Proppant Conveyance System For Fracturing Operations

Abstract

A proppant conveyance system at a well site. The system comprises a sand hopper configured to receive and hold the proppant. The system also includes a prime mover. The system further includes one or more plunger assemblies. Each plunger assembly resides proximate a base of the sand hopper. Each of the plunger assemblies is configured to receive a defined volume of proppant, and transport the defined volume of proppant into a sand manifold in response to power provided by the prime mover. The sand manifold, in turn, is configured to reside in series along a high-pressure frac line. As fracturing fluid moves through the sand manifold, it is mixed with proppant, producing a frac slurry. Methods of forming a frac slurry for use in wellbore fracturing operations are also provided.

I claim: 
     
         1 . A proppant conveyance system, comprising:
 a sand hopper configured to receive proppant;   a prime mover;   a sand manifold; and   one or more pistons residing at a base of the sand hopper, with each of the one or more pistons being configured to receive a defined volume of proppant from the sand hopper, and transport the defined volume of proppant into the sand manifold in response to power provided by the prime mover;   and wherein the sand manifold is configured to reside in series along a high-pressure frac line.   
     
     
         2 . The proppant conveyance system of  claim 1 , wherein:
 the prime mover comprises a hydraulic fluid pump for pumping a clean oil, an electric motor, or an internal combustion engine.   
     
     
         3 . The proppant conveyance system of  claim 1 , wherein:
 the one or more pistons comprises two or more pistons;   each of the pistons resides within an elongated tubular housing, wherein each respective elongated tubular housing has a first end connected to the sand hopper, and a second end connected to the sand manifold; and   together, the pistons and respective elongated tubular housings form plunger assemblies.   
     
     
         4 . The proppant conveyance system of  claim 3 , wherein:
 the elongated tubular housing further comprises an opening along an upper side configured to receive the volume of proppant; and   each of the one or more respective pistons comprises a front body and a rear body, with a trough residing between the front body and the rear body, and wherein each piston cycles between a retracted position and an extended position such that:
 when the piston is in its retracted position, the trough is aligned with the opening along the corresponding elongated tubular housing to receive the volume of proppant, and 
 when the piston is in its extended position, the trough delivers the volume of proppant into the sand manifold. 
   
     
     
         5 . The proppant conveyance system of  claim 4 , further comprising:
 a manifold that sealingly secures each elongated tubular housing for the respective plunger assemblies to the sand manifold; and   wherein the sand manifold comprises an inlet end for receiving a fracturing fluid upstream of the plunger assemblies, and an outlet end for delivering a frac slurry comprising the fracturing fluid and the proppant.   
     
     
         6 . The proppant conveyance system of  claim 5 , wherein the proppant comprises sand. 
     
     
         7 . The proppant conveyance system of  claim 5 , wherein each of the one or more respective pistons further comprises:
 a rod that reciprocates linearly along the elongated tubular housing in response to motive power provided by the prime mover;   a first end residing at the sand hopper that slidingly receives the rod;   a stationary plate residing proximate the first end, with the stationary plate having an opening for receiving the rod and serving as a stop member for the rear body when the plunger moves to its retracted position; and   a second end residing at a distal end of the front body.   
     
     
         8 . The proppant conveyance system of  claim 5 , wherein each of the one or more respective pistons further comprises:
 an elastomeric dart residing at the distal end of the front body but within the sand manifold, serving as a seal to the elongated tubular housing when the plunger moves to its retracted position;   a first O-ring residing around an outer diameter of the front body; and   a second O-ring residing around an outer diameter of the rear body;   wherein the first O-ring and the second O-ring provide a fluid seal for the trough when the plunger moves to its retracted position.   
     
     
         9 . The proppant conveyance system of  claim 5 , wherein each of the one or more respective pistons further comprises:
 a rod that reciprocates linearly along the elongated tubular housing in response to motive power provided by the prime mover; and   a push plate connecting the rod to the first end of the rear body;   and wherein:
 the rear body is connected to the rod, such that the rear body cycles within the elongated tubular housing between retracted and extended positions in response to reciprocation of the rod; and 
 in its retracted position the rear body resides between the base of the sand hopper and the opening along the upper side of the elongated tubular housing. 
   
     
     
         10 . The proppant conveyance system of  claim 9 , further comprising:
 a one-way valve residing proximate the second end of the elongated tubular housing, wherein the one-way valve extends into the sand manifold.   
     
     
         11 . The proppant conveyance system of  claim 10 , wherein:
 the front body of each of the one or more respective pistons is stationary, and resides at the distal end of its respective elongated tubular housing; and   the one-way valve resides at the distal of and is connected to the front body of each of the one or more respective pistons.   
     
     
         12 . The proppant conveyance system of  claim 11 , wherein the prime mover reciprocates the rods at a frequency selected to provide a desired concentration of the proppant into the frac slurry. 
     
     
         13 . The proppant conveyance system of  claim 11 , wherein the prime mover reciprocates the rods in a staggered manner such that the injection of the volumes of proppant into the sand manifold is at a generally constant rate. 
     
     
         14 . A method of forming a hydraulic fracturing slurry, comprising:
 fluidically connecting a sand manifold to a high-pressure injection line, in series with the high-pressure injection line;   receiving a stream of hydraulic fracturing fluid from the high-pressure injection line into the sand manifold;   moving pulses of proppant into the sand manifold such that proppant is mixed with the hydraulic fracturing fluid to form a frac slurry;   delivering the frac slurry out of the sand manifold and back into the high-pressure injection line; and   moving the frac slurry to a frac tree positioned over a wellbore at a well site.   
     
     
         15 . The method of  claim 14 , wherein:
 the frac slurry is exposed to no frac iron at the well site other than a pressure relief valve until it reaches the frac tree; and   the proppant is moved into the sand manifold at a generally constant rate.   
     
     
         16 . A method of forming a hydraulic fracturing slurry, comprising:
 providing a sand hopper;   providing a prime mover;   fluidically connecting a sand manifold to a high-pressure injection line, in series with the high-pressure injection line;   receiving a stream of hydraulic fracturing fluid from the high-pressure injection line into the sand manifold;   providing one or more plunger assemblies residing at a base of the sand hopper, with each of the one or more plunger assemblies being configured to receive a defined volume of proppant, and transport the defined volume of proppant into the sand manifold in response to motive power provided by the prime mover;   conveying proppant into the sand hopper; and   actuating the one or more plunger assemblies in order to move the defined volume of proppant from each of the one or more plunger assemblies as pulses while the hydraulic fracturing fluid moves through the sand manifold.   
     
     
         17 . The method of  claim 16 , wherein:
 the prime mover comprises a hydraulic fluid pump for pumping a clean oil, an electric motor, or an internal combustion engine.   
     
     
         18 . The method of  claim 17 , wherein:
 the one or more plunger assemblies comprises two or more plunger assemblies;   each plunger assembly comprises an elongated tubular housing and a piston residing within the tubular housing; and   each of the respective elongated tubular housings has a first end connected to the sand hopper and a second end connected to the sand manifold.   
     
     
         19 . The method of  claim 18 , wherein:
 the elongated tubular housing further comprises an opening along an upper side configured to receive the volume of proppant; and   each of the respective pistons comprises a front body and a rear body, with a trough residing between the front body and the rear body, and wherein each of the respective pistons cycles between a retracted position and an extended position such that:
 when the piston is in its retracted position the trough is aligned with the opening along the corresponding elongated tubular housing to receive a volume of proppant, and 
 when the piston is in its extended position, the trough delivers the volume of proppant into the sand manifold. 
   
     
     
         20 . The method of  claim 18 , wherein:
 the proppant comprises sand;   the elongated tubular housing of each of the one or more plunger assemblies is connected to the sand manifold via a housing manifold; and   the sand manifold comprises an inlet end for receiving the hydraulic fracturing fluid upstream of the pistons, and an outlet end for delivering the frac slurry comprising the hydraulic fracturing fluid and the proppant.   
     
     
         21 . The method of  claim 20 , wherein:
 the prime mover reciprocates the rod and connected piston at a frequency selected to provide a desired concentration of the sand in the frac slurry;   the proppant is moved into the sand manifold at a generally constant rate; and   the method further comprises determining a concentration of sand for the frac slurry.   
     
     
         22 . The method of  claim 20 , wherein each of the respective pistons further comprises:
 a rod that reciprocates linearly along the elongated tubular housing in response to motive power provided by the prime mover;   a first end residing at the sand hopper that slidingly receives the rod;   a stationary plate residing proximate the first end with the stationary plate having an opening for receiving the rod and serving as a stop member for the rear body when the plunger moves to its retracted position; and   a second end residing at a distal end of the front body.   
     
     
         23 . The method of  claim 22 , wherein each of the one or more respective plunger assemblies further comprises:
 an elastomeric dart residing at the distal end of the front body but within the sand manifold, serving as a seal to the elongated tubular housing when the plunger moves to its retracted position;   a first O-ring residing around an outer diameter of the front body; and   a second O-ring residing around an outer diameter of the rear body;   wherein the first O-ring and the second O-ring provide a fluid seal for the trough when the plunger moves to its retracted position.   
     
     
         24 . The method of  claim 20 , wherein each of the one or more respective pistons further comprises:
 a rod that reciprocates linearly along the elongated tubular housing in response to motive power provided by the prime mover; and   a push plate connecting the rod to the first end of the rear body;   and wherein:
 the rear body is connected to the rod, such that the rear body cycles within the elongated tubular housing between retracted and extended positions in response to reciprocation of the rod; and 
   in its retracted position the rear body resides between the base of the sand hopper and the opening along the upper side of the elongated tubular housing.   
     
     
         25 . The method of  claim 24 , wherein each of the respective plunger assemblies further comprises a one-way valve residing proximate the second end of the elongated tubular housing, wherein the one-way valve extends into the sand manifold. 
     
     
         26 . The method of  claim 25 , wherein:
 the front body of each of the respective pistons is stationary and resides at the distal end of its respective elongated tubular housing; and   the one-way valve resides at the distal of and is connected to the front body of the one or more respective pistons.   
     
     
         27 . The method of  claim 20 , further comprising:
 adjusting a rate of cycling of the pistons.   
     
     
         28 . The method of  claim 20 , wherein the frac slurry is exposed to no frac iron at the well site until it reaches the frac tree. 
     
     
         29 . A method of forming a hydraulic fracturing slurry, comprising:
 receiving a plurality of sand boxes at a well site, wherein each of the plurality of sand boxes contains proppant;   receiving water and chemicals for a wellbore fracturing operation at the well site;   mixing the water and chemicals in selected portions in a blender to form an aqueous frac medium;   moving the blended aqueous frac medium through one or more high-pressure pumps;   releasing the pressurized and blended aqueous frac medium from the one or more high-pressure pumps into a high-pressure frac line;   pumping the blended aqueous frac medium from the high-pressure frac line through a sand manifold;   transferring proppant from the sand boxes into the sand manifold in pulses while pumping the blended aqueous frac medium, forming a frac slurry;   releasing the frac slurry from the sand manifold back into the high-pressure frac line; and   passing the frac slurry from the high-pressure frac line through a frac tree and into the wellbore.   
     
     
         30 . The method of  claim 29 , wherein:
 the proppant comprises sand;   the proppant is moved into the sand manifold at a generally constant rate; and   the frac slurry is pumped into the wellbore at a pressure that is greater than a formation parting pressure of a downhole formation.