Drain Hole Drilling in a Fractured Reservoir

Abstract

Method for increasing production rate of horizontal wells having hydraulic fractures formed along a horizontal segment of the well by drilling drain holes to intersect the hydraulic fractures is provided.

1 . A method for producing fluid from a subsurface reservoir, comprising:
 drilling and completing a horizontal well having a horizontal segment in the subsurface reservoir and a casing;   creating a plurality of hydraulic fractures spaced apart along the horizontal segment of the well;   cutting a window at a selected location in the casing of the well and drilling a drain hole having a main body from the window, the main body of the drain hole being spaced apart from the horizontal segment of the well and drilled so as to intersect a hydraulic fracture extending from the horizontal segment; and   producing fluid from the well.   
     
     
         2 . The method of  claim 1  wherein fluid is produced from the well at a production rate for a selected time before cutting a window in the casing of the well and drilling a drain hole. 
     
     
         3 . The method of  claim 1  wherein a plurality of drain holes having main bodies spaced apart from the horizontal segment of the well are drilled at spaced apart angles with respect to the horizontal well in a plane perpendicular to the axis of the horizontal well. 
     
     
         4 . The method of  claim 2  wherein the selected time is after the time required for the production rate of the well to decrease from an initial production rate of the well to less than one-half (½) the initial production rate. 
     
     
         5 . The method of  claim 1  wherein the drain hole is further drilled so as to intersect a zone of natural fractures in the subsurface reservoir or selected zones in the reservoir. 
     
     
         6 . The method of  claim 1  wherein the selected location to drill a drain hole is in a vertical segment of the horizontal well. 
     
     
         7 . The method of  claim 1  wherein the drain hole is drilled with a drilling motor and bent sub assembly. 
     
     
         8 . The method of  claim 1  wherein the drain hole is drilled with a jet drilling assembly. 
     
     
         9 . The method of  claim 1  wherein the main body of the drain hole is drilled at a selected distance from the horizontal segment of the well, the selected distance being greater than the estimated radius of a damage zone around the horizontal segment. 
     
     
         10 . The method of  claim 1  wherein the drain hole is drilled to be undulating or sinusoidal. 
     
     
         11 . The method of  claim 1  wherein the drain hole is branched before intersecting a hydraulic fracture such that two or more branches of the drain hole intersect a hydraulic fracture. 
     
     
         12 . The method of  claim 1  wherein at least a segment of the main body of the drain hole is drilled with fluid pressure in the drain hole less than fluid pressure in the subsurface reservoir. 
     
     
         13 . The method of  claim 1  further comprising placing a slotted liner, a pierced plastic pipe, a sand screen, resin-coated sand or a casing in the drain hole. 
     
     
         14 . The method of  claim 1  further comprising injecting fluid at hydraulic fracturing conditions from a drain hole by placing straddle packers on a work string and pumping fluid from the work string between the straddle packers. 
     
     
         15 . The method of  claim 14  wherein the straddle packers are placed across an existing hydraulic fracture. 
     
     
         16 . The method of  claim 14  wherein the straddle packers are placed between existing hydraulic fractures. 
     
     
         17 . A method for producing fluid from a subsurface reservoir, comprising:
 drilling and completing a first horizontal well having a horizontal segment in the subsurface reservoir;   creating a plurality of hydraulic fractures spaced apart along the horizontal segment of the first horizontal well;   drilling a second horizontal well having a horizontal segment drilled so as to intersect a hydraulic fracture extending from the horizontal segment of the first horizontal well; and   producing fluid from the at least one of the wells.   
     
     
         18 . The method of  claim 17  wherein the second horizontal well is drilled so as to intersect a hydraulic fracture nearer to the heel of the horizontal segment of the first well. 
     
     
         19 . The method of  claim 17  wherein the second horizontal well is drilled so as to intersect a hydraulic fracture nearer to the toe of the horizontal segment of the first well. 
     
     
         20 . A method for producing fluid from a subsurface reservoir, comprising:
 drilling and completing a horizontal well having a horizontal segment in the subsurface reservoir and a casing;   cutting a window in the casing of the well and drilling a drain hole having a main body from a selected location in the well, the main body of the drain hole being directed so as to intersect a natural fracture zone in the reservoir; and   producing fluid in the well.   
     
     
         21 . A method for producing fluid from a subsurface reservoir, comprising:
 drilling a horizontal well having a horizontal segment in the subsurface reservoir, the horizontal segment being an open hole;   creating a plurality of hydraulic fractures spaced apart along the horizontal segment of the well;   drilling a drain hole having a main body at a selected location along the horizontal segment, the main body of the drain hole being spaced apart from the horizontal segment of the well and drilled so as to intersect a hydraulic fracture extending from the horizontal segment; and   producing fluid from the well.