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Schlumberger Limited is the world's largest oilfield services company. Schlumberger employs approximately 120,000 peoplerepresenting more than 140 nationalities working in more than 85 countries. Its principal offices are in Houston, Paris, London, and the Hague. Wikipedia.

Horne S.A.,Schlumberger
Geophysical Prospecting | Year: 2013

Mudrocks, defined to be fine-grained siliclastic sedimentary rocks such as siltstones, claystones, mudstones and shales, are often anisotropic due to lamination and microscopic alignments of clay platelets. The resulting elastic anisotropy is often non-negligible for many applications in the earth sciences such as wellbore stability, well stimulation and seismic imaging. Anisotropic elastic properties reported in the open literature have been compiled and statistically analysed. Correlations between elastic parameters are observed, which will be useful in the typical case that limited information on a rock's elastic properties is known. For example, it is observed that the highest degree of correlation is between the horizontal elastic stiffnesses C11 and C66. The results of statistical analysis are generally consistent with prior observations. In particular, it is observed that Thomsen's e{open} and γ parameters are almost always positive, Thomsen's e{open} and γ parameters are well correlated, Thomsen's δ is most frequently small and Thomsen's e{open} is generally larger than Thomsen's δ. These observations suggest that the typical range for the elastic properties of mudrocks span a sub-space less than the five elastic constants required to fully define a Vertical Transversel Isotropic medium. Principal component analysis confirms this and that four principal components can be used to span the space of observed elastic parameters. © 2013 European Association of Geoscientists & Engineers. Source

Sayers C.M.,Schlumberger
Geophysics | Year: 2013

The elastic properties of reservoir rocks are important for geomechanics applications; the most important of which are: analysis of stress changes due to production, analysis of rock deformation and failure, wellbore trajectory optimization, and the design of hydraulic fractures. Organic-rich shales are often observed to be strongly anisotropic due to the partial alignment of anisotropic clay minerals and the beddingparallel lamination of organic material within the shale. Neglecting shale anisotropy may lead to incorrect estimates of the in situ stress or stress changes resulting from production. As a result, isotropic models may fail to describe geomechanical behavior correctly. The distribution of the organic phase plays an important role in determining the elastic properties of organic-rich shales, and this has a significant effect on production-induced stress changes. The presence of kerogen leads to a decrease in all of the elastic moduli, and has a significant effect on the geomechanical behavior of shales. The change in horizontal effective stress for a given change in pore pressure resulting from production is greater for kerogen-rich shales, and the neglect of anisotropy in predicting such stress changes may lead to significant errors. © 2013 Society of Exploration Geophysicists. Source

Rickett J.,Schlumberger
Geophysical Prospecting | Year: 2013

This paper compares three alternative algorithms for simultaneously estimating a source wavelet at the same time as an earth model in full-waveform inversion: (i) simultaneous descent, (ii) alternating descent and (iii) descent with the variable projection method. The latter is a technique for solving separable least-squares problems that is well-known in the applied mathematics literature. When applied to full-waveform inversion, it involves making the source wavelet an implicit function of the earth model via a least-squares filter-estimation process. Since the source wavelet becomes purely a function of medium parameters, it no longer needs to be treated as a separate unknown in the inversion. Essentially, the predicted data are projected onto the measured data in a least-squares sense at every function evaluation, making use of the fact that the filter estimation problem is trivial when compared to the full-waveform inversion problem. Numerical tests on a simple 1D model indicate that the variable projection method gives the best result; actually producing results in quality that are very similar to control experiments with a known, correct wavelet. © 2013 Schlumberger Cambridge Research Ltd. Source

Mullins O.C.,Schlumberger
Annual Review of Analytical Chemistry | Year: 2011

Asphaltenes, the most aromatic of the heaviest components of crude oil, are critical to all aspects of petroleum utilization, including reservoir characterization, production, transportation, refining, upgrading, paving, and coating materials. The asphaltenes, which are solid, have or impart crucial and often deleterious attributes in fluids such as high viscosity, emulsion stability, low distillate yields, and inopportune phase separation. Nevertheless, fundamental uncertainties had precluded a first-principles approach to asphaltenes until now. Recently, asphaltene science has undergone a renaissance; many basic molecular and nanocolloidal properties have been resolved and codified in the modified Yen model (also known as the Yen-Mullins model), thereby enabling predictive asphaltene science. Advances in analytical chemistry, especially mass spectrometry, enable the identification of tens of thousands of distinct chemical species in crude oils and asphaltenes. These and other powerful advances in asphaltene science fall under the banner of petroleomics, which incorporates predictive petroleum science and provides a framework for future developments. Copyright © 2011 by Annual Reviews. All rights reserved. Source

Mullins O.C.,Schlumberger
Energy and Fuels | Year: 2010

Asphaltenes, the most aromatic of the heaviest components of crude oil, are critical to all aspects of petroleum use, including production, transportation, refining, upgrading, and heavy-end use in paving and coating materials. As such, efficiency in these diverse disciplines mandates proper chemical accounting of structure-function relations of crude oils and asphaltenes, the vision of petroleomics (Asphaltenes, Heavy Oils and Petroleomics; Mullins, O. C., Sheu, E. Y., Hammami, A., Marshall, A. G., Eds.; Springer: New York, 2007). Indeed, the molecular characterization of asphaltenes is required as well as the detailed understanding of the hierarchical colloidal structures of asphaltenes and petroleum. With great prescience, Professor Teh Fu Yen and co-workers proposed a hierarchical model of asphaltenes to account for many of their characteristics known at that time (Dickie, J. P.; Yen, T. F. Macrostrucutres of asphaltic fractions by various instrumental methods. Anal. Chem. 1967, 39, 1847 -1852). This model is rightfully known as the Yen model. Nevertheless, at the time the Yen model was formulated, there were many order-of-magnitude uncertainties in asphaltene science that precluded establishing structure-function relations and causality, thereby rendering the Yen model somewhat phenomenological. Petroleum science has advanced greatly in recent years enabling development of a much more specific model yet still based on precepts of the Yen model; we call this the "modified Yen model". The modified Yen model is shown to account for wide ranging, myriad properties of asphaltenes, including their dynamics. In addition, the modified Yen model has even proven successful for understanding interfacial phenomena involving asphaltenes. Moreover, the modified Yen model accounts for fundamental observations in oil reservoirs and is now propelling significantly improved efficiency in oil production. The modified Yen model is a simple, yet powerful construct that provides the foundation to test future developments in asphaltene and petroleum science; refinement of the modified Yen model is an expected outcome of this process. © 2010 American Chemical Society. Source

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