Effect of Natural Fractures on the Stress-Dependent Permeability and Long-Term Gas Production for the Naturally-Fractured Tight Sandstone in Tarim Basin, China

2019 ◽  
Author(s):  
Hongyan Qu ◽  
Fujian Zhou ◽  
Jiawei Hu ◽  
Yan Peng ◽  
Yuechen Zhong ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Gas Production ◽  
Natural Fractures ◽  
Tight Sandstone ◽  
Naturally Fractured ◽  
Stress Dependent

A Comprehensive Approach for Fracability Evaluation in Naturally Fractured Sandstone Reservoirs

2018 ◽  
Author(s):  
Zhaozhong Yang ◽  
Rui He ◽  
Xiaogang Li ◽  
Zhanling Li ◽  
Ziyuan Liu
Keyword(s):  
Large Scale ◽  
Evaluation Model ◽  
Gas Production ◽  
Natural Fracture ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Related Factors ◽  
Gas Field ◽  
Tight Gas Reservoir ◽  
Naturally Fractured

The tight sandstone gas reservoir in southern Songliao Basin is naturally fractured and is characterized by its low porosity and permeability. Large-scale hydraulic fracturing is the most effective way to develop this tight gas reservoir. Quantitative evaluation of fracability is essential for optimizing a fracturing reservoir. In this study, as many as ten fracability-related factors, particularly mechanical brittleness, mineral brittleness, cohesion, internal friction angle, unconfined compressive strength (UCS), natural fracture, Model-I toughness, Model-II toughness, horizontal stress difference, and fracture barrier were obtained from a series of petrophysical and geomechanical experiments are analyzed. Taking these influencing factors into consideration, a modified comprehensive evaluation model is proposed based on the analytic hierarchy process (AHP). Both a transfer matrix and a fuzzy matrix were introduced into this model. The fracability evaluation of four reservoir intervals in Jinshan gas field was analyzed. Field fracturing tests were conducted to verify the efficiency and accuracy of the proposed evaluation model. Results showed that gas production is higher and more stable in the reservoir interval with better fracability. The field test data coincides with the results of the proposed evaluation model.

scholarly journals Rate Decline Analysis for Limited-Entry Well in Abnormally High-Pressured Composite Naturally Fractured Gas Reservoirs

2019 ◽  
Vol 9 (9) ◽  
pp. 1821
Author(s):  
Mingtao Wu ◽  
Xiaodong Wang ◽  
Wenqi Zhao ◽  
Lun Zhao ◽  
Meng Sun ◽  
...  
Keyword(s):  
Production Rate ◽  
High Efficiency ◽  
Negative Impact ◽  
Gas Production ◽  
Production Performance ◽  
Gas Reservoirs ◽  
Naturally Fractured ◽  
Limited Entry ◽  
Permeability Anisotropy ◽  
Stress Dependent

Most naturally fractured gas reservoirs in China exhibit strongly heterogeneous, abnormally high-pressured and, stress-sensitive behaviors. In this work, a semianalytical solution is developed to study the production performance for limited-entry well in composite naturally fractured formations. The pressure-dependent porosity and permeability, anisotropy and limited-entry characteristics are taken into consideration. Furthermore, conventional Warren-Root model is amended to accommodate for permeability anisotropy. Laplace and finite Fourier cosine transforms are used to solve the diffusivity equations. The model is verified on the basis of previous literature’s results and data of a field example from Moxi gas field in Southwest China. Through the parameters sensitivity analysis, the effects of prevailing factors on production performance are investigated. Results indicate that a large inner region radius and high mobility ratio can improve gas production rate in the early stage, while they also lead to a drastic decline of production rate in the late stage. Large permeability stress-dependent coefficient and low penetrated interval both have a negative impact on production rate. With its high efficiency and simplicity, this proposed approach can serve as a convenient tool to evaluate the behavior of partially penetrated production well in abnormally high-pressured composite naturally fractured gas reservoirs.

scholarly journals Fold-Related Fracture Distribution in Neogene, Triassic, and Jurassic Sandstone Outcrops, Northern Margin of the Tarim Basin, China: Guides to Deformation in Ultradeep Tight Sandstone Reservoirs

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Junpeng Wang ◽  
Lianbo Zeng ◽  
Xianzhang Yang ◽  
Chun Liu ◽  
Ke Wang ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Gas Production ◽  
Shear Mode ◽  
Fracture Density ◽  
Tight Sandstone ◽  
Supply Source ◽  
Northern Margin ◽  
Fracture Patterns ◽  
Fracture Development ◽  
Opening Mode

Abstract Ultradeep (6-8 km depth) low-porosity sandstone oil and gas reservoirs, in the Kuqa thrust belt of Tarim Basin, are an important natural gas supply source of China. Both opening and shear-mode fractures are extremely necessary reservoir elements for gas production in these rocks but are challenging to characterize with sparse core and well log observations. Here, we use outcrops of some of the same units from four exposed folds to describe fracture types and patterns. These four folds have a range of shapes that are representative of folds at depth. At the Dongq, Kuqa, Misib, and Tuger anticlines, we analyzed fracture type, cross-cutting and abutting relations, density, spatial arrangement, kinematic aperture, orientation, and mineral fill. One-dimensional inventories, field sketches, photographs, and LiDAR imagery documented fracture patterns. Most dips of all fractures shown everywhere on the fold are greater than 60 degrees (over 50%). Fracture kinematic apertures are 3 mm to ~6 mm, and fracture density is 0.5 traces/m to ~1.5 traces/m. All fractures are divided into shear mode (or small faults) and opening mode. Shear-mode fractures, with high dips that strike N-S, mutually crosswise arranged with intersection angles of 30-60 degrees, are found extensively on the flanks of these folds. In contrast, most opening-mode fractures strike E-W, are arranged parallel to each other, and are localized in fold hinges. Besides, exposed folds (reservoir analogues, figure 1) in a proximal (hinterland, Tuger and Misib) position have fracture abundance distributions and aperture size patterns compatible with fold-related fracture development whereas distal (basinward, Kuqa and Dongq) folds lack this correlation, but patterns in distal folds might be explained by overprinted effects of lithological heterogeneity on fracture abundance or the effects of nearby faults. The positive correlation between fold-related strain and fracture spatial distribution in the northern (proximal) folds permitted inference of fracture patterns in deep wells.

Natural fractures in tight gas sandstones: a case study of the Upper Triassic Xujiahe Formation in Xinchang gas field, Western Sichuan Basin, China

2021 ◽  
pp. 1-18
Author(s):  
Yunzhao Zhang ◽  
Lianbo Zeng ◽  
Wenya Lyu ◽  
Dongsheng Sun ◽  
Shuangquan Chen ◽  
...  
Keyword(s):  
Production Capacity ◽  
Gas Production ◽  
Upper Triassic ◽  
Tight Gas ◽  
Natural Fractures ◽  
Carbon And Oxygen Isotopes ◽  
Gas Field ◽  
Xujiahe Formation ◽  
Western Sichuan ◽  
Tight Gas Reservoir

Abstract The Upper Triassic Xujiahe Formation is a typical tight gas reservoir in which natural fractures determine the migration, accumulation and production capacity of tight gas. In this study, we focused on the influences of natural fractures on the tight gas migration and production. We clarified characteristics and attributes (i.e. dips, apertures, filling degree and cross-cutting relationships) of the fractures based on image logging interpretations and core descriptions. Previous studies of electron spin resonance, carbon and oxygen isotopes, homogenization temperature of fluid inclusions analysis and basin simulation were considered. This study also analysed the fracture sequences, source of fracture fillings, diagenetic sequences and tight gas enrichment stages. We obtained insight into the relationship between fracture evolution and hydrocarbon charging, particularly the effect of the apertures and intensity of natural fractures on tight gas production. We reveal that the bedding fractures are short horizontal migration channels of tight gas. The tectonic fractures with middle, high and nearly vertical angles are beneficial to tight gas vertical migration. The apertures of fractures are controlled by the direction of maximum principal stress and fracture angle. The initial gas production of the vertical wells presents a positive correlation with the fracture abundance, and the intensity and aperture of fractures are the fundamental factors that determine the tight gas production. With these findings, this study is expected to guide the future exploration and development of tight gas with similar geological backgrounds.

scholarly journals A numerical investigation on the performance of hydraulic fracturing in naturally fractured gas reservoirs based on stimulated rock volume

2020 ◽  
Vol 10 (8) ◽  
pp. 3333-3345
Author(s):  
Ali Al-Rubaie ◽  
Hisham Khaled Ben Mahmud
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Natural Fracture ◽  
Shear Stresses ◽  
Individual Element ◽  
Natural Fractures ◽  
Gas Reservoirs ◽  
Stimulated Reservoir Volume ◽  
Reservoir Volume ◽  
Naturally Fractured

Abstract All reservoirs are fractured to some degree. Depending on the density, dimension, orientation and the cementation of natural fractures and the location where the hydraulic fracturing is done, preexisting natural fractures can impact hydraulic fracture propagation and the associated flow capacity. Understanding the interactions between hydraulic fracture and natural fractures is crucial in estimating fracture complexity, stimulated reservoir volume, drained reservoir volume and completion efficiency. However, because of the presence of natural fractures with diffuse penetration and different orientations, the operation is complicated in naturally fractured gas reservoirs. For this purpose, two numerical methods are proposed for simulating the hydraulic fracture in a naturally fractured gas reservoir. However, what hydraulic fracture looks like in the subsurface, especially in unconventional reservoirs, remain elusive, and many times, field observations contradict our common beliefs. In this study, the hydraulic fracture model is considered in terms of the state of tensions, on the interaction between the hydraulic fracture and the natural fracture (45°), and the effect of length and height of hydraulic fracture developed and how to distribute induced stress around the well. In order to determine the direction in which the hydraulic fracture is formed strikethrough, the finite difference method and the individual element for numerical solution are used and simulated. The results indicate that the optimum hydraulic fracture time was when the hydraulic fracture is able to connect natural fractures with large streams and connected to the well, and there is a fundamental difference between the tensile and shear opening. The analysis indicates that the growing hydraulic fracture, the tensile and shear stresses applied to the natural fracture.

Volume reduction of produced water generated from natural gas production process using membrane technology

2000 ◽  
Vol 41 (10-11) ◽  
pp. 117-123 ◽  
Author(s):  
C. Visvanathan ◽  
P. Svenstrup ◽  
P. Ariyamethee
Keyword(s):  
Natural Gas ◽  
Produced Water ◽  
Hollow Fibre ◽  
Gas Production ◽  
Oil And Grease ◽  
Natural Gas Production ◽  
Pre Treatment ◽  
Selection Of ◽  
Spiral Wound

This paper presents a case study of a natural gas production site covering various technical issues related to selection of an appropriate Reverse Osmosis (RO) system. The long-term field experience indicates the necessity of the selection of appropriate pretreatment systems for fouling-free RO operational conditions. The produced water has a variety of impurities such as oil and grease, process chemicals used for corrosion and scaling control, and dehydration of natural gas, etc. This situation leads to a complicated and extremely difficult task for a membrane specialist to design RO systems, especially the pre-treatment section. Here as part of the pretreatment selection, two types of UF membrane modules viz. spiral wound and hollow fibre, with MWCO of 8000 and 50,000 Dalton respectively, were tested in parallel with NF membranes of the spiral wound type with MWCO 200 Dalton. The UF permeate is used as feed for RO compatibility testing. Both configurations of UF failed to be compatible, due to irreversible fouling of the RO membrane. The NF membrane, however, showed interesting results, due to membrane stability in terms of cleaning and fouling. The NF plant with 50% capacity gave a recovery of 75% and the RO plant gave a recovery of 60% versus the expected 92–95%. The long-term tests have indicated that the reminder of the membranes could be installed to achieve full capacity of the plant. This study also demonstrates the importance of selection of proper pre-treatment set-up for the RO system design.

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