Genome diversity in Ukraine.

BACKGROUND: The main goal of this collaborative effort is to provide genome-wide data for the previously underrepresented population in Eastern Europe, and to provide cross-validation of the data from genome sequences and genotypes of the same individuals acquired by different technologies. We collected 97 genome-grade DNA samples from consented individuals representing major regions of Ukraine that were consented for public data release. BGISEQ-500 sequence data and genotypes by an Illumina GWAS chip were cross-validated on multiple samples and additionally referenced to 1 sample that has been resequenced by Illumina NovaSeq6000 S4 at high coverage. RESULTS: The genome data have been searched for genomic variation represented in this population, and a number of variants have been reported: large structural variants, indels, copy number variations, single-nucletide polymorphisms, and microsatellites. To our knowledge, this study provides the largest to-date survey of genetic variation in Ukraine, creating a public reference resource aiming to provide data for medical research in a large understudied population. CONCLUSIONS: Our results indicate that the genetic diversity of the Ukrainian population is uniquely shaped by evolutionary and demographic forces and cannot be ignored in future genetic and biomedical studies. These data will contribute a wealth of new information bringing forth a wealth of novel, endemic and medically related alleles.

Laws and principles governing fluid flow in porous media.

Currently, it is impossible to imagine the petroleum industry without utilising numerical simulation methods for reservoir analysis and production. Investigating the petroleum reservoir performance calls for a comprehensive understanding of the physical processes that govern flow transport in porous media. Irrespective of the goals of the analysis whether pertaining to core investigations, reservoir simulation and planning of enhanced recovery methods, flow processes obey the same physical laws. In this paper, the basic laws and principles describing fluid flow and flow patterns manifesting in subsurface porous media are discussed. Appreciating the applicability and limitations of the physical laws allows us to develop and employ modelling methods for flow behaviour analysis and reservoir performance prediction which is the main goal of petroleum engineering. Concluding, we present the black-oil model, the compositional model and the complex models as applied to petroleum field applications.

New insights from shale gas production at the microscopic scale.

Until recently, natural gas encountered in tight shales, which provided the source and seal of the gas, was considered uneconomical to produce. Although unconventional formations may be as porous as other reservoir rocks, their exceedingly small pore sizes and low permeability render them resistant to gas movement. Considering their importance to gas transport, we outline the characteristics of shale rocks, the mechanisms of Fickian and Knudsen diffusion as well as Klinkenberg's permeability. Given the challenges in unlocking natural gas from tight formations, various techniques such as the generation of artificial fractures and the introduction of pressurised fluids are detailed. To identify the parameters which govern natural gas production, we propose a computational porous rock model inspired from an actual image of a shale formation. The solution of the conservation of mass, momentum and energy equations appear to adequately capture the physics of gas transport at the microscopic level. Permitting the comparison between numerical and analytical gas velocity results, the validation framework we developed, demonstrates good agreement of numerical with theoretical findings. Gas pressure and velocity results point to the importance of pore throats, shale permeability and pressure maintenance in dislodging gas from the shale formations.