Supramolecular dynamic binary complexes with pH and salt-responsive properties for use in unconventional reservoirs

Hydraulic fracturing of unconventional reservoirs has seen a boom in the last century, as a means to fulfill the growing energy demand in the world. The fracturing fluid used in the process plays a substantial role in determining the results. Hence, several research and development efforts have been geared towards developing more sustainable, efficient, and improved fracturing fluids. Herein, we present a dynamic binary complex (DBC) solution, with potential to be useful in the hydraulic fracturing domain. It has a supramolecular structure formed by the self-assembly of low molecular weight viscosifiers (LMWVs) oleic acid and diethylenetriamine into an elongated entangled network under alkaline conditions. With less than 2 wt% constituents dispersed in aqueous solution, a viscous gel that exhibits high viscosities even under shear was formed. Key features include responsiveness to pH and salinity, and a zero-shear viscosity that could be tuned by a factor of ~280 by changing the pH. Furthermore, its viscous properties were more pronounced in the presence of salt. Sand settling tests revealed its potential to hold up sand particles for extended periods of time. In conclusion, this DBC solution system has potential to be utilized as a smart salt-responsive, pH-switchable hydraulic fracturing fluid.

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Supramolecular Viscosity Modifiers With Salt-responsive and Ph-switchable Characteristics for Hydraulic Fracturing Applications

10.21203/rs.3.rs-453320/v1 ◽

2021 ◽

Author(s):

Shuhao Liu ◽

Yu-Ting Lin ◽

Martin L. Sentmanat ◽

Joseph Kwon ◽

Mustafa Akbulut ◽

...

Keyword(s):

Hydraulic Fracturing ◽

Self Assembly ◽

Energy Demand ◽

Low Molecular Weight ◽

Binary Complex ◽

Solution System ◽

Fracturing Fluid ◽

Zero Shear Viscosity ◽

Fracturing Fluids ◽

Alkaline Conditions

Abstract Hydraulic fracturing has seen a boom in the last century, as a means to fulfill the growing energy demand in the world. The fracturing fluid used in the process plays a substantial role in determining the results. Hence, several research and development efforts have been geared towards developing more sustainable, efficient, and improved fracturing fluids. Herein, we present a dynamic binary complex (DBC) solution, with potential to be useful in the hydraulic fracturing domain. It has a supramolecular structure formed by the self-assembly of low molecular weight viscosifiers (LMWVs) oleic acid and diethylenetriamine into an elongated entangled network under alkaline conditions. With less than 2 wt% constituents dispersed in aqueous solution, a viscous gel that exhibits high viscosities even under shear was formed. Key features include sensitivity to pH and salinity, and a zero-shear viscosity that could be tuned by a factor of ~280 by changing the pH. Furthermore, its viscous properties were pronounced in the presence of salt. Sand settling tests revealed its potential to hold up sand particles for extended periods of time. In conclusion, this DBC solution system has potential to be utilized as a smart salt-responsive, pH-switchable hydraulic fracturing fluid that can be prepared using seawater.

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Insight into the Methods for Improving the Utilization Efficiency of Fracturing Liquid in Unconventional Reservoirs

Geofluids ◽

10.1155/2021/6438148 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Tianlu Xu ◽

Yingxian Lei ◽

Chengmei Wu ◽

Yinghao Shen

Keyword(s):

Hydraulic Fracturing ◽

Formation Energy ◽

Large Scale ◽

Utilization Efficiency ◽

Unconventional Reservoirs ◽

Main Function ◽

Shale Oil ◽

Pressure Balance ◽

Fracturing Fluid ◽

Fracturing Fluids

A large amount of fracturing fluid will be injected into the unconventional reservoirs during hydraulic fracturing. At present, the maximum amount of fracturing fluid injected into shale oil reaches 70000 m3 in Jimsar. The main function of fracturing fluid is to make fractures for traditional reconstruction of fracturing; for unconventional reservoirs, fracturing fluid is also used to increase formation energy by large-scale injection. It is of great significance to improve the utilization efficiency of large-scale hydraulic fracturing fluid for shale oil to increase production and recovery. In this study, the method of improving the utilization efficiency of the large-scale hydraulic fracturing fluids is explored by experiment, numerical simulation, and field test of Jimsar shale oil formation. This research shows that fracture complexity can effectively increase the contact area between the fracturing fluids and the formation. The water absorption rate of the fractured core is increased, which lays the foundation for improving the liquid utilization efficiency. Reasonably, well shutting before production ensures the pressure balance in the fractures, and the fluid pressure can be transmitted to the far end, which improves the fracture effectiveness, increases formation energy, and promotes imbibition and oil displacement. By using the additive of enhanced imbibition displacement, the displacement efficiency and the displacement amount of crude oil in the micro-nanopores can be greatly improved, and the utilization ratio of liquid can be further enhanced. The experiment adopted in the field proves that improving energy utilization efficiency has an important impact on production. This study has great guiding significance for the efficient development and practical production of unconventional reservoirs.

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Laboratory Testing of Fracture Conductivity Damage by Foam-Based Fracturing Fluids in Low Permeability Tight Gas Formations

Energies ◽

10.3390/en14061783 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1783

Author(s):

Klaudia Wilk-Zajdel ◽

Piotr Kasza ◽

Mateusz Masłowski

Keyword(s):

Hydraulic Fracturing ◽

Guar Gum ◽

Polymer Concentration ◽

Laboratory Research ◽

Damage Effect ◽

Tight Gas ◽

Fracturing Fluid ◽

Fracture Conductivity ◽

Fracturing Fluids ◽

Sandstone Rock

In the case of fracturing of the reservoirs using fracturing fluids, the size of damage to the proppant conductivity caused by treatment fluids is significant, which greatly influence the effective execution of hydraulic fracturing operations. The fracturing fluid should be characterized by the minimum damage to the conductivity of a fracture filled with proppant. A laboratory research procedure has been developed to study the damage effect caused by foamed and non-foamed fracturing fluids in the fractures filled with proppant material. The paper discusses the results for high quality foamed guar-based linear gels, which is an innovative aspect of the work compared to the non-foamed frac described in most of the studies and simulations. The tests were performed for the fracturing fluid based on a linear polymer (HPG—hydroxypropyl guar, in liquid and powder form). The rheology of nitrogen foamed-based fracturing fluids (FF) with a quality of 70% was investigated. The quartz sand and ceramic light proppant LCP proppant was placed between two Ohio sandstone rock slabs and subjected to a given compressive stress of 4000–6000 psi, at a temperature of 60 °C for 5 h. A significant reduction in damage to the quartz proppant was observed for the foamed fluid compared to that damaged by the 7.5 L/m3 natural polymer-based non-foamed linear fluid. The damage was 72.3% for the non-foamed fluid and 31.5% for the 70% foamed fluid, which are superior to the guar gum non-foamed fracturing fluid system. For tests based on a polymer concentration of 4.88 g/L, the damage to the fracture conductivity by the non-foamed fluid was 64.8%, and 26.3% for the foamed fluid. These results lead to the conclusion that foamed fluids could damage the fracture filled with proppant much less during hydraulic fracturing treatment. At the same time, when using foamed fluids, the viscosity coefficient increases a few times compared to the use of non-foamed fluids, which is necessary for proppant carrying capacities and properly conducted stimulation treatment. The research results can be beneficial for optimizing the type and performance of fracturing fluid for hydraulic fracturing in tight gas formations.

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Performance Evaluation of Enzyme Breaker for Fracturing Applications under Simulated Reservoir Conditions

Molecules ◽

10.3390/molecules26113133 ◽

2021 ◽

Vol 26 (11) ◽

pp. 3133

Author(s):

Yuling Meng ◽

Fei Zhao ◽

Xianwei Jin ◽

Yun Feng ◽

Gangzheng Sun ◽

...

Keyword(s):

Hydraulic Fracturing ◽

Shear Resistance ◽

Ammonium Persulfate ◽

Fracturing Fluid ◽

Medium Temperature ◽

Fracture Conductivity ◽

Wide Range ◽

Reservoir Conditions ◽

Alkaline Conditions ◽

Resistance Performance

Fracturing fluids are being increasingly used for viscosity development and proppant transport during hydraulic fracturing operations. Furthermore, the breaker is an important additive in fracturing fluid to extensively degrade the polymer mass after fracturing operations, thereby maximizing fracture conductivity and minimizing residual damaging materials. In this study, the efficacy of different enzyme breakers was examined in alkaline and medium-temperature reservoirs. The parameters considered were the effect of the breaker on shear resistance performance and sand-suspending performance of the fracturing fluid, its damage to the reservoir after gel breaking, and its gel-breaking efficiency. The experimental results verified that mannanase II is an enzyme breaker with excellent gel-breaking performance at medium temperatures and alkaline conditions. In addition, mannanase II did not adversely affect the shear resistance performance and sand-suspending performance of the fracturing fluid during hydraulic fracturing. For the same gel-breaking result, the concentration of mannanase II used was only one fifth of other enzyme breakers (e.g., mannanase I, galactosidase, and amylase). Moreover, the amount of residue and the particle size of the residues generated were also significantly lower than those of the ammonium persulfate breaker. Finally, we also examined the viscosity-reducing capability of mannanase II under a wide range of temperatures (104–158 °F) and pH values (7–8.5) to recommend its best-use concentrations under different fracturing conditions. The mannanase has potential for applications in low-permeability oilfield development and to maximize long-term productivity from unconventional oilwells.

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Leak-Off Coefficient Analysis in Stimulation Treatment Design

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.933.202 ◽

2014 ◽

Vol 933 ◽

pp. 202-205

Author(s):

Bo Cai ◽

Yun Hong Ding ◽

Yong Jun Lu ◽

Chun Ming He ◽

Gui Fu Duan

Keyword(s):

Hydraulic Fracturing ◽

Field Method ◽

Oil Field ◽

Low Permeability ◽

Analysis Model ◽

Fracturing Fluid ◽

Real Time Analysis ◽

Fracturing Fluids ◽

Common Technique ◽

Treatment Design

Hydraulic fracturing was first used in the late 1940s and has become a common technique to enhance the production of low-permeability formations.Hydraulic fracturing treatments were pumped into permeable formations with permeable fluids. This means that as the fracturing fluid was being pumped into the formation, a certain proportion of this fluid will being lost into formation as fluid leak-off. Therefore, leak-off coefficient is the most leading parameters of fracturing fluids. The accurate understanding of leak-off coefficient of fracturing fluid is an important guidance to hydraulic fracturing industry design. In this paper, a new field method of leak-off coefficient real time analysis model was presented based on instantaneous shut-in pressure (ISIP). More than 100 wells were fractured using this method in oil field. The results show that average liquid rates of post-fracturing was 22m3/d which double improvement compared with the past treatment wells. It had an important role for hydraulic fracturing stimulation treatment design in low permeability reservoirs and was proven that the new model for hydraulic fracturing treatment is greatly improved.

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Modeling Hydraulic Fracturing Using Natural Gas Foam as Fracturing Fluids

Energies ◽

10.3390/en14227645 ◽

2021 ◽

Vol 14 (22) ◽

pp. 7645

Author(s):

Shuang Zheng ◽

Mukul M. Sharma

Keyword(s):

Equation Of State ◽

Natural Gas ◽

Hydraulic Fracturing ◽

Gas Emission ◽

Fracturing Fluid ◽

Fracturing Fluids ◽

Water Based ◽

Simulation Results ◽

The Cost ◽

Stranded Gas

Stranded gas emission from the field production because of the limitations in the pipeline infrastructure has become one of the major contributors to the greenhouse effects. How to handle the stranded gas is a troublesome problem under the background of global “net-zero” emission efforts. On the other hand, the cost of water for hydraulic fracturing is high and water is not accessible in some areas. The idea of using stranded gas in replace of the water-based fracturing fluid can reduce the gas emission and the cost. This paper presents some novel numerical studies on the feasibility of using stranded natural gas as fracturing fluids. Differences in the fracture creating, proppant placement, and oil/gas/water flowback are compared between natural gas fracturing fluids and water-based fracturing fluids. A fully integrated equation of state compositional hydraulic fracturing and reservoir simulator is used in this paper. Public datasets for the Permian Basin rock and fluid properties and natural gas foam properties are collected to set up simulation cases. The reservoir hydrocarbon fluid and natural gas fracturing fluids phase behavior is modeled using the Peng-Robinson equation of state. The evolving of created fracture geometry, conductivity and flowback performance during the lifecycle of the well (injection, shut-in, and production) are analyzed for the gas and water fracturing fluids. Simulation results show that natural gas and foam fracturing fluids are better than water-based fracturing fluids in terms of lower breakdown pressure, lower water leakoff into the reservoir, and higher cluster efficiency. NG foams tend to create better propped fractures with shorter length and larger width, because of their high viscosity. NG foam is also found to create better stimulated rock volume (SRV) permeability, better fracturing fluid flowback with a large water usage reduction, and high natural gas consumption. The simulation results presented in this paper are helpful to the operators in reducing natural gas emission while reducing the cost of hydraulic fracturing operation.

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A Novel Hydraulic Fracturing Method Based on the Coupled CFD-DEM Numerical Simulation Study

Applied Sciences ◽

10.3390/app10093027 ◽

2020 ◽

Vol 10 (9) ◽

pp. 3027

Author(s):

Cong Lu ◽

Li Ma ◽

Zhili Li ◽

Fenglan Huang ◽

Chuhao Huang ◽

...

Keyword(s):

Numerical Simulation ◽

Hydraulic Fracturing ◽

Variable Viscosity ◽

Oil Reservoirs ◽

Fluid Viscosity ◽

Low Density ◽

Fracturing Fluid ◽

Proppant Transport ◽

Fracturing Fluids ◽

Transport Experiment

For the development of tight oil reservoirs, hydraulic fracturing employing variable fluid viscosity and proppant density is essential for addressing the problems of uneven placement of proppants in fractures and low propping efficiency. However, the influence mechanisms of fracturing fluid viscosity and proppant density on proppant transport in fractures remain unclear. Based on computational fluid dynamics (CFD) and the discrete element method (DEM), a proppant transport model with fluid–particle two-phase coupling is established in this study. In addition, a novel large-scale visual fracture simulation device was developed to realize the online visual monitoring of proppant transport, and a proppant transport experiment under the condition of variable viscosity fracturing fluid and proppant density was conducted. By comparing the experimental results and the numerical simulation results, the accuracy of the proppant transport numerical model was verified. Subsequently, through a proppant transport numerical simulation, the effects of fracturing fluid viscosity and proppant density on proppant transport were analyzed. The results show that as the viscosity of the fracturing fluid increases, the length of the “no proppant zone” at the front end of the fracture increases, and proppant particles can be transported further. When alternately injecting fracturing fluids of different viscosities, the viscosity ratio of the fracturing fluids should be adjusted between 2 and 5 to form optimal proppant placement. During the process of variable proppant density fracturing, when high-density proppant was pumped after low-density proppant, proppants of different densities laid fractures evenly and vertically. Conversely, when low-density proppant was pumped after high-density proppant, the low-density proppant could be transported farther into the fracture to form a longer sandbank. Based on the abovementioned observations, a novel hydraulic fracturing method is proposed to optimize the placement of proppants in fractures by adjusting the fracturing fluid viscosity and proppant density. This method has been successfully applied to more than 10 oil wells of the Bohai Bay Basin in Eastern China, and the average daily oil production per well increased by 7.4 t, significantly improving the functioning of fracturing. The proppant settlement and transport laws of proppant in fractures during variable viscosity and density fracturing can be efficiently revealed through a visualized proppant transport experiment and numerical simulation study. The novel fracturing method proposed in this study can significantly improve the hydraulic fracturing effect in tight oil reservoirs.

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Performance and field implementation of a new fracturing fluid consisting of hydrophobically associating polyacrylamide and anionic surfactant

Journal of Polymer Engineering ◽

10.1515/polyeng-2014-0344 ◽

2016 ◽

Vol 36 (1) ◽

pp. 13-21 ◽

Cited By ~ 5

Author(s):

Zhongcong Zhao ◽

Tongyi Liu ◽

Pingya Luo ◽

Yan Li ◽

Jianxin Liu ◽

...

Keyword(s):

Network Structure ◽

Anionic Surfactant ◽

Self Assembly ◽

Fracturing Fluid ◽

Hydroxypropyl Guar ◽

Fluid Field ◽

Fracturing Fluids ◽

Hydrophobically Associating Polyacrylamide ◽

Hydrophobically Associating ◽

Static Conditions

Abstract The fundamental cause of the proppant suspension behavior in hydraulic fracturing fluids lies in its internal microcosmic network structure and structural strength. In addition to chemical crosslinking, another method to form a network structure is established in this paper. Hydrophobically associating polyacrylamide and an anionic surfactant self-assembly process was applied to form a network structure. Compared with crosslinked hydroxypropyl guar gel, the new fracturing fluid even has better proppant suspending properties in static conditions. The capability does not result from crosslinkage but from reinforced physical associations between chains. The performance of this new fracturing fluid was tested and the results showed that it can fully satisfy the requirement of fracturing fluid. Field test shows excellent stimulation effects during its applications in 400 wells in eight oilfields in China.

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In vitro cytotoxicity assessment of a hydraulic fracturing fluid

Environmental Chemistry ◽

10.1071/en14010 ◽

2015 ◽

Vol 12 (3) ◽

pp. 286 ◽

Cited By ~ 5

Author(s):

Madeleine E. Payne ◽

Heather F. Chapman ◽

Janet Cumming ◽

Frederic D. L. Leusch

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Human Health ◽

Produced Water ◽

Coal Seam Gas ◽

Fracturing Fluid ◽

Human Health Risks ◽

Fracturing Fluids ◽

Hydraulic Fracturing Fluid

Environmental context Hydraulic fracturing fluids, used in large volumes by the coal seam gas mining industry, are potentially present in the environment either in underground formations or in mine wastewater (produced water). Previous studies of the human health and environmental effects of this practice have been limited because they use only desktop methods and have not considered combined mixture toxicity. We use a novel in vitro method for toxicity assessment, and describe the toxicity of a hydraulic fracturing fluid on a human gastrointestinal cell line. Abstract Hydraulic fracturing fluids are chemical mixtures used to enhance oil and gas extraction. There are concerns that fracturing fluids are hazardous and that their release into the environment – by direct injection to coal and shale formations or as residue in produced water – may have effects on ecosystems, water quality and public health. This study aimed to characterise the acute cytotoxicity of a hydraulic fracturing fluid using a human gastrointestinal cell line and, using this data, contribute to the understanding of potential human health risks posed by coal seam gas (CSG) extraction in Queensland, Australia. Previous published research on the health effects of hydraulic fracturing fluids has been limited to desktop studies of individual chemicals. As such, this study is one of the first attempts to characterise the toxicity of a hydraulic fracturing mixture using laboratory methods. The fracturing fluid was determined to be cytotoxic, with half maximal inhibitory concentrations (IC50) values across mixture variations ranging between 25 and 51mM. When used by industry, these fracturing fluids would be at concentrations of over 200mM before injection into the coal seam. A 5-fold dilution would be sufficient to reduce the toxicity of the fluids to below the detection limit of the assay. It is unlikely that human exposure would occur at these high (‘before use’) concentrations and likely that the fluids would be diluted during use. Thus, it can be inferred that the level of acute risk to human health associated with the use of these fracturing fluids is low. However, a thorough exposure assessment and additional chronic and targeted toxicity assessments are required to conclusively determine human health risks.

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FORMATION HYDRAULIC FRACTURING FLUID BASED ON CARBOXYMETHYL CELLULOSE: ITS ADVANTAGES AND LIMITATIONS, APPLICATION PROSPECTS

Oil and Gas Studies ◽

10.31660/0445-0108-2016-2-49-57 ◽

2016 ◽

pp. 49-57

Author(s):

V. R. Kalinin

Keyword(s):

Hydraulic Fracturing ◽

Carboxymethyl Cellulose ◽

Low Cost ◽

Low Permeability ◽

Laboratory Studies ◽

Fracturing Fluid ◽

Fracturing Fluids ◽

Low Permeability Reservoirs ◽

Manufacturing Features ◽

Hydraulic Fracturing Fluid

The article considers the advantages and limitations of hydraulic fracturing fluid based on carboxymethyl cellulose determined as a result of laboratory studies. As a result of testing the studied fluid manufacturing features compared with similar fracturing fluids it was determined that the fluid of interest can be effectively used as a fluid for formation hydraulic fracturing especially in low permeability reservoirs. This fluid is widely available and has a low cost. It can easily replace the foreign analogues.

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