scholarly journals Multifractal Analysis of Pore Structure and Evaluation of Deep-Buried Cambrian Dolomite Reservoir with Image Processing: A Case from Tarim Basin, NW China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Xiaojun Zhang ◽  
Haodong Han ◽  
Jun Peng ◽  
Yingchun Gou
Keyword(s):  
Pore Structure ◽  
Thin Section ◽  
Tarim Basin ◽  
Clustering Analysis ◽  
Multifractal Analysis ◽  
Pore Space ◽  
Tectonic Activity ◽  
Petrophysical Properties ◽  
Nw China ◽  
Crystalline Dolomite

Reservoir pore space assessment is of great significance for petroleum exploration and production. However, it is difficult to describe the pore characteristics of deep-buried dolomite reservoirs with the traditional linear method because these rocks have undergone strong modification by tectonic activity and diagenesis and show significant pore space heterogeneity. In this study, 38 dolostone samples from 4 Cambrian formations of Tarim Basin in NW China were collected and 135 thin section images were analyzed. Multifractal theory was used for evaluation of pore space heterogeneity in deep-buried dolostone based on thin section image analysis. The physical parameters, pore structure parameters, and multifractal characteristic parameters were obtained from the digital images. Then, the relationships between lithology and these parameters were discussed. In addition, the pore structure was classified into four categories using K-means clustering analysis based on multifractal parameters. The results show that the multifractal phenomenon generally exists in the pore space of deep-buried dolomite and that multifractal analysis can be used to characterize the heterogeneity of pore space in deep-buried dolomite. For these samples, multifractal parameters, such as αmin, αmax, ΔαL, ΔαR, Δf, and AI, correlate strongly with porosity but only slightly with permeability. However, the parameter Δα, which is usually used to reveal heterogeneity, does not show an obvious link with petrophysical properties. Of dolomites with different fabrics, fine crystalline dolomite and medium crystalline dolomite show the best petrophysical properties and show significant differences in multifractal parameters compared to other dolomites. More accurate porosity estimations were obtained with the multifractal generalized fractal dimension, which provides a new method for porosity prediction. The various categories derived from the K-means clustering analysis of multifractal parameters show distinct differences in petrophysical properties. This proves that reservoir evaluation and pore structure classification can be accurately performed with the K-means clustering analysis method based on multifractal parameters of pore space in deep-buried dolomite reservoirs.

scholarly journals Bi-Fractal Characterization of the Pore Network of Tight Sandstone

2021 ◽  
Vol 9 ◽  
Author(s):  
Zezhang Song ◽  
Junyi Zhao ◽  
Yuanyin Zhang ◽  
Dailin Yang ◽  
Yunlong Wang ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Thin Section ◽  
Fractal Analysis ◽  
Pore Space ◽  
Fractal Dimensions ◽  
Pore Network ◽  
Physical Analysis ◽  
Tight Sandstone ◽  
Gas Bearing

Fluid seepage performance and accumulation in tight sandstone is a critical research topic for in-depth exploration and development, closely related to the heterogeneity of the pore network. The fractal characterization is one of the most compelling and direct ways for quantitative investigation of heterogeneity. However, only one kind of fractal is used in most studies, and the differences and relations between different fractal dimensions are rarely discussed. This paper chose one of the most representative tight sandstone formations in China, the second member of the Xujiahe Formation, as the research object. First, based on physical analysis and XRD analysis, we carried out a qualitative investigation on pore structure utilizing thin-section and scanning electron microscopy. Then, detailed pore structure parameters were obtained using high-pressure mercury intrusion (HPMI). Lastly, we combined two-dimensional fractal analysis on thin-section images and three-dimensional fractal analysis on HPMI data to characterize the pore network heterogeneity quantitatively. The Xu2 tight sandstone is mainly medium- to fine-grained lithic feldspathic sandstone or feldspathic lithic sandstone with low porosity and permeability. Also, the Xujiahe tight sandstone is mainly composed of quartz, feldspar, and clay. The pore types of Xu2 tight sandstones are primarily intergranular pores, micro-fractures, and intra- and intergranular dissolution pores. Moreover, most of the micro-fractures in gas-bearing formation are open-ended, while most are filled by clay minerals in the dry formation. The r50 (median pore radius) is the most sensitive parameter to seepage capability (permeability) and gas-bearing status. The 2D fractal dimension (Ds) of gas-bearing samples is significantly larger than that of dry samples, while the 3D fractal dimension (D1, D2) of gas-bearing samples is lower than that of dry samples. There is a strong negative correlation between D2 and gas-bearing status, permeability, quartz content, and r50, but a positive correlation between Ds and these parameters. D2 represents the heterogeneity of pore space, while the Ds indicates the development of the pore network. Tectonic movements that generate micro-fractures and clay cementation that blocks the seepage channels are the two main controlling factors on fractal dimensions. Combining 2D and 3D fractal analysis could give a more in-depth investigation of pore structure.

scholarly journals Palaeo-earthquake events during the late Early Palaeozoic in the central Tarim Basin (NW China): evidence from deep drilling cores

Geologos ◽  
2014 ◽  
Vol 20 (2) ◽  
pp. 105-123 ◽  
Author(s):  
Bizhu He ◽  
Xiufu Qiao ◽  
Cunli Jiao ◽  
Zhiqin Xu ◽  
Zhihui Cai ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Spatial Association ◽  
Late Ordovician ◽  
Tectonic Activity ◽  
Earthquake Activity ◽  
Seismogenic Fault ◽  
Upper Ordovician ◽  
Deep Drilling ◽  
Stress Regime ◽  
Nw China

Abstract Various millimetre-, centimetre- and metre-scale soft-sediment deformation structures (SSDS) have been identified in the Upper Ordovician and Lower-Middle Silurian from deep drilling cores in the Tarim Basin (NW China). These structures include liquefied-sand veins, liquefaction-induced breccias, boudinage-like structures, load and diapir- or flame-like structures, dish and mixed-layer structures, hydroplastic convolutions and seismic unconformities. The deformed layers are intercalated by undeformed layers of varying thicknesses that are petrologically and sedimentologically similar to the deformed layers. The SSDS developed in a shelf environment during the early Late Ordovician and formed initially under shear tensile stress conditions, as indicated by boudinage-like structures; during the latest Ordovician, SSDS formed under a com-pressional regime. The SSDS in the Lower-Middle Silurian consist mainly of mixed layers and sand veins; they formed in shoreline and tidal-flat settings with liquefaction features indicating an origin under a compressional stress regime. By Silurian times, the centre of tectonic activity had shifted to the south-eastern part of the basin. The SSDS occur at different depths in wells that are close to the syn-sedimentary Tazhong 1 Fault (TZ1F) and associated reversed-thrust secondary faults. Based on their characteristics, the inferred formation mechanism and the spatial association with faults, the SSDS are interpreted as seismites. The Tazhong 1 fault was a seismogenic fault during the later Ordovician, whereas the reversed-direction secondary faults became active in the Early-Middle Silurian. Multiple palaeo-earthquake records reflect pulses and cyclicity, which supports secondary tectonic activity within the main tectonic movement. The range of SSDS structures reflects different developments of tectonic activity with time for the various tectonic units of the centralbasin. The effects of the strong palaeo-earthquake activity coincide with uplift, fault activity and syn-tectonic sedimentation in the study area during the Late Ordovician to Middle Silurian.

Analysis of Chalk Petrophysical Properties by Means of Submicron-Scale Pore Imaging and Modeling

2007 ◽  
Vol 10 (03) ◽  
pp. 285-293 ◽  
Author(s):  
Liviu Tomutsa ◽  
Dmitriy Borisovich Silin ◽  
Velimir Radmilovic
Keyword(s):  
Sample Preparation ◽  
Pore Structure ◽  
3D Imaging ◽  
Pore Space ◽  
Ion Beam ◽  
Pore Network ◽  
Stochastic Methods ◽  
Petrophysical Properties ◽  
Pore System ◽  
Submicron Scale

Summary For many rocks of high economic interest such as chalk, diatomite, shale, tight gas sands, or coal, a submicron-scale resolution is needed to resolve the 3D pore structure, which controls the flow and trapping of fluids in the rocks. Such a resolution cannot be achieved with existing tomographic technologies. A new 3D imaging method based on serial sectioning, which uses the focused-ion-beam (FIB) technology, has been developed. FIB technology allows for the milling of layers as thin as 10 nm by using accelerated gallium (Ga+) ions to sputter atoms from the sample surface. After each milling step, as a new surface is exposed, a 2D image of this surface is generated, and the 2D images are stacked to reconstruct the 3D pore structure. Next, the maximum-inscribed-spheres (MIS) image-processing method computes the petrophysical properties by direct morphological analysis of the pore space. The computed capillary pressure curves agree well with laboratory data. Applied to the FIB data, this method generates the fluid distribution in the chalk pore space at various saturations. Introduction Field-scale oil-recovery processes are the result of countless events happening in individual pores. To model multiphase flow in porous media at pore scale, the resolution of the 3D images must be adequate for the rock of interest. Chalk formations in the oil fields of Texas, the Middle East, the North Sea, and other areas hold significant oil reserves. The extremely small typical pore sizes in chalk impose very high requirements on imaging resolution. In the last decade, X-ray microtomography has been used extensively for direct visualization of the pore system and the fluids within sandstone (Jasti et al. 1993; Coles et al. 1998; Wildenschild et al. 2003; Seright et al. 2003). While this approach is fast and nondestructive, its applicability is limited mostly to micron resolutions, although recent developments are bringing the resolution to submicron range (Stampanoni et al. 2002). For chalk pore systems, which are characterized by submicron- to nanometer-length scales, 3D stochastic methods based on 2D scanning-electron-microscope (SEM) images of thin sections have been used to reconstruct the pore system (Talukdar et al. 2001). The advent of FIB technology has it made possible to reconstruct submicron 3D pore systems for diatomite and chalk (Tomutsa and Radmilovic 2003) (Fig. 1). FIB technology is used in microelectronics to access individual components with nanoscale accuracy for design verification, failure analysis, and circuit modification (Orloff et al. 2002). FIB has been used in material sciences for sectional sample preparation for SEM and for 3D imaging of alloy components (Kubis et al. 2004). In earth sciences, the FIB also has been used for sample preparation for SEM and to access inner regions for performing microanalysis (Heaney et al. 2001).To access the pore structure at submicron scale, the FIB mills successive layers of the rock material as thin as 10 nm. As successive 2D surfaces are exposed, they are imaged with either the electron or the ion beam. After processing, the images are stacked to reconstruct the 3D pore structure. The geometry of the pore space of the obtained structure can be analyzed further to estimate petrophysical rock properties through computer simulations. To analyze the 3D chalk images obtained by the FIB method, we applied the MIS technique (Hazlett 1995; Silin et al. 2003, 2004; Silin and Patzek 2006). The MIS method analyzes the 3D pore-space image directly, without construction of pore networks. It bypasses the nontrivial task of extracting a simple but representative network of pore throats linking pore bodies from the 3D data (Lindquist 2002). Moreover, the pore-network extraction methods, which are based on relatively simple grain and pore shapes in sandstones (Øren and Bakke 2002), may not always be feasible for the complex pore structures of carbonates. Although a pore-network-based flow-modeling approach enjoyed a significant interest from the researchers and resulted in theoretically and practically sound conclusions (Øren et al. 1998; Xu et al. 1999; Patzek 2001; Blunt 2001), we believe that direct pore-space analysis deserves more attention. In addition, direct analysis of the pore space provides an opportunity to study alteration of the rock flow properties (e.g., those resulting from mechanical transformations or mineralization) (Jin et al. 2003).

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.

PORE STRUCTURE OF TRANSITIONAL SHALES IN THE ORDOS BASIN, NW CHINA: EFFECTS OF COMPOSITION ON GAS STORAGE MECHANISM

2017 ◽  
Author(s):  
Fengyang Xiong ◽  
◽  
Zhenxue Jiang ◽  
Mohammad Amin Amooie ◽  
Mohamad Reza Soltanian ◽  
...  
Keyword(s):  
Pore Structure ◽  
Ordos Basin ◽  
Gas Storage ◽  
Nw China ◽  
Storage Mechanism ◽  
The Ordos Basin

scholarly journals Forced Fold Amplitude and Sill Thickness Constrained by Wireline and 3-D Seismic Data Suggest an Elastic Magma-Induced Deformation in Tarim Basin, NW China

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 293
Author(s):  
Wei Tian ◽  
Xiaomin Li ◽  
Lei Wang
Keyword(s):  
Tarim Basin ◽  
Seismic Data ◽  
Inelastic Deformation ◽  
Northwest China ◽  
Well Log ◽  
Total Thickness ◽  
Nw China ◽  
Seismic Method ◽  
Two Parameters ◽  
Outer Area

Disparities between fold amplitude (A) and intrusion thickness (Hsill) are critical in identifying elastic or inelastic deformation in a forced fold. However, accurate measurements of these two parameters are challenging because of the limit in separability and detectability of the seismic data. We combined wireline data and 3-D seismic data from the TZ-47 exploring area in the Tarim Basin, Northwest China, to accurately constrain the fold amplitude and total thickness of sills that induced roof uplift in the terrain. Results from the measurement show that the forced fold amplitude is 155.0 m. After decompaction, the original forced fold amplitude in the area penetrated by the well T47 ranged from 159.9 to 225.8 m, which overlaps the total thickness of the stack of sills recovered by seismic method (171.4 m) and well log method (181.0 m). Therefore, the fold amplitude at T47 area is likely to be elastic. In contrast, the outer area of the TZ-47 forced fold is characterized by shear-style deformation, indicating inelastic deformation at the marginal area. It is suggested that interbedded limestone layers would play an important role in strengthening the roof layers, preventing inelastic deformation during the emplacement of intrusive magma.

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