Preparation method of petroleum coke proppant particles for hydraulic fracturing

Abstract

The invention relates to a method for preparing petroleum coke proppant particles for hydraulic fracturing. The method includes providing feed petroleum coke particles comprising particles greater than a predetermined critical dimension, particles less than the predetermined critical dimension, and optionally petroleum coke microproppant particles, where the predetermined critical dimension is greater than 105 [mu] m, and sieving the particles to obtain a first portion of petroleum coke particles and a second portion of petroleum coke particles wherein at least 75% by volume of the first portion has a particle size not less than a predetermined critical size and substantially all of the second portion has a particle size not greater than the critical particle size, and the second portion comprises no more than 25% by volume of petroleum coke microproppant particles having a size of no more than 74 [mu] m. The method includes size grading the second portion to yield a petroleum coke proppant particle portion comprising no more than 10% by volume of petroleum coke microproppant particles having a size of no more than 74 [mu] m.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to the field of hydraulic fracturing operations and fracturing fluids and proppant particles employed therein. More specifically, the present disclosure relates to a method of making petroleum coke proppant particles for use in hydraulic fracturing. BACKGROUND

[0002] This section is intended to introduce the reader to various aspects of art that can be related to aspects and implementations of the present disclosure and are not necessarily all drawn from the patent literature. This discussion is believed to enhance understanding of the technological background of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.

[0003] Wells can be drilled in subterranean formations to facilitate the extraction of desired resources, such as hydrocarbons, coal, minerals, water, and the like, from the subterranean formations. In many cases, it is desirable to stimulate the subterranean formation in some manner to facilitate the extraction of the resources. Stimulation can include any operation performed on the matrix of the subterranean formation to improve the conductivity of fluids therethrough, including hydraulic fracturing, which is commonly used in unconventional reservoirs.

[0004] Hydraulic fracturing generally includes pumping a large volume of fracturing fluid into a subterranean formation (e.g., a low permeability subterranean formation) under high hydraulic pressure to facilitate the formation of one or more fractures within the matrix of the subterranean formation and to create high conductivity flow paths. Primary fractures extending from the wellbore, and in some cases, secondary fractures extending from the primary fractures, are formed during the hydraulic fracturing operation. These fractures can be vertical, horizontal, or a combination of directions that form tortuous paths.

[0005] Proppant particles are often included in the fracturing fluid. Once the fracturing fluid has been pumped into the formation, it is desirable that such proppant particles can be transported into the fractures and settle therein. Upon pressure release, the proppant particles that remain in the fractures keep the fractures open by preventing the fractures from collapsing, facilitating the flow of the desired resources from the fractured formation through the propped fractures to the wellbore. The performance of the proppant can significantly affect the recovery of the desired resources.

[0006] Sand has traditionally been used as a proppant in hydraulic fracturing for the production of hydrocarbon fluids from unconventional subterranean formations. Various other types of proppants have been proposed and can be used in place of sand. However, all of these existing proppants have one or more drawbacks, such as high cost and limited hydrocarbon recovery. Thus, there is a real need in the industry for high performance proppants. The present disclosure meets these needs and others. SUMMARY

[0007] One aspect of the present disclosure provides a method of making petroleum coke proppant particles for hydraulic fracturing. The method can include providing feed petroleum coke particles comprising particles greater than a predetermined critical size, particles less than the predetermined critical size, and optionally petroleum coke microproppant particles, wherein the predetermined critical size is greater than 105 μιη. The method can also include sizing the feed petroleum coke particles to obtain a first portion of petroleum coke particles and a second portion of petroleum coke particles, wherein at least 75% by volume of the first portion has a particle size no less than the predetermined critical size, based on the total volume of petroleum coke particles in the first portion, and substantially all of the second portion has a particle size no greater than the critical particle size, and the second portion comprises no more than 25% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μιη, based on the total volume of petroleum coke particles in the second portion. The method can further include sizing the second portion of petroleum coke particles to obtain a petroleum coke proppant particle portion comprising no more than 10% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μιη, based on the total volume of the petroleum coke proppant particle portion.

[0008] Another aspect of the present disclosure provides another method of making petroleum coke proppant particles for hydraulic fracturing. The method can include providing dry petroleum coke comprising particles greater than 297 μιη and milling the dry petroleum coke to obtain milled petroleum coke particles. The method can also include sizing the milled petroleum coke particles to obtain a first portion of petroleum coke particles and a second portion of petroleum coke particles, wherein at least 75% by volume of the first portion has a particle size of at least 297 μιη, based on the total volume of the first portion, and substantially all of the second portion has a particle size of at most 297 μιη, and the second portion comprises no more than 25% by volume of petroleum coke microproppant particles, based on the total volume of the second portion. The method can further include elutriating the second portion of petroleum coke particles to obtain a petroleum coke proppant particle portion and a third portion of petroleum proppant particles, wherein the petroleum coke proppant particle portion has a particle size of greater than 105 μιη to at most 297 μιη, based on the total volume of the petroleum coke proppant particle portion, the petroleum coke proppant particle portion comprises at most 10% by volume of petroleum coke microproppant particles, and substantially all of the third portion has a particle size of at most 105 μιη.

[0009] These and other features and attributes of the disclosed aspects and embodiments of the present disclosure and their advantages and / or uses will become apparent to those of ordinary skill in the relevant art from the detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0010] To aid the relevant ordinary skill in preparing and using the subject matter described herein, reference is made to the drawings, in which:

[0011] Figure 1 is a graph showing the particle size of four un-sieved fluid coke samples;

[0012] Figure 2 is a graph showing the permeability of un-sieved fluid coke samples and sieved, 40 / 140-mesh fluid coke samples as a function of closure stress;

[0013] Figure 3 is a graph showing the settling velocity of several different sieve sizes of sand and petroleum coke as a function of particle size;

[0014] Figure 4 is a process flow diagram of an exemplary method of making petroleum coke proppant particles and using such particles during hydraulic fracturing;

[0015] Figure 5A illustrates a petroleum coke sample;

[0016] Figure 5B illustrates the petroleum coke sample of Figure 5A after grinding and sieving;

[0017] Figure 6A is a graph showing the permeability of the fluid coke samples of Table 3;

[0018] Figure 6B is a graph showing the permeability of the sand samples of Table 3;

[0019] Figure 7A includes a graph of the volume-weighted cumulative distribution function of the circular equivalent diameters of the fluid coke samples of Table 3 and an inset of the number-weighted cumulative distribution function of the circular equivalent diameters of the fluid coke samples of Table 3;

[0020] Figure 7B includes a graph of the volume-weighted cumulative distribution function of the circular equivalent diameters of the sand samples of Table 3 and an inset of the number-weighted cumulative distribution function of the circular equivalent diameters of the sand samples of Table 3;

[0021] Figure 8A includes graphs of the volume-weighted and number-weighted distribution functions of the particle aspect ratios of the fluid coke samples of Table 3, respectively;

[0022] Figure 8B includes graphs of the volume-weighted and number-weighted distribution functions of the particle aspect ratios of the sand samples of Table 3, respectively;

[0023] Figure 9 is a process flow diagram of an exemplary method of making petroleum coke proppant particles for use in hydraulic fracturing; and

[0024] Figure 10is a process flow diagram for another exemplary method of making petroleum coke proppant particles for hydraulic fracturing.

[0025] It should be noted that the drawings are examples only of the present disclosure and are not intended to limit the scope of the present disclosure. Further, the drawings are generally not to scale, but are drawn for the purpose of clarity and convenience in the explanation of the aspects of the present disclosure. DETAILED DESCRIPTION

[0026] In the following detailed description section, specific examples of the present disclosure are described in connection with preferred aspects and embodiments. However, if the following description is directed to one or more aspects or embodiments of the present disclosure, this is intended solely for the purpose of exemplification and is merely provided to describe such aspect(s) or embodiment(s). Thus, the present disclosure is not limited to the specific aspects and embodiments described below, but includes all alternatives, modifications and equivalents falling within the true spirit and scope of the appended claims.

[0027] At the outset, and for convenience, a list of some of the terms used in this application and their meanings as used in this context are set forth. If a term used herein is not defined below, it should be given its broadest definition as would be given to one of ordinary skill in the art, as reflected in at least one printed publication or published patent. Additionally, the present disclosure is not limited to the use of the terms shown below, as all equivalents, synonyms, developments and terms or methods serving the same or similar purpose are considered to be within the scope of the claims of the present invention.

[0028] In the present disclosure, a method is described as comprising at least one "step". It is understood that each step is an action or operation that can be performed one or more times in the method, either consecutively or non-consecutively. Unless specifically noted otherwise, or the context clearly indicates otherwise, the steps of the method can be performed consecutively in the order they are listed, overlapping or non-overlapping with one or more other steps, or in any other order, as the case can be. Additionally, one or more or even all of the steps can be performed simultaneously, with respect to the same or different batches of material. For example, in a continuous process, while the first step of the method is being performed with respect to feedstock that has just entered the beginning of the method, the second step can be performed simultaneously with respect to intermediate product that has been produced from feedstock that was fed into the method at an earlier time in the first step. Preferably, the steps are performed in the order described.

[0029] Unless otherwise indicated, all numbers expressing quantities of items in the specification are to be understood as being modified in all instances by the term "about." The precise numerical values

[0030] As used herein, the singular forms "a", "an" and "the" mean one or more than one, unless the context clearly dictates otherwise. The use of "one", "an" and / or "the" are not limited to the meaning of the singular form, unless the specifically contrary is clearly indicated.

[0031] The terms "about" and "approximately" mean a relative quantity of material or characteristic sufficient to provide the intended effect. The exact degree of deviation permissible can depend on the context, e.g., ±1%, ±5%, ±10%, ±15% etc. Those skilled in the art will understand that these terms are intended to permit description of certain features while not limiting the scope of those features to the exact numerical range provided. Thus, these terms are to be interpreted as indicating that insubstantial or immaterial modifications or alterations of the described subject matter are considered to be within the scope of the disclosure.

[0032] The term "and / or", placed between a first entity and a second entity, means one of (1) the first entity, (2) the second entity, and (3) the first entity and the second entity. Multiple entities listed with "and / or" should be construed in the same fashion as "one or more of the entities recited." Other entities can optionally be present other than the entities specifically named, whether related or unrelated to those named. As a non-limiting example, a reference to "A and / or B" when used in conjunction with open-ended language such as "comprising" can refer, in one implementation, to only A, optionally including entities other than B; in another implementation, to only B, optionally including entities other than A; or, in yet another implementation, to both A and B, optionally including entities other than A or B. The entities can refer to elements, actions, structures, steps, operations, values, etc.

[0033] As used herein, the term "any" means one, some, or all of the specified entity or group of entities, the quantity being arbitrary.

[0034] As used herein, with respect to the density of a proppant particle, the term "apparent density" refers to the density of the individual particle itself, which can be expressed in grams per cubic centimeter (g / cm3) or pounds per cubic foot (lb / ft3). 3expressed in units of g / cc. The apparent density values provided herein are based on the American Petroleum Institute’s Recommended Practice 19C (hereinafter “API RP-19C”) standard, entitled “Measurement of Properties of Proppants Used in Hydraulic Fracturing and Gravel-packing Operations” (1st Edition, May 2008, reaffirmed June 2016).

[0035] When used with reference to a list of one or more entities (or elements), the phrase “at least one of’ shall be understood to mean at least one entity from among those entities in the entity list, but not necessarily including at least one of each and every entity specifically listed within the entity list, and not excluding any combinations of entities in the entity list. This definition also allows that entities can optionally be present other than the entities specifically identified within the list of phrases “at least one of’ as a non-limiting example. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B”, or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with there being no B (and optionally including entities other than B); in another embodiment, to at least one, optionally including more than one, B, with there being no A (and optionally including entities other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other entities). In other words, the phrases “at least one of’, “one or more of’ and “and / or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B, and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and / or C” can mean A alone, B alone, C alone, A and B together, A and C together, B and C together, A, B, and C together, and optionally any of these with at least one other entity.

[0036] As used herein, the term "delayed coke" refers to a solid concentrated carbon material produced within a delayed coking unit via a delayed coking process. According to the delayed coking process, a preheated feedstock is introduced into a fractionator, where a thermal cracking process occurs in which long chain hydrocarbons are split into shorter chain hydrocarbons. The resulting lighter fraction is then removed as a side stream product. The fractionator bottoms, which include a recycle stream of heavy products, are heated in a furnace, which can have an outlet temperature of, for example, about 895 °F to about 960 °F. The heated feedstock then enters a reactor, often referred to as a "coke drum," which can be operated at a temperature of, for example, about 780 °F to about 840 °F. Within the coke drum, cracking reactions continue. The resulting cracked products then exit the coke drum as an overhead stream, while coke is deposited in the coke drum. Typically, the process continues for a period of about 16 hours to about 24 hours to allow the coke drum to fill with coke. Further, to allow the delayed coking unit to operate on an intermittent-continuous (or semi-continuous) basis, two or more coke drums are used. While one coke drum is online filling with coke, another coke drum can be undergoing steam stripping, cooling, decoking (e.g., by hydro- cutting the deposited coke with water), pressure inspection, and warming up. Further, the overhead stream exiting the coke drum enters a fractionator, where naphtha and heating oil fractions are recovered. The heavy recovery material is then typically combined with preheated fresh feedstock and recycled back into the process.

[0037] As used herein, the terms "example," "exemplary," and "embodiment" when used with respect to one or more components, features, structures, or methods according to the present disclosure are intended to express that the described component, feature, structure, or method is an illustrative, non-exclusive example of a component, feature, structure, or method according to the present disclosure. Thus, the described component, feature, structure, or method is not intended to be limiting, required, or exclusive / exhaustive; and other components, features, structures, or methods, including structurally and / or functionally similar and / or equivalent components, features, structures, or methods, are also within the scope of the present disclosure.

[0038] As used herein, the term "flexicoke" refers to a solid concentrated carbon material produced via a FLEXICOKING TM process, which is a fluidized solids and gasified thermal cracking process used to convert heavy low grade hydrocarbon feedstocks into lighter hydrocarbon products (e.g., upgraded more valuable hydrocarbons). In brief, FLEXICOKING TMThe process integrates the cracking reactor, heater, and gasifier into a common fluidized solids (coke) circulation system. A feed stream of (resid) is fed into the fluidized bed, while a hot recycle material stream is fed to the reactor. From the reactor, a stream containing coke is circulated to the heater vessel where the stream is heated. The hot coke stream from the heater is fed to the gasifier where it is reacted with air and steam. The gasifier product gas containing entrained coke particles, called coke oven gas, is returned to the heater and cooled by the cold coke from the reactor to provide a portion of the reactor heat requirement, which is typically in the range of about 496°C to about 538°C. The return stream of coke from the gasifier to the heater provides the remaining heat requirement. The coke that satisfies the heat requirement is then circulated to the reactor and the feed stream is thermally cracked to produce light hydrocarbon liquids, which are removed from the reactor and recovered using conventional fractionation equipment. Fluidized coke is formed from the thermal cracking process and settles (deposits) onto the "seed" fluidized bed coke already present in the reactor. The resulting at least partially gasified coke is flexible coke. In some cases, the coke from the thermal cracking process is deposited in a ring-like pattern on the surface of the seed coke. In normal FLEXICOKING TM Flexible coke is continuously withdrawn from the system during processing, for example from the reactor or after it flows into the heater via an elutriator, to ensure that the system maintains the coke particles in the flowable particle size range. Thus, flexible coke is FLEXICOKING TM A readily available byproduct of the process.

[0039] Relatedly, the terms "wet flexible coke fines" and "dry flexible coke fines" refer to FLEXICOKING TM Two byproducts of the process. Such byproducts are collected as particles that are not recovered in the secondary cyclone separator of the heater. More specifically, the particles are first collected in a tertiary cyclone separator, which are dry flexible coke fines, and then the smaller particles that pass through the tertiary cyclone separator are recovered in a venturi scrubber, which are wet flexible coke fines.

[0040] As used herein, the term "fluid coke" refers to the solid concentrated carbon material remaining from fluid coking. The term "fluid coking" refers to a thermal cracking process that uses fluidized solids to convert heavy, low-grade hydrocarbon feedstocks into lighter products (e.g., upgraded hydrocarbons), producing fluid coke as a byproduct. The fluid coking process is different from the FLEXICOKING TM process because the fluid coking process does not include a gasifier.

[0041] The term "fracture" (or "hydraulic fracture") refers to a crack or fractured surface within a subterranean formation caused by an applied pressure or stress.

[0042] As used herein, the term "hydraulic conductivity" (or simply "conductivity") refers to the ability of a fluid within a subterranean formation to flow through a fracture including proppant at various stress (or pressure) levels, which is based at least in part on the permeability of the proppant deposited within the hydraulic fracture. The hydraulic conductivity values provided herein are based on the American Petroleum Institute Recommended Practice 19D (API RP-19D) standard entitled "Measuring the Long-Term Conductivity of Proppants" (First Edition, May 2008, reaffirmed May 2015).

[0043] The term "particle size(s)" when used herein in reference to a particle type refers to the diameter(s) of the particle(s). The term "average particle size" refers to the median particle size of the particles.

[0044] The term "petroleum coke" refers to a final carbon-rich solid material derived from refining oil. More specifically, petroleum coke is a carbonization product of high-boiling hydrocarbon fractions resulting as a consequence of petroleum processing operations. Petroleum coke is produced within a coking unit via a thermal cracking process in which long-chain hydrocarbons are split into shorter-chain hydrocarbons. As described herein, there are at least three main types of petroleum coke: delayed coke, fluid coke, and flexi-coke. Each type of petroleum coke is produced using a different coking process; however, all three coking processes have the common goal of maximizing the yield of distillate products within a refinery by expelling a large amount of carbon in the residue as petroleum coke.

[0045] As used herein, the terms "proppant" and "proppant particle" refer to a solid material capable of maintaining an induced fracture open during and after a hydraulic fracturing treatment. The term "proppant pack" refers to a collection of proppant particles.

[0046] The terms "coke proppant" and "coke proppant particles" refer to proppants that are based on or derived from solid carbonaceous material resulting from processing carbonaceous material (e.g., oil (e.g., crude oil, vacuum pipestill distillates, etc.), coal, and hydrocarbons) at elevated temperatures in an oxygen-deficient environment. The elevated temperature can be at least 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, or even 1000 °C. The carbonaceous material comprises carbon elements and optionally additional elements, including but not limited to hydrogen, sulfur, vanadium, iron, etc. The carbonaceous material preferably comprises carbon elements at a concentration of > 50 wt.%, e.g., from 50, 55, 60, 65, 70 wt.% to 75, 80, 85, 90, 95 wt.% to 96, 97, 98, 99 wt.%, or even 100 wt.%, based on the total weight of all elements in the carbonaceous material. The carbonaceous material preferably comprises carbon elements and hydrogen elements at a combined concentration of > 55 wt.%, e.g., from 55, 60, 65, 70 wt.% to 75, 80, 85, 90, 95 wt.% to 96, 97, 98, 99 wt.%, or even 100 wt.%, based on the total weight of all elements in the carbonaceous material.

[0047] The term "petroleum coke proppant particles" refers to coke proppant particles derived from petroleum coke source material. The terms "petroleum coke fines" and "petroleum coke microproppant particles" refer to petroleum coke proppant particles having a particle size of at most 105 μιη, but possibly in the range of about 0.1 μιη to 105 μιη (e.g., about 0.0001, 0.001, 0.01, 0.1 μιη to 0.5, 1.0, 2.0, 5.0, 8.0 10 μιη to 15, 20, 25, 30, 35, 40, 45 μιη to 50, 53, 55, 60, 63, 65 μιη to 74, 75, 80, 85, 88, 90, 95, 100, 105 μιη).

[0048] The term "non-coke proppant" means any proppant that is not a coke proppant. Examples of non-coke proppants include sand, ceramic proppants, glass proppants, and polymeric proppants.

[0049] The term "lightweight proppant (LWP)" refers to proppants having an apparent density in the range of about 1.2 g / cm 3 to about 2.2 g / cm 3 (e.g., from about 1.2, 1.3, 1.4, 1.5, 1.6 g / cm 3 to about 1.7, 1.8, 1.9, 2.0, 2.1, 2.2 g / cm 3 ) while the term "ultra-lightweight proppant (ULWP)" refers to proppants having an apparent density in the range of about 0.5 g / cm 3 to about 1.2 g / cm3 (e.g., from about 0.5, 0.6, 0.7, 0.8 g / cm 3 to about 0.9, 1.0, 1.1, 1.2 g / cm 3 ) range. The coke proppant can or can not be LWP. The term "non-LWP proppant" refers to a proppant having an apparent density higher than 2.2 g / cm 3 (e.g., from about 2.3, 2.4, 2.5 to about 2.6, 2.8, 3.0, to 3.2, 3.4, 3.5 g / cm 3 ) range. The non-coke proppant can or can not be non-LWP.

[0050] As used herein, the term "pyrolysis coke" refers to a type of coke produced via pyrolysis of hydrocarbons at temperatures higher than those of a coking process to produce petroleum coke.

[0051] The term "substantially" when used in reference to quantities or amounts of materials or specific properties of them, is meant to refer to an amount sufficient to provide the effect intended by the material or property. The exact degree of deviation allowable can in some cases depend on specific context.

[0052] The term "substantially all" when used in reference to a collection of particles means at least 90 vol.%, preferably at least 95 vol.%, based on the total volume of the collection of particles.

[0053] As used herein, the term "heat post-treated coke" refers to a petroleum coke that has been heated to a temperature in the range of about 400 °C to 1200 °C (e.g., about 400, 500, 600 °C, to 700, 800, 900 °C, to 1000, 1100, 1200 °C) for a predetermined duration in the range of about 1 minute to about 24 hours (e.g., about 1 minute, 30 minutes, 1 hour, to 4 hours, 8 hours, 12 hours, to 16 hours, 20 hours, 24 hours).

[0054] The term "wellbore" refers to a borehole drilled into a subterranean formation. The borehole can include vertical, deviated, highly deviated, and / or horizontal sections. The term "wellbore" also includes well equipment associated with the borehole, such as casing strings, production tubing, gas lift valves, and other subterranean equipment. Relatedly, the term "hydrocarbon well" (or simply "well") includes the wellbore in addition to the wellhead and other associated surface equipment.

[0055] Certain embodiments and features are described herein using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. All numerical values are "about," "around," "approximately," the indicated value, and take into account experimental error and variations.

[0056] During drilling of a hydrocarbon well, a wellbore is formed within a subterranean formation using a drill bit that can be advanced at the lower end of a drill string until it reaches a predetermined location in the subsurface. The drill string and drill bit can then be removed and the wellbore can be lined with a string of steel pipe, commonly referred to as casing. As a result, an annulus can be formed between the casing string and the surrounding subterranean formation. A cementing operation can be performed to fill the annulus with a string of cement. The combination of the casing string and cement strengthens the wellbore and isolates or resists fluid flow and pressure transmission along the annulus.

[0057] It is common to place several casing strings into the wellbore with progressively smaller outside diameters. The first casing string can be referred to as the "surface casing string." The surface casing string serves to isolate and protect shallower fresh water bearing aquifers from contamination by any other wellbore fluids. As a result, this casing string can be cemented all the way back to the surface.

[0058] The process of drilling and then cementing progressively smaller casing strings can be repeated several times beneath the surface casing string until the hydrocarbon well reaches total depth. The final casing string, referred to as the "production casing string," can extend through the hydrocarbon bearing section of the subterranean formation, referred to as the "reservoir." In some cases, the production casing string is a production liner, i.e., a casing string that is not cemented back to the surface. The production casing string can also be cemented in place. In some completions, the production casing string has expansion packers or plugs spaced across selected production intervals. This creates compartments between the packers for staging and specific treatment. In this case, the annulus can simply be filled with sand.

[0059] As part of the completion process, sections of the wellbore (referred to as "stages") can be isolated by setting packers or plugs. Then, the production casing string can be perforated at one or more desired intervals along the wellbore, meaning that a perforating gun is used to create perforation clusters through the production casing string and the cement column surrounding the production casing string. In operation, a perforating gun can form a perforation cluster by firing multiple very close perforations (e.g., 12 to 18 perforations) at one time over a 1 foot (ft) (0.3 meters (m)) to 3 ft (3 m) area, where each perforation can be, for example, about 0.3 inch (in) (0.8 centimeter (cm)) to 0.5 in (1.3 cm) in diameter. The perforating gun can then be moved up the wellbore, for example, about 10 ft (3 m) to 100 ft (30 m), and a second perforating gun can be used to form a second perforation cluster. This process of forming perforation clusters can be repeated to create additional perforation clusters within each stage of the hydrocarbon well. The resulting perforation clusters can allow hydrocarbon fluids to flow from the surrounding subterranean formation into the hydrocarbon well. Note, however, that in some cases, the production casing string is instead provided as a sliding sleeve pipe or other type of casing string with pre-formed perforation clusters. In such cases, the pre-formed perforations can initially be closed, but can be opened by various forms of action to control fluid flow through the perforations.

[0060] After the perforation process is complete, the subterranean formation can be hydraulically fractured at each stage of the wellbore to increase the productivity of the subterranean formation. Hydraulic fracturing consists of injecting a volume of fracturing fluid through the created perforations and into the surrounding subterranean formation at a high pressure and rate, such that the subterranean rock near the perforations cracks open, and the resulting hydraulic fracture extends outward into the subterranean formation in direct proportion to the volume of injected fluid. Ideally, each perforation cluster emits a separate hydraulic fracture outward, forming a set of hydraulic fractures, commonly referred to as a "fracture network." Ideally, such a fracture network includes a series of parallel fracture planes, creating as much fracturing of the subterranean rock as possible. Near the wellbore, the complex topology of the hydraulic fractures can sometimes be due to the perforation breaks within each perforation cluster, but it is generally believed that these hydraulic fractures eventually link up to form a single main fracture plane that is hydraulically connected to the wellbore. In operation, to create a hydraulic fracture, the injection pressure of the fracturing fluid must exceed the water pressure in the subterranean formation plus the strength of the rock, and often even the static pressure of the rock in the subterranean formation.

[0061] Hydraulic fracturing is most widely used to enhance the productivity of "unconventional" (or "tight") subsurface formations, which are subsurface formations that have very low permeability and are not typically economical to produce without hydraulic fracturing. Examples of unconventional subsurface formations include tight sandstone formations, tight carbonate formations, shale gas formations, coalbed methane formations, and tight oil formations. During hydraulic fracturing of such subsurface formations, the pump rate (or injection rate) of the fracturing fluid can be increased until it reaches a maximum pump rate of about 20 barrels per minute (bbl / min) (0.05 cubic meters per second (m 3 / s)) to about 150 bbl / min (0.41 m 3 / s) (e.g., 20, 60, 90 bbl / min to 120, 150 bbl / min). For example, in operation, each stage of a hydrocarbon well can inject about 5000 barrels to about 15000 barrels (e.g., 5000, 6000, 7000, 8000 barrels, to 9000, 10000, 11000, 12000 barrels, to 13000, 14000, 15000 barrels) of fracturing fluid.

[0062] In operation, a small fraction (e.g., often about 5% to about 10%) of the fracturing fluid can be pumped into the wellbore during a pad phase of the hydraulic fracturing operation of each stage. The pad phase is designed to initiate and grow a hydraulic fracture to a size and volume to accommodate the injection of proppant, such as sand, crushed granite, ceramic beads, or other particulate material (which are generally referred to herein as "non-char proppant particles"). The remainder of the fracturing fluid can then be mixed with the proppant and pumped into the wellbore and through the perforations into the stimulated reservoir volume (SRV). The proppant serves to keep the hydraulic fracture open after the hydraulic pressure is released. Ideally, the resulting hydraulic fracture grows radially from the wellbore to several hundred feet into the subsurface formation. In the case of unconventional subsurface formations, the combination of the hydraulic fracture and the injected proppant greatly enhances the flow capacity of the treated formation.

[0063] This application of hydraulic fractures is a routine part of petroleum industry operations applied to individual subsurface formations. Such subsurface formations can represent a total vertical thickness of several hundred feet of subsurface formation. More recently, hydrocarbon wells are completed with horizontal sections that typically extend at least 1000 feet, in which case the hydrocarbon well can be referred to as an "extended-reach lateral well," or in some cases, at least 10000 feet, in which case the hydrocarbon well can be referred to as a "super-extended-reach lateral well."

[0064] When there are multiple zones or very thick zones to be hydraulically fractured, or when a large- or ultra-large- displacement horizontal well is being completed, then more complex treatment techniques can be used to treat the entire target area. Thus, the operating company can isolate individual stages (as described above) to ensure that each individual stage is not only perforated, but also sufficiently fractured and treated. In this manner, the operator can ensure that the fracturing fluid is injected through each perforation cluster and into each zone of interest to effectively increase the flow capacity at each desired depth and horizontal location.

[0065] Treatment of a zone of interest can include isolating that zone from all zones that have already been treated. This can include using so-called diversion methods, in which the injected fracturing fluid is directed to one selected zone of interest while diverting away from other zones. In many cases, a frac plug is disposed between zones and serves to prevent the injected fluid from entering zones that have already been fractured and propped.

[0066] This hydraulic fracturing process can be repeated for each zone of a hydrocarbon well. In the case of a well that includes a horizontal section, the first zone is typically located near the end (or "toe") of the horizontal section, and the last zone is typically located near the beginning (or "heel") of the horizontal section. For example, for a large-displacement horizontal well, there can be about 20 to about 50 individual zones. For example, for an ultra-large-displacement horizontal well, there can be more than 100 zones.

[0067] After the hydraulic fracturing process is complete, the frac plugs (and / or other diversion material) can be drilled out of the hydrocarbon well. The hydrocarbon well can then begin production, meaning that it can be used to recover hydrocarbon fluids from the subterranean formation. In operation, a pressure differential between the formation and the hydrocarbon well can be used to force the hydrocarbon fluids to flow through the hydraulic fractures within the formation and into the production casing string via the corresponding perforation clusters. The hydrocarbon fluids then flow up the hydrocarbon well to the surface.

[0068] In operation, the success of the hydraulic fracturing process directly impacts the ultimate production performance of the hydrocarbon well. Specifically, the number, size, compliance, and location of the hydraulic fractures within the zones of the hydrocarbon well that correspond to the perforation clusters directly impact the amount of hydrocarbon fluid that can flow and flow into the hydrocarbon well. However, the success of the hydraulic fracturing process is limited by the ability of the fracturing fluid to penetrate deeply into the formation, thereby enabling the proppant to be deposited within the extended area of the hydraulic fracture.

[0069] According to conventional techniques, sand is often used as a proppant within fracturing fluids. However, sand tends to settle out of the fracturing fluid relatively quickly, thereby limiting the effectiveness of the hydraulic fracturing operation. To mitigate the low transportability of sand, a high viscosity carrier fluid is often used with the sand to keep the sand suspended within the fracturing fluid for a longer period of time, and thus to penetrate the sand deeper into the formation. slickwater includes an added friction reducer, such as a high molecular weight polyacrylamide, for example, that is designed to reduce turbulent friction in the wellbore and through the fracture to achieve higher injection rates with lower pumping pressures. However, the friction reducer and / or other viscosity increasing additives within the slickwater are costly and often result in formation damage, thereby reducing the conductivity of the resulting hydraulic fracture. Moreover, even with the use of such friction reducers, the sand tends to settle out of the fracturing fluid relatively quickly.

[0070] With this in mind, lower density proppants are desirable in certain situations. However, despite the development of low density proppants (e.g., LWP and ULWP), such proppants have not been able to exhibit the mechanical, thermal, and / or chemical stability necessary to be an effective proppant within a hydrocarbon well. Specifically, currently available low density proppants have not exhibited sufficient compressive strength and hydraulic conductivity to successfully compete with conventional, sand-based proppants and / or are not cost competitive with conventional, sand-based proppants.

[0071] Accordingly, we have developed proppants formed from petroleum coke (referred to herein as "petroleum coke proppant particles"). Petroleum coke proppant particles include several properties and features that alleviate difficulties commonly encountered by subterranean formations during hydraulic fracturing of a hydrocarbon well. First, the lower density characteristic of petroleum coke enables petroleum coke proppant particles to be transported further within the wellbore and corresponding hydraulic fracture as compared to non-coke proppant particles (e.g., sand). Additionally, we have found that petroleum coke proppant particles are less likely than non-coke proppant particles to flow back into the wellbore once the hydraulic fracturing operation is complete and the hydrocarbon well begins production. Moreover, we have found that petroleum coke proppant particles are less likely than non-coke proppant particles to settle around any diverter material within the wellbore, thereby enabling the effective use of dissolvable, biodegradable, or self-destructible diverter material (e.g., dissolvable plugs) within the wellbore. Additionally, the use of petroleum coke proppant particles reduces the likelihood of cluster-level screen-out as compared to the use of non-coke proppant particles. Each of these factors, among others, facilitate the reduction or elimination of the need to perform a wellbore clean-out procedure.

[0072] Further, the lower density characteristics of the petroleum coke particles enable the petroleum coke proppant particles to travel farther within each stage and farther throughout the perforation cluster as compared to non-coke proppant particles. Thus, we have found that fracturing fluids including petroleum coke proppant particles flow more smoothly and efficiently throughout the stages and into the perforation cluster and, thus, more efficiently into the tip of the formed hydraulic fracture (or at least within the vicinity of the tip).

[0073] As described herein, the petroleum coke particles have sufficient crush strength to maintain a propped fracture upon removal of the water pressure, as well as efficient conductivity once the wellbore begins production. In addition, the relatively low density of the petroleum coke can reduce or eliminate the need to use a gelled fracturing fluid, thereby avoiding the costs associated with gelling. In addition, the use of petroleum coke can reduce the injection pressure needed, reduce the overall water consumption, and avoid the need for frequent wellbore cleanouts.

[0074] Effective proppant particles are generally associated with various specific characteristics or properties, including efficient proppant particle transport within the carrier fluid, sufficient strength to maintain a propped fracture upon removal of the water pressure, and efficient conductivity once the wellbore begins production. With respect to the proppant particle transport property, the settling rate of the proppant particles within the fracturing fluid at least partially determines their transportability within the hydraulic fracture. The settling rate of the proppant particles can be determined using Equation (1).

[0075]

[0076] In Equation (1), v is the settling rate of the proppant particles; p p - p f is directly proportional to the difference in density between the proppant particles and the carrier fluid; η is the viscosity of the carrier fluid; g is the gravitational constant; and s 2 and is directly proportional to the square of the size of the proppant particles. As will be appreciated, proppant particles having a lower apparent density and / or a smaller average particle size settle at a slower rate (and thus have better transportability) within the same carrier fluid as compared to proppant particles having a higher apparent density and / or a larger average particle size. We have found that coke particles, and particularly petroleum coke particles, are thus particularly well suited for use as a proppant during hydraulic fracturing operations, at least in part due to the relatively low apparent density of the petroleum coke particles as compared to non-coke proppants (e.g., sand).

[0077] With respect to particle size, fluid coke particles and flexible coke particles are produced in a wide range of sizes. This is due to the fact that the coke particles are produced by the partial combustion of coal, which is a naturally occurring material. The size of the coke particles can be controlled by adjusting the conditions under which the coke particles are produced. For example, the size of the coke particles can be controlled by adjusting the temperature and pressure under which the coke particles are produced. Figure 1As illustrated, this is a plot 100 showing the particle size of four un- sized fluid coke samples. Particle size was measured using laser particle size analysis (LPSA), which is a fast and accurate optical sieve technique for particle size analysis that works on the principle of measuring the intensity of light scattering when a laser beam passes through a dispersed sample of microparticles. In this case, particles having a particle size in excess of 3000 micrometers (pm) were removed prior to analysis. As illustrated in Figure 1 all four un-sized fluid coke samples exhibited a wide range of particle sizes as they exited the reactor.

[0078] Based on Stokes' Law and Equation (1), it is expected that particles having a smaller particle size will have a lower settling velocity than particles having a larger particle size. In the case of petroleum coke particles, this was confirmed via conductivity testing, as Figure 2 illustrated. Specifically, Figure 2 is a plot 200 showing the conductivity (in millidarcy-feet (mD-ft)) of un-sized fluid coke samples and sized 40 / 140-mesh fluid coke samples as a function of closure stress (in pounds per square inch (psi)), where the conductivity test was performed at a 2 pounds per square foot (lb / ft 2 ) load for 2 hours. As illustrated, plot 200 confirms that sizing petroleum coke particles to yield sized petroleum coke proppant particles having a particular size range (e.g., 40-mesh to 140-mesh in this example) results in improved performance of the proppant particles in terms of conductivity.

[0079] Figure 3 is a plot 300 showing the settling velocity of several different mesh sizes of sand and petroleum coke as a function of particle size. Specifically, plot 300 shows the settling velocity (in feet per minute (ft / min)) of 40 / 70-mesh regional sand (represented by a first region 302), 100-mesh regional sand (represented by a second region 304), 40 / 70-mesh petroleum coke (represented by a third region 306), and 100-mesh petroleum coke (represented by a fourth region 308) as a function of particle size (in pm), where the settling velocity values are based on modified Stokes settling velocity. As illustrated by plot 300, petroleum coke has a significantly lower settling rate (or velocity) compared to sand of comparable particle size. Thus, proppant particles formed from petroleum coke will perform better than proppant particles formed from sand in terms of transportability within a fracture formed during a hydraulic fracturing operation.

[0080] Based on the foregoing discussion, it is clear that the petroleum coke proppant particles should be properly sized to provide efficient use of the petroleum coke proppant particles during hydraulic fracturing operations. If the particles are too large, such particles can become heavy and lose their advantageous low settling rates. In addition, too large of particles can cause operational problems in pumping through rotating equipment and in attempting to flow the particles through narrow perforations and perforation channels. On the other hand, if the particles are too small, such particles can be useful as petroleum coke microproppant particles in certain situations, but can be unsuitable for other situations, such as when there are concerns about the fine particles reducing the conductivity of the primary proppant pack. Thus, because petroleum coke proppant particles are produced from various refinery types and are distributed over a wide size range, the present disclosure alleviates the foregoing difficulties and also provides related advantages by providing methods of making petroleum coke proppant particles for use in hydraulic fracturing. More specifically, in accordance with the present disclosure, methods are provided for converting petroleum coke particles into properly sized petroleum coke proppant particles for efficient use as proppant during hydraulic fracturing operations.

[0081] In various embodiments, the petroleum coke particles can be received from one or more refineries. In various embodiments, it can be ensured that the separately collected petroleum coke fines in the refinery are not mixed into the primary petroleum coke product prior to receiving such product from the refinery. In addition, in various embodiments, it can be ensured that the petroleum coke particles are not sprayed with any type of liquid (for dusting purposes). Such dusting is currently a routine practice for petroleum coke products. However, wet particles are very difficult to screen to produce the proper sized proppant particles. Thus, for the purposes of hydraulic fracturing, such dusting is generally not preferred.

[0082] For hydraulic fracturing purposes, the received petroleum coke particles can then be size classified. In various embodiments, this includes screening the petroleum coke particles for a first size classification (or size-classifying). In some embodiments, the remaining petroleum coke particles are then ground and screened again to maximize the yield of particles having a desired size range. However, in other embodiments, depending on the specifics of the particular implementation, grinding can be performed prior to screening, or grinding can be performed both prior to and after screening. Additionally, in various embodiments, an elutriation system or any other suitable type of size classifier is then used to carefully remove any remaining particles that are not properly size classified (e.g., any remaining petroleum coke fines), resulting in the production of petroleum coke proppant particles having a desired particle size range for hydraulic fracturing purposes. In some embodiments, such a desired particle size range is, for example, about 88 μιη (170-mesh) to 297 μιη (50-mesh) or about 105 μιη (140-mesh) to 210 μιη (70-mesh), although the desired particle size range can vary depending on the specifics of the particular implementation. For example, the desired particle size range can be about 88, 105, 125, 149 μιη to about 177, 210, 250, 297, 354 μιη.

[0083] According to aspects and embodiments described herein, any suitable type(s) of petroleum coke product(s) can be obtained from one or more refineries. For example, the petroleum coke product(s) can include, but are not limited to, fluid coke particles, flexible coke particles, delayed coke particles, thermally after-treated coke particles, and / or pyrolysis coke particles.

[0084] For embodiments in which the petroleum coke product(s) from one or more refineries include flexible coke particles, such flexible coke particles are produced via FLEXICOKING TM process. Briefly, FLEXICOKING TMThe process integrates the cracking reactor, heater and gasifier into a common fluidized solids (coke) circulation system. A feed stream (of resid) is fed into the fluidized bed, while at the same time a stream of hot recycled material is fed to the reactor. From the reactor, a stream containing coke is circulated to the heater vessel where the stream is heated. The hot coke stream from the heater is fed to the gasifier where it reacts with air and steam. The gasifier product gas containing entrained coke particles, called coke oven gas, is returned to the heater and provides part of the reactor heat demand by cooling the coke from the reactor. The return stream of coke from the gasifier to the heater provides the remainder of the heat demand. The coke that meets the heat demand is then circulated to the reactor and the feed stream is thermally cracked to produce light hydrocarbon liquids that are removed from the reactor and recovered using conventional fractionation equipment. Fluidized coke is formed from the thermal cracking process and settles (deposits) on the "seed" fluidized bed coke already present in the reactor. At least a portion of the produced gasified coke is flexible coke. In some cases, the coke from the thermal cracking process is deposited in a ring-like pattern on the surface of the seed coke. In normal FLEXICOKING TM Flexible coke is continuously withdrawn from the system (e.g. from the reactor or after it flows into the heater via an elutriator) during processing, thereby ensuring that the system maintains the coke particles in the flowable particle size range. Thus, flexible coke is FLEXICOKING TM process is an easily available by-product.

[0085] FLEXICOKING TM The gasification process of FLEXICOKING

[0086] In various embodiments, the flexible coke particles can have a carbon content ranging from about 85 weight percent (wt%) to about 99 wt% (e.g., from about 85, 87, 89, 91 wt% to 93, 95, 97, 99 wt%); a weight ratio of carbon to hydrogen ranging from about 80: 1 to about 95: 1 (e.g., from about 80: 1, 85: 1 to 90: 1, 95: 1); and an impurity content (i.e., the weight percent of all components other than carbon and hydrogen) ranging from about 1 wt% to about 10 wt% (e.g., from about 1, 2, 3, 4, 5 wt% to 6, 7, 8, 9, 10 wt%). The flexible coke also has a higher metal content than other coals. In particular, the flexible coke can have a combined vanadium and nickel content ranging from about 3000 parts per million (ppm) to about 45,000 ppm (e.g., from about 3000, 10,000, 15,000 ppm, to 20,000, 25,000, 30,000 ppm, to 35,000, 40,000, 45,000 ppm). Additionally, the flexible coke particles can have a sulfur content ranging from 0 wt% to about 5 wt% (e.g., from 0, 1, 2 wt% to 3, 4, 5 wt%) and a nitrogen content ranging from 0 wt% to about 3 wt% (e.g., from 0, 0.5, 1.0, 1.5 wt% to 2.0, 2.5, 3.0 wt%).

[0087] The apparent density of the flexible coke particles can range from about 1.0 g / cm 3 to about 2.0 g / cm 3 (e.g., from about 1.0, 1.1, 1.2, 1.3 g / cm 3 , to 1.4, 1.5, 1.6, 1.7 g / cm 3 , to 1.8, 1.9, 2.0 g / cm 3 ). Conventional sand-based proppants typically have an apparent density of at least about 2.5 g / cm 3 . Thus, the flexible coke particles have a substantially lower apparent density compared to conventional sand-based proppants, which indicates their relatively more efficient transport and lower settling rate within fractures formed as part of a hydraulic fracturing operation.

[0088] For embodiments in which the petroleum coke product(s) from one or more refineries comprises fluidized coke particles, such fluidized coke particles are obtained via a fluid coking process. The fluid coking process can be manipulated in various ways to produce fluidized coke particles having a number of unique characteristics. For example, the fluidized coke particles can have a carbon content in the range of about 75 wt% to about 93 wt% (e.g., about 75, 77, 79, 81, 83 wt% to 85, 87, 91, 93 wt%); a weight ratio of carbon to hydrogen in the range of about 30: 1 to about 50: 1 (e.g., about 30: 1, 35: 1 to 40: 1, 45: 1, 50: 1); and an impurity content in the range of about 5 wt% to about 25 wt% (e.g., about 5, 10, 15 wt% to 20, 25 wt%). The fluidized coke particles can also have a sulfur content in the range of about 3 wt% to about 10 wt% (e.g., about 3, 4, 5, 6 wt% to 7, 8, 9, 10 wt%) and a nitrogen content in the range of about 0.5 wt% to about 3 wt% (0.5, 1.0, 1.5 wt% to 2.0, 2.5, 3.0 wt%). Additionally, the apparent density of the fluidized coke particles can be in the range of about 1.4 g / cm 3 to about 2.0 g / cm 3 (e.g., about 1.4, 1.5, 1.6 g / cm 3 to 1.7, 1.8, 1.9, 2.0 g / cm 3 ).

[0089] For embodiments in which the petroleum coke product(s) from one or more refineries comprises delayed coke particles, such delayed coke particles are produced within a delayed coking unit via a delayed coking process. According to the delayed coking process, preheated feedstock is introduced into a fractionator, where the feedstock undergoes a thermal cracking process in which long chain hydrocarbons are split into shorter chain hydrocarbons. The resulting lighter fraction is then removed as a side stream product. The fractionator bottoms, which include a recycle stream of heavy products, are heated in a furnace, which typically has an outlet temperature in the range of about 480 °C to about 515 °C. The heated feedstock then enters a reactor, referred to as a "coke drum," which is typically operated at a temperature in the range of about 415 °C to about 450 °C. Within the coke drum, cracking reactions continue to occur. The resulting cracked products then exit the coke drum as an overhead stream, while coke deposits on the interior surface of the coke drum. Typically, the process continues for a period of time of about 16 hours to about 24 hours to allow the coke drum to fill with coke. Additionally, to allow the delayed coking unit to operate on an intermittent-continuous (or semi-continuous) basis, typically two or more coke drums are used. While one coke drum is online filling with coke, another coke drum is being steam stripped, cooled, decoked (e.g., via hydrojetting the deposited coke with water), pressure checked, and warmed up. Furthermore, the overhead stream exiting the coke drum enters a fractionator, where naphtha and heating oil fractions are recovered. The heavy recycle material is then typically combined with preheated fresh feedstock and recycled back into the process.

[0090] The delayed coke particles can exhibit the following properties: (1) a carbon content in the range of about 82 wt% to about 90 wt% (e.g., about 82, 83, 84, 85 wt% to 86, 87, 88, 89, 90 wt%); (2) a weight ratio of carbon to hydrogen in the range of about 15: 1 to about 30: 1 (e.g., about 15: 1, 20: 1 to 25: 1, 30: 1); (3) a combined vanadium and nickel content in the range of about 100 ppm to about 3000 ppm (e.g., about 100, 500, 1000, 1500 ppm to 2000, 2500, 3000 ppm); (4) a sulfur content in the range of about 2 wt% to about 8 wt% (e.g., about 2, 3, 4, 5 wt% to 6, 7, 8 wt%); and / or (5) a nitrogen content in the range of about 1 wt% to about 2 wt% (e.g., about 1.0, 1.2, 1.4 wt% to 1.6, 1.8, 2.0 wt%), where such properties are measured on a dry ash-free basis (or in other words, without accounting for residual ash content, and with moisture removed prior to analysis). Additionally, the delayed coke particles can have a moisture content in the range of about 6 wt% to about 14 wt% (e.g., about 6, 8, 10 wt% to 12, 14 wt%), and a volatile matter content in the range of about 6 wt% to about 18 wt% (e.g., about 6, 8, 10, 12 wt% to 14, 16, 18 wt%), as measured on a as-received basis. Furthermore, the apparent density of the delayed coke particles can be in the range of about 1.0 g / cm 3 to about 1.7 g / cm 3 (e.g., about 1.0, 1.1, 1.2, 1.3 g / cm 3 to 1.4, 1.5, 1.6, 1.7 g / cm 3 ). Additionally, the crush strength of the delayed coke particles can be comparable to the crush strength of other types of petroleum coke particles.

[0091] For embodiments in which the petroleum coke product(s) from one or more refineries includes petroleum coke microproppant particles, such petroleum coke microproppant particles can include wet flexible coke fines and / or dry flexible coke fines produced as byproducts of a FLEXICOKING TM process. Such wet flexible coke fines and / or dry flexible coke fines are collected as particles that are not recovered in the secondary cyclone of the heater within the flexicoking unit. More specifically, the particles are first collected in a tertiary cyclone, as dry flexible coke fines, and then the smaller particles that pass through the tertiary cyclone are recovered in a venturi scrubber, as wet flexible coke fines.

[0092] In various embodiments, the petroleum coke microproppant particles according to the embodiments described herein have a particle size of at most 105 pm (140 mesh), or in some cases, at most 88 pm (170 mesh), but can range from about 0.0001 pm to 105 pm (e.g., from about 0.0001, 0.001, 0.01, 0.1 pm to 0.5, 1.0, 2.0, 5.0, 8.0, 10 pm, to 15, 20, 25, 30, 35, 40, 45 pm, to 50, 53, 55, 60, 63, 65 pm, to 74, 75, 80, 85, 88, 90, 95, 100, 105 pm). Further, in various embodiments, such petroleum coke microproppant particles have an apparent density ranging from about 1.0 g / cm 3 to about 2.0 g / cm 3 ( e.g., from about 1.0, 1.1, 1.2, 1.3 g / cm 3 , to 1.4, 1.5, 1.6, 1.7 g / cm 3 , to 1.8, 1.9, 2.0 g / cm 3 ), although the exact apparent density of the particles can vary depending on the specific type(s) of coke used. In contrast, sand typically has an apparent density of at least about 2.5 g / cm 3 . Thus, because the settling rate is directly proportional to the difference in density between the solid particles and the carrying fluid (as shown in the expressions for the Stokes terminal settling velocity and the Ferguson & Church settling velocity), such petroleum coke microproppant particles have a substantially lower settling rate than sand. Thus, in terms of transportability within a hydraulic fracture generated, reopened, and / or extended during a hydraulic fracturing operation, such petroleum coke microproppant particles will perform better than sand and other non-coke proppant particles.

[0093] Figure 4 is a flowchart of an exemplary method 400 of making petroleum coke proppant particles and using such particles during hydraulic fracturing. In particular relation to the aspects and embodiments described herein, Figure 4 the sub-process 402 of making petroleum coke proppant particles is highlighted. The sub-process 402 includes receiving petroleum coke particles from one or more refineries at block 404, and size fractionating the petroleum coke particles at block 406.

[0094] As described herein, the petroleum coke particles received from the refineries at block 404 can include any suitable type(s) of petroleum coke. For example, the petroleum coke particles can include fluid coke, flexible coke, delayed coke, thermally after-treated coke, pyrolysis coke, or any combination thereof.

[0095] Further, with respect to block 404, certain actions can be taken at the refinery to improve the suitability of the petroleum coke particles for use as proppants. In particular, the petroleum coke particles can be prevented from becoming wet. For dusting purposes, it is current practice at refineries to spray water with surfactant or diesel on the petroleum coke particles. However, it is very difficult to screen wet particles; thus, in various embodiments, this dusting process can be prevented. Additionally, dry particles can be less oil wet and can be more easily mixed into the fracturing fluid at the production site, providing improved operational efficiency. Notably, in some embodiments, it can be desirable to increase the oil wetness of the particles to reduce the water-to-oil ratio of the resulting produced hydrocarbon fluid; in such cases, it can be preferable to spray or coat the particles with diesel. However, generally, operational efficiency is prioritized, and the dusting process is not performed in accordance with the aspects and embodiments described herein.

[0096] Another action that can be taken at the refinery to improve the suitability of the petroleum coke particles for use as proppants is to separate collected dust. In particular, according to current practice, petroleum coke dust collected from dust collection chambers is often dumped into the main petroleum coke product. However, once such dust is mixed together with the main petroleum coke product, it can be very difficult and expensive to separate the dust particles from the larger petroleum coke particles. Thus, in accordance with the aspects and embodiments described herein, such dust can not be added to the main petroleum coke product. In this way, higher efficiency can be achieved by avoiding the difficult and expensive dust separation process.

[0097] The petroleum coke produced from the refinery can then be converted into petroleum coke proppant particles via sizing at block 406. Generally, such sizing can include separating the petroleum coke into multiple sets of particles having different size ranges, for example, a first set of petroleum coke particles having a desired particle size range suitable for use as petroleum coke proppant particles, a second set of smaller petroleum coke particles suitable for use as petroleum coke microproppant particles, and a third set of larger petroleum coke particles unsuitable for use for hydraulic fracturing purposes.

[0098] More specifically, in various embodiments, the size fractionation can include sieving the petroleum coke to separate such petroleum coke into smaller petroleum coke particles having a desired maximum particle size and larger petroleum coke particles that exceed the desired maximum particle size. The desired maximum particle size can be 297 μιη (50-mesh), 210 μιη (70-mesh), or any other maximum particle size suitable for the intended hydraulic fracturing operation. In various embodiments, the sieved smaller petroleum coke particles can include both a first set of petroleum coke particles having a desired particle size range suitable for use as petroleum coke proppant particles and a second set of smaller petroleum coke particles suitable for use as petroleum coke microproppant particles, while the sieved larger petroleum coke particles can include a third set of larger petroleum coke particles unsuitable for use in hydraulic fracturing purposes. In some embodiments, the sieved smaller petroleum coke particles can be further sieved to remove petroleum coke particles that do not meet a desired minimum particle size. The desired minimum particle size can be 74 μιη (200-mesh), 88 μιη (170-mesh), 105 μιη (140-mesh), or any other minimum particle size suitable for the intended hydraulic fracturing operation. In such embodiments, the resulting sieved petroleum coke particles can include a large proportion of particles having a desired particle size range (e.g., 50 / 170-mesh or 70 / 140-mesh), although some amount of fines (e.g., petroleum coke microproppant particles) can still be present.

[0099] In various embodiments, depending on the details of the particular implementation, any suitable type(s) of filter, screen, and / or related machinery can be used for the sieving process. In some embodiments, the sieving equipment can be specifically designed or configured to provide particles having a desired particle size range.

[0100] Next, the sieved petroleum coke particles can be further separated into a first set of petroleum coke particles having a desired particle size range suitable for use as petroleum coke proppant particles (e.g., particles in the 50 / 170-mesh or 70 / 140-mesh size range) and a second set of smaller petroleum coke particles suitable for use as petroleum coke microproppant particles (e.g., particles having a size of 88 μιη (170-mesh) or less, or 105 μιη (140-mesh) or less). In various embodiments, this is accomplished via air classification. In such embodiments, an air elutriator and / or any other suitable type(s) of air classifier can be used for this purpose. Furthermore, in some embodiments, a water elutriator, hydrocyclone, fluidized bed dryer, and / or other type of size classifier can additionally or alternatively be used.

[0101] In various embodiments, the combination of first screening the petroleum coke particles and then air classifying (e.g., air elutriating) the petroleum coke particles advantageously maximizes the resulting number of petroleum coke particles having a desired particle size range that are suitable for use as petroleum coke proppant particles.

[0102] In some embodiments, the desired particle size range of the petroleum coke proppant particles is about 105 μιη (140-mesh) to about 210 μιη (70-mesh) (in which case the petroleum coke microproppant particles can have a particle size of up to 105 μιη (140-mesh)). In other embodiments, the desired average particle size range of the petroleum coke proppant particles is about 88 μιη (170-mesh) to about 297 μιη (50-mesh) (in which case the petroleum coke microproppant particles can have a particle size of up to 88 μιη (170-mesh)). However, as such ranges can be adjusted for the particulars of a particular implementation, these are provided merely as exemplary desired particle size ranges for the petroleum coke proppant particles.

[0103] In some embodiments, at least a portion of the petroleum coke can be ground prior to the initial screening process. This can increase the yield of petroleum coke particles having a desired particle size range by breaking larger particles into the desired size range prior to the screening process. Any suitable type(s) of grinding / milling technique(s) can be used for this purpose. For example, in some embodiments, hammer milling techniques, jet milling techniques, ball milling techniques, etc. can be used to process the petroleum coke particles, where each of these techniques generally involves crushing or pulverizing the particles into a size and shape suitable for use as petroleum coke proppant particles. Moreover, those skilled in the art will appreciate that any number of other grinding, milling, or other processing techniques can additionally or alternatively be used, depending on the particulars of a particular implementation.

[0104] At block 408, the resulting petroleum coke proppant particles can optionally be subjected to thermal post-treatment. In various embodiments, this can include heating the petroleum coke proppant particles to a temperature in a range of about 400°C to about 1200°C (e.g., about 400, 500, 600, 700, 800°C, to about 900, 1000, 1100, 1200°C) for a predetermined duration in a range of about 1 minute to about 24 hours (e.g., about 1 minute, 30 minutes, 1 hour, 4 hours, 8 hours to about 12 hours, 16 hours, 20 hours, 24 hours). Moreover, in some embodiments, the petroleum coke proppant particles can be thermally post-treated in any other suitable manner, e.g., via coating with a wax and / or resin. In some such embodiments, the coating of the particles can be performed subsequent to the thermal post-treatment of the particles.

[0105] At block 410, the petroleum coke proppant particles can be transported to the production site and stored in any suitable manner. In some embodiments, the petroleum coke proppant particles can be transported via truck or rail. When the hydraulic fracturing operation begins, then the petroleum coke proppant particles can be mixed with a carrier fluid, additives (if any), and non-coke proppant particles (if any) to form a fracturing fluid. This mixing can be performed using a hopper or any other suitable mixing device.

[0106] Finally, at block 412, the petroleum coke proppant particles can be used in the field during the hydraulic fracturing operation via the introduction of the fracturing fluid containing the petroleum coke proppant particles into the subterranean formation. More specifically, in various embodiments, this can include pumping the fracturing fluid containing the petroleum coke proppant particles into the subterranean formation at a high pump rate (e.g., an average pump rate of at least 25 bbl / min (0.07 m 3 / s) and at most 250 bbl / min (0.68 m 3 / s) to form a hydraulic fracture within the subterranean formation. In various embodiments, such a process is performed one stage at a time along the wellbore, with each stage being hydraulically isolated from any other stages that have been previously fractured. Moreover, in various embodiments, the stage being fractured has perforation clusters that allow the flow of the fracturing fluid through a metal tubing string to the subterranean formation.

[0107] Turning to additional details regarding the size fractionation process according to aspects and embodiments described herein, we find that the combination of petroleum coke screening and then air classification (e.g., elutriation) is effective to produce petroleum coke proppant particles having a desired particle size. In fact, we find that such a combination of screening and air classification is effective even if the petroleum coke has been previously ground (thus producing a greater number of particles and fines compared to the original petroleum coke). Notably, in some embodiments, such ground petroleum coke can be performed to break larger particles into smaller particles that include the desired particle size range.

[0108] We found that air classification without sieving was not very effective in providing petroleum coke particles having a desired particle size range. This is illustrated by Table 1, which shows that air classification of a ground petroleum coke sample that initially contained about 50% fines (where such fines have a particle size of at most 105 μιη (140 mesh)) successfully reduced the fines content to less than 20% (results varied depending on the type of analytical technique used). As a specific example, see the test labeled "3 coarse" in Table 1, where despite removing over 50% of the sample, the remaining sample still did not meet the critical requirement of less than 5% fines content. Thus, we concluded that it is difficult to obtain a desired fines content of less than about 5% using air classification without sieving, and it is preferred to first sieve and then air classify, as described herein.

[0109] Table 1

[0110]

[0111] As described above, we found that sieving followed by air classification (e.g., elutriation) is very effective in providing petroleum coke particles having a desired particle size range. This is further illustrated by Table 2, which shows the results of a test where a petroleum coke sample was first ground, then sieved, and then air classified. The fines content of the sample was successfully reduced from about 18% to less than 1%. The yield (meaning the percentage of the volume of the resulting product having a desired particle size range, based on the total volume of the original petroleum coke sample) was about 72%. Thus, we found that sieving the sample enabled removal of a large proportion of the fines. This then allowed the air classifier (e.g., elutriator) to remove a large amount of the remaining fines without a large reduction in yield.

[0112] Table 2

[0113]

[0114]

[0115] Turning now to a discussion of the ways in which the size classification process can affect the conductivity of the resulting petroleum coke proppant particles, Figure 5A and 5B illustrates the effect of grinding and sieving a 70 / 140-mesh petroleum coke sample. In particular, Figure 5A illustrates petroleum coke sample 500, while Figure 5B illustrates petroleum coke sample 502 after grinding and sieving. As Figure 5BAs shown, the attrition process can result in at least a portion of the particles experiencing a decrease in sphericity. However, we found that once the fines are sufficiently removed via air classification, the resulting proppant conductivity is maintained at a level that is substantially the same as the proppant conductivity prior to size classification.

[0116] To examine the relative importance of attrition, particle shape, and fines content on the resulting conductivity characteristics of the proppant, 40 / 70-mesh samples of fluid coke and sand were ground using a high-speed crusher operating at 25,000 revolutions per minute (rpm), and the 100-mesh fraction of the product was captured via mechanical sieving. These samples were then evaluated for API conductivity under standard conditions at 150 degrees Fahrenheit (°F) and 2 lb / ft 2 The particle size and shape distribution of each sample were characterized using automated digital imaging microscopy. The instrument captures images of the particles in the field of view of a microscope objective and converts the pixelated two-dimensional images into a series of geometric size and shape descriptors of the imaged particles. Statistical distributions are then generated from the collection of images. A summary of some of the relevant size and shape characteristics is presented in Table 3, where σ vol，50 and are the volume-weighted median and mean circle-equivalent diameter (in μιη), respectively, and the aspect ratio 50 is the volume-weighted median aspect ratio.

[0117] Table 3

[0118]

[0119] Figure 6A is a plot 600 showing the conductivity of the fluid coke samples of Table 3, while Figure 6B is a plot 602 showing the conductivity of the sand samples of Table 3. More specifically, in each of plots 600 and 602, the conductivity (in mD / ft) is shown as a function of closure stress (in psi) for the 40 / 70-mesh sample, the attrited 40 / 70-mesh to 100-mesh sample, the 100-mesh sample, and the attrited 100-mesh sample (fines removed) for each of the 40 / 70-mesh samples. All measurements were conducted at 150 °F and 2 lb / ft 2 We found that the larger size fractions have higher conductivity, and the stress dependence of the conductivity is similar. One notable difference for the attrited 100-mesh fluid coke sample is that the conductivity of the attrited material exhibits a much larger decrease with stress compared to the unattrited counterpart. We also noted that the attrited sand sample exhibits a higher conductivity at low stress compared to the unattrited 100-mesh sample; however, similar to the fluid coke samples, the degree of decrease in conductivity with increasing stress is much larger compared to the unattrited 100-mesh sample.

[0120] Figure 7A FIG. 700, including a plot of the volume-weighted cumulative distribution function of the circle-equivalent diameters of the fluid coke samples of Table 3, and an inset 702 of the number-weighted cumulative distribution function of the circle-equivalent diameters of the fluid coke samples of Table 3, where the circle-equivalent diameter is calculated as the diameter of a circle having an area equal to the captured pixelated area of the particle. We observed very little difference in the overall distribution in the fluid coke samples in the nominally 100-mesh range. It is worth noting that the 100-mesh sand sample has a slightly higher polydispersity than the other sand samples, which can partially explain Figure 7B FIG. 704, including a plot of the volume-weighted cumulative distribution function of the circle-equivalent diameters of the sand samples of Table 3, and an inset 706 of the number-weighted cumulative distribution function of the circle-equivalent diameters of the sand samples of Table 3, where the circle-equivalent diameter is calculated as the diameter of a circle having an area equal to the captured pixelated area of the particle. We observed very little difference in the overall distribution in the fluid coke samples in the nominally 100-mesh range. It is worth noting that the 100-mesh sand sample has a slightly higher polydispersity than the other sand samples, which can partially explain Figure 6B The ground sand samples seen in FIGS. 600 and 602 show a significant increase in the conductivity of the milled samples with the removal of the fine particles, nearly restoring the conductivity to that of the original unground 100-mesh sample. Thus, this data shows that the presence of fine particles in the initial proppant pack has a significant effect on the resulting conductivity.

[0121] Recognizing this effect, we tested the effect of removing the fine particles by air classification (i.e., in this case, elutriation). A quantity of the sample was placed in a vertical tube with 100-mesh screens at the top and bottom of the column, and air was flowed from the bottom to aerosolize and remove the fine particles. The resulting material collected exhibited nearly identical volume-weighted particle size distributions. Figure 7A and 7B The insets 702 and 706, respectively, show that the number of very small particles in the sample is significantly reduced due to the elutriation process. Furthermore, Figure 6A and 6B The plots 600 and 602, respectively, show that the conductivity of the milled samples with the removal of the fine particles is significantly improved, nearly restoring the conductivity to that of the original unground 100-mesh sample. Thus, this data shows that the presence of fine particles in the initial proppant pack has a significant effect on the resulting conductivity.

[0122] Figure 8A FIGS. 800 and 802, respectively, include the volume-weighted and number-weighted distribution functions of the aspect ratios of the particles of the fluid coke samples of Table 3, while Figure 8BFIGS. 804 and 806, respectively, include volume-weighted and number-weighted distribution functions of the aspect ratios of the sand samples of Table 3, where the aspect ratio is defined as the width-to-length ratio of the projected two-dimensional particle images. Based on FIGS. 800 and 804, we see that there is little evidence on a volume basis that particle shape has a significant impact on the conductivity behavior of the samples. In this case, the attrition process has produced a slightly more skewed population toward higher elongations, which is more pronounced for the fluid coke samples than for the sand samples. This also suggests that each material type (i.e., fluid coke vs. sand) has its own breakage path when attrited, and thus should be examined explicitly.

[0123] In summary, we conclude that the primary impact of attrition is to introduce fines into the system, which, if retained, can lead to a substantial reduction in permeability of the particle pack. Even after attrition, the particle shape distribution does not appear to have changed significantly, and the recovery of conductivity after removal of fines will also suggest that particle shape is a minor player in determining the flow characteristics of fluids through these packs.

[0124] Turning to the details of an example method according to the present disclosure, Figure 9 is a process flow diagram of an example method 900 of making petroleum coke proppant particles for use in hydraulic fracturing. Method 900 can be performed using feed petroleum coke particles. Such feed petroleum coke particles can include fluid coke, flexi coke, delayed coke, thermally post-treated coke, pyrolysis coke, and any combination thereof. Further, such particles can have an apparent density in the range of about 1.0 g / cm3to about 2.0 g / cm3. In various embodiments, such particles can be obtained (e.g., produced here or received from here) from one or more refineries (e.g., from a fluid coking plant, a flexi coking plant, a delayed coking plant, etc.) and can or can not be further treated, such as by thermal post-treatment, attrition, and / or sieving. 3 to about 2.0 g / cm3. In various embodiments, such particles can be obtained (e.g., produced here or received from here) from one or more refineries (e.g., from a fluid coking plant, a flexi coking plant, a delayed coking plant, etc.) and can or can not be further treated, such as by thermal post-treatment, attrition, and / or sieving. 3 range of about 1.0 g / cm3to about 2.0 g / cm3. In various embodiments, such particles can be obtained (e.g., produced here or received from here) from one or more refineries (e.g., from a fluid coking plant, a flexi coking plant, a delayed coking plant, etc.) and can or can not be further treated, such as by thermal post-treatment, attrition, and / or sieving.

[0125] Example method 900 can begin at block 902, where feed petroleum coke particles can be provided, where such feed petroleum coke particles can include particles greater than a predetermined critical size (i.e., a predetermined sieve size), particles less than the predetermined critical size, and optionally petroleum coke microproppant particles. In various embodiments, the predetermined critical size can be greater than 105 pm. In some embodiments, the predetermined critical size can be no greater than 297 pm. Further, in some embodiments, at block 902, precursor petroleum coke particles can be attrited to obtain at least a portion of the feed petroleum coke particles.

[0126] At block 904, the feedstock petroleum coke particles can be sized to obtain a first portion of petroleum coke particles and a second portion of petroleum coke particles. At least 75 vol% of the first portion can have a particle size no smaller than a predetermined threshold size, based on the total volume of petroleum coke particles in the first portion. Substantially all of the second portion can have a particle size no greater than the threshold particle size, and the second portion can include no more than 25 vol% of petroleum coke microproppant particles having a particle size no greater than 74 pm (in some embodiments, no more than 25 vol% of petroleum coke microproppant particles having a particle size no greater than 88 pm, in some other embodiments, no more than 25 vol% of petroleum coke microproppant particles having a particle size no greater than 105 pm), based on the total volume of petroleum coke particles in the second portion. In some embodiments, the second portion can include no more than 15 vol% of petroleum coke microproppant particles having a particle size no greater than 74 pm (in some embodiments, no more than 15 vol% of petroleum coke microproppant particles having a particle size no greater than 88 pm, in some other embodiments, no more than 15 vol% of petroleum coke microproppant particles having a particle size no greater than 105 pm), based on the total volume of petroleum coke particles in the second portion. In some embodiments, the second portion can include no more than 10 vol% of petroleum coke microproppant particles having a particle size no greater than 74 pm (in some embodiments, no more than 10 vol% of petroleum coke microproppant particles having a particle size no greater than 88 pm, in some other embodiments, no more than 10 vol% of petroleum coke microproppant particles having a particle size no greater than 105 pm), based on the total volume of petroleum coke particles in the second portion. In some embodiments, the second portion can include no more than 5 vol% of petroleum coke microproppant particles having a particle size no greater than 74 pm (in some embodiments, no more than 5 vol% of petroleum coke microproppant particles having a particle size no greater than 88 pm, in some other embodiments, no more than 5 vol% of petroleum coke microproppant particles having a particle size no greater than 105 pm), based on the total volume of petroleum coke particles in the second portion.

[0127] In some embodiments, at block 904, a fourth portion of petroleum coke particles can be obtained. The fourth portion can have an average particle size smaller than the average particle size of the second portion, and such a fourth portion can include a higher concentration of petroleum coke microproppant particles than the second portion.

[0128] In various embodiments, the feed petroleum coke particles can be prevented from contacting liquids prior to and during performance of block 904. To that end, for example, the feed petroleum coke particles can be prevented from undergoing a dusting process at one or more refineries. In addition, the feed petroleum coke particles can be shielded with a covering or otherwise protected from contact with a source of moisture.

[0129] At block 906, the second portion of petroleum coke particles can be size classified to obtain a petroleum coke proppant particle portion that includes no more than 10% by volume of petroleum coke microproppant particles having a particle size of no more than 74 μιη, based on the total volume of the petroleum coke proppant particle portion. In various embodiments, this can be performed using an air elutriator; a water elutriator, a hydrocyclone, and / or a fluidized bed dryer.

[0130] In some embodiments, the petroleum coke proppant particle portion can include no more than 5% by volume of petroleum coke microproppant particles having a particle size of no more than 74 μιη, based on the total volume of the petroleum coke proppant particle portion. In some such embodiments, the second portion can include no more than 5% by volume of petroleum coke microproppant particles having a particle size of no more than 88 μιη, based on the total volume of the petroleum coke particles in the second portion. In other such embodiments, the second portion can include no more than 5% by volume of petroleum coke microproppant particles having a particle size of no more than 105 μιη, based on the total volume of the petroleum coke particles in the second portion.

[0131] In some embodiments, the petroleum coke proppant particle portion can include no more than 3% by volume of petroleum coke microproppant particles having a particle size of no more than 74 μιη, based on the total volume of the petroleum coke proppant particle portion. In some such embodiments, the second portion can include no more than 3% by volume of petroleum coke microproppant particles having a particle size of no more than 88 μιη, based on the total volume of the petroleum coke particles in the second portion. In other such embodiments, the second portion can include no more than 3% by volume of petroleum coke microproppant particles having a particle size of no more than 105 μιη, based on the total volume of the petroleum coke particles in the second portion.

[0132] In some embodiments, substantially all of the petroleum coke proppant particle portion can have a particle size of 74 μιη to 210 μιη. In other embodiments, substantially all of the petroleum coke proppant particle portion can have a particle size of 88 μιη to 210 μιη. In other embodiments, substantially all of the petroleum coke proppant particle portion can have a particle size of 105 μιη to 210 μιη.

[0133] In some embodiments, at block 906, a third portion of the petroleum coke particles can be obtained. Such third portion can have an average particle size that is less than the average particle size of the petroleum coke proppant particle portion, and such third portion can include petroleum coke microproppant particles at a higher concentration than the petroleum coke proppant particle portion.

[0134] Those skilled in the art will appreciate that the exemplary method 900 allows for modification. For example, in some embodiments, one or more blocks can be omitted from the method 900, and / or one or more blocks can be added to the method 900. In practice, the exact manner in which the method 900 is implemented will depend at least in part on the specifics of the particular implementation. Figure 9 Those skilled in the art will appreciate that the exemplary method 900 allows for modification. For example, in some embodiments, one or more blocks can be omitted from the method 900, and / or one or more blocks can be added to the method 900. In practice, the exact manner in which the method 900 is implemented will depend at least in part on the specifics of the particular implementation.

[0135] Figure 10 is a process flow diagram of another exemplary method 1000 of making petroleum coke proppant particles for hydraulic fracturing. The exemplary method 1000 can begin at block 1002, which can provide a dry petroleum coke including particles greater than 297 pm. The petroleum coke can include fluid coke, flexi-coke, delayed coke, thermally post-treated coke, pyrolysis coke, or any combination thereof. Further, the petroleum coke particles can have an apparent density in the range from about 1.0 g / cm3to about 2.0 g / cm3. In various embodiments, such particles can be obtained (e.g., produced at or received from) from one or more refineries (e.g., from a fluid coking plant, a flexi-coking plant, a delayed coking plant, etc.) and can or can not be further treated, such as by thermal post-treatment, milling, and / or sieving. 3 3 3

[0136] At block 1004, the dry petroleum coke can be milled to obtain milled petroleum coke particles.

[0137] At block 1006, the milled petroleum coke particles can be sieved to obtain a first portion of the petroleum coke particles and a second portion of the petroleum coke particles. At least 75% by volume of the first portion can have a particle size of at least 297 pm, based on the total volume of the first portion. Substantially all of the second portion can have a particle size of at most 297 pm, and the second portion can include no more than 25% by volume of petroleum coke microproppant particles, based on the total volume of the second portion.

[0138] ​In some embodiments, at least 75 vol% of the first portion can have a particle size of at least 250 pm, and substantially all of the petroleum coke particles of the second portion can have a particle size of at most 250 pm, based on the total volume of the first portion. In other embodiments, at least 75 vol% of the first portion can have a particle size of at least 210 pm, and substantially all of the petroleum coke particles of the second portion can have a particle size of at most 210 pm, based on the total volume of the first portion. Further, in some embodiments, the second portion can include no more than 15 vol% of petroleum coke microproppant particles, based on the total volume of the second portion.

[0139] At block 1008, the second portion of petroleum coke particles can be elutriated to obtain a petroleum coke proppant particle portion and a third portion of petroleum proppant particles. The petroleum coke proppant particle portion can have a particle size in a range of greater than 105 pm to at most 297 pm; the petroleum coke proppant particle portion can include at most 10 vol% of petroleum coke microproppant particles, based on the total volume of the petroleum coke proppant particle portion; and substantially all of the third portion can have a particle size of at most 105 pm. Further, in some embodiments, the petroleum coke proppant particle portion can include no more than 5 vol% of petroleum coke microproppant particles, based on the total volume of the petroleum coke proppant particle portion.

[0140] Those skilled in the art will appreciate that the exemplary method 1000 allows for modification, Figure 10 The exemplary method 1000 allows for modification. For example, in some embodiments, one or more blocks can be omitted from the method 1000, and / or one or more blocks can be added to the method 1000. In practice, the exact manner in which the method 1000 is implemented will depend at least in part on the specifics of the particular implementation.

[0141] The present disclosure can include one or more of the following non-limiting aspects and / or embodiments:

[0142] A1. A method comprising: (I) providing a feed petroleum coke particle comprising particles larger than a predetermined critical size, particles smaller than the predetermined critical size, and optionally petroleum coke microproppant particles, wherein the predetermined critical size is greater than 105 μιη; (II) sizing the feed petroleum coke particles to obtain a first portion of petroleum coke particles and a second portion of petroleum coke particles, wherein at least 75% by volume of the first portion has a particle size no smaller than the predetermined critical size, based on the total volume of petroleum coke particles in the first portion, and substantially all of the second portion has a particle size no greater than the critical particle size, and the second portion comprises no more than 25% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μιη, based on the total volume of petroleum coke particles in the second portion; and (III) size grading the second portion of petroleum coke particles to obtain a petroleum coke proppant particle portion comprising no more than 10% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μιη, based on the total volume of the petroleum coke proppant particle portion.

[0143] A2. The method of A1, wherein step (I) comprises milling precursor petroleum coke particles to obtain at least a portion of the feed petroleum coke particles.

[0144] A3. The method of A1 or A2, wherein step (III) is performed using at least one of: an air elutriator; a water elutriator, a hydrocyclone, and a fluidized bed dryer.

[0145] A4. The method of any one of A1 to A3, wherein the second portion comprises no more than 15% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μιη, based on the total volume of the second portion.

[0146] A5. The method of A4, wherein the second portion comprises no more than 15% by volume of petroleum coke microproppant particles having a particle size no greater than 88 μιη, based on the total volume of petroleum coke particles in the second portion.

[0147] A6. The method of A4, wherein the second portion comprises no more than 15% by volume of petroleum coke microproppant particles having a particle size no greater than 105 μιη, based on the total volume of petroleum coke particles in the second portion.

[0148] A7. The method of any one of A1 to A6, wherein the petroleum coke proppant particle portion comprises no more than 5% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μιη, based on the total volume of the petroleum coke proppant particle portion.

[0149] A8. The method of A7, based on the total volume of petroleum coke particles in the second portion, the second portion comprising no more than 5% by volume of petroleum coke microproppant particles having a particle size no greater than 88 μιη.

[0150] A9. The method of A7, based on the total volume of petroleum coke particles in the second portion, the second portion comprising no more than 5% by volume of petroleum coke microproppant particles having a particle size no greater than 105 μιη.

[0151] A10. The method of any one of A1 to A9, wherein the pre-determined critical size in step (I) is no greater than 297 μιη.

[0152] A11. The method of any one of A1 to A10, wherein substantially all of the petroleum coke proppant particle portion has a particle size of 74 μιη to 210 μιη.

[0153] A12. The method of any one of A1 to A10, wherein substantially all of the petroleum coke proppant particle portion has a particle size of 88 μιη to 210 μιη.

[0154] A13. The method of any one of A1 to A10, wherein substantially all of the petroleum coke proppant particle portion has a particle size of 105 μιη to 210 μιη.

[0155] A14. The method of any one of A1 to A13, wherein the feed petroleum coke particles in step (I) have an apparent density of 1.0 grams per cubic centimeter (g / cm 3 ) to 2.0 g / cm 3 .

[0156] A15. The method of any one of A1 to A14, wherein the feed petroleum coke particles in step (I) comprise at least one of: fluid coke, flexi-coke, delayed coke, hot- after-treated coke, and pyrolysis coke.

[0157] A16. The method of any one of A1 to A15, comprising preventing the feed petroleum coke particles from contacting a liquid prior to and during step (II).

[0158] A17. The method of any one of A1 to A16, wherein in step (III), a third portion of petroleum coke particles is obtained, and the third portion has an average particle size that is smaller than the average particle size of the petroleum coke proppant particle portion, and the third portion comprises petroleum coke microproppant particles at a higher concentration than the petroleum coke proppant particle portion.

[0159] A18. The method of any one of A1 to A17, wherein in step (II), a fourth portion of the petroleum coke particles is obtained, and the fourth portion has an average particle size that is less than the average particle size of the second portion, and the fourth portion comprises a higher concentration of the petroleum coke microproppant particles than the second portion.

[0160] B1. A method comprising: providing a dry petroleum coke comprising particles greater than 297 μιη; milling the dry petroleum coke to obtain milled petroleum coke particles; sieving the milled petroleum coke particles to obtain a first portion of the petroleum coke particles and a second portion of the petroleum coke particles, wherein at least 75% by volume of the first portion has a particle size of at least 297 μιη, based on the total volume of the first portion, and substantially all of the second portion has a particle size of at most 297 μιη, and the second portion comprises no more than 25% by volume of petroleum coke microproppant particles, based on the total volume of the second portion; and elutriating the second portion of the petroleum coke particles to obtain a petroleum coke proppant particle portion and a third portion of the petroleum proppant particles, wherein: the petroleum coke proppant particle portion has a particle size of greater than 105 μιη to at most 297 μιη; the petroleum coke proppant particle portion comprises no more than 10% by volume of petroleum coke microproppant particles, based on the total volume of the petroleum coke proppant particle portion; and substantially all of the third portion has a particle size of at most 105 μιη.

[0161] B2. The method of B1, wherein: at least 75% by volume of the first portion has a particle size of at least 250 μιη, based on the total volume of the first portion; and substantially all of the petroleum coke particles of the second portion have a particle size of at most 250 μιη.

[0162] B3. The method of B1 or B2, wherein: at least 75% by volume of the first portion has a particle size of at least 210 μιη, based on the total volume of the first portion; and substantially all of the petroleum coke particles of the second portion have a particle size of at most 210 μιη.

[0163] B4. The method of any one of B1 to B3, wherein the second portion comprises no more than 15% by volume of petroleum coke microproppant particles, based on the total volume of the second portion.

[0164] B5. The method of any one of B1 to B4, wherein the petroleum coke proppant particle portion comprises no more than 5% by volume of petroleum coke microproppant particles, based on the total volume of the petroleum coke proppant particle portion.

[0165] B6. The method of any one of B1 to B5, wherein the dry petroleum coke comprises at least one of: fluid coke, flexi-coke, delayed coke, hot after-treated coke, and pyrolysis coke.

[0166] While the embodiments described herein are well calculated to achieve the advantages presented, it will be appreciated that such embodiments are permissible for modification, variation, and alteration without departing from their spirit. In other words, the specific embodiments described herein are illustrative only, as the teachings of this disclosure can be modified and implemented in different but equivalent ways, which will be apparent to those skilled in the art who have benefited from the teachings herein. Furthermore, the systems and methods disclosed herein may be suitably implemented in the absence of any elements not specifically disclosed herein and / or any optional elements disclosed herein. Although compositions and methods are described in terms of “comprising” or “including” various components or steps, said compositions and methods may also “consist substantially of various components and steps” or “comprise various components and steps.” In fact, this disclosure includes all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims.

Claims

1. A method comprising: (I) providing a feed petroleum coke particulate comprising particles greater than a predetermined critical size, particles less than the predetermined critical size, and optionally petroleum coke microproppant particles, wherein the predetermined critical size is greater than 105 μm; (II) sizing the feed petroleum coke particulate to obtain a first portion of petroleum coke particulate and a second portion of petroleum coke particulate, wherein at least 75% by volume of the first portion has a particle size no less than the predetermined critical size, based on the total volume of petroleum coke particulate in the first portion, and substantially all of the second portion has a particle size no greater than the critical particle size, and the second portion comprises no more than 25% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μm, based on the total volume of petroleum coke particulate in the second portion; and (III) size fractionating the second portion of petroleum coke particulate to obtain a petroleum coke proppant particulate portion comprising no more than 10% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μm, based on the total volume of the petroleum coke proppant particulate portion.

2. The method of claim 1, wherein step (I) comprises milling precursor petroleum coke particulate to obtain at least a portion of the feed petroleum coke particulate.

3. The method of claim 1, wherein step (III) is performed using at least one of: an air elutriator; a water elutriator, a hydrocyclone, and a fluidized bed dryer.

4. The method of claim 1, wherein the second portion comprises no more than 15% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μm, based on the total volume of petroleum coke particulate in the second portion.

5. The method of claim 4, wherein the second portion comprises no more than 15% by volume of petroleum coke microproppant particles having a particle size no greater than 88 μm, based on the total volume of petroleum coke particulate in the second portion.

6. The method of claim 4, wherein the second portion comprises no more than 15% by volume of petroleum coke microproppant particles having a particle size no greater than 105 μm, based on the total volume of petroleum coke particulate in the second portion.

7. The method of claim 1, wherein the petroleum coke proppant particulate portion comprises no more than 5% by volume of petroleum coke microproppant particles having a particle size no greater than 74 μm, based on the total volume of the petroleum coke proppant particulate portion.

8. The method of claim 7, wherein the second portion comprises no more than 5% by volume of petroleum coke microproppant particles having a particle size no greater than 88 μm, based on the total volume of petroleum coke particulate in the second portion.

9. The method of claim 7, wherein the second portion comprises no more than 5% by volume of petroleum coke microproppant particles having a particle size no greater than 105 μm, based on the total volume of petroleum coke particulate in the second portion.

10. The method of claim 1, wherein the predetermined critical size in step (I) is no greater than 297 μm.

11. The method of claim 1, wherein substantially all of the petroleum coke proppant particle fraction has a particle size of 74 μιη to 210 μιη.

12. The method of claim 1, wherein substantially all of the petroleum coke proppant particle fraction has a particle size of 88 μιη to 210 μιη.

13. The method of claim 1, wherein substantially all of the petroleum coke proppant particle fraction has a particle size of 105 μιη to 210 μιη.

14. The process of claim 1, wherein the feed petroleum coke particles in step (I) have an apparent density of 1.0 grams per cubic centimeter (g / cm 3 ) to 2.0 g / cm 3 .

15. The method of claim 1, wherein the feed petroleum coke particles in step (I) comprise at least one of: fluid coke, flexible coke, delayed coke, thermally post-treated coke, and pyrolysis coke.

16. The method of claim 1, comprising preventing the feed petroleum coke particles from contacting a liquid prior to and during step (II).

17. The method of claim 1, wherein in step (III), a third fraction of petroleum coke particles is obtained, and the third fraction has an average particle size that is less than the average particle size of the petroleum coke proppant particle fraction, and the third fraction comprises a higher concentration of petroleum coke microproppant particles than the petroleum coke proppant particle fraction.

18. The method of claim 1, wherein in step (II), a fourth fraction of petroleum coke particles is obtained, and the fourth fraction has an average particle size that is less than the average particle size of the second fraction, and the fourth fraction comprises a higher concentration of petroleum coke microproppant particles than the second fraction.

19. A method comprising: providing a dry petroleum coke comprising particles greater than 297 μιη; milling the dry petroleum coke to obtain milled petroleum coke particles; sieving the milled petroleum coke particles to obtain a first fraction of petroleum coke particles and a second fraction of petroleum coke particles, wherein at least 75% by volume of the first fraction has a particle size of at least 297 μιη, based on the total volume of the first fraction, and substantially all of the second fraction has a particle size of at most 297 μιη, and the second fraction comprises no more than 25% by volume of petroleum coke microproppant particles, based on the total volume of the second fraction; and elutriating the second fraction of petroleum coke particles to obtain a petroleum coke proppant particle fraction and a third fraction of petroleum proppant particles, wherein: the petroleum coke proppant particle fraction has a particle size of greater than 105 μιη to at most 297 μιη; the petroleum coke proppant particle fraction comprises at most 10% by volume of petroleum coke microproppant particles; and substantially all of the third fraction has a particle size of at most 105 μιη.

20. The method of claim 19, wherein: at least 75% by volume of the first fraction has a particle size of at least 250 μιη, based on the total volume of the first fraction; and substantially all of the second fraction of petroleum coke particles has a particle size of at most 250 μιη.

21. The method of claim 19, wherein: at least 75% by volume of the first fraction has a particle size of at least 210 μιη, based on the total volume of the first fraction; and substantially all of the second fraction of petroleum coke particles has a particle size of at most 210 μιη. Substantially all of the petroleum coke particles of the second portion have a particle size of at most 210 μιη.

22. The method of claim 19, wherein the second portion comprises no more than 15 volume percent of petroleum coke microproppant particles, based on the total volume of the second portion.

23. The method of claim 19, wherein the petroleum coke proppant particle portion comprises no more than 5 volume percent of petroleum coke microproppant particles, based on the total volume of the petroleum coke proppant particle portion.

24. The method of claim 19, wherein the dry petroleum coke comprises at least one of: fluid coke, flexi-coke, delayed coke, hot- after-treated coke, and pyrolysis coke.

Images