuss the challenges and benefits of reprocessing 3D seismic data acquired on the Shtokman field in the Barents Sea, the largest gas field in Europe.

The single most important parameter for accurate statics corrections is an accurate time model of the weathering, when the replacement statics model is used. Representative seismic velocities in the weathering are generally adequate. The resolution achieved with the generalized reciprocal method (GRM) and the refraction convolution section (RCS) is comparable to that achieved with the delay time method (DTM) together with one application of residual statics. It is proposed that the long wavelength components of the statics represent gross variations in the thickness of the weathered layer, and that the short wavelength components represent variations in the surface soil layers. The head wave amplitudes are inverted to generate a model of the head coefficients. Like the time model, the head coefficient model is separated into a long wavelength component which is representative of the seismic parameters at the base of the weathering, and a short wavelength component representative of the surface soil layers. In the study area, the inhomogeneities in the surface soil layer produce static variations of ±3 ms and ±2 db. It is concluded that the surface soil layer is as important a source of intra-array statics as variations in topography and thickness of the weathered layer.

We demonstrate the ability of the controlled source electromagnetic (CSEM) technique to reveal hydrocarbon reservoirs by reinvestigating the North Sea Troll field with a 3D acquisition grid. Unlike previous applications of 2D CSEM surveys over this field, which have shown a large electromagnetic response over the gas province, the focus in this study is on the thinner and smaller oil reservoir. A weak but consistent anomaly enables detection and delineation of the oil zone and reduces the ambiguity associated with traditional 2D lines. This holds true even for a sparse receiver grid where the target is located between the receiver and source lines. The 3D data show the extent of the oil zone and that it is matched to the top reservoir structural high as well as north-south aligned faults. Variation in magnitude of the anomaly is qualitatively in good correlation with resistivity logs at the well locations. This suggests that 3D CSEM data pave the way for exploration use because of its superiority over 2D data in terms of reduced sensitivity to survey layouts.