Parallel structural interpretation of drill cores and microresistivity scanner images from gas-bearing shale (Baltic Basin, Poland)

2018 ◽  
Vol 6 (3) ◽  
pp. SH25-SH38 ◽  
Author(s):  
Kinga Bobek ◽  
Marek Jarosiński
Keyword(s):  
Striking Difference ◽  
Data Sets ◽  
Fracture Density ◽  
Baltic Basin ◽  
Structural Interpretation ◽  
The Core ◽  
Calcite Veins ◽  
Fracture Intensity ◽  
Core Profile ◽  
Drill Cores

Having access to drill cores and microresistivity scanner images from five shale gas exploration boreholes, we were able to compare the results of structural interpretation based on two data sets. The most frequent structures observed in shale complexes are subvertical strata-bound joints that commonly create calcite veins. We have applied a modified approach for statistical analysis of strata-bound fractures taking into account their height. For comparison of cores and scanner image log structural interpretations, we used the fracture number and fracture intensity parameters. We found significant discrepancies between results of cores and image log interpretations. The much greater number of fractures recognized in the image log than in the core is explained by differences in the observation space related to the core and borehole diameters. To predict which fracture that was visible in the scanner image should be represented in the core, we introduced a “critical angle” parameter and used it in the filtering procedure, which gave satisfactory results. In general, the systematically observed superiority of fracture intensity in the scanner image over the core profile is explained by a large number of tiny noncracked veins that are better recorded by a scanner then are visible by the unaided eye. The most striking difference was found in carbonate-rich formations, in which noncracked veins are more numerous. On the contrary, fracture intensity in intervals enriched in total organic carbon (TOC) is always higher in core than in the scanner image, due to a resistivity enhancement related to gas presence. We also compared a record of en echelon arrays of open fractures that allow us to discriminate enhanced natural fractures from borehole-induced tensile fractures. A major difference in the bedding fracture density between the core and image log we attribute to core relaxation during its extraction to the surface. A tectonic inversion phase was also possible to recognize based on the integrated core and scanner interpretation.

Analyzing the Impacts of Meshing and Grid Alignment in Dual-Porosity Dual-Permeability Upscaling

2021 ◽  
pp. 1-20
Author(s):  
Ziming Xu ◽  
Juliana Y. Leung
Keyword(s):  
Fracture Network ◽  
Fracture Plane ◽  
Fracture Density ◽  
Shape Factors ◽  
Stimulated Reservoir Volume ◽  
Reservoir Volume ◽  
Multiple Length Scales ◽  
Fracture Intensity ◽  
Cumulative Production ◽  
The Difference

Summary The discrete fracture network (DFN) model is widely used to simulate and represent the complex fractures occurring over multiple length scales. However, computational constraints often necessitate that these DFN models be upscaled into a dual-porositydual-permeability (DPDK) model and discretized over a corner-point grid system, which is still commonly implemented in many commercial simulation packages. Many analytical upscaling techniques are applicable, provided that the fracture density is high, but this condition generally does not hold in most unconventional reservoir settings. A particular undesirable outcome is that connectivity between neighboring fracture cells could be erroneously removed if the fracture plane connecting the two cells is not aligned along the meshing direction. In this work, we propose a novel scheme to detect such misalignments and to adjust the DPDK fracture parameters locally, such that the proper fracture connectivity can be restored. A search subroutine is implemented to identify any diagonally adjacent cells of which the connectivity has been erroneously removed during the upscaling step. A correction scheme is implemented to facilitate a local adjustment to the shape factors in the vicinity of these two cells while ensuring the local fracture intensity remains unaffected. The results are assessed in terms of the stimulated reservoir volume calculations, and the sensitivity to fracture intensity is analyzed. The method is tested on a set of tight oil models constructed based on the Bakken Formation. Simulation results of the corrected, upscaled models are closer to those of DFN simulations. There is a noticeable improvement in the production after restoring the connectivity between those previously disconnected cells. The difference is most significant in cases with medium DFN density, where more fracture cells become disconnected after upscaling (this is also when most analytical upscaling techniques are no longer valid); in some 2D cases, up to a 22% difference in cumulative production is recorded. Ignoring the impacts of mesh discretization could result in an unintended reduction in the simulated fracture connectivity and a considerable underestimation of the cumulative production.

High-resolution stratigraphic characterization of natural fracture attributes in the Woodford Shale, Arbuckle Wilderness and US-77D Outcrops, Murray County, Oklahoma

2018 ◽  
Vol 6 (1) ◽  
pp. SC29-SC41 ◽  
Author(s):  
Sayantan Ghosh ◽  
John N. Hooker ◽  
Caleb P. Bontempi ◽  
Roger M. Slatt
Keyword(s):  
Natural Fracture ◽  
Fracture Aperture ◽  
Aperture Size ◽  
Fracture Density ◽  
Area Formula ◽  
Woodford Shale ◽  
Fracture Spacing ◽  
Spacing Ratio ◽  
Fracture Intensity ◽  
Bed Thickness

Natural fracture aperture-size, spacing, and stratigraphic variation in fracture density are factors determining the fluid-flow capacity of low-permeability formations. In this study, several facies were identified in a Woodford Shale complete section. The section was divided into four broad stratigraphic zones based on interbedding of similar facies. Average thicknesses and percentages of brittle and ductile beds in each stratigraphic foot were recorded. Also, five fracture sets were identified. These sets were split into two groups based on their trace exposures. Fracture linear intensity (number of fractures normalized to the scanline length [[Formula: see text]]) values were quantified for brittle and ductile beds. Individual fracture intensity-bed thickness linear equations were derived. These equations, along with the average bed thickness and percentage of brittle and ductile lithologies in each stratigraphic foot, were used to construct a fracture areal density (number of fracture traces normalized to the trace exposure area [[Formula: see text]]) profile. Finally, the fracture opening-displacement size variations, clustering tendencies, and fracture saturation were quantified. Fracture intensity-bed thickness equations predict approximately 1.5–3 times more fractures in the brittle beds compared with ductile beds at any given bed thickness. Parts of zone 2 and almost entire zone 3, located in the upper and middle Woodford, respectively, have high fracture densities and are situated within relatively organic-rich (high-GR) intervals. These intervals may be suitable horizontal well landing targets. All observed fracture cement exhibit a lack of crack-seal texture. Characteristic aperture-size distributions exist, with most apertures in the 0.05–1 mm (0.00016–0.0032 ft) range. In the chert beds, fracture cement is primarily bitumen or silica or both. Fractures in dolomite beds primarily have calcite cement. The average fracture spacing indices (i.e., bed thickness-fracture spacing ratio) in brittle and ductile beds were determined to be 2 and 1.2, respectively. Uniform fracture spacing was observed along all scanlines in the studied beds.

The Stratigraphy of Pre-Tertiary Economic Basement in South Jambi B Block, South Sumatra Basin

2021 ◽  
Keyword(s):  
Significant Contribution ◽  
Fracture Network ◽  
Natural Fracture ◽  
Fracture Density ◽  
The South ◽  
The North ◽  
Fracture Intensity ◽  
Parent Rocks ◽  
Major Fault ◽  
Essential Function

As one of the most promising plays, the Pre-Tertiary basement play holds a significant contribution to the latest success of exploration efforts in the South Sumatra Basin, which then includes the South Jambi B Block. Yet, the natures of the Pre-Tertiary unit in this block remains unsolved. Lithology variability, spatial irregularity, genetic ambiguity, and different reservoir characteristic are indeterminate subjects in the block are the main focus here. The ultimate goals of this study are to better characterize the unit and gain more understanding in calibrating the remaining potential. Based on this study, The Pre-Tertiary units are mainly originated from layered marine-deltaic sedimentary parent rocks with carbonate, intruded by spotty granite where the concentration of each parent rocks varies at the north, the middle, and southern part. Secondly, both lithology heterogeneity and natural fracture density create distinctive reservoir deliverability at each structure. The storage concept is an essential function of natural fracture intensity and diversity, supported by matrix porosity that varies across a different succession of lithology. Lastly, this study observes that major fault orientation is essential in constructing the fracture network. Evidence from several image logs across the study area concludes that most of the interpreted fractures are oriented subparallel to the major faults. The northern belt area is relatively affected by NW-SE Neogene structure, where the southern area is recognized to be affected by both Neogene compression and pre-existing Paleogene structure.

The Religious Divide in Voting Preferences and Attitudes in the 2019 Election

2019 ◽  
Vol 7 (2) ◽  
pp. 161-175 ◽  
Author(s):  
Shreyas Sardesai
Keyword(s):  
Sufficient Evidence ◽  
Data Sets ◽  
Election Study ◽  
Large Measure ◽  
National Elections ◽  
Election Result ◽  
The Core ◽  
National Election Study ◽  
Bharatiya Janata Party ◽  
The Government

This article attempts to empirically test the claims made by several commentators that religious polarization was at the core of the 2019 Lok Sabha election verdict. Relying heavily on the National Election Study (NES) data sets, it finds that the election result was in large measure an outcome of massive vote consolidation on religious lines, with the majority Hindu community preferring the Bharatiya Janata Party (BJP)-led National Democratic Alliance (NDA) in unprecedented proportion and the main religious minorities largely staying away from it, although there were some exceptions. It shows that, for two national elections in a row, the Narendra Modi- and Amit Shah-led BJP has been able to overcome the caste hierarchies among Hindus and systematically construct a Hindu category of voters versus others. This chasm between Hindus and the minorities is also seen with respect to their attitudes regarding the government, its leadership and contentious issues like the Ayodhya dispute. This article, however, does not find sufficient evidence with regard to the claims that a large part of the Hindu support for the BJP-led alliance may have been on account of anti-minority sentiments.

Energy-Dispersive XRF Analysis of Intact Salt Drill Cores

1984 ◽  
Vol 28 ◽  
pp. 189-194
Author(s):  
R. J. Arthur ◽  
J. C. Laul ◽  
N. Hubbard
Keyword(s):  
Laboratory Analysis ◽  
Energy Dispersive ◽  
Drill Core ◽  
Chemical Analyses ◽  
Chemical Profile ◽  
Xrf Analysis ◽  
The Core ◽  
Drill Cores

Several kilometers of drill core are sometimes obtained when the geology of a particular area is explored. The cores are visually inspected and a limited number of samples are taken for laboratory analysis. Accurate chemical analyses are usually performed on only a small number of core sections because of the expense involved. A chemical profile along the core may provide useful information not available by any other means. This information may be of primary value for geological investigations or it may provide an additional basis for selecting samples for detailed laboratory analyses.

scholarly journals CoreCruncher: Fast and Robust Construction of Core Genomes in Large Prokaryotic Data Sets

2020 ◽  
Author(s):  
Connor D Harris ◽  
Ellis L Torrance ◽  
Kasie Raymann ◽  
Louis-Marie Bobay
Keyword(s):  
Core Genome ◽  
Genomic Data ◽  
Data Sets ◽  
The Core ◽  
Genomic Analyses ◽  
Massive Accumulation ◽  
Genome Comparisons

Abstract The core genome represents the set of genes shared by all, or nearly all, strains of a given population or species of prokaryotes. Inferring the core genome is integral to many genomic analyses, however, most methods rely on the comparison of all the pairs of genomes; a step that is becoming increasingly difficult given the massive accumulation of genomic data. Here, we present CoreCruncher; a program that robustly and rapidly constructs core genomes across hundreds or thousands of genomes. CoreCruncher does not compute all pairwise genome comparisons and uses a heuristic based on the distributions of identity scores to classify sequences as orthologs or paralogs/xenologs. Although it is much faster than current methods, our results indicate that our approach is more conservative than other tools and less sensitive to the presence of paralogs and xenologs. CoreCruncher is freely available from: https://github.com/lbobay/CoreCruncher. CoreCruncher is written in Python 3.7 and can also run on Python 2.7 without modification. It requires the python library Numpy and either Usearch or Blast. Certain options require the programs muscle or mafft.

New techniques of applying multi-wavelength anomalous scattering data

1993 ◽  
Vol 442 (1914) ◽  
pp. 13-32 ◽  
Keyword(s):  
Fourier Coefficients ◽  
Structural Model ◽  
Real Data ◽  
Scattering Data ◽  
Anomalous Scattering ◽  
Data Sets ◽  
New Techniques ◽  
The Core ◽  
Multi Wavelength ◽  
Do So

Several different methods of using multi-wavelength anomalous scattering data are described and illustrated by application to the solution of the known protein structure, core streptavidin, for which data at three wavelengths were available. Three of the methods depend on the calculation of Patterson-like functions for which the Fourier coefficients involve combinations of the anomalous structure amplitudes from either two or three wavelengths. Each of these maps should show either vectors between anomalous scatterers or between anomalous scatterers and non-anomalous scatterers. While they do so when ideal data are used, with real data they give little information; it is concluded that these methods are far too sensitive to errors in the data and to the scaling of the data-sets to each other. Another Patterson-type function, the P s function, which uses only single-wavelength data can be made more effective by combining the information from several wavelengths. Two analytical methods are described, called AGREE and ROTATE, both of which were very successfully applied to the core streptavidin data. They are both made more effective by preprocessing the data with a procedure called REVISE which brings a measure of mutual consistency to the data from different wavelengths. The best phases obtained from AGREE lead to a map with a conventional correlation coefficient of 0.549 and this should readily be interpreted in terms of a structural model.

Research of Improved Attribute Reduction Algorithm Based on Data Mining of Rough Set

2014 ◽  
Vol 644-650 ◽  
pp. 2120-2123 ◽  
Author(s):  
De Zhi An ◽  
Guang Li Wu ◽  
Jun Lu
Keyword(s):  
Data Mining ◽  
Rough Set ◽  
Rough Set Theory ◽  
Attribute Reduction ◽  
Large Data ◽  
Large Data Sets ◽  
Data Sets ◽  
Reduction Algorithm ◽  
The Core ◽  
Rules Extraction

At present there are many data mining methods. This paper studies the application of rough set method in data mining, mainly on the application of attribute reduction algorithm based on rough set in the data mining rules extraction stage. Rough set in data mining is often used for reduction of knowledge, and thus for the rule extraction. Attribute reduction is one of the core research contents of rough set theory. In this paper, the traditional attribute reduction algorithm based on rough sets is studied and improved, and for large data sets of data mining, a new attribute reduction algorithm is proposed.

scholarly journals AGES Observations of Abell 1367

2007 ◽  
Vol 3 (S244) ◽  
pp. 350-351
Author(s):  
L. Cortese ◽  
R. F. Minchin ◽  
R. R. Auld ◽  
J. I. Davies ◽  
B. Catinella ◽  
...  
Keyword(s):  
Optical Imaging ◽  
Large Scale ◽  
Striking Difference ◽  
Scaling Relations ◽  
Local Cluster ◽  
X Ray ◽  
The Core ◽  
Cluster Of Galaxies ◽  
Abell Cluster ◽  
Galaxy Environment

AbstractWe present 21 cm observations of 5×1 square degrees centered on the local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment Survey. This represents the first HI selected sample covering the core and the outskirts of a local cluster of galaxies. Combining the HI data with SDSS optical imaging we show that in HI selected samples follow scaling relations similar to the ones usually observed in optically selected samples. The most striking difference between HI and optically selected samples resides in their large scale distribution: while optical and X-ray observations trace the cluster potential very well, at radio wavelengths there is almost no evidence of the cluster presence.

Sign in / Sign up

Export Citation Format

Share Document