Low pressure direct proppant injection

Abstract

A multi-tank system for preparing fluids for hydraulic fracturing of reservoirs and methods of injecting the prepared fluid upstream from pumping units are disclosed. The multi-tank system allows for a proppant slurry to be continuously formed and mixed with a proppant carrier in staggered phases to form a fracturing fluid. This fracturing fluid can then be injected into the reservoir at normal injection pressures, thus reducing wear and downtime on the blender, and allowing continuous flow of proppant.

1 . An apparatus for preparing a proppant fluid for injection into a reservoir, comprising:
 a) a first vessel, a second vessel and a third vessel, wherein each vessel has a hopper containing particulates above the vessel, such that the particulates can gravity feed into the vessel;   b) a clean fluid line in fluid communication with each vessel, the clean fluid line transporting a clean fluid from a source to each vessel;   c) a concentrated proppant carrier fluid line in fluid communication with each vessel, the concentrated proppant carrier fluid line transporting a concentrated proppant carrier fluid;   d) a recycle fluid line in communication with each vessel, the recycle fluid line transporting a clean fluid from the vessel to form a make-up flow for the clean fluid line; and   e) a displaced proppant slurry line in fluid communication with each vessel, wherein the proppant slurry line feeds into the concentrated proppant carrier fluid line to form a proppant fluid for introduction into a hydrocarbon-containing reservoir.   
     
     
         2 . The method of  claim 1 , further comprising a dilution line having a dilution pump that connects the clean fluid line and the concentrated proppant carrier fluid line such that the clean fluid can dilute the concentrated proppant carrier fluid before the proppant carrier fluid combines with the proppant slurry line. 
     
     
         3 . The apparatus of  claim 1 , further comprising a makeup fluid line connecting the recycle fluid line to the displaced proppant slurry line. 
     
     
         4 . The apparatus of  claim 1 , wherein the particulates are sand. 
     
     
         5 . The apparatus of  claim 1 , wherein the clean fluid is treated water. 
     
     
         6 . The apparatus of  claim 1 , wherein the number of the vessels is a multiple of three. 
     
     
         7 . A method of preparing a proppant fluid for injection into a reservoir using the apparatus in  claim 1 , comprising:
 a) filling the first vessel with a clean fluid;   b) partially displacing the clean fluid from the first vessel, wherein the displaced clean fluid serves as a make-up flow for the clean fluid into a subsequent vessel;   c) adding particulates into the first vessel to refill the first vessel without creating fluid overflow;   d) mixing the particulates and clean fluid in the first vessel to form a proppant slurry;   e) displacing the proppant slurry and flushing the first vessel with a fluid mixture, wherein the fluid mixture comprises clean fluid and displaced clean fluid from another vessel, combining the displaced proppant slurry with the concentrated proppant carrier fluid to form the proppant fluid for injection into a reservoir;   g) repeating steps a)-f) in the second vessel and the third vessel sequentially; and   h) introducing the proppant fluid into a low pressure side of a direct proppant injection system.   
     
     
         8 . The method of  claim 7 , further comprising using the clean fluid to dilute the concentrated proppant carrier fluid before combination with the displaced proppant slurry. 
     
     
         9 . The method of  claim 7 , further comprising using the displaced clean fluid to dilute the displaced proppant slurry. 
     
     
         10 . The method of  claim 7 , wherein the particulates are sand. 
     
     
         11 . The method of  claim 7 , wherein the clean fluid is treated water. 
     
     
         12 . A method of fracturing a reservoir, comprising:
 a) injecting a first fluid into a reservoir at an injection pressure high enough to fracture the reservoir forming fractures;   b) continuously combining a proppant slurry with a proppant carrier to make a proppant fluid, wherein the proppant slurry is continuously made in at least three tanks in staggered phases such that one tank is being washed with water partially obtained from a previously washed tank, a second tank is partially full of wash water and is receiving proppant, and a third tank is dispensing proppant slurry; and   c) injecting the proppant fluid into to the reservoir to prop open the fractures.   
     
     
         13 . The method of  claim 12 , further comprising adding one or more additives to the proppant slurry or the proppant carrier or the proppant fluid. 
     
     
         14 . The method of  claim 13 , wherein the proppant carrier is in the form of a gel, emulsion, foam, micelle, or viscoelastic surfactant.