scholarly journals Experimental Study on the Damage of Artificial Fracture Permeability in Coal during the Flow Back of Guar-Based Fracturing Fluid

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Shenggui Liu ◽  
Jinkuang Huang ◽  
Songlei Tang ◽  
Shixiong Shi ◽  
Xuan Wu ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Fracture Permeability ◽  
High Concentration ◽  
Fracturing Fluid ◽  
Irreversible Damage ◽  
Damage Degree ◽  
Damage Rate ◽  
Fluid Concentration ◽  
Artificial Fracture ◽  
Coal Reservoir

After the completion of fracturing operation in coalbed methane (CBM), the fracturing fluid needs to flow back to the ground in time to reduce the damage to the coal reservoir. The damage of guar-based fracturing fluid to the coal reservoir has an adverse effect on the fracturing stimulation. A series of flow experiments were carried out with the unconventional natural gas reservoir damage evaluation equipment. This paper investigates the evolution of fracture permeability in coal samples during the process of hydroxypropyl guar (HPG) fracturing fluid flow back. The experimental results show that the fracturing fluid concentration, proppant type, proppant particle size, and proppant concentration all affect fracture permeability. The high concentration of fracturing fluid caused irreversible damage to fracture permeability of coal samples. With the increase of fracturing fluid concentration, the permeability damage rate increased from 65.31% to 84.57%, and the damage degree was strong. KCL brine flushing can only decrease the damage rate of coal sample fracture permeability within a certain range. The proppant embedment and the generation of pulverized coal exacerbated the damage of fracture permeability. The research results can be beneficial for optimizing the type and performance of fracturing fluid for hydraulic fracturing in CBM reservoir.

Study on Fracture Conductivity of Mahu Sandy Conglomerate Tight Oil Reservoir

2021 ◽  
Author(s):  
Liu Yang ◽  
Jingwei Gao ◽  
Shilei Chang ◽  
Qianbing Wan ◽  
Canhua Liu
Keyword(s):  
Oil And Gas ◽  
Stress Sensitivity ◽  
Tight Oil ◽  
Fracturing Fluid ◽  
Microscopic Mechanism ◽  
Irreversible Damage ◽  
Fracture Conductivity ◽  
Cyclic Loading Condition ◽  
Damage Rate ◽  
Tight Oil And Gas

Abstract Objectives/Scope: Effective development of tight oil and gas depends on the generation of artificial fractures, and continuous and efficient development of tight oil and gas requires the use of proppants to maintain the diversion effect of artificial fractures. At present, the microscopic mechanism of damage to fracture conductivity of sand conglomerate reservoir is not clear. Methods, Procedures, Process: Taking the sandstone conglomerate in Mahu sag as the research object, the experimental study on the fracture conductivity of the sandstone conglomerate in Mahu sag is carried out. First, the stress sensitivity analysis of the sandstone conglomerate is performed on a pore scale using a self-made permeability measurement method, then, the fracture width, pressure and flow rate are measured under the condition of fracture scale to analyze the change law of conductivity during fracturing fluid injection. Results, Observations, Conclusions: The results show that the permeability of gravel decreases with the increase of confining pressure, and the stress sensitive damage is strong. After a cyclic loading condition, permeability will not recover to the initial value, causing irreversible damage to the pore and roar. As the fracturing fluid continues to be injected, a large amount of proppant becomes embedded in the fracture and leads to a decrease in conductivity. The whole diversion curve can be divided into two stages. In the first stage, the diversion damage is great, and in the second stage, the diversion damage decreases somewhat. The damage of conductivity is closely related to the content of clay minerals.With the increase of clay mineral content, the conductivity damage rate increases rapidly, especially the existence of illite and Aimonite mixed beds can significantly improve the conductivity damage rate. Novel/Additive Information:The results provide a solution for the optimization of proppant concentration, the improvement of tight oil production and the study of gravel diversion damage mechanism in the Mahu area.

Simulation Study on Microscopic Penetration of Coalbed Gas

2014 ◽  
Vol 1073-1076 ◽  
pp. 2145-2148
Author(s):  
Jian Hua Zhao
Keyword(s):  
Coalbed Methane ◽  
Single Phase ◽  
Fracture Morphology ◽  
Coal Bed ◽  
Flow Conditions ◽  
Fracture Permeability ◽  
Coal Reservoir ◽  
The Impact

The fracture system plays a very important role in the coalbed methane migration because they dominate the coal reservoir fluid flow. For this reason, determination of fracture permeability properties control mechanism for forecasting capacity is very important. This thesis fracture morphology of the role of coal-bed methane migration control, in single-phase flow conditions to simulate the fluid nature of the gas, the deduction of the macroscopic permeability, numerical calculations of the impact fracture surface morphology of permeability.

Comparative Advantage of Using Biopesticides in Ukrainian Agroecosystems

2020 ◽  
Vol 2 (6) ◽  
Author(s):  
Hasrat Arjjumend ◽  
Konstantia Koutouki ◽  
Olga Donets
Keyword(s):  
Shelf Life ◽  
Crop Production ◽  
Plant Protection ◽  
Agricultural Practices ◽  
Crop Productivity ◽  
Poor Quality ◽  
Soil Biology ◽  
Chemical Contamination ◽  
High Concentration ◽  
Irreversible Damage

The use of unsustainable levels of chemical fertilizers and plant protection chemicals has resulted in a steady decline in soil and crop productivity the world over. Soil biology has undergone irreversible damage, coupled with a high concentration of toxic chemical residues in plant tissues and human bodies. Agricultural practices must evolve to sustainably meet the growing global demand for food without irreversibly damaging soil. Microbial biocontrol agents have tremendous potential to bring sustainability to agriculture in a way that is safe for the environment. Biopesticides do not kill non-target insects, and biosafety is ensured because biopesticides act as antidotes and do not lead to chemical contamination in the soil. This article is part of a larger study conducted in Ukraine by researchers at the Université de Montréal with the support of Mitacs and Earth Alive Clean Technologies. The responses of farmers who use biofertilizers (“user farmers”) and those who do not (“non-user farmers”), along with the responses of manufacturers or suppliers of biofertilizers, and research and development (R&D) scientists are captured to demonstrate the advantages of applying microbial biopesticides to field crops. Participants reported a 15-30% increase in yields and crop production after the application of biopesticides. With the use of biopesticides, farmers cultivated better quality fruits, grains, and tubers with a longer shelf life. Moreover, while the risk of crop loss remains high (60-70%) with chemically grown crops, this risk is reduced to 33% on average if crops are grown using biopesticides. The findings indicate that a large proportion of farmers would prefer to use biopesticides if they are effective and high quality products. In this context, the quality and effectiveness of products is therefore very important. Despite their benefits to soil, human health, and ecosystems, biopesticides face significant challenges and competition vis-à-vis synthetic pesticides for a variety of reasons. Therefore, the development of biopesticides must overcome the problems of poor quality products, short shelf life, delayed action, high market costs, and legal/registration issues.

scholarly journals A Comprehensive Coal Reservoir Classification Method Base on Permeability Dynamic Change and Its Application

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 644 ◽  
Author(s):  
Xinlu Yan ◽  
Songhang Zhang ◽  
Shuheng Tang ◽  
Zhongcheng Li ◽  
Yongxiang Yi ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Dynamic Change ◽  
Initial Permeability ◽  
Gas Production ◽  
Gas Desorption ◽  
Reservoir Permeability ◽  
Geological Conditions ◽  
Production Stages ◽  
Productivity Potential ◽  
Coal Reservoir

Due to the unique adsorption and desorption characteristics of coal, coal reservoir permeability changes dynamically during coalbed methane (CBM) development. Coal reservoirs can be classified using a permeability dynamic characterization in different production stages. In the single-phase water flow stage, four demarcating pressures are defined based on the damage from the effective stress on reservoir permeability. Coal reservoirs are classified into vulnerable, alleviative, and invulnerable reservoirs. In the gas desorption stage, two demarcating pressures are used to quantitatively characterize the recovery properties of permeability based on the recovery effect of the matrix shrinkage on permeability, namely the rebound pressure (the pressure corresponding to the lowest permeability) and recovery pressure (the pressure when permeability returns to initial permeability). Coal reservoirs are further classified into recoverable and unrecoverable reservoirs. The physical properties and influencing factors of these demarcating pressures are analyzed. Twenty-six wells from the Shizhuangnan Block in the southern Qinshui Basin of China were examined as a case study, showing that there is a significant correspondence between coal reservoir types and CBM well gas production. This study is helpful for identifying geological conditions of coal reservoirs as well as the productivity potential of CBM wells.

Numerical Simulation of Gas Injection for CBM Openhole Cavity Completion Considering the Coal Vertical Fracture System

2011 ◽  
Vol 101-102 ◽  
pp. 298-301
Author(s):  
Xiao Yi Li ◽  
Zhi Ming Wang ◽  
Xin Wan ◽  
Yang Cao
Keyword(s):  
Coalbed Methane ◽  
Displacement Vector ◽  
Fluid Velocity ◽  
Stress Gradient ◽  
Fracture System ◽  
Vertical Fracture ◽  
Matrix Deformation ◽  
Vector Distribution ◽  
Tensile Fractures ◽  
Coal Reservoir

A discrete element numerical model simulating the process of gas pressurization in coalbed methane wells is built based on UDEC software. The model considers the unique vertical fracture system of the coal. Simulates the distribution of effective stress, pore pressure and the node displacement vector around the wellbore in the process of pressurization under different terrestrial stress conditions. The analysis shows that, reservoir fluid flow and matrix deformation in the pressurization of cavity completion can be better represented by taking coal's unique fracture system into consideration. Coal reservoir with anisotropic stress is more prone to rupture and collapse than that under isotropic condition. In the vertical fracture system, the discrepancy of the fluid velocity will lead to differences in formation stress gradient and help generate shearing fracture. Tensile fractures’ formation and growing trend can be reflected by nodal displacement vector distribution.

Research on Nano-Emulsion Relieving Coal Seam Water Block Damage

2021 ◽  
Author(s):  
Wei Sun ◽  
LongHao Zhao ◽  
Qian Wang ◽  
Yanchi Liu ◽  
Weiping Zhu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coalbed Methane ◽  
Mixed Micelles ◽  
Polymer Adsorption ◽  
Coal Seams ◽  
Fracturing Fluid ◽  
Flow Experiment ◽  
Nano Emulsion ◽  
Water Block ◽  
Lock In

Abstract Hydraulic fracturing is the most effective reservoirstimulation techniques in the coalbed methane. However, the polymer in the fracturing fluid has a strong effect on the surface of the coal, causing the water lock damage as high as 70% to 90%. It is important to develop an efficient method for releasing coal seam water lock. In this paper, adsorption experiment, SEM, particle size experiment, core flow experiment, wettability and surface tension experiment are used to study the cause of coal seam water lock damage during fracturing and the effect of nano-emulsion on releasing water lock damage in coal seams. Experimental results show that after coal fracturing, the adsorption amount of polymer on the surface of coal is 14.81 mg/g. The large amount of hydrophilic polymer adsorption causes the pore radius of the coal to narrow. And the surface wettability changes from weak hydrophilic to strong hydrophilic, which increase the water lock damage. Compared with conventional slick water, fracturing fluid, the composite of nano-emulsion and fracturing fluid forms mixed micelles, which reduces the polymer adsorption capacity from 14.81 mg/g to 7.42 mg/g. After scanning by electron microscope, it is observed that the surface roughness of the rock sample is restored; The size of the nano-emulsion is about 10nm, and the very small volume can act deep in the pores of the coal seam; After using nano-emulsion, the gas/water interfacial tension is reduced by 45.1mN/m, and the wettability of coal is improved from hydrophilic to neutral, which reduces the capillary pressure in the pores of the coal and reduces the breakthrough pressure of coalbed methane by 11.1KPa; The water lock release rate is as high as 53.09%. The Nano-emulsion is an ideal choice to remove water lock damage.

Differences in petrophysical and mechanical properties between low- and middle-rank coal subjected to liquid nitrogen cooling in coalbed methane mining

2021 ◽  
pp. 1-10
Author(s):  
Menglin Du ◽  
Feng Gao ◽  
Chengzheng Cai ◽  
Shanjie Su ◽  
Zekai Wang
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
Liquid Nitrogen ◽  
Coalbed Methane ◽  
Bituminous Coal ◽  
Thermal Damage ◽  
Physical And Mechanical Properties ◽  
Damage Degree ◽  
Lignite Coal ◽  
The Difference

Abstract Exploring the damage differences between different coal rank coal reservoirs subjected to liquid nitrogen (LN2) cooling is of great significance to the rational development and efficient utilization of coalbed methane. For this purpose, the mechanical properties, acoustic emission (AE) characteristics and energy evolution law of lignite and bituminous coal subjected to LN2 cooling were investigated based on the Brazilian splitting tests. Then, pore structure changes were analyzed to reveal the difference in the microscopic damage between lignite and bituminous coal after LN2 cooling. The results showed that compared with bituminous coal, the pore structure of lignite coal changed more obviously, which was manifested as follows: significant increases in porosity, pore diameters, and pore area; a larger transformation from micropores and transition pores to mesopores and macropores. After LN2 cooling, the thermal damage inside lignite and bituminous coal was 0.412 and 0.069, respectively. The thermal damage reduced the cohesive force between mineral particles, leading to the deterioration of the macroscopic physical and mechanical properties. Simultaneously, denser AE ringing counts and larger accumulated ringing counts were observed after LN2 cooling. Moreover, the random distribution of thermal damage enhanced the randomness of the macrocrack propagation direction, resulting in an increase in the crack path tortuosity. With more initial defects inside coal, a more obvious thermal damage degree and wider damage distribution will be induced by LN2 cooling, leading to more complicated crack formation paths and a higher fragmentation degree, such as that of lignite coal.

scholarly journals Petrophysical characterization of high-rank coal by nuclear magnetic resonance: a case study of the Baijiao coal reservoir, SW China

2018 ◽  
Vol 5 (12) ◽  
pp. 181411 ◽  
Author(s):  
Dongming Zhang ◽  
Yapei Chu ◽  
Shujian Li ◽  
Yushun Yang ◽  
Xin Bai ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coalbed Methane ◽  
High Rank ◽  
Free Fluid ◽  
Permeability Model ◽  
Cutoff Value ◽  
Coal Reservoir ◽  
Nuclear Magnetic

To better apply nuclear magnetic resonance (NMR) to evaluate the petrophysical characterization of high-rank coal, six anthracite samples from the Baijiao coal reservoir were measured by NMR. The porosity, T 2 cutoff value, permeability and pore type were analysed using the transverse relaxation time ( T 2 ) spectrum before and after centrifugation. The results show that the T 2 spectrum of water-saturated anthracite can be divided into a discontinuous and continuous trimodal distribution. According to the connectivity among pores, three T 2 spectrum peaks were identified at the relaxation times of 0.01–1.7 ms, 1.7–65 ms and greater than 65 ms, which correspond to the micropores (less than 100 nm), mesopores (100–1000 nm) and macropores (greater than 1000 nm), respectively. Based on the T 2 cutoff value, we divided the T 2 spectrum into two parts: bound fluid and free fluid. By comparing two classic permeability models, we proposed a permeability model to calculate the permeability of anthracite. This result demonstrates that NMR has great significance to the exploration of coal reservoirs and to the understanding of the development of coalbed methane.

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