Well sealing via thermite reactions

Abstract

Wells are sealed by means of thermite reaction charges inserted into the wells. The reaction charge can be diluted by addition of metal oxides, silica, or the like control reaction pressure, peak temperature, reaction rate, and expansion characteristics of the resulting thermite plug. The use of dilution of the thermite reactants can take the form of a thermite charge with specific layers, including relatively high and low reaction temperature layers. The ignition source can be oriented to achieve directional control on the product expansion including radial or axial expansion. The charge can be loaded with a large mass to compress the resulting thermite plug into the borehole wall and reduce its porosity during the reaction process. A further variation involves continuous feed of the thermite reactants to the reaction zone. Various combinations and permutations of the above inventive concepts are described.

1 . A method of sealing a well, comprising the steps of:
 lowering a thermite reaction charge into the well at a location where the well is to be sealed,   wherein the thermite reaction charge lowered into the well has been diluted by addition of one or more additives to moderate an exothermic reaction produced by the thermite reaction charge when ignited, the moderating comprising both substantially lowering the reaction temperature to less than 1700° C. and substantially slowing reaction velocity to less than 1 cm/sec within the thermite reaction charge from what they would otherwise be without the one or more additives to meet a specific design objective for the sealing of the well; and   igniting the thermite reaction charge, the thermite reaction charge burning so as to form a plug in the well.   
     
     
         2 . The method of  claim 1 , wherein the one or more additives comprises a metal oxide. 
     
     
         3 . The method of  claim 1 , wherein the thermite reaction charge is diluted by an amount of between 5 and 75 percent by mass. 
     
     
         4 . The method of  claim 3 , wherein the thermite reaction charge is diluted by addition of aluminum oxide and wherein the reaction velocity of the thermite material is reduced to below 1 cm/second. 
     
     
         5 . The method of  claim 1 , further comprising the step of placing a platform into the well below or at the location where the well is to be sealed and placing the thermite material onto the platform. 
     
     
         6 . A method of sealing a well, comprising the steps of:
 lowering a thermite reaction charge into the well at a location where the well is to be sealed, the thermite reaction charge comprising at least two layers of thermite reaction charge including a first relatively lower reaction temperature layer and a second relatively higher reaction temperature layer,   wherein the first layer comprises a thermite reaction material which has been diluted by addition of one or more additives to moderate an exothermic reaction produced by the thermite reaction material when ignited, the moderating comprising substantially lowering the reaction temperature to less than 1700° C. and substantially slowing the reaction velocity to less than 1 cm/sec within the thermite reaction material from what they would otherwise be without the one or more additives; and   igniting the first and second layers of the thermite reaction charge.   
     
     
         7 . The method of  claim 6 , wherein the one or more additives comprises a metal oxide. 
     
     
         8 . The method of  claim 7 , wherein the thermite reaction material in the first layer material is diluted by an amount of between 5 and 75 percent by mass. 
     
     
         9 . The method of  claim 8 , wherein the thermite material is diluted by addition of aluminum oxide and wherein the reaction velocity of the thermite material is reduced to below 1 cm/second. 
     
     
         10 . The method of  claim 7 , further comprising the step of placing a platform into the well below or at the location where the well is to be sealed and placing the thermite reaction charge onto the platform. 
     
     
         11 . The method of  claim 6 , wherein the first layer is positioned below the second layer, and wherein the second layer is ignited after the first layer is ignited. 
     
     
         12 . A method of sealing a well, comprising the steps of:
 lowering a thermite reaction charge into the well at a location where the well is to be sealed, the thermite reaction charge comprising at least two layers of thermite reaction charge including a first relatively lower reaction temperature layer and a second relatively higher reaction temperature layer,   wherein the first layer comprises a thermite reaction material which has been diluted by addition of one or more additives to moderate an exothermic reaction produced by the thermite reaction material when ignited, the moderating comprising substantially lowering the reaction temperature and substantially slowing the reaction velocity within the thermite reaction material from what they would otherwise be without the one or more additives; and   igniting the first and second layers of the thermite reaction charge;   wherein the first layer is positioned below the second layer, and wherein the second layer is ignited after the first layer is ignited; and   wherein the well further comprises a casing, and wherein ignition of the first layer causes the casing to be swaged outwardly into contact with a formation surrounding the casing.   
     
     
         13 . A method of sealing a well, the well having a casing and a borehole wall, the casing separated from the borehole wall by an annular gap comprising:
 forming a swage at a first location in the well by igniting a diluted thermite material lowered into the well proximate the first location so as to heat the casing to a plastic but not molten state and expand the plastic casing against the borehole wall and thereby close the annular gap, and   igniting a second thermite material above the first location to melt the casing and surrounding borehole wall and form a plug in the well.   
     
     
         14 . A well sealing apparatus comprising:
 a thermite reaction charge having a cylindrical body sized to fit within a well, the thermite reaction charge comprising at least two layers of thermite reaction charge including a first relatively lower reaction temperature layer and a second relatively higher reaction temperature layer, wherein the first layer comprises a thermite reaction material which has been diluted by addition of one or more additives to moderate an exothermic reaction produced by the thermite reaction material when ignited, the moderating comprising substantially lowering the reaction temperature to less than 1700° C. and substantially slowing the reaction velocity to less than 1 cm/sec within the thermite reaction material from what they would otherwise be without the one or more additives;   wherein the first layer is positioned below the second layer; and   an igniter for the relatively lower reaction temperature layer.   
     
     
         15 . The well sealing apparatus of  claim 14 , further comprising a plug placed in the well below the thermite reaction charge. 
     
     
         16 . (canceled)