bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Injection Well Fracturing in Extra Low-Permeability Oilfields
Authors: Jinfang Wang , Xingfan Zheng , Zhengmao Wang , Changbing Tian , Lei Xu , Xiaocui Gao 
Published: August 2016

Abstract
For the oil reservoirs with permeability less than 10×10-3μm2, the recovery rate is unsatisfactory because of poor reserve abundance, low pressure, low injection rate and high initial water saturation. This paper discusses the necessity and rationality of injection well fracturing, and optimizes the well spacing and fracture length of the production and injection well in extra low-permeability oilfields. The production wells are usually fractured for higher yield, however, injection wells are rarely fractured.
Mass data from field practice are analyzed in this paper. Changqing, Daqing and Jilin oilfield have all witnessed the journey of square inverted nine-spot well pattern, diamond shaped inverted nine-spot well pattern, square five-spot well pattern, rectangular well pattern, and linear injection pattern. The sweep efficiency and water flow direction are confirmed by core data in lab from 9 infill wells in a square inverted nine-spot well group in Changqing oilfield. Good agreement is obtained with field observations and lab. Using oil reservoir engineering method and numerical simulation with the Non-Darcy flow, this paper describes the optimization well pattern with injection and production wells fracturing.
After water flooding in the conventional areal well pattern, the injection water will flow toward the direction of the maximum principle stress, and finally forms the linear water injection, resulting in the low oil recovery due to the heterogeneous lateral water flooding. After a near 30-year water flooding development, the core data from 9 infill wells have proved the vertical sweep efficiency achieved only 50%, while the plane sweep efficiency 60%. Both water injection rate and oil production decrease with the increase of water cut. However, as water injection channel is formed with injection well fracturing, lateral water flood will displace homogeneously from the row of water wells to the row of oil wells. The injection wells fracturing increase the perforation and the injecting efficiency. Through the optimization of wells and the fracture length with the numerical simulation, an effective displacement pressure system is established for extra low-permeability oilfields. Compared with the adjacent area, Zhaozhou oilfield pilot tests were carried out according to the simulation studies and have achieved encouraging results in Daqing oilfield.
The novelty of injection well fracturing is in the ability to improve the injection efficiency and displace homogeneously toward the channel designed. The higher injecting efficiency is, the less injectors, well spacing density, and cost will be required, which properly serves the situation of low oil price.
Development and Application of a Recyclable Fluid for Sulige Tight Gas Fracturing
Authors: Huaqiang Shi , Xianwen Li , Li Ding , Yajuan Wang , Xiaolin Qiu , Ningjun Li 
Published: August 2016

Abstract
The pay zone of Sulige gas field is the most typical tight sandstone rservior in China. In recent years, multi-stage completion practices of vertiacal and horizontal wells brought about significant enhancement of single well production rate and economic benefit and caused a sharp increase of water consumption as well. Currently guar-based polymers are largely used in fracturing operations in Sulige gas wells. The system exhibit good rheological properties on one hand, and it can not meet the requirement of water saving, environmental protection and factory fracturing mode on the other due to its tendency to degrade, complex disposal and high cost. As a response, a low-cost recyclable fracturing fluid is developed and tried for the gas field.
A polyacrylamide polymer with surface activity is synthesized based on the consideration of reservoir characteristics, requirements in fracturing and well pad situation. The polymer and alkyl sulfonate surfactant additive formed a reversible structure in water by the action between hydrogen bonds and molecular chains. The fluid provides a good viscoelastic behavior and can meet the needs of fracturing treatment. It can be broken upon contact with formation fluid and rock minerals without destroying the molecular structure of the polymer. The flowback fluid can regain the viscoelasticity and be reused after simple settling and adding in proper dosage of the polymer. Lab experiment shows that the novel fluid has good temperature/shear resistance and excellent proppant transport capability. It is also easy to be cleaned up without leaving residue. Moreover, the performance of the recycled fracturing fluid can reach the level of that of prepared with fresh water. From 2014 to 2015, the recyclable fluid has been applied successfully in 230 wells in Sulige with a total volume of approximate 1,000,000 m3. The recovered flowback fluid is 400,000 m3, of which 380,000 m3 was reused. The recycling rate is as high as 95%. The fluid can meet the needs for continuous-mixing and low friction during treatment. The flowback fluid is also easier and less costly to be recycled in comparasion to guar gel fracs. These advantages promise its wide adaptability.
Maximizing Productivity with Ultra-Lightweight Proppant in Unconventional Wells: Simulations and Field Cases
Authors: Han Jianhang , Pirogov Alexander , Li Chunlou , Hurt Robert , Sookprasong Andy , Min Kim Jeong 
Published: August 2016

Abstract
Proppants are placed in fractures to provide highly conductive paths for hydrocarbons to flow from the reservoir to the wellbore. Hydraulic fracturing technology is constantly improving to achieve better production performance. Ultra-lightweight (ULW) proppants are one of the technologies introduced to improve fracturing effectiveness. Compared to sand, ULW proppants can be carried farther and distributed more evenly within fractures, resulting in more propped fracture area. This paper evaluates the impact of ULW proppants on production performance in tight reservoirs and examines characteristics of formations where ULW proppants are most beneficial.
To explore the advantages of ULW, hydraulic fracture models are developed. These models help in understanding the fracture geometric properties. This information is then incorporated into reservoir production models to evaluate the impact on production performance. Fractures using ULW proppants and the resulting well productivity are compared to those using sand. No technology provides a solution for all situations, and neither do ULW proppants. To better understand if ULW proppants bring the most benefit for production performance, data-mining techniques were used to identify ULW proppant field applications.
Results showed that ULW proppants had better vertical distribution within the fractures than sand (sand had a tendency to settle to the lower part of fractures, leaving the upper part unpropped). In a thick reservoir formation with insufficient vertical conductivity, fractures created by ULW proppants connected larger volumes of rock, leading to higher well productivity and increased EUR.
This study discusses the benefits that ULW proppants can bring to unconventional producers and identifies potential candidate formations where ULW proppant may be very effective. Field cases are included to show the benefits of ULW and the circumstances where they can bring the most value.
Fracturing Evaluation for Fractured-Caved Carbonate Reservoirs through Pressure Transient Analysis and Rate Transient Analysis
Authors: Li Yong , Wang Qi , Li Baozhu , Deng Xingliang , She Zhicheng , Liu Zhiliang 
Published: August 2016

AbstractNaturally fractured-caved carbonate reservoirs in China have some distinctive characteristics: deeply buried, multi-scale fractures, vugs and caves developed, strong heterogeneity, poor reservoir connectivity and no oil in matrix. Hydraulic fracturing is commonly used in order to connect offset fracture-cave system with wellbore and improve well performance for this kind of reservoirs, while how to properly evaluate hydraulic fracturing efficiency is still a major challenge. This paper presents an integrated evaluation method to solve this problem.The method mainly involves pressure transient analysis and rate transient analysis. Firstly, typical diagnostic curves of different fracture-cave patterns with and without hydraulic fracturing respectively are established through design analysis of numerical conceptual models. Then the curves are used for actual well stimulation and evaluation. Finally, reservoir properties of fracturing wells such as OOIP, hydraulic fracture properties, reservoir permeability, etc. are evaluated based on the integrated pressure transient analysis and rate transient analysis method.This new method has been applied to Tazhong No.I fractured-caved carbonate gas condensate reservoir in China. The reservoir's mid-depth is around 6000m and is currently under primary depletion development with an average annual production declining rate higher than 25%. Based on the understanding of seismic interpretation and geological study, 3 major reservoir patterns and 7 sub-patterns are classified. Then corresponding conceptual numerical models of these patterns with and without hydraulic fracturing are established, and typical diagnostic curves of pressure transient analysis and rate transient analysis for identification of these patterns are generated. And then, the results are applied to the actual well fracturing evaluation in Tazhong NO. I carbonate gas condensate reservoir.This systematic technique has been successfully applied to Tazhong No. I fractured-caved carbonate reservoir in Tarim Basin of China, which properly and correctly evaluates the properties of the hydraulic fracturing wells. It also provides a reliable method for decision making of hydraulic fracturing, which is helpful for effective and economic development of the reservoir.
Investigating and Optimizing the Use of High-Hardness Produced Water as Fracturing Fluid: A Simulation Approach
Authors: Bao Chen , Han Jiahang , Sun Hong , Sookprasong P. A. 
Published: August 2016

Abstract
The ongoing low oil price environment has profound impact on all the operators and service providers. Efficiency improvements and cost reductions are two key strategies to capture the opportunities in current situation. It is now imperative for engineers to improve engineering practices to gain efficiency and drive down the cost. However, in well stimulation practices, it is vital to all stakeholders to obtain fracturing fluids with desirable fluid viscosity, and thermal and chemical properties with cost as low as reasonably possible.
Preparing fracturing fluids with high-hardness produced water is one option to drive down cost. Such a practice eliminates the need to transport fresh water and dispose wastewater. However, it may not be possible because of the reaction tendencies between cations and functioning polymers within fracturing fluids. Although combinations of chemicals including polymers, chemical additives, stabilizers, and buffers can be added to prevent such reactions, the dosages of each component are often hard to quantify and often dependent on the experience of field engineers. A fast prognosis tool has been developed to facilitate such a decision-making process by identifying the lowest possible dosages of chemicals dependent on produced water hardness. With such a prognosis tool, it is now possible to make more educated and cost-effective plans to optimize the engineering practice.
In this work, the underlying physics of hard water damage to fracturing fluids is discussed, followed by a demonstration of the simulations that reproduced the lab rheology experiment results. The viscosity profiles of a number of rheology experiments were first matched as model calibrations. The effects of different stabilizers were then discussed by parametric comparison of different cases. With the predictive model successfully capturing the reaction system, a dynamic algorithm was built to compute the lowest cost possible solution of functioning fracturing fluids in a given system. Due to the non-linear nature of the chemical reaction system, a searching algorithm was implemented to minimize the cost of fracturing fluids as functions of local produced water hardness, cost of each chemical component and operational expenses.
This work demonstrates that good engineering practices are achieved through carefully understanding and modeling a working system, and through dynamic planning of the overall workflow with cost optimization as a target. All in the form of a prognosis tool that could be easily implemented in the current fracturing fluid preparation work flow.
Magnetic Recovery-Injecting Newly Designed Magnetic Fracturing Fluid with Applied Magnetic Field for EOR
Authors: Shekhawat Dushyant Singh , Aggarwal Avi , Agarwal Soham , Imtiaz MD 
Published: August 2016

Abstract
Ferrofluids are Fe3O4 based Magnetic Nano Particles (MNPs) and can be coated with a layer to form a super-hydrophobic material which selectively adsorbs oil. These colloidal ferromagnetic nano-particles show remarkable magnetic susceptibility. The ability of ferrorfluids was at display in the Gulf of Mexico and other oil spill clean-up. Excellent on-surface results suggest us to exploit its potential under sub-surface conditions too. The paper puts forward the potential on MNPs in EOR/IOR, proper production scenarios and techniques to inject this magnetically-controlled oil-adsorbing fluid through pad during hydraulic-fracturing operations.
Sodium oleate coated magnetite (Fe3O4) is found to be the best suited MNP constituent for pad fluid. Fe3O4 particles modified with sodium oleate have successfully been able to generate super-hydrophobic surfaces. Their average size ranges from ~5nm to 10nm, thus are capable of getting suspended in pad fluid during injection and passing through the oil bearing zone without plugging the pores during fracturing operation. MNP's motion can be forced and controlled by applying magnetic field which makes MNPs a great asset for improvisation of fracturing techniquesn (Experimentally tested over 100 different oil and heavy crude oil at FERMILAB, Batavia Illinois).
Injecting highly viscous Frackfluid ‘pad’ is amongst the primary part of fracturing job as it is used to initiate/propagate the fracture. Continuous loss of pad to formation will cause fracture propagation and at the final stage pad will be completely lost to the formation. Oleate coated MNP injected along with pad will selectively adsorb oil in the region where pad interacts with oil in formation. Initially applying outward magnetic field will cause solid MNPs to reach farther in formations, leaving behind the injected fluid in nearby formation, to sweep maximum reservoir volume. Second step is to apply an inward field towards the bore hole, which will force the MNPs to trace back into the wellbore along with adsorbed hydrocarbon on their surface. Magnetic field can easily drive these nanoparticles through tight/low permeable reserves and during heavy crude recovery. Their selective adsorption and hydrophobic nature can be of great significance in production through water bearing zones. Prepared MNP is both hydrophobic and lipophilic. Therefore Fe3O4 with sodium oleate could be soundly dispersed in the oil medium present in formations and recovered by applying magnetic field directed toward producing well.
This technique shows a new path for the industry in advanced fracturing operations involving fracturing through deep, heavy oil reserves, HPHT and highly water saturated reserves. Validity of the proposed process has been elucidated in the paper considering various technical and operational variables.
Source Mechanism Studies of Acoustic Emission in Large-Scale Hydraulic Fracturing Experiment
Authors: Tiancheng Liang , Haifeng Fu , Yongjun Lu , Yunzhi Liu , Jingjing Dou , Nailing Xiu , Guorong Tian 
Published: August 2016

Abstract
Hydraulic fracturing plays a significant role in unconventional oil and gas reservoirs. The hydraulic fracture initiation and propagation mechanism is fundamental important, but is understood unclearly. The large-scale hydraulic fracturing experiment, with the sample size of 30in*30in*36in, can simulate reservoir stimulation under the in-situ stress with the acoustic emission (AE) monitoring. AE is used to monitor fracture initiation and propagation in real-time and analyze the source mechanism of rocks.
The shear slippage can effectively enhance reservoir permeability, which makes the source of AE events important. In order to characterize the source mechanism, two methods are used in this paper: (1) the moment tensor inversion analysis, using P-wave first-motion polarities and amplitudes to determine crack type classifications from a unified decomposition of eigenvalues; (2) the single wave characteristic parameter analysis, using RA value (=the rise time/the maximum amplitude in mV) and average frequency (= AE ring down-count/the duration time) respectively as horizontal axis and vertical axis to plot a scatter diagram.
According to large-scale experiments with sandstone, coal and shale, results show that: (1) The conclusions obtained by the two methods are similar. Using the single wave characteristic parameter analysis to evaluate fracture mechanism in fracturing simulation experiment, the fractures are classified into two major groups: tensile fractures and shear fractures. (2) Tight sandstone only produces tensile fractures. The coal, shale and naturally fractured sandstone blocks have more complex mechanism with tensile and shear fractures, due to the existence of favorable natural fractures under specific in-situ stress and the injection pressure. (3) Spatial and temporal distribution of hypocenters is observed. A bi-wing planar fracture is formed in tight sandstone, but non- planar fracture networks exist in coal and shale blocks.
This work can help engineers establish a proper model for the estimation of effective stimulated reservoir volume (ESRV) using the microseismic data in hydraulic fracturing.
Eco-Friendly Hydraulic Fracturing Fluid: Field Deployment and Performance Evaluation in Saudi Arabia's Tight Gas Reservoirs
Authors: AlKhowaildi Mustafa A. , AlGhazal Mohammed A. , Al-Driweesh Saad , Abbad Emad , Abdrabalnabi Hussain 
Published: August 2016

Abstract
With the increase in demand for energy, natural gas from tight reservoirs is being targeted abundantly around the globe by different operators using hydraulic fracture technology. Reducing the environmental footprint associated with hydraulic fracturing is a priority in optimizing this technology. An environment friendly, polymer-free fracturing fluid has shown remarkably consistent results, following multiple deployments in Saudi Arabian tight gas formations.
Alongside laboratory tests, field studies such as fracture geometry and conductivity, ecological impact and well productivity were investigated over several wells targeting the same formation. The main objective was to test the field performance consistency of the fluid. Also, integrated post treatment results were collected as case histories for comparison to offset wells.
Flowback data indicated significant reduction in fracture cleanup time with 95% retrieved fluids compared to 40-60% in polymer-based fluid. Therefore, improvement in early production response was noticed due to higher retained permeability and proppant pack was left damage-free due to minimal residue left inside the formation. The post treatment reports indicated improved fracture conductivity and geometry containment in the pay zone compared to offset wells that used conventional polymer-based fluids. Additionally, because of its enhanced viscoelastic nature, the fluid system exhibited excellent proppant transport capacity at low viscosity without compromising fracture half length.
The environmentally friendly surfactant-based fracturing fluid demonstrated superior performance in tight sand formations of Saudi Arabia, especially while stimulating zones in close proximity to water zones where contamination must be prevented. This paper will also discuss the potential of further development to this fluid such as improving its overall efficiency that could mark future technological advances in the petroleum industry.
The Effect of Rock Properties on Fracture Conductivity in the Marcellus Shale
Authors: Perez Pena P.. , Zhu D.. , Hill A. D. 
Published: August 2016

Abstract
The success of fracture stimulations depends on the ability to fracture the rock and to maintain fracture conductivity. Therefore, in order to have a successful treatment, the effect of rock and proppant characteristics should be understood. This paper investigates the relationship between fracture conductivity and rock properties for two different locations in the Marcellus shale.
In this work, a series of experiments were performed in order to better understand the mechanical behavior of the Marcellus Shale. Multiple cores from Allenwood and Elimsport locations in Pennsylvania were collected to ensure repeatability in the results. The core samples were cut parallel and perpendicular to the bedding planes in order to analyze the effect of anisotropy in fracture conductivity. Additionally, compressive triaxial tests were performed to obtain the rock mechanical properties such as Young's Modulus, Poisson's Ratio and Ultimate Compressive Strength, and X-ray Diffraction analysis was used to obtain mineralogy composition.
The laboratory results were carefully compared with previous fracture conductivity data and surface roughness data from the same Marcellus shale locations where proppant concentration was kept constant to reduce the variables affecting the fracture conductivity behavior. The findings showed that the anisotropy effect is present for this formation and reflected in the fracture conductivity values, where samples parallel to the bedding plane seem to have higher Young's Modulus. It was confirmed that at proppant monolayer concentration the main mechanism for conductivity loss is proppant embedment, where due to the high localized stress, the rock-proppant interaction goes directly to permanent deformation of the rock. It was also observed that a higher Young's Modulus helps to maintain the fracture width which translates in lower rate of conductivity loss with increasing closure stress, therefore, rock mechanical properties have impact on fracture conductivity. The phenomenon observed is less pronounced if a multilayer proppant concentration is used, where the proppant pack characteristics become an important parameter in fracture conductivity.
In this paper, we present an analysis of the effect of rock properties in the fracture conductivity behavior based on a series of experimental results from the Marcellus Shale, where the role of permanent deformation was taken into consideration as a parameter causing fracture conductivity lost. This is the first time the effect of rock characteristics in fracture conductivity is analyzed based on experimental work for the Marcellus shale.