Fluid Stimulation of Long Well Intervals

Abstract

Systems and methods for accessing and/or harvesting hydrocarbons from a wellbore. A method may include modeling a well to determine a length of a stimulation zone in the production interval, wherein the model is based, at least in part, on a reaction time for a stimulation process. Packers are placed in the well to fluidically isolate the stimulation zone from other zones in the well. The targeted zone is stimulated, such as by acid treatment. Hydrocarbons may be recovered from the stimulation zone.

What is claimed is: 
     
         1 . A method for fluid stimulation of long well intervals, comprising:
 drilling a well to reach an interval within a reservoir;   selecting locations for packers to fluidically isolate zones in the interval, wherein the selection is based, at least in part, on a model of the response of a rock to a stimulation fluid over a period of time;   positioning the packers at the selected locations; and   stimulating the reservoir within selected zones using an acid solution.   
     
     
         2 . The method of  claim 1 , comprising designing the well to reach the interval within the reservoir. 
     
     
         3 . The method of  claim 1 , comprising simulating fluid flow of a stimulation fluid in a well and surrounding a stimulation conduit and surrounding rock. 
     
     
         4 . The method of  claim 1 , comprising modeling the influence of an acid solution on the rock. 
     
     
         5 . The method of  claim 1 , comprising taking core samples during the drilling or any other suitable logging of the well to map the permeability of the rock along the well. 
     
     
         6 . The method of  claim 1 , comprising producing hydrocarbons from the well. 
     
     
         7 . The method of  claim 1 , comprising isolating a zone of higher permeability rock from a zone of lower permeability rock. 
     
     
         8 . The method of  claim 5 , comprising acid-treating the zone of lower permeability rock. 
     
     
         9 . The method of  claim 1 , comprising drilling a well that is less than about 3 kilometers in length. 
     
     
         10 . The method of  claim 7 , wherein the zone is less than about 500 meters in length along the well. 
     
     
         11 . The method of  claim 1 , comprising modeling the response of a rock in the well to acid stimulation, wherein the modeling provides a time of exposure to the acid solution to obtain a plurality of wormholes of a particular length. 
     
     
         12 . The method of  claim 1 , comprising modeling the response of a rock in the well to acid stimulation, wherein the modeling provides a concentration of the acid solution to obtain a plurality of wormholes of a particular size. 
     
     
         13 . The method of  claim 1 , comprising modeling the response of a rock in the well to acid stimulation, wherein the modeling provides a length of a stimulation zone. 
     
     
         14 . A system for fluid stimulation in wells, comprising:
 a well drilled through an interval in a reservoir;   a plurality of packers placed in the well, wherein a zone is defined by the location of two sequential packers in the well, and wherein the location of each of the plurality of packers is selected from a model of wormhole growth dynamics over time during an acid stimulation procedure; and   a well string configured to convey acid to a zone in the production interval.   
     
     
         15 . The system of  claim 14 , wherein the production interval comprises a zone comprising a carbonate rock. 
     
     
         16 . The system of  claim 14 , wherein the zone is fluidically isolated from an adjoining zone by a packer. 
     
     
         17 . The system of  claim 14 , comprising an offshore rig for drilling the well in a sub-sea environment. 
     
     
         18 . A method for harvesting hydrocarbons from a production interval, comprising:
 modeling a well to determine a length of a stimulation zone in the production interval, wherein the model is based, at least in part, on a reaction time for a stimulation process;   placing packers in the well to fluidically isolate the stimulation zone from other zones in the well;   stimulating the zone by acid treatment; and   recovering hydrocarbon from the stimulation zone.   
     
     
         19 . The method of  claim 18 , comprising stimulating only a portion of a plurality of zones in a production interval. 
     
     
         20 . The method of  claim 18 , comprising placing preinstalled packers to isolate a zone comprising an annulus between a well and a liner. 
     
     
         21 . The method of  claim 18 , comprising placing retractable packers to isolate a zone comprising an annulus between a drill pipe and a liner. 
     
     
         22 . The method of  claim 18 , comprising placing a retractable packer to isolate a zone by blocking a liner. 
     
     
         23 . The method of  claim 18 , comprising calculating an efficiency curve for a stimulation process for a selected rock type, acid concentration, and temperature.