Mobile Sand Slurry Delivery System

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.

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.

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.

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.

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

shows a flow systemincluding a collapsible flow conduit of hosemade of sections S, S, S, S, S, Sand S. The hose may be, for example, extruded through the weave thermoplastic polyurethane (TPU) covered lay-flat hose, such as the HYPERFLOWhose 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. 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.HYPERFLOW™ is a trademark of 5Elem located in Shanghai, China.

With section Sin place the hoseforms a continuous loop capable of recycling slurry water through slurry mixing station. Section Smay 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 hoseis 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, the sections Sto Sare connected by hose couplings HC, HC, HC, HC, HC, HC, HC, HC, HC, HCand HC. Densometers Dand Dare positioned in the flow systemto sense the density of slurry within the corresponding sections of the hosewhere they reside, as are pressure gauges P, P, P, P, and Pwhich are configured to sense pressure within their corresponding sections of hose. Flow meters Fand Fmay be magnetic flowmeters sensing volumetric flowrates within the hose. Pitot tube sample collectors SC, SC, SC, SCare installed to obtain fluid samples from within the hose. The sample collectors SC-SCmay be optionally installed to bleed slurry from different depths within the hoseto 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 hosesuggests that the flow of slurry is non-homogenous in the sense that the flow within the hoseis 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 C, C, C, and Cmay be powered by natural gas, electricity, or diesel, and provide motive force for the movement of slurry through the hose.

A conveyance, such as a front end loader, is used to move sand from a sand pileinto a hopperthat feeds a conveyor. In turn, the conveyormoves the sand into the slurry mixing stationwhich 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 G, G, G, Gand Gare installed in the flow systemand may be selectively opened and closed to facilitate mixing operations from the slurry mixing stationthat combines sand from the sandpilewith water from frac tanksand/or open tanks,to form a slurry. The hoseplaces the slurry in fluidic communication with well site locations,where the slurry is dewatered and stored in pilesA,A. Water from the dewatered slurry may be stored in tanksB,B or recycled through the hoseeither for storage in open tanks,or for reuse through the slurry mixing station. More particularly, the gate valves G-Gmay be respectively opened and closed as shown in Table 1 below to configure the flow systemfor different modes of operation.

Gate valves G, Gmay be respectively opened and closed to place the flow systemin different flow modes. For example, the gate valve Gmay be opened to permit flow into locationand the gate valve Gmay be closed to prevent flow into locationwhile the gate valves G, Gare closed. This is a first mode that facilitates flow into locationunder the motive force of centrifugal pump C. Alternatively, with the gate valves G, G, Gand Gremaining in the same position, the centrifugal pump Cmay be shut down while activating the centrifugal pump Cto provide a second mode that delivers recycled water from locationto water tanks,through sections S, S, S, S, and S. When converting from the second mode, a third mode may be provided by closing gate valve Gto prevent flow into location, closing the gate valve Gand opening the gate valve Gto permit flow into locationunder motive force from the centrifugal pump C. From there, a fourth flow mode may be provided by closing the gate valve Gto prevent access to location, opening the gate valve Gto permit access to the water tank, and activating the centrifugal pump Cto provide motive force for delivery of recycled water through sections S, S, Sto the water tank. Those of ordinary skill in the art will appreciate that the respective components of the flow systemmay be further manipulated to provide a variety of different flow modes as shown by way of example in Table 1.

One or more boost pumps (not shown) may be located in the hoseas 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 C. 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 Cand the boost pumps described above), densometers Dand D, conveyer, flowmeters Fand F, and pressure gauges P-Pmay be configured to transmit data representative of sensed measurements to a wireless controller. The wireless controllermay be provided with program instructions operating on the transmitted data to adjust the gate valves G-Gin 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.

shows a radial stackerthat may be deployed at one of the well site locations,for the dewatering of sand. The radial stackeris anchored onto a heavy pivoting basepermitting arcuate motionof a hydraulically extensible boom. The pivoting motionis actuated by a drive mechanism. Incoming slurry arrives through hosewhich conducts the slurry upwardly along the length of the hydraulically extensible boomtowards a vortex or cyclonic separatorthat is mounted at the forwardmost (highest) position of the hydraulically extensible boom. The hoseis selectively placed in fluidic communication with hosefor the receipt of slurry as may happen, for example, by the opening of one of gates G, Gas described above. The vortex separatorstrips sandfrom the slurry, which falls into one or more sand piles,,that may be used to supply the conveyance(see). The vortex separatoralso separates water from the sand, the water being returned through hose, 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 tanksB,B. The hydraulically extensible boomis supported by frame members,to position the hydraulically extensible boomat a predetermined height suitable for use with one of the sand piles,,. In other embodiments, the vortex separatormay 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,,.

provides additional detail with respect to the slurry mixing stationand the conveyoras described above. The conveyoris fed sandthrough a first hopper. This may be done, for example, by use of the conveyance(see). The conveyorcarries the sandupwardly for discharge into a second hopperthat receives a simultaneous discharge of water from lineand sandfrom the conveyor. As is known by those of ordinary skill in the art, the conveyormay 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 slurrythat discharges into an intake lineof a centrifugal pump. The centrifugal pumpdischarges the slurryinto section Sof the hose(see). 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.

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.

System pumping components were selected to build a flow systemas shown inaccording to one embodiment. An electric motor made by WEG of Duluth Georgia was used to power the centrifugal pump C. 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 C. The centrifugal pump Cwas 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 S-S, which were connected using stainless steel couplings HCto HCprovided by the manufacturer:

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 SCto SCat 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.

is a factory-provided pump performance chartfor the pump in use as Conto which have been plotted curves,,A andB. Curveshows 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. Curveshows the pump efficiency when pumping the same slurry into the same hose using selected rates from 55 bpm to 83 bpm. SectionA of curveshows 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 sectionB 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.

The pump performance was then tested for the efficiency of pumping water into various lengths of ten-inch hose.is a factory-provided pump performance chartonto which have been plotted pump efficiency curves(pumping into 2618 feet of hose),(3244 feet),(3933 fect), and(4454 fect). Curverepresents about the maximum length that is pumpable using this particular centrifugal pump. At 950 rpm (while pumping into the head within hose) the pump was providing 68.5 bpm, which was only slightly above the target rate of 62.3 bpm. Chartsuggests 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.

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 systemwas 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.