First Break - Volume 28, Issue 3, 2010

Mohammed N. Alfaraj, Ming-Ren Hong, Saleh A. Al-Dossary, Jinsong Wang, and James L. Rice of Saudi Aramco argue that wavelets extracted solely on the basis of seismic-data statistics with no regard to well information are inferior than when well data is used, and shall therefore be excluded from any quantitative seismic interpretation techniques.

Claudio Turrini and Glen Burridge advocate a Google Earth flying view over geological structures to gain extra insight and to prove their point provide a guided tour across the Alps from northern Italy to Switzerland.

Kevin Sherwood, Jostein Lima, Sverre Brandsberg-Dahl and Tim Bird of Petroleum Geo-Services (PGS) describe the development of a real-time velocity model-building solution around three core technologies: visualization, model building and workflow.

Geoffrey A. Dorn describes the road ahead for 3D visualization for the geosciences in the E&P industry from being a tool focused mainly on allowing the user to view integrated data in 3D to one which enables the interpretation of the data in 3D.

Michael S. Zhdanov, Evgeny P. Velikhov, Martin Čuma, Glenn Wilson, Noel Black and Alexander Gribenko argue that the key to deriving a reliable quantitative interpretationfrom marine controlled-source electromagnetic (CSEM) data is through the integration of shared earth modelling and robust 3D CSEM inversion. An iterative migration method for CSEM data is presented that is equivalent to rigorous inversion, illustrated with a case study of the Shtokman gas field in the Barents Sea.

Secondary microbial methane is a terminal product of anaerobic petroleum biodegradation. It is possible to recognize such gas in subsurface using geological (e.g., association with biodegraded oils in the same or deeper reservoirs) and geochemical (e.g., ‘dry’ hydrocarbon composition with δ13C of methane from -40‰ to -55‰ and often positive δ13C of CO2) evidence. Occurrences of secondary microbial methane formed during petroleum biodegradation have been documented in oil, gas, and gas hydrate accumulations in >20 basins around the world (e.g., in San Joaquin, Los Angeles, Carnarvon, South Caspian, and other basins, Fig. 1).

The US Geological Survey (USGS) recently assessed the undiscovered, conventional, technically recoverable crude oil, natural gas, and natural gas liquids resources in potentially petroliferous basins north of the Arctic Circle. The assessment of the Yenisey-Khatanga Basin was part of this project and is presented to exemplify the USGS assessment process. This presentation describes the geology of the Yenisey-Khatanga Basin, the USGS methodology used to assess undiscovered petroleum resources, and provides the results of this assessment.

The Barents Sea Basin is the greatest sedimentary basin of the Arctic. The geology of the basin is quite well investigated by geophysics and deep wells. Geological history of the basin gives very good potential for substantial hydrocarbon field formation. But significant vertical movement and erosion in the last stages of geological history have probably destroyed some oil fields. Modelling of the burial history, hydrocarbon generation, and migration was done for the East Barents Sea region to determine the location of potential oilfields (Fig.1). Flexural modelling of recent vertical movement was done to explain erosion and the destruction of oilfields.

Geoffrey A. Dorn описывает опережающий способ трехмерной визуализации для наук о земле в поисково-разведочной отрасли на основании того, что, будучи сконцентрированным, главным образом, на предоставлении возможности пользователю рассматривать интегрированные данные в трехмерном пространстве, он позволяет проводить интерпретацию данных в трехмерном пространстве.

We demonstrate, using synthetic and real data, how simple symmetry properties of marine controlled source electromagnetic data can provide useful information about the main resistivity discontinuities below the seafloor. Our method can be used directly for detecting resistive bodies, such as mineralized reservoirs or geological discontinuities, and for improving inversion performance. We define an asymmetry attribute for the magnitude or phase of the inline electric field responses for source positions on either side of fixed receiver stations. The asymmetry attribute quickly provides a preliminary model of resistivity discontinuities that can be refined by modelling and inversion. Moreover, symmetry properties provide a constraint for speeding up the inversion itself. This integrated approach of spectral analysis of symmetry, using different frequencies and offsets, combined with modelling and inversion, is an effective methodology for localization of resistivity bodies, such as mineralized reservoirs. In contrast, the real data case demonstrates that direct inversion of CSEM data without a proper initial model can lead to an incorrect solution that is inconsistent with seismic and well information.

Discontinuities are an important feature of rock and rock mass. They control the hydraulic properties by connected fracture networks and also govern the mechanical behaviour. Rock fracture mechanics is the explicit analysis of fracture propagation. Fracture mechanics is based on physical principles, rather than empirical relationships as employed in classical rock mechanics. Here the basic relations and laboratory techniques in rock fracture mechanics are summarized and applications of fracture-mechanics-based numerical codes on rock mechanics issues are highlighted, such as borehole stability and hydraulic fracturing. Nowadays, the propagation of fractures and generation of fracture networks can be simulated satisfactorily in two dimensions. Outstanding difficulties which are not yet resolved are anisotropic behaviour, extension to three spatial dimensions, and inclusion of realistic fracture sets in the models. The potential of fracture-mechanics-based numerical modelling for meeting challenges in different industries is outlined. Such software tools might help, for example, in analysing the risk of a thermo/hydraulic short circuit in geothermal projects, in identifying the factors influencing borehole instability or sand production in reservoir geomechanics, or in improving hydraulic stimulation campaigns to optimize the connection of an existing fracture network to the wellbore.