Extended reach plug having degradable elements

Abstract

A frac plug narrow enough to pass through horizontal leg casing patches, and expandable enough to grip the casing and be used in fracing. The plug then degrades in place, permitting production from the well without milling out the plug.

1 . A settable isolation tool sized and configured to be capable of being used in fracing past at least one casing patch within 4½ inch to 5½ inch outer diameter (O.D.) casing in a horizontal leg of a hydrocarbon well, the tool comprising:
 a mandrel with a longitudinal axis; 
 first and second expanders around the mandrel, each expander having an outer surface which is not parallel to the mandrel's axis section and having a first end with a first outer diameter and a second end having a second outer diameter, the first outer diameter being larger than the second outer diameter; 
 first and second annular slips around the mandrel, the first expander and the first slip being a first expander/slip pair and the second expander and the second slip being a second expander/slip pair, each slip having an inner surface complementary to its paired expander's outer surface section and a slip outer surface having outer teeth or inclusions for setting into the casing; 
 the slips and expanders are sized and configured so each slip, in a retracted slip position, has a slip outer diameter of 3 inches to 3.8 inches, and the slip's outer diameter is smaller than the first outer diameter of the slip's associated expander and small enough so the slip may be moved past the casing patch in the horizontal leg while being inserted into the well; 
 
       the retracted tool has an outer diameter of 3.25 inches to 4.18 inches, and the retracted tool's outer diameter is small enough so the retracted tool may be moved past the casing patch in the horizontal leg while being inserted into the well;
 the mandrel, expanders and slips are configured, sized and comprised so the retracted slips' O.D. is small enough so the tool is capable of being run through and past a 0.125 inch thick casing patch with a 4 inch to 4.892 inch inner diameter (I.D.) casing in the horizontal leg; 
 
       each slip is movable radially outward by axial movement relative to its paired expander to an expanded slip position; the slips and expanders each being large enough to be located about the mandrel and large enough so axial movement of each slip over its paired expander will expand each slip to an expanded slip configuration where the slip has an outer diameter of 4.1 inches to 5.05 inches and is 15% wider than the slip's outer diameter in the retracted slip position;
 each expanded slip is capable of gripping the inner diameter of the casing and setting the outer teeth or inclusions into the casing during setting of the tool to the casing; 
 
       the tool is configured, sized and comprised so the retracted tool is capable of being run past the casing patch in the horizontal leg, and then expanded to set into the casing, and then used in isolating and fracing in the horizontal leg;
 wherein each of the mandrel, expanders and slips is comprised of a material degradable in a natural aqueous downhole fluid in the well produced from formation flow in the well having a pH less than about 7, wherein the degradable material or materials are selected from the group comprising magnesium, or magnesium alloys or polymer acids, and the degradable materials of each of the mandrel, expanders and slips are either the same or different such degradable materials; 
 the tool is configured and comprised to be interventionless, namely, within less than five days after the tool is immersed in a natural aqueous downhole fluid in the well produced from formation flow in the well having a pH less than about 7, the tool dissolves enough in the downhole fluid so the tool ceases to isolate the zone above the tool from a zone below the tool, without milling out the tool, retrieval of the tool from the well or other intervention on the tool from the surface; 
 the tool is capable of degrading in the wellbore fluid enough to not obstruct production of hydrocarbons from the well without drilling out the tool; 
 
       the tool is configured, sized and comprised so five such tools are capable of being run past the casing patch in the horizontal leg within the casing, set within the casing, and used in isolating and fracing zones in the horizontal leg past the casing patch; the first tool being run in, set and used in isolating and fracking, then the second tool being run in, set and used in isolating and fracking above the first tool, then the third tool being run in, set and used in isolating and fracking above the second tool, then the fourth tool being run in, set and used in isolating and fracking above the third tool, then the fifth tool being run in, set and used in isolating and fracking above the fourth tool, and
 the tool is configured, sized and comprised so production of hydrocarbons from the well can begin within less than five days after the tool is immersed in the well's downhole fluid without drilling out or retrieving the five such tools or other intervention on the  5  such tools from the surface. 
 
     
     
         2 . The tool of  claim 1 , wherein the tool's degradable materials are comprised of both magnesium or magnesium alloys and also polymer acids. 
     
     
         3 . The tool of  claim 2 , wherein the tool releases from the well's casing and ceases to isolate the zone above the tool from the zone below the tool more quickly than a similar tool in which the tool's degradable materials are comprised of only the tool's magnesium or magnesium alloys, or of only the tool's polymer acids. 
     
     
         4 . The tool of  claim 1 , wherein the ramp surface of the expander comprises a multiplicity of flat surfaces. 
     
     
         5 . The tool of  claim 1 , wherein the ramp surface defines a ramp angle of between 12° and 18°. 
     
     
         6 . The tool of  claim 1 , where the expanded slip's outer diameter is 20% wider than the retracted slip's outer diameter. 
     
     
         7 . The tool of  claim 1 , wherein the slips are comprised of a body that is comprised of the degradable material and also comprised of inserts or wickers which are not degradable. 
     
     
         8 . The tool of  claim 1 , wherein the tool is configured, sized and comprised so production of hydrocarbons from the well can begin within less than two days after the tool is immersed in the well's downhole fluid without drilling out or retrieving the five such tools or other intervention on the five such tools from the surface. 
     
     
         9 . The tool of  claim 1 , wherein the tool is configured, sized and comprised so production of hydrocarbons from the well can begin within less than two days after the tool is immersed in the well's downhole fluid without drilling out or retrieving the five such tools or other intervention on the five such tools from the surface. 
     
     
         10 . A method of working on a hydrocarbon well having a vertical leg and a horizontal leg extending into a hydrocarbon bearing formation, the horizontal leg including a heel and a toe, the well having casing in the horizontal leg with an at least a 4½ inch outer diameter (O.D.) and not more than a 5½ inch outer diameter (O.D.), the casing having an inner diameter (I.D.) in the horizontal leg, and the casing having a series of casing patches reducing the ID of the casing in the horizontal leg, the method comprising:
 providing at least five retracted settable downhole tools according to  claim 1 ; 
 selecting five such retracted tools, each retracted tool narrow enough to be run through and past a 0.125 inch thick casing patch in the horizontal leg, and each tool having slips which are expandable enough so after the tool passes through the casing patch the slips can be expanded to an expanded slip configuration having an O.D. within the range of a radial inner limit of a 15% expansion of the retracted tool's O.D. and the inner diameter the casing and the expanded tool's slips are capable of setting against the casing of the horizontal leg and holding the tool to the casing during fracing to isolate an upper zone in the horizontal leg above the tool from a lower zone below the tool; 
 the method further comprising: the steps of running the five tools into the well and immersing the tools in a natural aqueous downhole fluid in the well produced from formation flow in the well having a pH less than 7, running the tools past the casing patch, setting the tools within the casing, and using the tools in isolating and fracing zones in the horizontal leg past one or more of the casing patches; the first tool being run in and set and used in isolating and fracing, then the second tool being run in and set above the first tool and used in isolating and fracing, then the third tool being run in and set above the second tool and used in isolating and fracing, then the fourth tool being run in and set above the third tool and used in isolating and fracing, then the fifth tool being run in and set above the fourth tool and used in isolating and fracing; 
 waiting less than five days after the tools are immersed in the downhole fluid in the well for the tools to degrade in the wellbore fluid enough to permit production of hydrocarbons from the well; and 
 producing hydrocarbons from the horizontal leg within less than 5 days after the tools are immersed in the downhole fluid in the well, without milling out or retrieving the five tools, or intervening on the tools from the surface after the five tools have been used in the fracing operations. 
 
     
     
         11 . The method of  claim 10 , further comprising:
 selecting tools which will degrade within less than two days;   waiting less than two days after the tools are immersed in the downhole fluid in the well for the tools to degrade in the wellbore fluid enough to permit production of hydrocarbons from the well; and   producing hydrocarbons from the horizontal leg within less than two days after the tools are immersed in the downhole fluid in the well, without milling out or retrieving the five tools, or intervening on the tools from the surface after the five tools have been used in the fracing operations.   
     
     
         12 . The method of  claim 10 , further comprising:
 selecting tools which will degrade within less than one day;   waiting less than one day after the tools are immersed in the downhole fluid in the well for the tools to degrade in the wellbore fluid enough to permit production of hydrocarbons from the well; and   producing hydrocarbons from the horizontal leg within less than one day after the tools are immersed in the downhole fluid in the well, without milling out or retrieving the five tools, or intervening on the tools from the surface after the five tools have been used in the fracing operations.   
     
     
         13 . A method of working over a hydrocarbon well having a horizontal leg having casing of at least 4½″ O.D. and not more than 5½″ O.D. which was fraced through a series of first horizontally spaced perforations opening into a series of first horizontally spaced fractures comprising:
 providing at least five retracted settable downhole tools according to  claim 1 ; 
 selecting five such retracted tools, each retracted tool narrow enough to be run through and past a 0.125 inch thick casing patch in the horizontal leg, and each tool having slips which are expandable enough so after the tool passes through the casing patch the slips can be expanded to an expanded slip configuration having an O.D. within the range of a radial inner limit of a 15% expansion of the retracted tool's O.D. and the inner diameter the casing and the expanded tool's slips are capable of setting against the casing of the horizontal leg and holding the tool to the casing during fracing to isolate an upper zone in the horizontal leg above the tool from a lower zone below the tool; 
 running casing patches in the well, expanding the casing patches past an elastic limit into sealing engagement with the casing over the first series of horizontally spaced perforations and thereby covering up the first series of horizontally spaced perforations; 
 
       producing second perforations in the casing past at least some of the casing patches and fracing the second perforations;
 selecting tools narrow enough to fit through casing patches in the horizontal leg's casing having an inner diameter which is 0.25 inches smaller than the horizontal leg's casing's inner diameter, each tool being expandable enough so after the tool passes through the casing patches, each tool's slips can be expanded to set against the casing, each tool's seal can be expanded to seal the tool to the casing, and each set tool can hold in the casing against fracing pressure; 
 
       running a first selected tool into the casing past at least two of the casing patches and setting the first selected tool against the casing by expanding the tool's slips to within the range of a radial inner limit of a 15% expansion of the tool's O.D. and a radial outer limit of the interior diameter of the casing so the tool's slips set against the casing, and the set tool can hold in the casing against fracing pressure thereby isolating the second perforations;
 producing third perforations in the casing past at least some of the casing patches and fracing the third perforations; 
 running a second selected tool into the casing past at least two of the casing patches and setting the second selected tool against the casing by expanding the tool's slips to within the range of a radial inner limit of a 15% expansion of the tool's O.D. and a radial outer limit of the interior diameter of the casing so the tool's slips set against the casing, and the set tool can hold in the casing against fracing pressure thereby isolating the third perforations; 
 
       producing fourth perforations in the casing past at least one of the casing patches and fracing the fourth perforations;
 running a third selected tool into the casing past at least two of the casing patches and setting the third selected tool against the casing by expanding the tool's slips to within the range of a radial inner limit of a 15% expansion of the tool's O.D. and a radial outer limit of the interior diameter of the casing so the tool's slips set against the casing, and the set tool can hold in the casing against fracing pressure thereby isolating the fourth perforations; 
 
       producing fifth perforations in the casing past at least some of the casing patches and fracing the fifth perforations;
 waiting less than five days after the tools are immersed in the downhole fluid in the well for the tools to degrade in the wellbore fluid enough to permit production of hydrocarbons from the well; and 
 producing hydrocarbons from the horizontal leg within less than two days after the tools are immersed in the downhole fluid in the well, without milling out or retrieving the five tools, or intervening on the tools from the surface after the five tools have been used in the fracing operations. 
 
     
     
         14 . The method of  claim 13 , further comprising:
 selecting tools which will degrade within less than two days;   waiting less than two days after the tools are immersed in the downhole fluid in the well for the tools to degrade in the wellbore fluid enough to permit production of hydrocarbons from the well; and   producing hydrocarbons from the horizontal leg within less than two days after the tools are immersed in the downhole fluid in the well, without milling out or retrieving the five tools, or intervening on the tools from the surface after the five tools have been used in the fracing operations.   
     
     
         15 . The method of  claim 13 , further comprising:
 selecting tools which will degrade within less than one day;   waiting less than one day after the tools are immersed in the downhole fluid in the well for the tools to degrade in the wellbore fluid enough to permit production of hydrocarbons from the well; and   producing hydrocarbons from the horizontal leg within less than one day after the tools are immersed in the downhole fluid in the well, without milling out or retrieving the five tools, or intervening on the tools from the surface after the five tools have been used in the fracing operations.