scholarly journals Characterization and Consecutive Prediction of Pore Structures in Tight Oil Reservoirs

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2705 ◽  
Author(s):  
Zhaohui Xu ◽  
Peiqiang Zhao ◽  
Zhenlin Wang ◽  
Mehdi Ostadhassan ◽  
Zhonghua Pan
Keyword(s):  
Pore Structure ◽  
Capillary Pressure ◽  
New Method ◽  
Tight Oil ◽  
Type I ◽  
Sweet Spot ◽  
Sem Images ◽  
Pore Structures ◽  
Lucaogou Formation ◽  
Two Samples

The Lucaogou Formation in Jimuaser Sag of Junggar Basin, China is a typical tight oil reservoir with upper and lower sweet spots. However, the pore structure of this formation has not been studied thoroughly due to limited core analysis data. In this paper, the pore structures of the Lucaogou Formation were characterized, and a new method applicable to oil-wet rocks was verified and used to consecutively predict pore structures by nuclear magnetic resonance (NMR) logs. To do so, a set of experiments including X-ray diffraction (XRD), mercury intrusion capillary pressure (MICP), scanning electron microscopy (SEM) and NMR measurements were conducted. First, SEM images showed that pore types are mainly intragranular dissolution, intergranular dissolution, micro fractures and clay pores. Then, capillary pressure curves were divided into three types (I, II and III). The pores associated with type I and III are mainly dissolution and clay pores, respectively. Next, the new method was verified by “as received” and water-saturated condition T2 distributions of two samples. Finally, consecutive prediction in fourteen wells demonstrated that the pores of this formation are dominated by nano-scale pores and the pore structure of the lower sweet spot reservoir is more complicated than that in upper sweet spot reservoir.

EVALUATION OF FORMATION DAMAGE USING MICROSTRUCTURE FRACTAL IN SHALE RESERVOIRS

Fractals ◽  
2015 ◽  
Vol 23 (01) ◽  
pp. 1540008 ◽  
Author(s):  
LIJUN YOU ◽  
QIANG CHEN ◽  
YILI KANG ◽  
YANGFENG YU ◽  
JINGAN HE
Keyword(s):  
Pore Structure ◽  
Threshold Value ◽  
New Method ◽  
Working Fluid ◽  
Formation Damage ◽  
Measurement Scales ◽  
Sem Images ◽  
Working Fluids ◽  
Sem Image ◽  
Shale Formation

Formation damage evaluation is a key and basic link in optimizing working fluids. It is widely accepted that formation damage is the reduction of core plugs permeability caused by working fluid invasion. However, the measurement of permeability faces a huge challenge for shale formation, such as overspending, time-consuming and the scarcity of unbroken core plug samples. A new method of fractal analysis derived from Scanning Electron Microscopy (SEM) image of shale pore structure was used to quantify the shale formation damage. This method needs to select optimal magnification and segmentation threshold value of SEM image to obtain exact Fractal Dimension (FD) of pore structure. In this paper, we take the black shale outcrops from Sichuan Basin for an example. The results shows that the optimal magnification for observation of the pore structure using SEM imaging in this area is 1000×, and the optimal threshold value for binary image is 29 (RGB). Microscopic pore structure of the shale follows the fractal law, and the FDs increase with increasing measurement scales. It is evident that the evaluation results of shale formation damage when exposed to 2 wt.% NaOH solution and 2 wt.% brine solution using microstructure fractal are exceptionally in good agreement with permeability reduction results. The microstructure fractal obtained from SEM images provides a new method for evaluation of shale formation damage. And it can be applied to optimize the screening working fluids used in shale formation in real time under the condition of high temperature and high pressure.

scholarly journals A New Method for Pore Structure Quantification and Pore Network Extraction from SEM Images

2019 ◽  
Vol 34 (1) ◽  
pp. 82-94
Author(s):  
Chenhui Wang ◽  
Kejian Wu ◽  
Gilbert G. Scott ◽  
Alfred R. Akisanya ◽  
Quan Gan ◽  
...  
Keyword(s):  
Pore Structure ◽  
Pore Network ◽  
New Method ◽  
Sem Images

scholarly journals Multivariate Statistical Analysis Reveals the Heterogeneity of Lacustrine Tight Oil Accumulation in the Middle Permian Jimusar Sag, Junggar Basin, NW China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Yuce Wang ◽  
Jian Cao ◽  
Keyu Tao ◽  
Xiuwei Gao ◽  
Erting Li ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Closed System ◽  
Multivariate Statistical Analysis ◽  
Tight Oil ◽  
Lateral Migration ◽  
Sweet Spot ◽  
Middle Section ◽  
Multivariate Statistical ◽  
Oil Accumulation ◽  
Lucaogou Formation

Tight oil and gas accumulation commonly has heterogeneities within the reservoir formation. This heterogeneity, however, is hard to investigate by conventional geological and (organic) geochemical tools and thus is critical and challenging to study. Here, we attempted multivariate statistical analysis to reveal the heterogeneity based on a case study in the lacustrine tight oil accumulation in the middle Permian Lucaogou Formation of the Jimusar sag, Junggar Basin, NW China. Clustering heat maps and multi-dimensional scaling analysis revealed the heterogeneity of tight oil accumulation. The heterogeneity is reflected by the complex relationship between the two reservoir sweet spots as well as the oil migration and accumulation vertically and spatially, rather than the previous thoughts that it is a closed system associated with proximal hydrocarbon accumulation patterns. Multiple biomarkers show that the source rocks and reservoirs have similar characteristics in the lower part of the formation, reflecting a proximal hydrocarbon accumulation pattern in the lower sweet spot (near-source accumulation, abbreviated as NA). This represents a relatively closed system. However, the upper sweet spot and the middle section mudstone sequence intervening the two sweet spots are not a completely closed system in a strict sense. These sequences can be divided into three tight oil segments, i.e., lower, middle, and upper from deep to shallow. The lower segment is sited in the lower part of the middle section mudstone sequence. The middle segment is composed of the upper part of the middle section mudstone sequence and the lower part of the upper sweet spot. The upper segment is composed of the upper part of the upper sweet spot and the overlying upper Permian Wutonggou Formation reservoirs. Oils generated in the lower segment migrated vertically to upper sweet spot reservoirs through faults/fractures, and laterally to distal reservoirs. Oils generated in the middle segment were preserved in reservoirs of the upper sweet spot. Oils in the upper segment require accumulation by vertical and lateral migration through faults/fractures. As such, the tight oil accumulation is complex in the Lucaogou Formation. From base to top, the accumulation mechanisms in the Lucaogou Formation were NA, VLMA (vertical and lateral migration and accumulation), NA and VLMA, thereby showing strong heterogeneities. Our data suggest that these processes might be typical of tight oil accumulations universally, and are important for future exploration and exploitation in the region to consider the heterogeneities rather than a closed system. The multivariate statistical analysis is an effective tool for investigating complex oil-source correlations and accumulation in petroleum basins.

A new method for assessing tight oil, with application to the Lucaogou Formation in the Jimusaer depression, Junggar Basin, China

AAPG Bulletin ◽  
2020 ◽  
Vol 104 (6) ◽  
pp. 1199-1229 ◽  
Author(s):  
Junqing Chen ◽  
Xiongqi Pang ◽  
Xulong Wang ◽  
Yingxun Wang
Keyword(s):  
Junggar Basin ◽  
New Method ◽  
Tight Oil ◽  
Lucaogou Formation

scholarly journals Pore Structure Characteristics of Tight Carbonate Reservoir in Qingxi Sag, Jiuquan Basin

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Xiangye Kong ◽  
Jianhui Zeng ◽  
Xianfeng Tan ◽  
Xianglu Gao ◽  
Yu Peng ◽  
...  
Keyword(s):  
Pore Structure ◽  
Tube Bundle ◽  
Pore Space ◽  
Carbonate Reservoir ◽  
Reservoir Rock ◽  
Tight Oil ◽  
Type I ◽  
Structure Characteristics ◽  
Small Pore ◽  
Tight Carbonate

Abstract The Xiagou Formation is the main tight oil reservoir in Qingxi Sag of Jiuquan Basin. Given the poor physical properties and other factors restricting tight oil exploitation and production in this area, studies should focus on microscopic pore structure characteristics. In this study, a nano-CT scanner, a SEM, and an NMR were used to study the pore structure characteristics of a tight carbonate reservoir in Qingxi Sag, Jiuquan Basin. The Xiagou Formation reservoir mainly consists of gray argillaceous dolomite and dolomitic mudstone. The pore categories are mainly elliptic, irregular, intergranular, and intragranular and mostly filled with clay and carbonate cement. Pore space is small, the intergranular or organic pores are mostly separated, and pore-throat is weakly connected. The throats mostly develop with lamellar and tube bundle-like characteristics and with poor seepage ability. The pore-throats mostly span from nanometer to micrometer sizes, and pore diameters are mainly concentrated in the range of 0.01–0.1 and 1–10 μm. It is a unimodal pattern mainly composed of micropores, or a bimodal regular allocation dominated by micropores supplemented by macropores. The relationship between micropore (<0.1 μm) and macropore (>1 μm) content allocation and mean pore diameter strongly controls the permeability of reservoir rocks. When macropore content reaches more than 85%, or when pore content totals less than 3%, the permeability of a reservoir remarkably increases. At a higher ratio of the average finest throat sectional area and throat-pore of reservoir rock, the throat radius lies closer to the connecting pore radius, pore and throat connectivity improves, and reservoir seepage ability becomes stronger. Based on reservoir capacity and seepage ability, pore structures of the tight carbonate reservoirs in study area are classified into type I (small-pore–thin-throat), type II (thin-pore–thin-throat), and type III (microporous-microthroat) with rock permeability>0.1 mD, 0.05–0.1 mD, and <0.05 mD, respectively. The type I pore structure reservoir should be regarded as an indicator of tight oil “sweet spots” reservoir in the study area.

Characteristics and origin of the pore structure of the lacustrine tight oil reservoir in the northwestern Jiuquan Basin, China

2019 ◽  
Vol 7 (3) ◽  
pp. T625-T636
Author(s):  
Chunyan Fan ◽  
Xianglu Tang ◽  
Yuanyin Zhang ◽  
Yan Song ◽  
Zhenxue Jiang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Oil Reservoir ◽  
Type I ◽  
Thin Sections ◽  
Tectonic Events ◽  
Tight Oil Reservoir ◽  
Tight Oil Reservoirs ◽  
Intercrystalline Pores

The pore structure controls the formation processes of tight oil reservoirs. It is meaningful to study the characteristics and origin of the pore structure of the tight oil reservoir. We have analyzed the pore structure of the tight oil reservoir by thin sections, scanning electron microscopy, and mercury intrusion porosimetry. We analyze the origin of the pore structure based on sedimentological, diagenetic, and tectonism processes. The porosity of the tight oil reservoirs is mainly approximately 2%–10%, and the permeability is mainly from 0.01 to 0.3 mD. The pores of the lacustrine tight oil reservoir can be classified into the primary pore and the secondary pore. The main pores are matrix micropores and clay intercrystalline pores, as well as a few dissolved pores. However, the primary residual intergranular pore has almost disappeared, leading to a poor connectivity with a general size between 20 and 50 μm. The pore throat is divided into three categories (type I, type II, and type III) according to the porosity, permeability, and throat size and distribution. We determine that the pore structure of the lacustrine tight oil reservoir is related to sedimentary, diagenetic processes, and later tectonic events. The compaction and cementation are the main factors, whereas the dissolution and tectonic events have minor effects.

scholarly journals Probability waves: pattern-based p-value correction in mass univariate analysis between two event-related potential waves

2019 ◽  
Author(s):  
Dimitri Marques Abramov
Keyword(s):  
Type I Error ◽  
Univariate Analysis ◽  
Event Related Potential ◽  
New Method ◽  
Multiple Point ◽  
P Value ◽  
Type I ◽  
P Values ◽  
Two Samples ◽  
Point To Point

AbstractBackgroundMethods for p-value correction are criticized for either increasing Type II error or improperly reducing Type I error. This problem is worse when dealing with hundreds or thousands of paired comparisons between waves or images which are performed point-to-point. This text considers patterns in probability vectors resulting from multiple point-to-point comparisons between two ERP waves (mass univariate analysis) to correct p-values. These patterns (probability waves) mirror ERP waveshapes and might be indicators of consistency in statistical differences.New methodIn order to compute and analyze these patterns, we convoluted the decimal logarithm of the probability vector (p’) using a Gaussian vector with size compatible to the ERP periods observed. For verify consistency of this method, we also calculated mean amplitudes of late ERPs from Pz (P300 wave) and O1 electrodes in two samples, respectively of typical and ADHD subjects.Resultsthe present method reduces the range of p’-values that did not show covariance with neighbors (that is, that are likely random differences, type I errors), while preserving the amplitude of probability waves, in accordance to difference between respective mean amplitudes.Comparison with existing methodsthe positive-FDR resulted in a different profile of corrected p-values, which is not consistent with expected results or differences between mean amplitudes of the analyzed ERPs.Conclusionthe present new method seems to be biological and statistically more suitable to correct p-values in mass univariate analysis of ERP waves.

Correlation of Pore Structure and Permeability by SEM-Image Analysis

1990 ◽  
Vol 48 (1) ◽  
pp. 428-429
Author(s):  
C. A. Callender ◽  
Wm. C. Dawson ◽  
J. J. Funk
Keyword(s):  
Image Analysis ◽  
Pore Structure ◽  
Imaging System ◽  
Pore Space ◽  
Simulation Models ◽  
Image Analyzer ◽  
Imaging Data ◽  
Sem Images ◽  
Thin Sections ◽  
Rock Types

The geometric structure of pore space in some carbonate rocks can be correlated with petrophysical measurements by quantitatively analyzing binaries generated from SEM images. Reservoirs with similar porosities can have markedly different permeabilities. Image analysis identifies which characteristics of a rock are responsible for the permeability differences. Imaging data can explain unusual fluid flow patterns which, in turn, can improve production simulation models.Analytical SchemeOur sample suite consists of 30 Middle East carbonates having porosities ranging from 21 to 28% and permeabilities from 92 to 2153 md. Engineering tests reveal the lack of a consistent (predictable) relationship between porosity and permeability (Fig. 1). Finely polished thin sections were studied petrographically to determine rock texture. The studied thin sections represent four petrographically distinct carbonate rock types ranging from compacted, poorly-sorted, dolomitized, intraclastic grainstones to well-sorted, foraminiferal,ooid, peloidal grainstones. The samples were analyzed for pore structure by a Tracor Northern 5500 IPP 5B/80 image analyzer and a 80386 microprocessor-based imaging system. Between 30 and 50 SEM-generated backscattered electron images (frames) were collected per thin section. Binaries were created from the gray level that represents the pore space. Calculated values were averaged and the data analyzed to determine which geological pore structure characteristics actually affect permeability.

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