MOBILE SAND SLURRY DELIVERY SYSTEM

Description

BACKGROUND

Field of the Invention

The presently disclosed instrumentalities pertain to the field of hydraulic fracturing operations to stimulate production from wells and, particularly, to the distribution of sand that is commonly used as a proppant in such operations.

Description of the Related Art

Hydraulic fracturing is a well-known well stimulation technique in which pressurized liquid is utilized to fracture rock in a subterranean reservoir. In the usual case, this liquid is primarily water that contains sand or other proppants intended to hold open fractures which form during this process. The resulting “frac fluid” may sometimes benefit from the use of thickening agents, but these fluids are increasingly water-based. Originating in the year 1947, use of fracturing technology has grown such that approximately 2.5 million hydraulic fracturing operations had been performed worldwide by 2012. The use of hydraulic fracturing is increasing. Massive hydraulic fracturing operations in shale reservoirs now routinely consume millions of pounds of sand. Hydraulic fracturing makes it possible to drill commercially viable oil and gas wells in formations that were previously understood to be commercially unviable. Other applications for hydraulic fracturing include injection wells, geothermal wells, and water wells.

Hydraulic fracturing operations pump proppant into fractures that form in geologic formations during intervals of pressure pumping. The proppant, usually sand, facilitates the flow of fluids, such as oil or gas, by remaining in the fractures to hold them open after the pressure pumping ceases. Conventionally, the sand is produced and processed at a mine where it is washed, dewatered, dried and sorted by size. Various problems arise from this use of dry sand, such as exposure leading to possible silicosis as reported by U.S. Pat. No. 9,637,671 to Bestaoui-Spurr et al., proposing to add a polyionic polymer to the sand in an effort to mitigate silica dust.

More recently, hydraulic fracturing operations have pumped wet sand that is not necessarily processed by washing, sorting and drying at the mine. These pumping operations require specialized surface equipment for the handling of wet sand, for example, as described in U.S. Pat. No. 11,408,247 to Ochler et al. The use of wet sand permits the use of mobile equipment for the mining of sand to be located in close proximity to a well site location where a hydraulic fracturing operation is to be performed. The mobile equipment advantageously does not require capital investment for fuel or equipment for the sieving and drying of sand. The sand is, however, usually loaded wet into boxes or trailers with belly-dump systems for transport to a well site for use in hydraulic fracturing operations.

U.S. Pat. No. 11,519,252 to Kramer et al. proposes to utilize a pipeline to carry a concentrated slurry of proppant from a sand mine in support of remotely conducted hydraulic fracturing operations. The concentrated slurry is mixed with chemical additives at the mine, especially a friction reducer to mitigate the need for pressure boost pumping operations. In practice, significant problems arise from pumping these concentrates under oilfield conditions, such as plugging of the pipeline which must sometimes then be cut into pieces for salvage and removal. The use of slurry concentrates is associated with high pumping pressures that many experts believe to be unsafe. The use of metal or plastic flow conduits or pipelines is expensive and, in the intended environment of use, such equipment is exposed to rough handling conditions leading to its premature failure. The temporary or transient nature of serving multiple well sites from a single mobile mine or other central location leads to frequent line movements which tend to deteriorate the pipeline integrity.

SUMMARY

The instrumentalities disclosed herein overcome the problems outlined above and advance the art by providing an improved flow system for use in distributing proppant slurries in support of hydraulic fracturing operations.

According to one embodiment, a flow system is provided for moving a slurry of proppant through a conduit to support hydraulic fracturing of a well. The flow system contains a slurry mixing station that combines water from a source of water with sand from a source of sand. This is done to form a slurry that is discharged from the slurry mixing station to the inlet of a first pump, such as a centrifugal pump driven by a motor that is capable of delivering at least 150 brake horsepower, or at least 200 brake horsepower. The pump has an outlet that discharges the slurry into a lay-flat hose which is in fluidic communication with a well site for delivery of the slurry in support of the hydraulic fracturing operation.

In one aspect, the first pump may be powered by an electric motor or, alternatively, the first pump may be driven by a gas powered engine. This is also the case with various boost pumps that may be added to the flow system as needed to maintain the requisite system flow rates. In the case of natural gas power, a pressurized gas may be trucked to the well site as either compressed natural gas, liquified natural gas or hydrogen gas. Another non-fossil fuel source is ammonia, which may also be used in an internal combustion engine. It is also possible to use field gas produced from a well, if available at a particular location. In the case of electrical power, a skid or truck including a generator set may be provided to provide the electricity. Alternatively, the electric motor may be powered using grid power from an overhead line, local power produced by a solar array, and/or a hydrogen fuel cell or hydrogen fuel.

Each of the pumps may be driven by a diesel engine, a natural gas engine, an electric motor or a combination of electric motors and internal combustion engines. The advantages of using diesel engines include a dense fuel source as compared to natural gas, and the elimination of a generator set or expensive power cabling as compared to the use of electric motors. Thus, according to one embodiment, the first pump, which is located at the slurry mixing station where a source of electricity could be more readily available, may be driven by an electric motor while the boost pumps may be driven by an internal combustion engine which may be a diesel engine.

Alternatively, all of the pumps may be driven by electric motors on the output of a variable frequency drive (VFD) for control of the pump speed. The advantages of excluding internal combustion engines include the elimination of a transmission, as the electric motors may be installed without a transmission to deliver a relatively constant torque throughout their operating range while the use of a VFD enhances the granularity of control over pump speed as compared to the use of internal combustion engines. Another advantage of using electric motors is an improved carbon footprint of about three times less emitted carbon as compared to the use of diesel in performing the same work. According to the presently described instrumentalities, which enable the short haul of sand from a mobile mine as compared to a longer haul from a traditional mine that is more remote, the improvement in carbon footprint would be even better because the amount of work required to transport the sand is less.

In one aspect, the slurry mixing station and the first pump may be co-mounted on a conventional blender for use in hydraulic fracturing operations.

In various aspects, the lay-flat hose has a diameter that is sufficient to flow sand to the well site at a sufficient rate to meet operational requirements in the intended environment of use. This may be, for example, the ability to provide 25 million pounds of sand over five to seven days. This may also be about 120 million pounds of sand over ten to fourteen days for a multi-well pad, provided the sand is arriving while the hydraulic fracturing operation is being simultaneously performed. Generally speaking, the lay-flat hose may have an internal flow diameter ranging from four inches to sixteen inches, eight to sixteen inches and this internal flow diameter is preferably about ten inches.

In one aspect, the lay-flat hose is made of extruded through the weave thermoplastic polyurethane covered material. This type of material is advantageously lightweight and much less bulky, as compared to metal or plastic pipeline conduits, while also being quite capable of extended use at the requisite pressures in the intended environment of use. The lay-flat hose may, for example, have a working pressure of 200 psi or 250 psi as rated by the manufacturer, but it is envisioned that actual pumping pressures can be as low as 100 psi or less and may even be 50 psi or less or a value ranging from 50 psi up to 100 psi. The lay-flat hose is advantageously resistant to wear by abrasion from exposure to slurries that are pumped at these pressures. This resistance to wear also includes the hose section connectors or field fittings or heads, especially stainless steel connectors, that are used to join discrete sections of hose. In addition to being wear resistant, the stainless steel connectors are advantageously stronger and have a larger internal diameter than coated connectors. For example, the internal diameter of a stainless steel connector used to connect ten inch lay-flat tubing is approximately 9 7/32 inches, which creates less of a flow restriction than other commercially available coated options. The joined lay-flat hose may be assembled, for example, in lengths of at least one mile, two miles, three miles, four miles, five miles, six miles, and even ten or fifteen miles or more; however, these hose assemblies of greater than one or two miles may require the use of boost pumps to maintain the required flow rates without exceeding design pressure limits. The pumps are preferably sized to deliver a linear flow velocity of at least 11.5 ft/sec through the lay-flat hose. This linear flow velocity is more preferably at least 13 ft/sec or greater. These flow rates are intended to mitigate potential problems with gravity segregated flow that may, otherwise, occur in the lay-flat hose.

In one aspect, the lay-flat hose is spoolable in the sense that it is flexible and can be rolled-up on a large spindle. Other types of conduits may advantageously be utilized where higher pressures are needed, such as plastic shielded polyethylene hose having a working pressure that ranges from 250 to 1000 psi.

In one aspect, the sand source may be a mobile mine or another central location, such as a sandpile that is created to provision all wells that are to be fractured on a single lease or a group of leases.

In one aspect, the slurry mixing station may also add chemicals, such as a friction reducer, to the slurry to increase the distance that a slurry may be pumped from the mobile mine without necessitating the use of boost pumps or for mitigating the number of boost pumps.

In one aspect, a vortex separator may be located at the well site. The vortex separator is configured to dewater the slurry, for example, by reducing the water content to a value of about fifteen to twenty percent by weight of the sand. The vortex separator may discharge sand into a sand pile that creates a store of sand for the hydraulic fracturing operation. The sand preferably resides in the sandpile for a sufficient time to further dewater the sand such that the water content is on average less than ten percent by weight, and in some embodiments the water content of the sand is less than about eight percent by weight. The vortex separator may have a separate discharge for communicating water to a tank or settling pit. The vortex separator may be located on the upper end of a rising boom forming part of a radial stacker. The vortex separator so mounted is capable of discharging sand into the sand pile at a predetermined height.

In one aspect, a system layout may be constructed and arranged to deliver slurry directly to a frac blender sitting at a remote location from a mine site or other source of sand. The slurry may be pumped as a concentrate that is mixed with water at the blender for use in pumping a diluted slurry downhole in support of a hydraulic fracturing operation. The concentrated slurry may be pumped at a variable rate while maintaining a consistent flow regime in the lay-flat hose.

In one aspect, the system layout may service multiple remote locations with the addition of centrifugal pumps located at pressure boost stations as needed to compensate for pressure losses along the way. The centrifugal pumps may be positioned in series to minimize the number of pressure boost stations together with minimizing logistical support to provide maintenance and power to the centrifugal pumps.

In one aspect, the lay-flat hose may be formed in a plurality of sections placed in series such that the lay-flat hose originates proximate the mixing station and terminates to discharge at the wellsite. A first section may be configured to discharge into a first pump boost station including a first pair of centrifugal pumps that are deployed in series with respect to one another. The first pair of centrifugal pumps being configured to receive the discharge from the first section of lay-flat hose and to discharge the same at increased pressure into a second section of the lay-flat hose.

In one aspect, the flow system may be made more durable by providing a rigid pipe, such as a steel or plastic pipe, that is located immediately downstream of the first pump and between the first pump and the lay-flat hose. In such instances, the discharge of slurry from the first pair of centrifugal pumps does not go directly into the second section of lay-flat hose, rather, the discharge first enters the rigid pipe and then enters the second section of lay-flat hose. Any number of additional sections of lay-flat hose may be provided in series with supplemental pressurization by additional pump boost stations.

In one aspect, a fuel source may be located at one or more of the pressure boost stations. The fuel may be used to power an internal combustion engine, such as a diesel or gasoline engine, or a natural gas engine, that drives each centrifugal pump at the pressure boost station. Alternatively, the respective centrifugal pumps may be driven by electric motors, and the fuel may be provided to drive the generator. This type of arrangement advantageously minimizes the footprint required for logistical support of centrifugal pumping operations.

In one aspect, the lay-flat hose has sufficient flexion to expand a diameter of the hose by about one percent, under system operating pressures.

In one aspect, the flow system does not necessarily have to discharge slurry for separation of water from sand at the well site, and the separation equipment for doing this is advantageously not required. This happens when the one or more sections of lay-flat hose ultimately discharge the slurry directly to a blender at the well site. In such instances, the slurry may be initially mixed as a concentrate that is then diluted with water at the blender before being pumped downhole in support of a hydraulic fracturing operation. The source of the water may be, for example, a water tank that is filled with produced water from wells that have recently been subjected to hydraulic fracturing at the well site. This type of arrangement prevents the produced water from leaking or spilling as it is being recycled to the original slurry mixing site.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flow system utilizing lay-flat hose that may be reconfigured to mix a slurry of sand and water for transport to one or more well sites for support of hydraulic fracturing operations by the actuation of valves according to various embodiments;

FIG. 2 shows a radial stacker equipped with a vortex separator for use in dewatering the slurry at a well site to create a store of sand for use in the hydraulic fracturing operations;

FIG. 3 shows a slurry mixing station for combining water with sand to form the slurry that includes a metering conveyor to feed sand to a sump and a centrifugal pump configured to receive the slurry as it is discharged from the sump and pressurize the slurry into the lay-flat hose;

FIG. 4 is a pump performance curve demonstrating observed efficiency of a centrifugal pump during a flow test comparing the flow of water to that of sand and water slurries having different concentrations of sand;

FIG. 5 is a pump performance curve demonstrating observed efficiency of a centrifugal pump during a flow test comparing the flow parameters of water pumped into lay-flat hose of varying lengths;

FIG. 6 is a chart comparing density and pressure values at different locations in a flow system of lay-flat hose when pumping sand and water at a concentration of 0.5 pounds per gallon (ppg) sand;

FIG. 7 is a chart comparing density and pressure values at different locations in a flow system of lay-flat hose when pumping sand and water at concentrations ranging from 0.5 ppg to 3.0 ppg sand;

FIG. 8 is a chart comparing density and pressure values at different locations in a flow system of lay-flat hose when stopping and restarting flow of a sand and water slurry having a concentration of 4 ppg sand;

FIG. 9 is a chart comparing density and pressure values at different locations in a recirculating flow system of lay-flat hose when stopping and restarting flow of a sand and water slurry having a concentration of 3 ppg sand after which the reenergized slurry is pumped at differing flow rates;

FIG. 10 is a chart comparing density and pressure values at different locations in a non-recirculating flow system of lay-flat hose when stopping and restarting flow of a sand and water slurry having a concentration of 3 ppg sand after which the reenergized slurry is pumped at differing flow rates;

FIG. 11 is a flowchart of program logic that may be implemented in a wireless controller for automated control of the flow system;

FIG. 12A shows a system layout according to an embodiment where sand slurry is pumped from a central location proximate a sand supply through lay-flat hose to a remote location at a frac site where there is dewatering of the slurry for recycle of water to the central location with FIG. 12B being a continuation of the system layout shown in FIG. 12A;

FIG. 13A shows a system layout according to an embodiment that is modified in comparison to that of FIG. 12A to include rigid tubular piping, as opposed to lay-flat hose, at key sections where it may be desirable to reinforce the lay-flat hose with FIG. 13B being a continuation of the system layout shown in FIG. 13A; and

FIG. 14A shows a system layout according to an embodiment that is simplified in comparison to that of FIG. 12A by discharging slurry directly to a blender, as opposed to forming a pile of wet sand on the remote location of FIG. 12B, with FIG. 14B being a continuation of the system layout shown in FIG. 14A.

DEFINITIONS

As used herein, “lay-flat hose” means a spoolable flexible conduit that is useful for the transport of liquids and slurries and is made of a synthetic resin which may also include fibers. The conduit assumes one shape when fully pressurized and lain horizontal for exposure to gravity but is incapable of sustaining this one shape when emptied and depressurized such that the conduit collapses into a relatively flat configuration as compared to the one shape. In the case of a cylindrical conduit, this is flat when one side of the conduit wall that would normally be opposed from another side of the conduit wall across a diameter of the cylinder is less than twenty percent of the diameter, less than ten percent of the diameter, and when the two sides of the wall are touching one another. Unless otherwise indicated, a lay-flat hose also includes the clamps, connectors and couplings needed to combine discrete sections of hose.

As used herein, a “mobile mine” is a place where sand is mined or dug for use in hydraulic fracturing operations, but the place is intended for transient use such that the mining operation does not utilize conventional equipment for sieving and drying the sand.

DETAILED DESCRIPTION

There will now be shown and described, by way of non-limiting examples, various instrumentalities for overcoming the problems discussed above.

FIG. 1 shows a flow system 100 including a collapsible flow conduit of hose 102 made of sections S1, S2, S3, S4, S5, S6 and S7. The hose may be, for example, extruded through the weave thermoplastic polyurethane (TPU) covered lay-flat hose, such as the HYPERFLOW^™1 hose manufactured by 5Elem of Shanghai, China which in the United States may be purchased on commercial order from Oasis of Midland, Texas. The hose may be purchased in different diameters depending upon the design of the flow system 100. By way of example, a preferred ten-inch diameter version of this hose has a working pressure of 250 psi, a burst pressure of 750 psi, excellent abrasion resistance, and weighs only 3.02 pounds per foot. The hose may be purchased on commercial order with couplings, such as stainless steel connectors, onto which the hose is clamped to assemble any length of hose in segments up to 660 feet in length. When the hose is empty and the couplings are removed, the hose collapses into a configuration that is flat and easily spooled or rolled-up for transport. ¹ HYPERFLOW™ is a trademark of 5Elem located in Shanghai, China.

With section S7 in place the hose 102 forms a continuous loop capable of recycling slurry water through slurry mixing station 112. Section S7 may be optionally removed where recycle is not required. This may happen when the volume of slurry water is less than what is required for use in a hydraulic fracturing operation, such as when a fracturing fluid that is to be pumped down a well is designed for 3 pounds per gallon (ppg) of sand and the slurry within hose 102 is at 4 ppg. In practice, slurries up to 4 ppg are not concentrates because these weights of sand are commonly pumped downhole during the course of hydraulic fracturing operations, but slurries of greater weight are increasingly at risk of screening out when they are so pumped.

As shown in FIG. 1, the sections S1 to S6 are connected by hose couplings HC2, HC3, HC4, HC5, HC6, HC7, HC8, HC9, HC10, HC11 and HC12. Densometers D1 and D2 are positioned in the flow system 100 to sense the density of slurry within the corresponding sections of the hose 102 where they reside, as are pressure gauges P1, P2, P3, P4, and P5 which are configured to sense pressure within their corresponding sections of hose 102. Flow meters F1 and F2 may be magnetic flowmeters sensing volumetric flowrates within the hose 102. Pitot tube sample collectors SC1, SC2, SC3, SC4 are installed to obtain fluid samples from within the hose 102. The sample collectors SC1-SC4 may be optionally installed to bleed slurry from different depths within the hose 102 to ascertain flow regime information where, for example, a liquid sample that is almost all water with very little sand content taken from the top of the hose 102 suggests that the flow of slurry is non-homogenous in the sense that the flow within the hose 102 is stratified by the effect of gravity with a layer of water flowing above a layer of sand in conditions of non-turbulent flow. Centrifugal pumps C1, C2, C3, and C4 may be powered by natural gas, electricity, or diesel, and provide motive force for the movement of slurry through the hose 102.

A conveyance 104, such as a front end loader, is used to move sand from a sand pile 106 into a hopper 108 that feeds a conveyor 110. In turn, the conveyor 110 moves the sand into the slurry mixing station 112 which may be a blender as is known to those of ordinary skill in the art and commonly used to mix fracturing fluids for use in hydraulic fracturing operations.

Gate valves G1, G2, G3, G4 and G5 are installed in the flow system 100 and may be selectively opened and closed to facilitate mixing operations from the slurry mixing station 112 that combines sand from the sandpile 106 with water from frac tanks 114 and/or open tanks 116, 117 to form a slurry. The hose 102 places the slurry in fluidic communication with well site locations 118, 120 where the slurry is dewatered and stored in piles 118A, 120A. Water from the dewatered slurry may be stored in tanks 118B, 120B or recycled through the hose 102 either for storage in open tanks 116, 117 or for reuse through the slurry mixing station 112. More particularly, the gate valves G1-G5 may be respectively opened and closed as shown in Table 1 below to configure the flow system 100 for different modes of operation.

Gate valves G4, G5 may be respectively opened and closed to place the flow system 100 in different flow modes. For example, the gate valve G4 may be opened to permit flow into location 118 and the gate valve G5 may be closed to prevent flow into location 120 while the gate valves G1, G2 are closed. This is a first mode that facilitates flow into location 118 under the motive force of centrifugal pump C2. Alternatively, with the gate valves G1, G2, G4 and G5 remaining in the same position, the centrifugal pump C2 may be shut down while activating the centrifugal pump C3 to provide a second mode that delivers recycled water from location 118 to water tanks 116, 117 through sections S3, S4, S5, S6, and S7. When converting from the second mode, a third mode may be provided by closing gate valve G4 to prevent flow into location 118, closing the gate valve G2 and opening the gate valve G5 to permit flow into location 120 under motive force from the centrifugal pump C2. From there, a fourth flow mode may be provided by closing the gate valve G5 to prevent access to location 120, opening the gate valve G2 to permit access to the water tank 117, and activating the centrifugal pump C4 to provide motive force for delivery of recycled water through sections S5, S6, S7 to the water tank 117. Those of ordinary skill in the art will appreciate that the respective components of the flow system 100 may be further manipulated to provide a variety of different flow modes as shown by way of example in Table 1.

TABLE 1
Flow Configuration Modes

Mode	G1	G2	G3	G4	G5	Comments
1	Closed	Closed	Closed	Open	Closed	G4 is open and other gates are
						closed to provide slurry to location
						118 without recycle of slurry.
2	Open	Open	Closed	Open	Closed	G4 is open to permit flow of recycle
						water from tank 118B under motive
						force from centrifugal pump C3 for
						delivery of the recycle water through
						G1, G2 into open tanks 116, 117
						while closure of G3 prevents flow of
						water to the slurry mixing station
						112.
3	Closed	Closed	Open	Open	Closed	G4 is open to permit flow of recycle
						water from tank 118B under motive
						force from centrifugal pump C3 for
						delivery of the recycle water through
						G3 into the slurry mixing station
						112.
4	Closed	Closed	Closed	Closed	Open	G5 is open and other gates are
						closed to provide slurry to location
						120 without recycle of slurry.
5	Open	Open	Closed	Closed	Open	G5 is open to permit flow of recycle
						water from tank 120B under motive
						force from centrifugal pump C4 for
						delivery of the recycle water through
						G1, G2 into open tanks 116, 117
						while closure of G3 prevents flow of
						water to the slurry mixing station
						112.
6	Closed	Closed	Open	Closed	Open	G5 is open to permit flow of recycle
						water from tank 120B under motive
						force from centrifugal pump C4 for
						delivery of the recycle water through
						G3 into the slurry mixing station
						112.

One or more boost pumps (not shown) may be located in the hose 102 as needed to boost slurry flow rates while keeping operational parameters within a set of predetermined design limits. Generally speaking, the boost pumps may be the same as or different from the centrifugal pump C1. Depending upon terrain and the slurry sand content the boost pumps may be placed, for example, from 2000 to 3000 feet apart.

The pumps (such as C1 and the boost pumps described above), densometers D1 and D2, conveyer 110, flowmeters F1 and F2, and pressure gauges P1-P5 may be configured to transmit data representative of sensed measurements to a wireless controller 122. The wireless controller 122 may be provided with program instructions operating on the transmitted data to adjust the gate valves G1-G5 in an automated manner to form combinations as shown in Table 1 such that system operating parameters are maintained within setpoints established by the system operator. The respective system components may be configured to exchange data using low power long distance technologies such as Low Power Wide Area Network (LPWAN), LoRa/LoRaWAN, NB-IOT, or LTE-M.

FIG. 2 shows a radial stacker 200 that may be deployed at one of the well site locations 118, 120 for the dewatering of sand. The radial stacker 200 is anchored onto a heavy pivoting base 202 permitting arcuate motion 204 of a hydraulically extensible boom 206. The pivoting motion 204 is actuated by a drive mechanism 207. Incoming slurry arrives through hose 208 which conducts the slurry upwardly along the length of the hydraulically extensible boom 206 towards a vortex or cyclonic separator 209 that is mounted at the forwardmost (highest) position of the hydraulically extensible boom 206. The hose 208 is selectively placed in fluidic communication with hose 102 for the receipt of slurry as may happen, for example, by the opening of one of gates G4, G5 as described above. The vortex separator 209 strips sand 210 from the slurry, which falls into one or more sand piles 212, 214, 216 that may be used to supply the conveyance 104 (see FIG. 1). The vortex separator 209 also separates water from the sand 210, the water being returned through hose 218, which is configured to carry water to storage at the well site. This water storage may be provided as, for example, a lined settling pit (not shown) that is dug into the earth for use as one of tanks 118B, 120B. The hydraulically extensible boom 206 is supported by frame members 218, 220 to position the hydraulically extensible boom 206 at a predetermined height suitable for use with one of the sand piles 212, 214, 216. In other embodiments, the vortex separator 209 may be replaced by other means for dewatering sand that are not necessarily mounted on the hydraulically extensible boom. These other means include, for example, a screen shaker, a settling pit, or a system of ditches to guide water draining from the sand piles 212, 214, 216.

FIG. 3 provides additional detail with respect to the slurry mixing station 112 and the conveyor 110 as described above. The conveyor 110 is fed sand 300 through a first hopper 302. This may be done, for example, by use of the conveyance 104 (see FIG. 1). The conveyor 110 carries the sand 300 upwardly for discharge into a second hopper 304 that receives a simultaneous discharge of water from line 306 and sand 300 from the conveyor 110. As is known by those of ordinary skill in the art, the conveyor 110 may be a metering conveyor that incorporates structure for ascertaining the weight or volume of sand that is moved on an endless belt. This structure may be, for example, load cells establishing a weight in motion system, a magnetic flowmeter, or a knife-edge gate producing a ribbon of sand having a uniform thickness. See for example U.S. Pat. No. 11,408,247 to Ochler et al which is hereby incorporated by reference to the same extent as though fully replicated herein. The combined discharge of sand and water creates agitation that mixes the sand and water into a slurry 308 that discharges into an intake line 310 of a centrifugal pump 312. The centrifugal pump 312 discharges the slurry 308 into section S1 of the hose 102 (see FIG. 1). It will be appreciated that various types of slurry mixing stations are known to those of ordinary skill in the art and may include, for example, paddle mixers, jet mixers, or even blender units as are commonly used to mix fluids for direct use in hydraulic fracturing operations. See for example United States Patent Application Publication No. 2022/0161212 to Wilson.

WORKING EXAMPLES

The following examples teach by way of example and not by limitation, so they should not be construed in a manner that unduly limits the claimed subject matter.

Example 1

Selection of System Components

System pumping components were selected to build a flow system 100 as shown in FIG. 1 according to one embodiment. An electric motor made by WEG of Duluth Georgia was used to power the centrifugal pump C2. This electric motor was rated to deliver 200 brake horsepower (bhp) at 1800 rpm on a 447 T frame and set to run at 1762 rpm. A variable drive speed reduction provided about 2:1 rpm reduction from motor to the centrifugal pump C2. The centrifugal pump C2 was a Warman® pump made by Weir Minerals of Australia as a 10×8 200 EEM Series A “M-WRTG Horizontal” pump at 881 rpm. This pump was a rubber-lined centrifugal model with impellers coated for sand slurry use. The pump housing was rated for a maximum working pressure of 150 psi. A variable frequency drive (VFD) was added to control volumetric pumping rates over a wide range up to 85 barrels per minute (bpm).

A generator set provided electricity to power the 200 bhp electric motor. Requirements included 200 bhp at 0.746 kW/bhp=149 kw, which was increased to 155 kW by assuming a 96% power and motor efficiency correction. Accordingly, a generator rated at 200 kW maximum load was selected to drive the 200 bhp electric motor. The generator was made by Taylor Power Systems, Inc. of Clinton, Mississippi. This unit burned 9.5 gallons of diesel per hour of operation.

A ten-inch diameter lay-flat hose with a working pressure of 200 psi was selected as described above. Table 2 below provides the lengths of sections S1-S6, which were connected using stainless steel couplings HC1 to HC12 provided by the manufacturer:

TABLE 2
Hose segment lengths

	Segment	Length, Feet

	S1	661.5
	S2	439.5
	S3	147.0
	S4	635.3
	S5	315.3
	S6	274.7
	S7	100.0

Example 2

Flow Rate Testing

Tests were conducted from 50 bpm to 85 bpm to gather pipe friction data, pump performance data and to make observations about sand flow in the pipe. Pressure characteristics of flow at the respective flowrates, as well as the contents of samples pulled from the sample collectors SC1 to SC4 at the various flowrates, suggested that the required pump rate for a linear velocity to transmit slurry sand was about 11.5 ft/sec, corresponding to 62.3 bpm in the ten-inch hose.

Example 3

Testing for Effects of Variable Pump Rates And Slurry Weight On Pump Efficiency

FIG. 4 is a factory-provided pump performance chart 400 for the pump in use as C1 onto which have been plotted curves 402, 404, 404A and 404B. Curve 402 shows pump efficiency when pumping sand in water at a constant 3 pounds per gallon (ppg) flowing into a ten-inch hose having a fixed length of 2,618 feet. Curve 404 shows the pump efficiency when pumping the same slurry into the same hose using selected rates from 55 bpm to 83 bpm. Section 404A of curve 404 shows data for pumping at a constant rate of 65 bpm (2,730 gpm) while increasing the sand concentration from 0.5 to 4 ppg. The upper section 404B shows pump efficiency data for holding a constant sand concentration of 4 ppg while increasing rates up to 78 bpm. This data shows that pump efficiency degrades as the sand content increases, but that the foregoing selection of system components is well-capable of meeting minimum requirements for the pumping of slurry.

Example 4

Testing for Effects of Variable Hose Length On Pump Efficiency

The pump performance was then tested for the efficiency of pumping water into various lengths of ten-inch hose. FIG. 5 is a factory-provided pump performance chart 500 onto which have been plotted pump efficiency curves 502 (pumping into 2618 feet of hose), 504 (3244 feet), 506 (3933 fect), and 508 (4454 fect). Curve 508 represents about the maximum length that is pumpable using this particular centrifugal pump. At 950 rpm (while pumping into the head within hose 102) the pump was providing 68.5 bpm, which was only slightly above the target rate of 62.3 bpm. Chart 500 suggests that each addition of 660 feet of hose reduces the top pumping rate by about 7 bpm. Any addition of sand at 4,464′ would have increased pressure and reduced rate below the target rate.

Because the maximum pump rate is about 950 rpm and this resulted in a head of about 51psi, this test shows that multiple centrifugal pumps will likely need to be deployed in series to move slurry over distances exceeding about 3000 to 4000 fect, with about 3500 feet being a most likely maximum distance when pumping slurry over flat terrain. The pumps may be deployed in close proximity to one another to boost output pressure or, alternatively, at staged intervals placing additional pumps where a pressure boost is needed.

Example 5

Testing for Frictional Losses

A search of the art provided no data for frictional pressure losses in ten-inch lay-flat hose with a working pressure of 200 psi. Steel pipe data for fresh water in ten-inch steel was consulted as a guideline, but no correction factors were known to convert from fresh water to slurry. The flow system 100 was reconfigured into multiple sections of equal 660 foot lengths with pressure gauges installed to measure pressure frictional loss through each of the sections. A total of seven sections were used to determine frictional pressure loss in the case of fresh water for flow rates of 65, 70, 75 and 80 bpm.

A comparison study was done in which sand slurries of different weights were pumped into four 660 foot sections of ten-inch hose at the rates of 65, 70, 75, and 80 bpm. The total length of the flow system approximated ½ mile. The sand slurries consisted of sand in water, and the respective slurries contained 1, 2, 2.5, 3 and 4 ppg of sand.

Table 3 reports the observed pressure loss data. The initial water-only tests were very encouraging. Specifically, friction values were ⅓ less than the equivalent steel pipe conditions. This was a surprise considering the roughness of the lay flat hose vs steel pipe. It was observed that the diameter of the lay flat hose does expand under pressure, which may explain at least part of the lower friction loss observations.

TABLE 3
Water only and sand slurry friction results in 10″ hose sections

Fresh Water Only

Sand Slurry

Section #	4	5	6	7	Avg.	Steel Pipe	1 ppg	2 ppg	2.5 ppg	3 ppg	4 ppg

65 bpm

Friction,	0.905	0.971	0.913	0.938	0.932	1.47	1.147	1.398	1.523	1.615	1.7423
psi/100
ft
Friction	6.0	6.4	6.0	6.2	6.1	9.7	7.6	9.2	10.1	10.7	11.5
per 660′
section
Miles of					5.1	3.2	4.1	3.4	3.1	2.9	2.7
Service
at 250
psi

70 bpm

Friction,	1.085	1.05	1.157	1.01	1.076	1.7				1.783	2.05
psi/100
ft
Friction	7.2	6.9	7.6	6.7	7.1	11.2				11.8	13.5
per 660′
section
Miles of					4.4	2.8				2.7	2.3
Service
at 250
psi

75 bpm

Friction,	1.192	1.161	1.106		1.153	1.94				1.756	2.08
psi/100
ft
Friction	7.9	7.7	7.3		7.6	12.8				12.6	13.8
per 660′
section
Miles of					4.1	2.4				2.7	2.3
Service
at 250
psi

80 bpm

Friction,	1.36	1.34			1.350	2.19				1.9134	2.088
psi/100
ft
Friction	9.0	8.8			8.9	14.5				12.6	13.8
per 660′
section
Miles of					3.5	2.2				2.5	2.3
Service
at 250
psi

While the fresh water data was encouraging, the addition of sand quickly increased the friction loss rates. In Table 3, the “Miles of Service” was computed by using the observed friction loss in psi per foot and calculating the distance to zero pressure based upon a starting pressure of 250 psi, which is a value approximating the maximum working pressure variant of ten-inch lay flat hose. With a 2.5 to 3 ppg range of slurry (23-26.5% by weight sand) the estimated service range for systems operating at 250 psi is approximately 3 miles before a pressure boost pump needs to be installed. At 2.5 ppg the friction loss of 1.523 psi per 100 feet of hose is proximal to the published steel pipe data for water.

Example 6

Flow Regime Study In Slurry Travel Through Long Distance Hose

The pitot style sample collectors yielded good information on the stratifying of sand in the hose. Table 4 shows the concentration of sand in samples collected from the hopper 304 referred to herein as the “sump” and 3 of the 4 in hose sample collectors in the flow system of Example 5. Note that sample collector SC3 was ported to retrieve sample material close to the bottom of the hose while sample collectors SC1 and SC2 sampled from the center of the hose.

TABLE 4
Sand concentrations in samples (values in ppg)

Stage Sand
Concentration	At	At	At	At
As Mixed	Sump	SC1	SC2	SC3

0.5	0.4	0.1	0.4	0.9
1.0	0.5		0.8	1.7
1.5	0.6		0.7	1.8
2.0	0.8		0.9	2.4
2.5	0.4		0.9	2.7
3.0			3.8	8.7
3.0				7.5
3.5			2.2	5.3
4.0			4.6	9.9

The values presented in Table 4 suggest that, at the flow velocities studied, the sand did not move as a homogenous slurry, rather, the sand moved in a segregated manner with a more concentrated layer of sand moving along the hose bottom. The sliding layer of concentrated sand likely moves slower than the equivalent liquid carrier linear velocity in the stratified upper layer of lower density slurry.

Example 7

Slurry Flow Performance With Addition of Sand

Additional flow tests were performed using the flow system of Example 4 to ascertain slurry and pressure density data characterizing the slurry flow regime. Curves D1′ and D2′ present this data in FIG. 6 and slurry density in units of “lb/gal” or ppg according to the Y-axis scale on the right of FIG. 6. Curve “Q” presents flow rate information as measured by flowmeter F1 in barrels per minute or bpm according to Y-axis scale at the left of FIG. 6. The remaining curves P1′, P2′, P3′, P4′, P5′ and P6′ present data observed at pressure gauges P1, P2, P3, P4, and P5 (see FIG. 1) in psi according to the Y-axis scale to the left of FIG. 6. An additional pressure gauge producing the value P6′ is not shown in FIG. 1 but was located in the lay-flat hose proximate the discharge, either into the slurry mixing station 112 or the open tanks 116, 117 depending upon the valving configuration of the lay-flat hose 102.

Densometer D1 was located at the sump of slurry mixing station 112. Beginning at time 15:21:36, D1′ records the first sand introduced at a 0.5 ppg concentration. There was a time delay of 6 minutes and 38 seconds until densometer D2 recorded this newly introduced sand. At a volume factor of 3.79 gal/linear ft and 2,595.5 feet between densometers D1 and D2, the time lapse corresponds to a flow rate equivalent of 35.3 bpm. The actual fluid rate was, however, 65.1 bpm during that time interval, which suggests that the slurry had segregated into two phases of non-homogenous flow. A certain amount of sand likely settled to the bottom of the hose, seeking equilibrium that occurred starting at about time 16:19.12. It is believed that in the time interval from 15:21:36 to 16:19:12 the sand was travelling in pseudo slug flow. This conclusion as to the segregated nature of flow is confirmed by the sampling reported in Table 4.

The flow test continued with additional sand being added in 0.5 ppg increments as shown in FIG. 7 to achieve sand contents in the slurry of 1, 1.5, 2, 2.5 and 3 ppg. Curves P1′ and P2′ show a more rapid increase of pressure, as compared to curves P3′, P4′, P5′ and P6′ with the more distant pressure gauges observing flatter pressures of significantly less magnitude.

Example 8

Shutdown and Restart

Under conditions of use in the field, flow systems of the nature studied must be able to recover from a flow sequence of shutdown and restart. This may happen, for example, if a pump fails or needs repair, or if the hose is plugged or develops a leak. A concern existed that it may be impossible to restart flow if settling of the slurry might plug the hose. Accordingly, a flow test was performed using the flow system of Example 4 where a 4 ppg slurry of sand in water was shut-in overnight, with FIG. 8 presenting the results.

Pumping restarted at time 8:52:48. After achieving a target flowrate of 85 bpm, flow was reduced to 65 bpm at time at about time 9:00:00. Note that at this higher rate the slugging/wave profile was diminished but returned as the rate was lowered to 65 bpm. The slurry was effectively reenergized and returned to its previous profile. There were several instances of shutdown in the flow testing for minutes to hours and all exhibited the same response.

FIG. 9 presents another shutdown-restart sequence, this time with 3 ppg slurry in the system. After restart at about time 10:04:48, flow rates were varied to various plateaus from 60 to 83 bpm. Flowrates above 75 bpm dampened the pressure and density oscillations, as did flowrates below 65 bpm. This data suggests that the sand for this 3 ppg slurry settled out into segregated flow below 65 bpm, entered a sliding bed flow at 65 bpm and above, then the slurry homogenized to increase the efficiency of sand flow at about 75 bpm.

Example 9

Straight Line Test of Sand Deliverability

The flow system 100 was reconfigured by opening valves G1, G2 and closing valve G3. This reconfiguration prevented recirculation of the slurry as in prior tests. The pumped slurry was discharged into open pit tanks 116,117 (500 barrels (bbl) each). FIG. 10 shows the flow performance of the reconfigured system.

At the start of the test the hose contained roughly 40,000 lbs of sand. An additional 96,000 lbs of sand was added via the slurry mixing station 112 for a total of 136,000 lbs of sand transmitted through the flow system 100.

FIG. 10 does not contain oscillating pressures and densities as were apparent in FIGS. 6-9. This suggests that recirculating slurry through the slurry mixing station caused the pressure oscillations noted above. The slurry mixing station appears to be more than adequate for mixing sand and water to be pumped down into the hose at the slurry weights and flow rates under study. Recirculation was done for the convenience of the study in not having to minimize materials consumed, but there is no design requirement for recirculation in a commercial system. If, however, density and pressure oscillations do appear in the flow data of a straight line system, these may be overcome by either: (1) changing the pumping pressures and flowrates as noted above, or (2) adding additional agitation to improve mixing of the slurry at the mixing station 112.

CONCLUSIONS

Sand transport for long distances in a 10″ lay flat hose is feasible, as is the option to shut down pumps for long periods of time and restart flow. The 11.5 ft/sec linear velocity guideline appears to be accurate, but flow efficiency is increased at rates above 13.3 bpm. The straight line test shown above did indeed deliver all the sand introduced into the line as the tanks were hydro-vac cleaned and the recovered sand was weighed for each load and a total of 136,000 lbs. of sand was recovered, allowing for an estimated moisture content of 16 percent.

The hose is sufficiently rugged for use in the intended environment of use. The hose was inspected at the conclusion of flow testing. No excessive wear due to sand erosion was found in the hoses along the loop or the stainless steel collar connectors.

Programmatic Logic For Automated Controller

FIG. 11 is a flowchart of program logic 1100 that may reside in memory and processing circuitry within the wireless controller 122 that monitors sensed measurements of flow parameters over time to maintain system operating parameters within predetermined operator setpoints. The flow parameters may include, for example, slurry flowrates, slurry density, pressure within the lay-flat tubing 102, and the flow configurations established by opening and closing the gate valves G1-G5 as shown on Table 1.

Step 1102 entails establishing operating setpoints for the flow parameters. These setpoints are constrained by limits according to system design and may be further limited by established practices in the intended environment of use. The setpoints may be, for example, a single value establishing an upper or lower range for an array of flow parameters or, alternatively, a range providing both an upper and lower limit. The setpoints may also be a single fixed value that the system endeavors to meet within a small range of tolerance accounting for normal variances in system operating conditions.

With the setpoints established, the program logic 1100 provides for mixing the slurry and pumping 1104 the same at increased pressure into the lay-flat hose 102 for uses as described above. As the slurry is being pumped, the program logic monitors 1106 the sensed flow parameters of flowrates, density, pressure and any other parameters that are normal and customary in the art.

The data thus obtained is used together with program logic to ascertain a mass balance 1108 in the lay-flat hose. This may be done, for example, by the use of Equation (1) below to quantify variances that transiently occur between mass inflows and outflows. If an imbalance exists 1110, as may be shown where the variances exceed a delimiting threshold value, then flowrates are adjusted to change the flowrates to resolve the imbalance. For example, if a growing mass of slurry is accumulating in the hose, this may indicate plug flow having the potential to block the hose. A suitable response in this case may include increasing the flow velocity of the slurry to expel the plug while decreasing the sand content. If the variance shows a shrinking mass in the hose, then a suitable response may be to increase the sand content of the slurry or to pump a higher velocity of the same slurry.

The sensed flow parameters provide a time-sequenced array of data values that, in one aspect, may be used to perform a mass balance 1108 of material in the hose. Ideally, the mass of slurry flowing into the lay-flat hose 102 through the pump C2 should equal the mass of slurry being discharged from the lay-flat hose. In practice, these mass values average-out to be equal over longer periods of pumping time, but are transiently different because variances arise, for example, from gravity segregated flow in the lay-flat hose 102, and the lay-flat hose 102 may also expand and contract depending upon localized pressure conditions within the hose. Equation (1) shows a mass balance equation that may be utilized to calculate a variance V between the slurry inflow and outflow.

ρ D ⁢ 1 * Q 1 - ρ D ⁢ 2 * Q ⁢ 2 = v ( 1 )

• • wherein ρ_D1 is an average of sensed density measurement of the slurry proximate an inlet to the lay-flat hose 102 taken over an interval of time, _Q1 is an average of sensed flowrate measurements proximate the inlet to the lay-flat hose taken over the interval of time, ρ_D2 is an average of density measurement proximate to a discharge from the lay-flat hose 102 taken over the interval of time, and _Q2 is an average of sensed flowrate measurements proximate the discharge opening from the lay-flat hose 102 taken over the interval of time.

The program logic utilizes the sensed pressure data in a pressure study 1114 that may have multiple modes of analysis. Initially, the logic ascertains whether the pressure slurry within the lay-flat hose 102 does not exceed a safety limit. This safety limit may be, for example, a burst pressure rating for the hose, a working pressure rating for the hose, or a lesser pressure determined as a safety factor such as ⅓ or ½ of the working pressure. The pressure array may also be submitted to numerical methods processing, such as the calculation of a first forward difference of adjacent values in a plot of pressure over time. This produces an array of pressure divided by time values analogous to a first order derivative that may be described as a pressure velocity which, if increasing, may be subjected to a first order least squares fit to estimate the time that will elapse before the pressure safety limit will be reached. The pressure velocity curve may be processed a second time and a third time using the first forward difference techniques to arrive at a pressure acceleration curve in the case of a second derivative and where the original time-pressure array is concave up or concave down in the case of a third derivative. These additional values may be utilized to improve the accuracy of the safety intercept value, as will be understood by those of ordinary skill in the art.

If the pressure is trending out of range 1116 then the setpoints may be adjusted 1118 to resolve this problem. This may be done, for example, by reducing the flow rate and/or the sand content of the slurry if the pressure is trending too high, or by increasing the flow rate and/or the sand content if the pressure is trending too low.

FIGS. 12A through 14B show system layouts according to various alternative embodiments. FIGS. 12A and 12B show system layout 1200, which originates from a central location 1202 that is preferably located proximate a sand mine or a transportation hub such as a rail line or highway (not shown). A sand pile 1204 is built at the location 1202 such that one or more front-end loaders 1206 may be utilized to move sand from the sand pile 1204 to a hopper 1208 feeding a conveyor belt assembly 1210 that discharges the sand into a sled-mounted mixer 1212. The mixer 1212 may be a conventional trailer mounted blender as is used to supply sand slurry to reciprocating pumps in hydraulic fracturing processes for the stimulation of oil, gas and geothermal wells. Optionally but preferably, however, the mixer 1212 differs from the conventional trailer mounted blenders that are in common use. While both the mixer 1212 and the conventional blender have a tub and functionally mix sand slurries for use in hydraulic fracturing, the mixer 1212 differs from the blender in that: (1) no moving parts are required in the mixing tub such that water jetted from line 1214 is sufficient for slurry mixing, (2) a centrifugal pump C5 receives mixed slurry directly from the mixer 1212 such that no multi-port discharge manifold is required, and/or (3) construction is much lighter because no trailer is required such that the blender tub and centrifugal pump C5 may be of heavier construction that is capable of increased slurry throughput per unit weight relative to a conventional blender. Water for mixing the slurry comes from a water tank 1216 and passes through centrifugal pump C6 to obtain a pressure boost that facilitates slurry mixing at the mixer 1212.

The centrifugal pump C5 optionally discharges into a second centrifugal pump C7 as needed to obtain a pressure boost before transferring the slurry into a first segment of lay-flat hose 1218. The lay-flat hose may travel large distances as described above. The lay-flat hose may have any diameter, but is usually in the range of from 4 to 16 inches in diameter with eight to sixteen inches being preferred and ten inches being most preferred. From time to time, one or more additional centrifugal pumps C8, C9 may be provided as needed for a pressure boost into an additional segment of lay-flat hose, and this concept may be repeated any number of times. The system also includes a system controller 1230 that operates in a similar fashion to the wireless controller 122 as shown in FIG. 1.

As shown in FIG. 12B, the additional line 1220 conveys slurry to a remote location 1222 that may be located, for example, several miles from the location 1202. Following an optional final pressure boost at centrifugal pump C10, the slurry enters a dewatering station 1224 that separates water from the slurry. A stream of water exits the dewatering station 1224 through lay-flat hose segment 1226 with a pressure boost at centrifugal pump C11 into lay-flat hose segment 1228 for return of recycled water to the water tank 1216. Wet sand exits the dewatering station 1224 and is provided to a discharge mechanism 1230, such as a radial stacker, that is used to form a wet sand pile 1232.

A front-end loader 1234 carries sand from the wet sand pile 1232 to a hopper 1236 feeding a conveyor belt 1238 that discharges sand into a conventional blender 1240 which forms a slurry by blending the sand with water from a water tank 1242. Ther blender supplies slurry to a missile 1244, which is a combined intake manifold feeding slurry to a first bank of frac pumps 1246 and a second bank of frac pumps 1248. The frac pumps in banks 1246, 1248 pressurize the slurry according to the design of a hydraulic fracturing operation and return the pressurized slurry to the discharge side of the missile to perform a hydraulic fracturing operation on a selected one of frac trees 1250, 1252, 1254, 1256, each of which are essentially valves and pressure control devices constituting a wellhead for hydraulic fracturing operations as are known in the art. In some embodiments, hydraulic fracturing operations are conducted simultaneously for more than one well at a time using any combination of the frac trees 1250-1256.

In one aspect, the centrifugal pumps of system layout 1200 are deployed in pairs that are connected in series forming respective boost stations for imparting sequential pressure increases to the slurry that is being pumped. By way of example as shown in FIG. 12A, a first pair is formed of centrifugal pumps C5, C7 and a second pair is formed of centrifugal pumps C8, C9. This manner of pairing sequential pumps in close proximity to one another advantageously permits a step-up to higher pressures using fewer boost stations. This simplifies the logistics of providing fuel and/or electrical power for operation of the centrifugal pumps.

A further advantage flowing from the use of paired pumps in this manner inures from the flexible nature of lay-flat hose. The diameter of lay-flat hose is not static, but varies under load by expanding at higher pressures. By way of example, a ten inch hose under pressure may increase by as much as a half inch or even an inch in diameter. This increase in diameter results in a significantly increased flow capacity over a given length of lay-flat hose. As the total system pressure drops, the diameter decreases such that the incremental pressure drop over a given length of hose may behave contrary to expectations in the art where, for example, a first pressure drop over a given length of lay-flat hose at a first flow rate where the hose is pressurized to a first total pressure may be greater than a second pressure drop over the same length of lay-flat hose that is pressurized to a second total pressure, even where the first flow rate and the first total pressure are less than the second total pressure and the second flow rate. In another example, the first pressure drop and the second pressure drop passing through the same length of lay-flat hose may be the same even though the first flow rate and the second flow rate may be significantly different. This seems counterintuitive when compared to established expectations for rigid conduits but advantageously results from the flexing of lay-flat hose to increase diameter under increased pressure. Moreover, the dominant flow regime in the intended environment of use is either plug flow or a velocity below minimum linear velocity which it turns out is sufficient to deliver slurry at steady state conditions while minimizing wear-in the lay-flat hose and, if consistently maintained, avoids the complexity of controlling for changes in pressure drop due to changes in the flow regime.

It will be appreciated that, in order to meet situational needs for longer pumping distances, the system layout 1200 may be upgraded by using additional segments of lay-flat hose which may be daisy-chained in series for servicing additional ones of remote locations 1222 and the system may be upgraded to accommodate higher pumping pressures. This is shown, by way of example, in system layout 1300 of FIGS. 13A and 13B where the numbering of identical components is retained with respect to system layout 1200. System layout is upgraded by the addition of one or more lengths of lay-flat hose 1302, which may be provided in any length to facilitate longer pumping distances. Additional centrifugal pumps C12, C13 are provided to compensate for pressure drops across the longer pumping distances. Any number of additional, sections of lay flat hose 1302 and centrifugal pumps C12, C13 may be provided in series in the intended environment of use. A further upgrade includes the use of steel or plastic pipe in one or more of sections 1304, 1306 1308, which are located immediately downstream from their corresponding centrifugal pumps, i.e., pumps C7, C9 and/or C12. The sections 1304-1308 may be, for example, high density polyethylene pipe having a higher operating pressure than does the lay-flat hose at 1218, 1302, or 1220. This use of pipe at these locations permits the centrifugal pumps C7, C9, and C12 to operate at a discharge pressure that would, otherwise, be detrimental to the lay-flat hose and facilitates the pumping of more concentrated slurries.

FIGS. 14A and 14B shows system layout 1400, which avoids the need for having the wet sand pile 1232 shown in FIG. 12B by delivering slurry direct to the blender 1240. More particularly, the lay-flat hose 1220 discharges slurry directly into the blender 1240 where the slurry is combined with water from the water tank 1242 under motive force imparted by centrifugal pump C12. The slurry discharged from lay-flat hose 1220 may advantageously be a concentrate that is diluted by water residing at the remote location 1222.

Those of ordinary skill in the art will understand that the foregoing discussion teaches by way of example and not by limitation. Accordingly, what is shown and described may be subjected to insubstantial change without departing from the scope and spirit of invention. The inventors hereby state their intention to rely upon the Doctrine of Equivalents, if needed, in protecting their full rights in the invention.