Abstract:
Hydraulic fracturing proppants for use in propping fractures in subterranean well bores comprising sand particles and methods for their manufacture are described. According to one or more embodiments, the proppants exhibit a narrow particle size distribution, crush resistance, sphericity, roundness and turbidity. Methods for propping open fractures during a hydraulic fracturing operation are also described.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to proppants and methods of using proppants in hydraulic fracturing of subterranean formations surrounding oil wells, gas wells, and similar boreholes.  
       BACKGROUND OF THE INVENTION  
       [0002]     Hydraulic fracturing is a technique designed to increase the productivity of a well, for example, an oil well or gas well, by creating highly conductive fractures or channels in the oil or gas producing formation surrounding the well. A hydraulic fracturing process normally involves two steps. First, a fluid is injected into the well at a sufficient rate and pressure to rupture the formation and create a fracture or crack in the reservoir rock surrounding the well. As a result, channels with high liquid conductivity are created from the wellbore into the formation. However, the fractures tend to close if they are not propped open. Accordingly, during formation of the fracture or after the fracture has been formed, a particulate material, which is referred to as a proppant or propping agent, is placed into the formation to “prop” open the fracture.  
         [0003]     Proppants must be able to withstand high pressures caused by closing walls of the fractured well and be inexpensive to produce in large quantities. In addition, it is desirable for the proppant particles to have the ability to form a porous structure for easy flow of liquid through the fracture. One property that enables the proppant particles to form a porous structure is the sphericity and roundness of the individual particles. Particles with greater sphericity and roundness tend to form a porous structure.  
         [0004]     Different types of particles have been used as acceptable propping agents. These particles include sand, metallic shot, bauxite, glass spheres, alumina ceramic materials, hardenable resins, and particles coated with bonding materials. Each of these materials has drawbacks. For example, sand usually cannot withstand high pressures created by the forces closing the fractures. It has been shown that at stresses of 10,000 psi and above, even the highest grade sand is inadequate because sand particles tend to disintegrate. At higher stress levels, the fine particles produced by the particle disintegration plug the interstices of the propped fracture, drastically reducing fracture permeability and conductivity. Proppants other than sand may be rather expensive for the use in large quantities necessary for well propping.  
         [0005]     The American Petroleum Industry (API) has established a commonly accepted standard in the industry which requires that the particle sizes be within pre-defined ranges. For example, particle size ranges are defined according to mesh size designations, such as 40/70, 30/50, 20/40, 16/30, 12/20, and 8/16. The first number in the designation refers to the ASTM U.S. Standard mesh size of the largest (top) sieve and the second number refers to the mesh size of the smallest (bottom) sieve. The API standards require that 90% of the spheres comprising the proppant material be retained between the top and bottom sieve when sieved through the mesh designations for the product.  
         [0006]     While specially screened (usually 20-40 mesh) high grade sand (e.g., Ottawa sand or Brady sand) can be used with higher closure stress formations, performance drops off drastically as stress increases, particularly above 8,000 psi. At stresses of 10,000 psi and above, even the highest grade sand has been inadequate. Brady sand and Ottawa sand have been accepted as proppant sands having a desirable combination of properties for hydraulic fracturing operations. Sand from the Bidahochi formation in Apache County, Ariz. has been used for several years in hydraulic fracturing operations. The mining techniques and processing operations that have been used to acquire sand from the Bidahochi formation in the past has resulted in a proppant material having less desirable proppant properties than Brady sand and Ottawa sand. Because of its abundant supply and low cost, sand is favored as a proppant. Accordingly, it would be desirable to provide improved sand proppants in addition to Brady Sand and Ottawa sand that has desirable properties such as particle size, crush resistance, sphericity, roundness, and turbidity for use in hydraulic fracturing.  
       SUMMARY OF INVENTION  
       [0007]     Embodiments of the invention relate to proppants and methods of use. The particles according to the various embodiments exhibit desirable crush resistance, sphericity, roundness, acid solubility, and turbidity, as determined by American Petroleum Institute Standard Recommended Practice 56 (RP-56). (See Recommended Practices for Testing Sand Used in Hydraulic Fracturing Operations, API Recommended Practice 56 Second Edition, December 1995, American Petroleum Institute). Other embodiments of the invention pertain to a method of propping open fractures during a hydraulic fracturing operation in a subterranean zone comprising placing the proppant particles of the various embodiments described herein in the fractures.  
         [0008]     According to a first embodiment, a proppant comprises sand particles having a sand mesh size of 40/70, a median diameter of between about 0.20 mm and 0.40 mm, a crush resistance of less than about 10% fine particles by weight produced at a crush stress of about 5000 psi and turbidity of less than about 100 FTU, preferably less than about 50 FTU. In preferred embodiments, the 40/70 mesh sized proppant particles have a median particle diameter of about 0.32 mm, a crush resistance of less than about 5% maximum fine particles produced at a crush stress of about 5000 psi and a turbidity of less than about 20 FTU. In a particular embodiment, the 40/70 mesh sized proppant particles, the particles are sized such that between about 4 weight percent and 6 weight percent of the particles are retained on a mesh size 40 sieve, between about 20 weight percent and 25 weight percent of the particles are retained on a mesh size 45 sieve, between about 32 weight percent and 37 weight percent of the particles are retained on a mesh size 50 sieve, between about 32 and 37 weight percent of the particles are retained on a mesh size 60 sieve and between about 0.5 and 2 weight percent of the particles are retained on a mesh size 70 sieve. According to one embodiment, the 40/70 mesh sized proppant particles exhibit a sphericity exceeding about 0.75 and a roundness exceeding about 0.65. Another feature of the 40/70 sized proppant particles is that the specific gravity of the particles is between about 2.55 and 2.65. In a particular aspect, the 40/70 mesh sized particles have a median diameter of about 0.32 mm and being sized such that about 5.5 weight percent are retained on a 40 mesh sieve, about 23.3 weight percent are retained on a 45 mesh sieve, about 35.0 weight percent are retained on a 50 mesh sieve, about 34.8 weight percent are retained on 60 mesh sieve and about 1.4 weight percent are retained on a 70 mesh sieve.  
         [0009]     In another embodiment, a proppant is provided which comprises sand particles having a 30/50 mesh size, a median diameter of between about 0.35 mm and 0.45 mm, a crush resistance of less than about 10% fine particles produced at a crush stress of about 4000 psi and a turbidity of less than about 100 FTU, preferably less than about 50 FTU. In a preferred embodiment, the median diameter of the 30/50 mesh sized particles is about 0.42 mm, have a crush resistance of less than about 3% fine particles produced at a crush stress of about 4000 psi and a turbidity of less than about 30 FTU. In a particular embodiment, the 30/50 mesh sized particles are sized such that between about 4 weight percent and 6 weight percent of the particles are retained on a mesh size 30 sieve, between about 20 weight percent and 25 weight percent of the particles are retained on a mesh size 35 sieve, between about 20 weight percent and 25 weight percent of the particles are retained on a mesh size 40 sieve, between about 20 and 25 weight percent of the particles are retained on a mesh size 45 sieve, between about 25 and 30 weight percent of the particles are retained on a mesh size 50 sieve, and between about 0.2 and 1 weight percent of the particles are retained on a mesh size 60 sieve, and the particles exhibiting a sphericity exceeding about 0.75 and a roundness exceeding about 0.70. According to one embodiment, another feature of 30/50 mesh sized proppant particles of is that the specific gravity of the particles is between about 2.55 and 2.65. According to a particular embodiment, the 30/50 mesh sized proppant particles are sized such that about 4.6 weight percent are retained on a 30 mesh sieve, about 22.8 weight percent are retained on a 35 mesh sieve, about 23.1 weight percent are retained on a 40 mesh sieve, about 22.1 weight percent are retained on 45 mesh sieve, about 26.8 weight percent are retained on a 50 mesh sieve and about 0.6 weight percent are retained on 60 mesh sieve.  
         [0010]     According to another embodiment, proppant particles are provided comprising sand particles having a mesh size of 20/40, a median diameter of between about 0.50 mm and 0.70 mm, exhibiting a crush resistance of less than about 10% fine particles produced at about 4000 psi crush stress, and a turbidity of less than about 100 FTU, preferably less than about 50 FTU. In a particular embodiment, the 20/40 mesh sized particles have a median particle diameter of about 0.60 mm, exhibit a crush resistance of less than about 4% fine particles produced at a crush stress of about 4000 psi and a turbidity of less than about 20 FTU. In one embodiment, the 20/40 mesh sized particles are sized such that between about 2 weight percent and 4 weight percent of the particles are retained on a mesh size 20 sieve, between about 17 weight percent and 22 weight percent of the particles are retained on a mesh size 25 sieve, between about 28 weight percent and 32 weight percent of the particles are retained on a mesh size 30 sieve, between about 25 and 29 weight percent of the particles are retained on a mesh size 35 sieve, between about 18 weight percent and 22 weight percent are retained on a mesh size 40 sieve and between about 0.5 and 2 weight percent of the particles are retained on a mesh size 45 sieve, and the particles exhibiting a sphericity exceeding about 0.75 and a roundness exceeding about 0.65. According to one embodiment, a feature of the 20/40 mesh sized particles is that the specific gravity of the particles is between about 2.55 and 2.65. According to a particular embodiment of the 20/40 mesh size proppant particles is that the particles have a median diameter of about 0.60 mm and being sized such that about 3.1 weight percent are retained on a 20 mesh sieve, about 19.6 weight percent are retained on a 25 mesh sieve, about 30.1 weight percent are retained on a 30 mesh sieve, about 26.7 weight percent are retained on 35 mesh sieve, about 19.9 weight percent are retained on a 40 mesh sieve and about 0.6 weight percent are retained on a 45 mesh sieve.  
         [0011]     Another embodiment is directed to a hydraulic fracturing proppant comprising sand particles having mesh size of 12/20, a median diameter of between about 0.90 mm and 1.10 mm, the particles exhibiting a crush resistance of less than about 10% fine particles produced at a crush stress of about 3000 psi and a turbidity of less than about 100 FTU, preferably less than about 50 FTU. In one embodiment, the 12/20 mesh size particles have a median diameter of about 1.02 mm, exhibit a crush resistance of about less than about 5% fine particles produced at a crush stress of about 3000 psi and a turbidity less than about 30 FTU. In a particular embodiment, 12/20 mesh size particles are sized such that between about 0 weight percent and 0.4 weight percent are retained on a mesh size 12 sieve, 3 weight percent and 4 weight percent of the particles are retained on a mesh size 14 sieve, between about 11 weight percent and 14 weight percent of the particles are retained on a mesh size 16 sieve, between about 25 weight percent and 30 weight percent of the particles are retained on a mesh size 18 sieve, between about 53 and 57 weight percent of the particles are retained on a mesh size 20 sieve and less than about 1.0 weight percent of the particles are retained on a mesh size 25 sieve. A feature of the particles according to the fourth embodiment is that they exhibit a sphericity exceeding about 0.70 and a roundness exceeding about 0.65. Another feature of the proppant particles is that the percentage of fine particles produced at a crush stress of about 5000 psi is less than about 5% and the specific gravity of the particles is between about 2.55 and 2.65. Still another feature of the proppant particles according to the fourth embodiment is that the turbity of the particles is less than about 20 FTU. Particular features of the proppant particles according to the fourth embodiments is that the particles have a median diameter of about 1.0 mm and are sized such that about 0.1 weight percent are retained on a 12 mesh sieve, about 3.6 weight percent are retained on a 14 mesh sieve, about 12.9 weight percent are retained on a 16 mesh sieve, about 27.5 weight percent are retained on 18 mesh sieve, about 55.1 percent are retained on a 20 mesh sieve and about 0.8 weight percent are retained on 25 mesh sieve. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  are graphs showing the long term conductivity and permeability versus closure stress of proppant sand particles according embodiments of the invention;  
         [0013]      FIG. 2  is a graph comparing the conductivity versus closure stress of proppant sand particles according to one embodiment to prior art proppant sand particles;  
         [0014]      FIG. 3  is a graph comparing the conductivity versus closure stress of proppant sand particles according to one embodiment to prior art proppant sand particles;  
         [0015]      FIG. 4  is a graph comparing the conductivity versus closure stress of proppant sand particles according to one embodiment to prior art proppant sand particles;  
         [0016]      FIG. 5  is a graph comparing the conductivity versus closure stress of proppant sand particles according to one embodiment to prior art proppant sand particles; and  
         [0017]      FIG. 6  is a graph comparing the crush resistance of proppant sand particles according to one embodiment with prior art proppant sand particles. 
     
    
     DETAILED DESCRIPTION  
       [0018]     Before describing several exemplary embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or being carried out in various ways.  
         [0019]     Embodiments of the invention relate to novel hydraulic fracturing proppants and methods for their manufacture and use. According to certain embodiments, the methods involve injecting a proppant suspended in a carrier fluid into a subterranean formation. The proppant particles, when so injected, are deposited in the fracture to “prop” the adjacent walls apart so that the fracture is not closed.  
         [0020]     It is recognized in the art that particle size, particle size distribution, acid solubility, turbidity, crush resistance measured in quantity of fine particles, roundness and sphericity and proppant density all have an impact on fracture conductivity. Proppant particles generally should have a sphericity of 0.5 or greater and a roundness of 0.3 or greater according to the Krumbein and Shoss chart for visual estimation of roundness and sphericity. In certain preferred embodiments the sand particles have a sphericity and roundness of 0.7 or greater.  
         [0021]     The “conductivity ratio” of a proppant material is its conductivity, usually measured in Darcy-feet, at a given closure stress divided by its conductivity, determined by the test procedure described below, measured in the same units and at the same closure stress. In general, siliceous sand, because it is widely available, inexpensive, and comparatively effective, is an ideal proppant, at least for use in comparatively shallow formations.  
         [0022]     According to embodiments of the invention, sand from Engelhard&#39;s Cheto, Ariz. clay mine from the Bidahochi formation has been found particularly suitable for use as a hydraulic fracturing proppant as the sand particles exhibit a variety of desirable properties as will be seen further below. In years past, sand has been mined from this location for use in hydraulic fracturing operations, however, the processing used to mine the sand resulted in certain undesirable properties in the final product. According to an embodiment of the invention, improved mining and processing operations strip away fine sand to expose a prime band of sand and selectively extract this prime band without removing excessive clay containing sand with the extracted prime band.  
         [0023]     The sand selectively removed from the prime band is preferably further processed utilizing wet processing to wash the sand, fluidized bed dryers, screens, etc. as is known in the art. In preferred embodiments, the selectively extracted sand is processed first with physical beneficiation by separating the loosely attached fines and clay. Intensive washing is accomplished by means of attrition scrubbing. It is conducted at solids loadings between 65-85%, preferably at 73% solids loading and contact time between 1.5-15 minutes.  
         [0024]     The washed materials continuously flow into the next step for classification into concentrates of target particles size ranges. It has been found that so called “density separators” allow for optimum wet sizing into −1 mm +40 mesh, −40+70 mesh and −70 mesh products. At times, the density separator controls are adjusted to produce a −1 mm +50 mesh and −50+70 mesh and −70 mesh concentrates. In certain embodiments, two density separators are placed in series, the first of which divides the incoming sand into coarse concentrate (12/40 mesh) and one finer concentrate of minus 40 mesh. The second separator can make a 50 or 70 mesh separation or polish the 40 mesh separation for a more accurate fractionation. A 30/50 mesh concentrate or a 40 mesh concentrate can be made one at a time and stockpiled separately.  
         [0025]     The output of the density separators can then be stockpiled for drying in a fluid bed dryer and/or other continuously drying device, for example rotary dryers. Exceeding recommended properties of size analysis, particle distributions and crush strengths are achieved by multi-deck dry screen polishing.  
         [0026]     Thus, in preferred embodiments, sizing that involves at least two sizing steps, namely first using density separation in a liquid followed by sizing using a second density separator or separator screens results in a proppant product that has a narrow particle size distribution, acceptable crush resistance and turbidity. In addition, washing with an attrition washer for at least about 5 minutes aids in producing sand from the Cheto mine that has properties that are comparable to, and in some cases better than Brady sand and Ottawa sand.  
         [0027]     Evaluations of the long-term conductivity of the samples of sand were completed as described below and are shown in  FIG. 1  below. In addition, the conductivity versus closure stress of various samples according to embodiments of the invention was compared to samples of prior art Brady and Ottawa sands are shown in  FIGS. 2-5 .  
         [0028]     The samples were dried, lightly disassociated and fractionated into −12+20, −20+40, −30+50 and −40+70. Then a sieve analysis was performed on each sample, and the results are shown in Tables 1-4. Median particle size as used herein is calculated from the measured size distribution of each sample.  
         [0029]     These samples were evaluated at 2.0 Lb/ft 2  and 150° F. at 2,000, 4,000 and 6,000-psi closure stresses for 50 hours each. Various properties of hydraulic fracturing proppant particles are shown further below in the Tables. The equipment for conductivity and permeability testing included a 75 ton Dake Press with air oil intensifier; API SS316 or Monel K-500 flow cells with 10 sq. in. flow paths; Rosemont (smart family) 40:1 pressure transducers for measuring pressure drop and rate plumbed with ¼ in. lines and calibrated with the smart system computer; two gallon nitrogen driven fluid reservoirs filled with 2% KCl and deoxygenated with nitrogen; internal gauges and calipers for measuring widths; a personal computer to process data and calculate conductivity and permeability; two 10 sq. in. core slabs of Ohio sandstone.  
         [0030]     The composition of the sand mined and processed according to embodiments of the present invention, particularly, by selective mining of the prime band and attrition washing of the sand was measured by inductively coupled plasma (ICP) analysis. The silica content is approximately 94.25%, the silica content is approximately 2.44%, the K 2 O content is approximately 1.10%, the Na 2 O content is about 0.38%, the Fe 2 O 3  content is about 0.40%, and the loss on ignition is about 0.67%.  
         [0031]     The conductivity and permeability measurement of the proppant sand properties were conducted as follows: 
    a) An API cell was loaded with proppant sample to be tested. The proppant was leveled with a blade device.     b) The proppant sample was placed between the core slabs and was made a part of a four-cell stack.     c) The cells were stacked to within 0.002 inches from top to bottom and positioned between the platens of the Dake Press. Pressure was increased to 500 psi and the system was evacuated and saturated with water at 70-75° F.     d) Once saturated, the closure pressure was increased to 1,000 psi, at a rate of 100 psi/minute. The proppant was allowed to equilibrate as outlined in the data tables.     e) The flow rate, pressure differential, and average width were measured at each pressure in order to calculate conductivity and permeability. Five measurements were taken and averaged to arrive at each reported conductivity. Flow rate was measured with a LiquiFlow meter, which was calibrated with a Mettler balance to 0.01 ml/min. Darcy&#39;s Law was used for the calculations to determine the conductivity and permeability.     f) The test temperature was increased to 150° F. and allowed to equilibrate. The temperature was left at 150° F. for 12 hours prior to increasing the closure.     g) The conductivity and permeability of the proppant were collected at 1,000 psi closure at both room temperature and 50° F. as stated in the data tables.     h) The pressure was increased at 100 psi per minute at 1,000 psi increments and the above measuring technique repeated.     i) The conductivity and permeability of the proppant were continuously monitored at 2,000 psi and 150° F. for 50 hours.     j) The conductivity and permeability of the proppant were continuously monitored at 4,000 psi and 150° F. for 50 hours.     k) The conductivity and permeability of the proppant were continuously monitored at 6,000 psi and 150° F. for 50 hours.    
 
         [0043]     All of the values provided in Table 5 were obtained using API RP-56 as described in Recommended Practices for Testing Sand Used in Hydraulic Fracturing Operations, API Recommended Practice 56, Second Edition, Dec. 1995, American Petroleum Institute, the contents of which are incorporated herein by reference. The values recited in the claims refer to values obtained according to API RP-56. Turbidity in water is the result of suspended clay, silt or finely divided organic matter in the proppant sand. Turbidity is a measure of an optical property of a suspension that results from scattering and absorbing of light by the particulate matter present. Crush resistance is a measure of the weight percent of sand passing through the smallest mesh sieve for a particular mesh size of sand (“fine particles”). For example, for 12/20 mesh size sand, the crush resistance is a measure of the weight percent of sand that passes through a 20 mesh size sieve using the test described in API RP-56. The acid solubility is a measure of the solubility of sand in 12-3 hydrochloric-hydrofluoric acid, which is an indication of undesirable contaminants such as carbonate, feldspars and iron oxides in the sand.  
         [0044]      FIG. 1  contains a summary of conductivity and permeability vs. stress for sand according to several embodiments. The data for generating  FIG. 1  is provided in Tables 1 thru 4 below. Table 5 shows a summary of the crush resistance, sphericity, roundness, acid solubility, and turbity, of proppant sand according to various embodiments, as determined by API RP-56. The recommended ranges according to API RP-56 are also shown in Table 5, where applicable. Table 6 also shows the specific gravity of various embodiments.  
                                                                 TABLE 1                       Conductivity and Permeability of 40/70       Product (See sieve analysis below)                                Hrs at                           Closure &amp;   Closure   Temp   Conductivity   Width   Permeability       Temperature   (psi)   (° F.)   (md-ft)   (in)   (Darcy)               −14   1000   75   1757   0.233   91       −2   1000   150   1589   0.232   82       0   2000   150   1435   0.229   75       10   2000   150   1406   0.228   73       20   2000   150   1378   0.228   72       30   2000   150   1372   0.228   72       40   2000   150   1363   0.228   72       50   2000   150   1355   0.228   71       0   4000   150   1082   0.222   59       10   4000   150   992   0.221   54       20   4000   150   954   0.220   52       30   4000   150   924   0.219   51       40   4000   150   902   0.219   49       50   4000   150   910   0.219   50       0   6000   150   676   0.215   38       10   6000   150   540   0.212   31       20   6000   150   509   0.211   29       30   6000   150   495   0.210   28       40   6000   150   486   0.210   28       50   6000   150   480   0.210   27                    Sieve Analysis of 40/70 Product in Table 1                zebra   Sieve   % Retained                       Median Dia. = 0.322 mm   30   0.0               35   0.0               40   5.5               45   23.3               50   35.0               60   34.8               70   1.4               80   0.0               100   0.0               pan   0.0               Total   100.0               % In Size   94.5                        
         [0045]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
               
               
                 Conductivity and Permeability of 30/50 
               
               
                 Product (See sieve analysis below.) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Hrs at 
                   
                   
                   
                   
                   
               
               
                 Closure &amp; 
                 Closure 
                 Temp 
                 Conductivity 
                 Width 
                 Permeability 
               
               
                 Temperature 
                 (psi) 
                 (° F.) 
                 (md-ft) 
                 (in) 
                 (Darcy) 
               
               
                   
               
               
                 −14 
                 1000 
                 75 
                 2739 
                 0.231 
                 142 
               
               
                 −2 
                 1000 
                 150 
                 2698 
                 0.230 
                 141 
               
               
                 0 
                 2000 
                 150 
                 2410 
                 0.228 
                 127 
               
               
                 10 
                 2000 
                 150 
                 2317 
                 0.227 
                 123 
               
               
                 20 
                 2000 
                 150 
                 2298 
                 0.227 
                 122 
               
               
                 30 
                 2000 
                 150 
                 2279 
                 0.226 
                 122 
               
               
                 40 
                 2000 
                 150 
                 2262 
                 0.226 
                 120 
               
               
                 50 
                 2000 
                 150 
                 2233 
                 0.226 
                 119 
               
               
                 0 
                 4000 
                 150 
                 1670 
                 0.220 
                 91 
               
               
                 10 
                 4000 
                 150 
                 1544 
                 0.219 
                 85 
               
               
                 20 
                 4000 
                 150 
                 1466 
                 0.219 
                 80 
               
               
                 30 
                 4000 
                 150 
                 1437 
                 0.218 
                 79 
               
               
                 40 
                 4000 
                 150 
                 1414 
                 0.218 
                 78 
               
               
                 50 
                 4000 
                 150 
                 1404 
                 0.218 
                 77 
               
               
                 0 
                 6000 
                 150 
                 957 
                 0.214 
                 54 
               
               
                 10 
                 6000 
                 150 
                 786 
                 0.211 
                 45 
               
               
                 20 
                 6000 
                 150 
                 745 
                 0.210 
                 43 
               
               
                 30 
                 6000 
                 150 
                 719 
                 0.209 
                 41 
               
               
                 40 
                 6000 
                 150 
                 691 
                 0.209 
                 40 
               
               
                 50 
                 6000 
                 150 
                 689 
                 0.209 
                 40 
               
               
                   
               
             
          
           
               
                 Sieve Analysis of 30/50 Product in Table 2 
               
             
          
           
               
                   
                 zebra 
                 Sieve 
                 % Retained 
               
               
                   
                   
               
               
                   
                 Median Dia. = 0.423 mm 
                 20 
                 0.0 
               
               
                   
                   
                 25 
                 0.0 
               
               
                   
                   
                 30 
                 4.6 
               
               
                   
                   
                 35 
                 22.8 
               
               
                   
                   
                 40 
                 23.1 
               
               
                   
                   
                 45 
                 22.1 
               
               
                   
                   
                 50 
                 26.8 
               
               
                   
                   
                 60 
                 0.6 
               
               
                   
                   
                 70 
                 0.0 
               
               
                   
                   
                 pan 
                 0.0 
               
               
                   
                   
                 Total 
                 100.0 
               
               
                   
                   
                 % In Size 
                 94.8 
               
               
                   
                   
               
             
          
         
       
     
         [0046]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
               
               
                 Conductivity and Permeability of 20/40 
               
               
                 Product (See sieve analysis below.) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Hrs at 
                   
                   
                   
                   
                   
               
               
                 Closure &amp; 
                 Closure 
                 Temp 
                 Conductivity 
                 Width 
                 Permeability 
               
               
                 Temperature 
                 (psi) 
                 (° F.) 
                 (md-ft) 
                 (in) 
                 (Darcy) 
               
               
                   
               
               
                 −14 
                 1000 
                 75 
                 5370 
                 0.230 
                 280 
               
               
                 −2 
                 1000 
                 150 
                 5205 
                 0.229 
                 273 
               
               
                 0 
                 2000 
                 150 
                 4707 
                 0.227 
                 249 
               
               
                 10 
                 2000 
                 150 
                 4612 
                 0.226 
                 245 
               
               
                 20 
                 2000 
                 150 
                 4524 
                 0.225 
                 241 
               
               
                 30 
                 2000 
                 150 
                 4491 
                 0.225 
                 240 
               
               
                 40 
                 2000 
                 150 
                 4471 
                 0.225 
                 239 
               
               
                 50 
                 2000 
                 150 
                 4460 
                 0.225 
                 238 
               
               
                 0 
                 4000 
                 150 
                 2997 
                 0.221 
                 163 
               
               
                 10 
                 4000 
                 150 
                 2659 
                 0.219 
                 146 
               
               
                 20 
                 4000 
                 150 
                 2546 
                 0.218 
                 140 
               
               
                 30 
                 4000 
                 150 
                 2465 
                 0.217 
                 136 
               
               
                 40 
                 4000 
                 150 
                 2388 
                 0.217 
                 132 
               
               
                 50 
                 4000 
                 150 
                 2361 
                 0.217 
                 131 
               
               
                 0 
                 6000 
                 150 
                 1567 
                 0.211 
                 89 
               
               
                 10 
                 6000 
                 150 
                 1252 
                 0.209 
                 72 
               
               
                 20 
                 6000 
                 150 
                 1184 
                 0.208 
                 68 
               
               
                 30 
                 6000 
                 150 
                 1121 
                 0.207 
                 65 
               
               
                 40 
                 6000 
                 150 
                 1098 
                 0.207 
                 64 
               
               
                 50 
                 6000 
                 150 
                 1080 
                 0.207 
                 63 
               
               
                   
               
             
          
           
               
                 Sieve Analysis of 20/40 Product in Table 3 
               
             
          
           
               
                   
                 zebra 
                 Sieve 
                 % Retained 
               
               
                   
                   
               
               
                   
                 Median Dia. = 0.602 mm 
                 16 
                 0.0 
               
               
                   
                   
                 18 
                 0.0 
               
               
                   
                   
                 20 
                 3.1 
               
               
                   
                   
                 25 
                 19.6 
               
               
                   
                   
                 30 
                 30.1 
               
               
                   
                   
                 35 
                 26.7 
               
               
                   
                   
                 40 
                 19.9 
               
               
                   
                   
                 45 
                 0.6 
               
               
                   
                   
                 50 
                 0.0 
               
               
                   
                   
                 pan 
                 0.0 
               
               
                   
                   
                 Total 
                 100.0 
               
               
                   
                   
                 % In Size 
                 96.3 
               
               
                   
                   
               
             
          
         
       
     
         [0047]    
       
         
               
             
               
               
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                   
               
               
                 Conductivity and Permeability 12/20 
               
               
                 Product (See sieve analysis below.) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Hrs at 
                   
                   
                   
                   
                   
               
               
                 Closure &amp; 
                 Closure 
                 Temp 
                 Conductivity 
                 Width 
                 Permeability 
               
               
                 Temperature 
                 (psi) 
                 (° F.) 
                 (md-ft) 
                 (in) 
                 (Darcy) 
               
               
                   
               
               
                 −14 
                 1000 
                 75 
                 18959 
                 0.230 
                 280 
               
               
                 −2 
                 1000 
                 150 
                 18135 
                 0.229 
                 273 
               
               
                 0 
                 2000 
                 150 
                 14423 
                 0.233 
                 743 
               
               
                 10 
                 2000 
                 150 
                 14225 
                 0.232 
                 736 
               
               
                 20 
                 2000 
                 150 
                 14179 
                 0.231 
                 737 
               
               
                 30 
                 2000 
                 150 
                 14166 
                 0.231 
                 736 
               
               
                 40 
                 2000 
                 150 
                 14135 
                 0.231 
                 734 
               
               
                 50 
                 2000 
                 150 
                 14119 
                 0.231 
                 734 
               
               
                 0 
                 4000 
                 150 
                 7514 
                 0.220 
                 410 
               
               
                 10 
                 4000 
                 150 
                 6703 
                 0.218 
                 369 
               
               
                 20 
                 4000 
                 150 
                 6365 
                 0.216 
                 354 
               
               
                 30 
                 4000 
                 150 
                 6095 
                 0.215 
                 340 
               
               
                 40 
                 4000 
                 150 
                 6033 
                 0.215 
                 337 
               
               
                 50 
                 4000 
                 150 
                 6013 
                 0.215 
                 336 
               
               
                 0 
                 6000 
                 150 
                 3577 
                 0.207 
                 207 
               
               
                 10 
                 6000 
                 150 
                 2864 
                 0.205 
                 168 
               
               
                 20 
                 6000 
                 150 
                 2712 
                 0.204 
                 160 
               
               
                 30 
                 6000 
                 150 
                 2634 
                 0.203 
                 156 
               
               
                 40 
                 6000 
                 150 
                 2583 
                 0.203 
                 153 
               
               
                 50 
                 6000 
                 150 
                 2563 
                 0.203 
                 152 
               
               
                   
               
             
          
           
               
                 Sieve Analysis of 12/20 Product in Table 4 
               
             
          
           
               
                   
                 zebra 
                 Sieve 
                 % Retained 
               
               
                   
                   
               
               
                   
                 Median Dia. = 1.024 mm 
                 8 
                 0.0 
               
               
                   
                   
                 10 
                 0.0 
               
               
                   
                   
                 12 
                 0.1 
               
               
                   
                   
                 14 
                 3.6 
               
               
                   
                   
                 16 
                 12.9 
               
               
                   
                   
                 18 
                 27.5 
               
               
                   
                   
                 20 
                 55.1 
               
               
                   
                   
                 25 
                 0.8 
               
               
                   
                   
                 30 
                 0.0 
               
               
                   
                   
                 pan 
                 0.0 
               
               
                   
                   
                 Total 
                 100.0 
               
               
                   
                   
                 % In Size 
                 99.1 
               
               
                   
                   
               
             
          
         
       
     
         [0048]    
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                   
               
               
                 Summary of Sand Properties 
               
             
          
           
               
                 Property 
                 Units 
                 12/20 
                 20/40 
                 30/50 
                 40/70 
               
               
                   
               
               
                 Crush Resistance 
                 % fine 
                  4.6% 
                  3.6% 
                  2.6% 
                  4.1% 
               
               
                   
                 particles 
               
               
                 Crush stress 
                 Psi 
                 3000       
                 4000       
                 4000       
                 5000       
               
               
                 API RP-56 Recom. 
                   
                 &lt;16%   
                 &lt;14%   
                 &lt;10%   
                 &lt;8%  
               
               
                 Sphericity 
                   
                 0.78 
                 0.80 
                 0.76 
                 0.71 
               
               
                 Roundness 
                   
                 0.66 
                 0.73 
                 0.71 
                 0.70 
               
               
                 API RP-56 Recom. 
                   
                 &gt;0.6  
                 &gt;0.6  
                 &gt;0.6  
                 &gt;0.6  
               
               
                 Acid Solubility 
                 % by wt 
                  4.9% 
                  5.5% 
                  4.5% 
                  4.6% 
               
               
                 API RP-56 Recom. 
                   
                 &lt;2.0%  
                 &lt;2.0%  
                 &lt;2.0%  
                 &lt;2.0%  
               
               
                 Turbidity 
                 FTU 
                 29    
                 15    
                 25    
                 19    
               
               
                 API RP-56 Recom. 
                   
                 &lt;250       
                 &lt;250       
                 &lt;250       
                 &lt;250       
               
               
                 Specific Gravity 
                 g/cm 3   
                 2.61 
                 2.63 
                 2.63 
                 2.63 
               
               
                   
               
             
          
         
       
     
         [0049]     The sand mined and processed according to embodiments of the present invention exhibits a number of desirable properties for use as a hydraulic fracturing proppant as compared to prior art sands. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.