First Break - Volume 31, Issue 1, 2013

Ruud Weijermars quantifies the major risks in the economic appraisal of shale gas projects. Sensitivity analyses of well roll-out rate scenarios in emergent shale plays show which field development strategies deliver the highest return on investment at the lowest cost of capital.

Malcolm Lansley describes the remarkable technological advances in land seismic that have paved the way for improved ways to design surveys and record data. The result has been a number of paradigm shifts in our understanding of the optimum ways to acquire data.

Michael L. Abrams and A. Keith Elder provide a detailed analysis of the effective dynamic range of land seismic equipment along with some misconceptions.

Zhouhong Wei and Thomas F. Phillips discuss the key factors limiting a vibrator’s highfrequency performance in land seismic acquisition and offer some solutions based on evaluation of each element in the vibrator system.

There is new and growing enthusiasm for hydrocarbon exploration in the Barents Sea after three recent discoveries: Skrugard, Havis, and Norvarg. We demonstrate how using wide-azimuth 3D controlled-source electromagnetic (CSEM) and 2D seismic data together can improve the identification of prospective areas in the region. An interpretation workflow is presented to show how the challenging resistivity background in the Barents Sea is handled. To do this, we introduce a new inversion attribute called the anomalous vertical resistivity. The inversion attribute is co-visualized with 2D seismic data and used to estimate recoverable reserves. The workflow is illustrated on both synthetic and real data for the Skrugard and Havis discoveries. Both discoveries are identified on CSEM maps and by integrating CSEM data with seismic data. In addition, a new lead is identified. We show that CSEM data carries structural information and that the horizontal resistivity trends can be used with 2D seismic data and well logs to interpret the distribution of good-quality sands. Hydrocarbon reserve calculations based on the 3D CSEM data for the Skrugard and Havis discoveries have P50 values consistent with the publicly available reserve estimates. The reserve estimate for the new lead also shows significant potential.

Seismic signal processing often involves the use of various data transforms. The concept of a transform is reviewed along with the notion of orthogonality, which is one of the main properties that make many transforms useful in segregating different parts of the input signal from each other. In addition, digital sampling of underlying continuous functions induces artefacts in the transforms, which are related to the sampling process itself. The nature and origin of these artefacts are described.