Experimental Investigations of the Critical Flowback Velocity for Various Types of Proppant in Hydraulic-fracturing Fluids with Different Viscosities PDF Download

Author: Sijie Wang
Publisher:
ISBN:
Category : Gas fields
Languages : en
Pages : 188

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Author:
Publisher:
ISBN:
Category : Hydraulic fracturing
Languages : en
Pages : 206

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Author: Sahil Malhotra
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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This dissertation presents an experimental investigation of fluid flow, proppant settling and horizontal proppant transport in hydraulic fractures. The work is divided into two major sections: investigation of proppant settling in polymer-free surfactant-based viscoelastic (VES) fluids and development of a new method of proppant injection, referred to as Alternate-Slug fracturing. VES fluid systems have been used to eliminate polymer-based damage and to efficiently transport proppant into the fracture. Current models and correlations neglect the important influence of fracture walls and fluid elasticity on proppant settling. Experimental data is presented to show that elastic effects can increase or decrease the settling velocity of particles, even in the creeping flow regime. Experimental data shows that significant drag reduction occurs at low Weissenberg number, followed by a transition to drag enhancement at higher Weissenberg numbers. A new correlation is presented for the sphere settling velocity in unbounded viscoelastic fluids as a function of the fluid rheology and the proppant properties. The wall factors for sphere settling velocities in viscoelastic fluids confined between solid parallel plates (fracture walls) are calculated from experimental measurements made on these fluids over a range of Weissenberg numbers. Results indicate that elasticity reduces the retardation effect of the confining walls and this reduction is more pronounced at higher ratios of the particle diameter to spacing between the walls. Shear thinning behavior of fluids is also observed to reduce the retardation effect of the confining walls. A new empirical correlation for wall factors for spheres settling in a viscoelastic fluid confined between two parallel walls is presented. An experimental study on proppant placement using a new method of fracturing referred to as Alternate-Slug fracturing is presented. This method involves alternate injection of low viscosity and high viscosity fluids into the fracture, with proppant pumped in the low viscosity fluid. Experiments are conducted in Hele-Shaw cells to study the growth of viscous fingers over a wide range of viscosity ratios. Data is presented to show that the viscous finger velocities and mixing zone velocities increase with viscosity ratio up to viscosity ratios of about 350 and the trend is consistent with Koval's theory. However, at higher viscosity ratios the mixing zone velocity values plateau signifying no further effect of viscosity contrast on the growth of fingers and mixing zone. The plateau in the velocities at high viscosity ratios is caused by an increase in the thickness of the displacing fluid and a reduction in the thin film of the displaced fluid on the walls of the Hele-Shaw cell. Fluid elasticity is observed to retard the growth of fingers and leads to growth of multiple thin fingers as compared to a single thick dominant finger in less elastic fluids. Observations show the shielding effect is reduced by fluid elasticity. Elastic effects are observed to reduce the thickness of thin film of displaced fluid on the walls of Hele-Shaw cell. The dominant wave number for the growth of instabilities is observed to be higher in more elastic fluids. At the onset of instability, the interface breaks down into a greater number of fingers in more elastic fluids. Experiments are performed in simulated fractures (slot cells) to show the proppant distribution using alternate-slug fracturing. Observations show alternate-slug fracturing ensures deeper placement of proppant through two primary mechanisms: (a) proppant transport in viscous fingers formed by the low viscosity fluid and (b) an increase in drag force in the polymer slug leading to better entrainment and displacement of any proppant banks that may have formed. The method offers advantages of lower polymer costs, lower pumping horsepower, smaller fracture widths, better control of fluid leak-off and less gel damage compared to conventional gel fracs.

Author: Mark D. Zoback
Publisher: Cambridge University Press
ISBN: 1107087074
Category : Business & Economics
Languages : en
Pages : 495

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A comprehensive overview of the key geologic, geomechanical and engineering principles that govern the development of unconventional oil and gas reservoirs. Covering hydrocarbon-bearing formations, horizontal drilling, reservoir seismology and environmental impacts, this is an invaluable resource for geologists, geophysicists and reservoir engineers.

Author: Vismay Shah
Publisher:
ISBN:
Category :
Languages : en
Pages : 116

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"Few studies have quantified proppant transport in static conditions using actual proppant and validated previously established correlation. The objective of this study is to investigate the rheological properties of the linear gel, and determine the effect of size, shape and specific gravity of the proppant, fracture walls and rheological properties of the fluid on the proppant settling velocity in static condition and validate the previously established correlation. Shear viscosity and dynamic frequency sweep tests were performed to investigate the viscous and viscoelastic behaviour of the HPG linear gel with five different concentrations. Proppant settling experiments were conducted with different proppant types and sizes with two different setups, one with a large diameter transparent cylinder and another with a parallel plexiglass plate model which imposes wall effects. Parameters used during the experiments were inserted into previously established correlation and the calculated settling values were compared with the experimental ones to identify the best suitable correlation. HPG linear gel behaved as non-Newtonian shear thinning fluid and showed very little elasticity for the angular frequency from 1 to 100 rad/sec. With increasing shear thinning behaviour of the linear gel it was found that the effect of proppant size, specific gravity and fracture walls got more pronounced. With increasing diameter and specific gravity of the proppant, the effect of viscosity of the unbounded fluid on the settling velocity decreased; however, it remained constant in the case of confined fracturing fluid. The correlation provided by Swanson (1967) and Liu and Sharma (2005) were identified as best suitable correlations based on this study for unbounded fracturing fluid and confined fracturing fluid respectively"--Abstract, page iii.

Author: Wenpei Ma
Publisher:
ISBN:
Category :
Languages : en
Pages : 121

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This study investigates proppant flow and transport in intersecting fractures at angles typical for intersections of pre-existing and new hydraulic fractures. Proppant is small granular material, which is placed into hydraulic fractures during geothermal and hydrocarbon reservoir stimulation and props the fluid paths open during reservoir exploitation. This study uses plexiglas laboratory slot experiments enhanced with an advanced image analysis for identifying particle trajectories and quantifying slurry velocities. Although proppant flow and transport has been broadly studied, the effects of intersecting fracture angles have not, especially coupled with fluid viscosities, flow rates, and proppant volumetric concentration effects. This study specifically investigates the role of intermediate fracture angles, which have been identified to occur most frequently when the new hydraulic fractures intercept the existing ones. Results show that proppant flow and transport behavior after the intersection is very sensitive to carrying fluid viscosity and flow rates alteration, while differentiating proppant volumetric concentrations have a limited effect. Fracture intersection angle itself has a clear effect on proppant flow velocities and proppant settlement; furthermore, it enhances the effects from fluid viscosity, fluid flow rates, and proppant volumetric concentrations. This study also studies the proppant agglomeration phenomenon in intersecting fractures. Different shapes of agglomerations are observed and categorized.

Author: Chen Yuan
Publisher:
ISBN:
Category :
Languages : en
Pages : 65

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"In the current petroleum fracturing industry, it is necessary to understand the downhole migration and settling velocity of the proppant. If we can master this information well, it will be a great help to obtain effective propped fracture conductivity. In order to study the transport of proppants in the well, we used laboratory experiments and computer numerical simulations to compare the results to get a meaningful conclusion. We spent a lot of time building models on a powerful computer and comparing the experimental conclusions. We finally decided to use computational fluid dynamics (CFD) as the simulation platform, discrete phase method (DPM) as the base model, and compare the simulation data with settling velocity experiment data to draw conclusions. Three cases were run and tested including fracture fluid type, proppant size, and fracture orientations. Results show a good integration between experimental results and simulation outputs. This work will help to provide a full understanding of the distinct changes of the mechanical characterization on the High Viscosity Friction Reducers (HVFRs). The findings provide an in-depth understanding of the behavior of HVFRs under confined effect, which could be used as guidance for fracture engineers to design and select better HVFR design"--Abstract, page iii.

Author: Mohammed Salem Ba Geri
Publisher:
ISBN:
Category :
Languages : en
Pages : 174

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"Over the last few recent years, high viscosity friction reducers (HVFRs) have been successfully used in the oil and gas industry across all premier shale plays in North America including Permian, Bakken, and Eagle Ford. However, selecting the most suitable fracture fluid system plays an essential role in proppant transport and minimizing or eliminating formation damage. This study investigates the influence of the use of produced water on the rheological behavior of HVFRs compared to a traditional linear guar gel. Experimental rheological characterization was studied to investigate the viscoelastic property of HVFRs on proppant transport. In addition, the successful implication of utilizing HVFRs in the Wolfcamp formation, in the Permian Basin was discussed. This study also provides a full comparative study of viscosity and elastic modulus between HVFRs and among fracturing fluids such as xanthan, polyacrylamide-based emulsion polymer, and guar. The research findings were analyzed to reach conclusions on how HVFRs can be an alternative fracture fluid system within many unconventional reservoirs. Compared to the traditional hydraulic fracture fluid system, the research shows the many potential advantages that HVFR fluids offer, including superior proppant transport capability, almost 100% retained conductivity, around 30% cost reduction, and logistics such as minimizing chemical usage by 50% and the ability to stoner operation equipment on location. Finally, this comprehensive investigation addresses up-to-date of using HVFRs challenges and emphasizes necessities for using HVFRs in high TDS fluids"--Abstract, page iv.

Author: Muhammad Jahanzaib Aijaz
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Proppant settling in the wellbore during hydraulic fracturing operations is an important consideration as it affects the efficiency and slurry distribution in perforation clusters. This phenomenon has been studied in the past and experiments have been conducted but no field scale simulations have been performed to quantify the amount of proppant settled in different sections of the wellbore. This study focuses on utilizing critical velocity correlations available in the literature and incorporates them into a numerical simulator for simulating hydraulic fracturing stages. Comparisons have been drawn between cases where no settling was considered to cases where settling is considered to demonstrate the difference in total proppant mass entering individual fractures in different sections of the wellbore. Effects of various parameters such as injection rates, viscosity, proppant diameter, proppant density, fluid density and number of clusters (for fracturing and refracturing) have been studied. Proppant settling has been observed starting at the toe side of the stage where fluid velocity drops below the critical velocity. The settling progresses progressively towards mid clusters as the toe side clusters are plugged and the critical velocity in that region drops below a threshold value. Proppant settling is limited because as proppant deposits in a section, the flow area is reduced and this in turn increases the flow velocity to above the resuspension velocity. Ultimately the volume of proppant deposited is limited by the volume of the wellbore. The study was further expanded to include inclined wellbores. Most wells are not perfectly horizontal but rather have small angle undulations resulting in inclinations and models that account for wellbore inclination were used to compute the critical velocity. The predictions were validated using experimental data. Our study was limited to inclinations between - 9 degrees to + 9 degrees as most wellbore surveys indicate inclinations within this range. Trends indicate that proppant settling increases with upward inclination and decreases with downward inclination. The effect of settling diminishes as the hole-angle is increased or decreased. The overall change in proppant settling within the studied range of hole-angles is small (less than 7%). A comparison is also drawn for the volume occupied by proppant in various sections of the wellbore at different angles. Various design parameters that affect the amount of proppant settled are discussed in this study

Author: P. Bedrikovetsky
Publisher: Springer Science & Business Media
ISBN: 9401722056
Category : Science
Languages : en
Pages : 596

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Book Description
It is a pleasure to be asked to write the foreword to this interesting new book. When Professor Bedrikovetsky first accepted my invitation to spend an extended sabbatical period in the Department of Mineral Resources Engineering at Imperial College of Science, Technology and Medicine, I hoped it would be a period of fruitful collaboration. This book, a short course and a variety of technical papers are tangible evidence of a successful stay in the UK. I am also pleased that Professor Bedrikovetsky acted on my suggestion to publish this book with Kluwer as part of the petroleum publications for which I am Series Editor. The book derives much of its origin from the unpublished Doctor of Science thesis which Professor Bedrikovetsky prepared in Russian while at the Gubkin Institute. The original DSc contained a number of discrete publications unified by an analytical mathematics approach to fluid flow in petroleum reservoirs. During his sabbatical stay at Imperial College, Professor Bedrikovetsky has refined and extended many of the chapters and has discussed each one with internationally recognised experts in the field. He received great encouragement and editorial advice from Dr Gren Rowan, who pioneered analytical methods in reservoir modelling at BP for many years.