Slurry recovery process

Abstract

Frac sand from a well completion operation is transported to a recycling facility by truck. The frac sand is passed into a washing facility where is it separated from frac sand carrier residue, clays, drilling mud and metal particles. The wash water used in the washing facility is settled and re-used. Mud from the settled wash water is removed and re-used in drilling operations. The frac sand is removed from the washing facility by an inclined dehydration screw, and discharged into a counterflow hot air drying facility. Dust from the drying facility is collected and removed. Hot frac sand from the drying facility is passed through a chiller, and collected. The collected material is sized, and stored for re-use.

I claim:  
     
         1 . A process comprising the steps of: 
 extracting frac sand from a well bore;    collecting the frac sand extracted from the well bore;    washing the frac sand;    drying the frac sand;    sizing the frac sand; and    accumulating the washed, dried and sized frac sand for re-use.    
     
     
         2 . The process of  claim 1  wherein the process includes the step of segregating the frac sand by size before accumulating the washed and dried frac sand for re-use.  
     
     
         3 . The process of  claim 1  further including the step of mixing the washed and dried frac sand with a suspension agent and injecting the suspended frac sand into a well.  
     
     
         4 . The process of  claim 1  wherein the step of collecting includes the step of collecting a slurry, a portion of the slurry being frac sand, settling the slurry to yield a free liquid portion, and decanting the free liquid portion from the settled slurry.  
     
     
         5 . A process for recovering used frac sand from a well completion operation, said process including the steps of: 
 collecting a deposit that includes frac sand and other materials;    introducing at least the frac sand into a washing facility;    washing said frac sand;    discharging at least a portion of said frac sand from said washing facility to a drying facility;    drying at least said portion of said frac sand;    passing at least said portion of said frac sand through a sizing apparatus to yield a remainder of washed, dried, and sized frac sand for re-use.    
     
     
         6 . The process of  claim 5  wherein the step of washing includes introducing the frac sand into a tub.  
     
     
         7 . The process of  claim 6  wherein the step of washing includes directing wash water at the frac sand as it is falling into said tub.  
     
     
         8 . The process of  claim 7  further including the step of re-cycling at least a portion of the wash water.  
     
     
         9 . The process of  claim 8  wherein the step of recycling includes the step of settling used wash water.  
     
     
         10 . The process of  claim 9  wherein the step of settling the used wash water is followed by the step of decanting clear, settled, wash water for re-use.  
     
     
         11 . The process of  claim 9  wherein the step of setting includes introducing used wash water into a settling tank, allowing solids to settle out, and removing settled solids from the tank.  
     
     
         12 . The process of  claim 8  further including the step of chemically treating the wash water for compatibility with recycled producing well water before directing it to an injection well.  
     
     
         13 . The process of  claim 8  including discarding a portion of the used wash water.  
     
     
         14 . The process of  claim 8  including the step of directing an outflow of wash water from the washing facility along a path having at least one weir, and passing said flow over said at least one weir.  
     
     
         15 . The process of  claim 14  wherein there is a settling zone upstream of said weir, and said process includes the step of passing the outflow through said settling zone on the way to said weir.  
     
     
         16 . The process of  claim 14  wherein there is a cascade of a plurality of weirs along said path, and said process includes removing precipitated material from upstream of said weirs.  
     
     
         17 . The process of  claim 16  wherein said process includes the step of directing the outflow to a settling tank downstream of said weirs.  
     
     
         18 . The process of  claim 16  wherein said process includes decanting wash water for re-use from said settling tank.  
     
     
         19 . The process of  claim 5  including the step of raising said frac sand from the tub with an inclined screw.  
     
     
         20 . The process of  claim 5  wherein the step of drying includes the step of introducing at least a portion of said frac sand discharged from said washing facility into a rotating drum and introducing hot air into the drum to dry the frac sand.  
     
     
         21 . The process of  claim 20  wherein the step of drying includes passing exhaust air from the drum through a dust collector.  
     
     
         22 . The process of  claim 5  wherein said step of washing includes magnetic separation of metal particles from said slurry.  
     
     
         23 . The process of  claim 5  wherein the process includes the step of screening the solids to remove oversize particles.  
     
     
         24 . The process of  claim 5  wherein the process includes the step of screening the solids to exclude undersized particles.  
     
     
         26 . The process of  claim 5  wherein the process includes the step of screening the solids to exclude both oversize and undersize particles.  
     
     
         27 . The process of  claim 5  wherein said process includes the step of screening the solids by size, and the step of screening includes the step of collecting dust arising from the step of screening.  
     
     
         28 . A process for recovering used frac sand from a well completion operation, said process comprising the steps of: 
 extracting a slurry from the well, the slurry including at least frac sand, drilling mud, and a liquid carrier;    passing at least a portion of the slurry through a washing facility to separate said drilling mud and said liquid carrier from at least a portion of said frac sand;    removing at least said portion of said frac sand from said washing facility, drying at least said portion of said frac sand;    passing at least said portion of said frac sand through a sizing apparatus to yield a re-usable remainder.    
     
     
         29 . A process for recovering re-usable frac sand from a hydrocarbon well completion operation, said process comprising the steps of: 
 extracting a slurry from a well bore of a well, the slurry including a carrier liquid, frac sand, and drilling mud;    passing at least a portion of the slurry into a washing facility;    washing said drilling mud off said frac sand to yield a frac sand rich remainder;    extracting said frac sand rich remainder from said washing facility;    passing said frac sand rich remainder through a dryer; and    passing said frac sand rich remainder through a sizing apparatus to yield re-usable washed, dried and sized frac sand.    
     
     
         30 . The process of  claim 29  wherein said step of passing at least a portion of said slurry into said washing facility includes a step of passing said portion of said slurry through an input sizing apparatus to reject oversize solids, and then washing said portion of said slurry, less the oversize solids.  
     
     
         31 . The process of  claim 29  wherein at least some of said slurry is at least partially settled to yield a free liquid portion and a solid rich portion, and said process includes the step of decanting the free liquid portion before introducing the solid rich portion of the slurry into the washing facility.  
     
     
         32 . The process of  claim 29  wherein: 
 an input sizing apparatus is mounted to receive said portion of said slurry, said input sizing apparatus including a reciprocating screen;  
 said washing facility includes a water delivery apparatus mounted to spray water over said portion of said slurry and said reciprocating screen; and  
 said process includes the steps of passing at least said portion of said slurry through said input sizing apparatus to reject off-spec solid material, spraying water on said solid rich portion as said solid rich portion is passed through said reciprocating screen.  
 
     
     
         33 . The process of  claim 29  wherein said washing facility includes a magnetic element and said process includes the step of operating said magnetic element to extract ferro-magnetic particles.  
     
     
         34 . The process of  claim 29  wherein said washing facility includes a washwater supply, an outflow, and a settling system, said outflow being located to discharge into said settling system, and said process includes the steps of providing washwater from said washwater supply to wash said drilling mud from said frac sand; and transporting at least a portion of said drilling mud in suspension in sand washwater through said outflow into said settling system.  
     
     
         35 . The process of  claim 34  further comprising the steps of accumulating a sludge of drilling mud in said settling system and removing the accumulated sludge of drilling mud.  
     
     
         36 . The process of  claim 35  further comprising re-using the drilling mud sludge in a down-hole drilling operation.  
     
     
         37 . The process of  claim 34  wherein said outflow systems includes a plurality of settling tanks arranged in series, a first of said settling tanks being located to receive the discharge from said outflow of said washing facility, a second of said settling tanks being located to receive a discharge from said first settling tank, and a weir located between said first and second settling tanks, said discharge from said first settling tank flowing across said weir, and said process including the step of skimming water from said settling system and re-using at least a portion of the water skimmed from said settling system.  
     
     
         38 . The process of  claim 37  wherein said process further comprises the step of redirecting at least a portion of the water skimmed from said settling system to said washing facility.  
     
     
         39 . The process of  claim 37  wherein said process further comprises the step of directing at least a portion of the water skimmed from said settling system to an injection well.  
     
     
         40 . The process of  claim 29  wherein: 
 the washing facility includes a bath and a screw mounted at least partially within said bath, said screw being operable to urge said frac sand rich remainder from said bath toward said dryer.  
 
     
     
         41 . The process of  claim 40  wherein a chute is mounted to direct said frac sand rich remainder discharged from said screw to said dryer, and said process includes the stop of directing air from said dryer into said chute.  
     
     
         42 . The process of  claim 29  wherein a dust extraction apparatus is connected to said dryer and said process includes the step of directing hot air exhaust from said dryer to through said dust extraction apparatus.  
     
     
         43 . The process of  claim 29  wherein a cooling apparatus is connected to receive at least a portion of the hot, dried frac sand rich remainder from said dryer and said process includes the step of passing said portion of the hot, dried frac sand rich remainder through said cooling apparatus.  
     
     
         44 . The process of  claim 29  wherein said sizing apparatus includes a means for rejecting oversized particles, a means for rejecting undersized particles, and a discharge for “on-spec” particles and said process includes the step of accumulating and storing said “on-spec” particles for re-use.  
     
     
         45 . A process for recovering re-usable frac sand from a hydrocarbon well completion operation, said process comprising the steps of: 
 extracting a slurry from a well bore of a well, the slurry including a carrier liquid, frac sand, and drilling mud;    settling said slurry to produce a free liquid portion and a solid rich portion;    removing the free liquid portion;    passing said solid rich portion through a first sizing apparatus to reject oversize solids;    passing said solid rich portion, less said rejected oversize solids, into a washing facility;    washing said drilling mud off said frac sand of said solid rich portion to yield a frac sand rich remainder;    extracting said frac sand rich remainder from said washing facility;    passing said frac sand rich remainder through a dryer; and    passing said frac sand rich remainder through a second sizing apparatus to yield re-usable washed, dried and sized frac sand.    
     
     
         46 . An apparatus for re-cycling used frac sand, the apparatus comprising: 
 machinery operable to collect used frac sand, and to transport the used frac sand;    a washing facility for washing the frac sand, located to receive transported frac sand;    a drying facility for drying the frac sand mounted to receive washed frac sand from the washing facility;    a sizing machine for segregating the frac sand from off-spec material, the sizing machine being located to receive the frac sand from the drying facility; and    a storage container for holding frac sand, the storage container being located to receive on-spec frac sand from the sizing machine.    
     
     
         47 . The use for re-cycling of frac sand of an apparatus comprising: 
 machinery operable to collect used frac sand, and to transport the used frac sand;    a washing facility for washing the frac sand, located to receive transported frac sand;    a drying facility for drying the frac sand mounted to receive washed frac sand from the washing facility;    a sizing machine for segregating the frac sand from off-spec material, the sizing machine being located to receive the frac sand from the drying facility; and    a storage container for holding frac sand, the storage container being located to receive on-spec frac sand from the sizing machine.    
     
     
         48 . A process for the treatment of slurry waste water from a well completion operation, the process comprising the steps of: 
 extracting a slurry from a well bore, 
 the slurry including at least an aqueous liquid, and solids suspended in the liquid;  
 the solids including sand;  
 the slurry including iron in at least one form chosen from the set of:  
 iron in solution in the aqueous liquid; and  
 iron particles suspended in the aqueous liquid amongst other solids;  
   separating the aqueous liquid from at least the majority of the solids by using a mechanical separation apparatus to produce a remainder including at least some of the aqueous solution and some of the iron;    converting at least some of the iron in the remainder to a compound form;    mechanically filtering the remainder to remove iron particles from suspension; to produce a treated output solution;    mixing the treated output solution with a solution of re-cycled hydrocarbon field production water; and    re-injecting the mixture of the treated output solution and the re-cycled oil field production water into a hydrocarbon producing stratum.    
     
     
         49 . The process of  claim 48  wherein said step of converting includes adding citric material to the remainder.  
     
     
         50 . The process of  claim 48  wherein said process includes the step of encouraging separation of iron particles from said aqueous liquid magnetically.