Compound cluster placement in fractures

Abstract

Compound cluster placement in fractures. A fracture treatment method includes forming propped regions having a larger coverage area than channels between the propped regions, and channelizing the propped regions in situ. Also disclosed are systems to treat a fracture interval and to produce reservoir fluids from a formation.

We claim: 
     
         1 . A fracture treatment method for a subterranean formation penetrated by a wellbore, comprising:
 considering closure stress and stiffness of an interval of the formation;   modeling the interval based on the closure stress and stiffness of the interval to determine a minimum coverage of propped regions in a fracture in the interval and maximum open channel breadth between the propped regions to inhibit collapse of the open channels;   formulating a treatment fluid stage comprising alternating solid particulate-rich and solid particulate-lean substages, wherein a volume of each of the particulate-rich substages is larger than a respective volume of an adjacent one of the particulate-lean substages;   injecting the formulated treatment fluid stage above a fracturing pressure into the formation by alternatingly injecting the solid particulate-rich and solid particulate-lean substages into the fracture;   forming a plurality of particulate-rich island regions in the fracture to provide at least the minimum coverage of propped regions as determined by the modeling;   forming an interconnected network of open channel regions between the island regions in the fracture having a channel breadth less than the maximum channel breadth as determined by the modeling;   reducing pressure in the fracture to close the fracture propped on the island regions; and   hydraulically conducting fluid flow through the open channel regions between the formation and the wellbore.   
     
     
         2 . The method of  claim 1 , further comprising channelizing the solid particulate rich island regions in situ in the fracture to form solid particulate clusters within the island regions separated from adjacent solid particulate clusters by open voids within the island regions. 
     
     
         3 . The method of  claim 1 , wherein the solid particulate-rich substages and the solid particulate-lean substages in the treatment stage fluid have an overall volumetric ratio from 60:40 to 95:5. 
     
     
         4 . The method of  claim 1 , wherein the solid particulate-rich substages and the solid particulate-lean substages in the treatment stage fluid have an overall volumetric ratio from 70:30 to 90:10. 
     
     
         5 . A method to treat a subterranean formation penetrated by a wellbore, comprising:
 injecting a treatment fluid stage above a fracturing pressure into the formation to distribute a mixture of a solid particulate in a fracture;   alternatingly injecting solid particulate-rich and solid particulate-lean substages of the treatment fluid stage into the fracture, wherein a volume of each of the solid particulate-rich substages is larger than a respective volume of an adjacent one [immediately preceding or following] of the solid particulate-lean substages to form a plurality of solid particulate-rich island regions in the fracture and an interconnected network of open channel regions between the island regions;   channelizing the particulate-rich island regions in situ in the fracture to form particulate clusters within the island regions separated from adjacent particulate clusters by open voids in the island regions;   reducing pressure in the fracture to close the fracture onto the island regions; and   hydraulically conducting fluid flow through the open channel regions between the formation and the wellbore.   
     
     
         6 . The method of  claim 5 , wherein the solid particulate-rich substages each comprise alternating pulses injected at different rates. 
     
     
         7 . The method of  claim 5 , wherein the solid particulate-rich substages each comprise alternating pulses comprising a substantially uniform distribution of one or more components in the alternate pulses and a heterogeneous distribution between alternate pulses of at least one other component. 
     
     
         8 . The method of  claim 5 , wherein the particulate-rich substages each comprise alternating pulses comprising a substantially uniform distribution of one or more components in the alternate pulses, and a heterogeneous distribution between alternate pulses of another component selected from the solid particulate, fibers, anchorant, agglomerant, agglomerant aid, agglomerant aid activator, binding liquid, an induced settling trigger, viscous gel macrostructures, and combinations thereof. 
     
     
         9 . The method of  claim 5 , wherein the treatment fluid stage comprises a carrying fluid. 
     
     
         10 . The method of  claim 5 , wherein the treatment fluid stage comprises an oil-in-water emulsion comprising a hydrophobic liquid dispersed in an aqueous carrying fluid. 
     
     
         11 . The method of  claim 5 , wherein the treatment fluid stage comprises a viscoelastic surfactant in a carrying fluid. 
     
     
         12 . The method of  claim 5 , wherein the treatment fluid stage comprises a pH control agent. 
     
     
         13 . The method of  claim 5 , wherein the treatment fluid stage comprises an ester and further comprising releasing an acid from the ester. 
     
     
         14 . The method of  claim 5 , wherein the solid particulate-lean substages comprise fiber. 
     
     
         15 . The method of  claim 5 , wherein the solid particulate-rich substages comprise a slurry of the solid particulate freely dispersed in fluid spaces around macrostructures [gel blobs or fibers] suspended in a carrying fluid. 
     
     
         16 . The method of  claim 5 , wherein the solid particulate-rich substages and the solid particulate-lean substages in the treatment stage fluid have an overall volumetric ratio from 60:40 to 95:5. 
     
     
         17 . The method of  claim 5 , wherein the solid particulate-rich substages and the solid particulate-lean substages in the treatment stage fluid have an overall volumetric ratio from 70:30 to 90:10. 
     
     
         18 . The method of  claim 5 , wherein the solid particulate-rich substages provide at least a minimum coverage of propped regions comprising the islands and a channel breadth between the propped regions sufficiently small to inhibit collapse of the open channel regions in the interconnected network. 
     
     
         19 . A system to produce reservoir fluids, comprising:
 a subterranean formation penetrated by a wellbore;   a fracture in fluid communication between the formation and the wellbore through a network of open channels between a plurality of propped regions;   the propped regions providing coverage greater than coverage of the open channels, and the open channels having a breadth to inhibit collapse of the open channels between the propped regions;   the propped regions each comprising a plurality of proppant clusters separated by open voids between the propped clusters in the respective propped region.   
     
     
         20 . A system to treat a fracture interval of a formation penetrated by a wellbore, comprising:
 a subterranean formation penetrated by a wellbore;   a treatment fluid stage disposed at least partially in the wellbore, the treatment fluid stage comprising solid particulate-rich and solid particulate-lean substages, wherein a volume of each of the solid particulate-rich substages is larger than a respective volume of an adjacent one [immediately preceding or following] of the solid particulate-lean substages to form a plurality of solid particulate-rich island regions in the fracture and an interconnected network of open channel regions between the island regions;   the solid particulate-rich substages each comprising alternating pulses comprising a substantially uniform distribution of one or more components in the alternate pulses and a heterogeneous distribution between alternate pulses of at least one other component to channelize the particulate-rich island regions in situ in the fracture to form particulate clusters within the island regions separated from adjacent particulate clusters by open voids within the island regions;   a pump system to inject the treatment fluid stage from the wellbore to the formation at a pressure above fracturing pressure to inject the treatment fluid stage into a fracture in the formation; and   a shut in system to close the fracture onto the solid particulate-rich island regions.