Hydraulic fracturing has been used by the oil and gas industry as a way to boost hydrocarbon production since 1947. Recent advances in fracturing technologies, such as multistage fracturing in horizontal wells, are responsible for the latest hydrocarbon produc- tion boom in the US. Linear or crosslinked guars are the most commonly used fluids in traditional fracturing operations. The main functions of these fluids are to open/propagate the fractures and transport proppants into the fractures. Proppants are usually applied to form a thin layer between fracture faces to prop the fractures open at the end of the fracturing process. Chemical breakers are used to break the polymers at the end of the fracturing process so as to provide highly conductive fractures. Concerns over fracture conduc- tivity damage by viscous fluids in ultra-tight formations found in unconventional reservoirs prompted the industry to develop an alter- native fracturing fluid called "slickwater". It consists mainly of water with a very low concentration of linear polymer. The low concentration polymer serves primarily to reduce the friction loss along the flow lines. Proppant-carrying capability of this type of fluids is still a subject of debate among industry experts. Constraints on local water availability and the potential for damage to formations have led the industry to develop other types of fracturing fluids such as viscoelastic surfactants and energized fluids. This article reviews both the traditional viscous fluids used in conventional hydraulic fracturing operations as well as the new family of fluids being devel- oped for both traditional and unconventional reservoirs. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131 ,4 0735.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/app.40735

A review of fracturing fluid systems used for hydraulic fracturing of oil and gas wells

A review of the current progress of CO2 injection EOR and carbon storage in shale oil reservoirs

http://nlhfrp.ca/wp-content/uploads/2015/01/1-s2.0-S0304389414003021-main.pdf

Physical, chemical, and biological characteristics of compounds used in hydraulic fracturing

Application of nanotechnology by means of nanoparticles and nanodispersions in oil recovery - A comprehensive review

The technology of hydraulic fracturing for hydrocarbon well stimulation is not new, but only fairly recently has become a very common and widespread technique, especially in North America, due to technological advances that have allowed extracting natural gas from so-called unconventional reservoirs (tight sands, coal beds and shale formations). The conjunction of techniques such as directional drilling, high volume fracturing, micro-seismic monitoring, etc. with the development of multi-well pads has been especially successful in the last years in their application to shales, making gas production from shales technically and economically feasible. In Europe, the potential application of this technology has led to both great worries and high expectations: worries regarding the alleged magnitude of the environmental impact, and expectations about production of indigenous hydrocarbons. Other types of formation stimulation exist that do not make use of water-based fluids (for instance, explosive fracturing, dynamic loading, etc.), or that make use of fluids other than water. These are currently not extensively applied due to performance considerations. As for any other industrial activity, the deployment of high-volume hydraulic fracturing could potentially entail some risks to the environment. Among the concerns raised are high usage of water, methane infiltration in aquifers, aquifer contamination, extended surface footprint, induced local seismicity, etc. New technologies could help addressing these concerns (for instance by using non-toxic chemicals, by reducing or eliminating altogether the usage of water, by considerably reducing the surface footprint of a well, etc.). This report reviews hydraulic fracturing and alternative fracturing technologies, by searching the open literature, patent databases and commercial websites (mainly in the English language). For each identified technique, an overview is given. The technique is then briefly explained, and its rationale (reasons for use) is identified. Potential advantages and disadvantages are identified, and some considerations on costs are given. Finally, the status of the technique (for instance, commercially applied, being developed, concept, etc.) is given for its application to shale gas production. As the Commission’s in-house science service, the Joint Research Centre’s mission is to provide EU policies with independent, evidence-based scientific and technical support throughout the whole policy cycle. Working in close cooperation with policy Directorates-General, the JRC addresses key societal challenges while stimulating innovation through developing new standards, methods and tools, and sharing and transferring its know-how to the Member States and international community. Key policy areas include: environment and climate change; energy and transport; agriculture and food security; health and consumer protection; information society and digital agenda; safety and security including nuclear; all supported through a cross- cutting and multi-disciplinary approach. L D -N A -2 6 3 4 7 -E N -N

/pdf/an-overview-of-hydraulic-fracturing-and-other-formation-b2rkdo3z29.pdf

An overview of hydraulic fracturing and other formation stimulation technologies for shale gas production

Effect of Shear Rate on the Activity of Enzymes Used in Hydraulic Fracture Cleanup of Tight Unconventional Reservoirs


 Simulation of gas huff-n-puff (HnP) in core models is often simplified by assuming homogenous, isotropic models, which are not representative of fine-grained multi-component shales with multiple types of pore space and anisotropic permeability. According to the previous literaturte, history matching of a 6-cycle HnP process and tuning of cross-phase effective diffusion coefficients using a homogeneous model presented a need for a detailed core-scale geomodel to capture variations in effective diffusion coefficients as a result of heterogeneity experienced during each diffusion cycle. A workflow for reconstructing a corescale volume of Lower Eagle Ford (LEF) shale is presented that combines rock characterization using high-resolution digital images at the micrometer/nanometer scale and transmitted light microscopy to provide models for detailed heterogeneity of the LEF shale for gas huff-n-puff simulation.
 Core-scale models form LEF are reconstructed using high-resolution SEM-EDS and FIB-SEM images. SEM-EDS and FIB-SEM images were coupled with transmitted light microsocpy and micro-computed tomography (CT) to constrain facies distribution, discrete fracture networks and to distribute petrophysical properties. The reconstruction method produced a more representative core model of the LEF and can be used for simulation of core-scale huff-n-puff experiments conducted in a diffusion cell.
 Common grain types observed in the SEM-EDS images at different resolutions include detrital quartz, calcite, microfossils and fragments, microfractures, clay minerals, traces of dolomite, and albite. Also common is diagenetic calcite, pyrite, kaolinite, and secondary organic matter (OM) infilling the chambers of foraminifer tests ("forams") and other mineral pores. FIB-SEM analysis provided organic bulk transport properties including tortuosity and permeability within the generated pore network models of the LEF shale. Transmitted light microscopy provided the lamina-scale variation of samples from the LEF shale to be incorporated in the core model.
 A detailed workflow is presented for reconstructtion of a LEF shale core-scale model using high- resolution images and photomicrographs. The model detailed the original core morphology, multiple pore space, and multicomponent mineral distributions for gas huff-n-puff simulation. Several realizations of the geomodel were prepared by varying mineral distributions within the layers as well as the range of petrophysical properties in order to present different gas huff-n-puff simulation scenarios. This provided the compositional model using a sophisticated heterogeneous component of tortuosity/permeability instead of a homogenous and isotropic model.

A Reconstructed Core-Scale Model of the Lower Eagle Ford Shale Through FIB-SEM, SEM-EDS, and Microscopy for Gas Huff-n-Puff Simulation


 Cavitation is among the most complex and common damages occurring in spillway structures, which is one of the most expensive parts of a dam. The cavitation index, as the one of the most efficient approaches, can be used to analyze this important hydraulic phenomenon. The present study examines the changes in the cavitation index caused by changes in the convergence angle of an ogee spillway's sidewalls with an arc in the plan. To this end, a spillway was constructed on the 1:50 scale. Then, it was tested with four different convergence angles, including 0°, 60°, 90°, and 120°, relative to the spillway's sidewalls and six different flow rates per unit width ranging from 6.74 to 48.42 (l/s)/m. The results indicated that as the flow rate increased, the cavitation index relatively declined at both crest and chute of the spillway while growing at its toe. It was observed that the lowest cavitation index was found to be 1.54 in.X/Hd = 2.42 at an angle of 0° and a flow rate per unit width of 40.52 (L/s)/m.

Experimental study of cavitation index in an ogee spillway by considering convergence angle of sidewalls


 A deep insight into tight gas transient flow behavior is important for understanding the production behavior of tight gas reservoirs. In this work, we constructed a two-dimensional model to illustrate one methodology of evaluating effective permeability of fractured flow media. Pulse-decay experiments on one fractured core to study porosity and permeability for both matrix and the fracture, under a series of pore pressure and effective stress. Based on the results, the approach proposed in this study has the advantage over the steady-state method that can capture the character of transient flow if the fracture network penetrates the core. The transient gas propagation in the matrix, fractured cored with the fracture width of 1 μm and 1 cm are in shapes of piston-like, arrow-like, and dumbbell-like, respectively. Though the fracture width is only 1 μm, it reduces the time to reach pressure equilibrium to about one-fourth and the effective permeably ratio is 3.98. Totally 59 pulse-decay experiments were performed on one fractured core. We successfully history matched all the pulse-decay experiments on a fractured core by a commercial simulator with the Global Match Error (GME) less than 0.2%, that the readers can readily adopt this approach. Based on the history matching of upstream and downstream pressure curves, the fracture permeability and porosity are 6 orders’ and 1 order's magnitude higher than the matrix. The matrix permeability is the most sensitive to the pore pressure and effective stress, and no consistent trend is observed for the fracture permeability and porosity as the pore pressure and effective stress change.

Reza Barati

Papers

Effect of Shear Rate on the Activity of Enzymes Used in Hydraulic Fracture Cleanup of Tight Unconventional Reservoirs

A Reconstructed Core-Scale Model of the Lower Eagle Ford Shale Through FIB-SEM, SEM-EDS, and Microscopy for Gas Huff-n-Puff Simulation

Experimental study of cavitation index in an ogee spillway by considering convergence angle of sidewalls

Insights into the Gas Transmission Test at Multiscale Based on Discrete-Fracture Model and History Matching

Hydraulic Fracturing Fluids and Production