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BACKGROUND 
     Field of the Invention 
     This invention relates to an apparatus and method for reversing well kill operations. More specifically, this invention provides a composition and method to displace killing fluids from a wellbore with naturally flowing oil or gas. 
     Background of the Invention 
     At various points in the lifetime of a well, it may be necessary to end the flow of oil, gas, and other reservoir fluids from the reservoir to the wellbore. This kind of operation is commonly referred to as a well kill. Well kills of producing wells typically involve pumping a high density kill fluid into the wellbore. The density of the kill fluid exerts sufficient pressure to prevent fluids from flowing from the reservoir into the wellbore. Kill fluids have the advantage of suppressing well production without the need for continued control from the surface. 
     Another advantage of using kill fluids to stop production is that such a well kill is reversible. When the well kill involves a heavy mud set in the wellbore, the reversal of the well kill requires the heavy mud to be removed. Typical removal operations involve pumping a gas into the wellbore at a high pressure. The pressure of the gas acts to remove the heavy mud from the wellbore. In some operations, the heavy mud is removed from the wellbore by being forced into the reservoir. This method is cheap, but runs the risk of causing damage to the reservoir. In an alternate method, coiled tubing is inserted into the wellbore. The high pressure gas is inserted through the coiled tubing, circulates out the bottom of the coiled tubing, and lifts the heavy mud up out of the wellbore. The coiled tubing method does not run the same risk to the reservoir, but requires more equipment making it a more expensive reversal option. 
     A well kill with injected gas is advantageous, because the injection gas is usually a cheap, inert gas such as nitrogen. The injected gases themselves do not prevent the flow of reservoir fluids into the wellbore allowing production to begin promptly upon removal of the kill fluid. 
     A method with the advantages of injected gas and the minimized risk to the reservoir of coiled tubing and without the operating costs of coiled tubing would be preferred. 
     SUMMARY OF THE INVENTION 
     This invention relates to an apparatus and method for reversing well kill operations. More specifically, this invention provides a composition and method to displace killing fluids from a wellbore with naturally flowing oil or gas. 
     In one aspect of the present invention, a reaction apparatus for providing reactants from a surface to a wellbore to create a generated gas when the reactants undergo a reaction in situ to affect a density of a fluid in the wellbore is provided. The reaction apparatus includes a reaction housing, the reaction housing includes a first reactant cell, the first reactant cell having a passing side and being fully enclosed within the reaction housing, where the first reactant cell is configured to contain a first reactant, a second reactant cell, the second reactant cell having a passing side and being fully enclosed within the reaction housing separate from the first reactant cell, where the second reactant cell is configured to contain a second reactant, a mixing chamber, the mixing chamber being fully enclosed within the reaction housing, being in fluid communication with the passing side of the first reactant cell and the passing side of the second reactant cell, where the mixing chamber is configured to allow the first reactant and the second reactant to mix, a first passage, the first passage in fluid communication with the passing side of the first reactant cell and with the mixing chamber, the first passage configured to allow the first reactant to pass from the first reactant cell to the mixing chamber, a second passage, the second passage in fluid communication with the passing side of the second reactant cell and with the mixing chamber, the second passage configured to allow the second reactant to pass from the second reactant cell to the mixing chamber, and an outlet, the outlet positioned in the mixing chamber, where the outlet is configured to allow the generated gas from the reaction in the mixing chamber to escape the mixing chamber when a reaction pressure in the mixing chamber exceeds a wellbore pressure in the wellbore. The reaction apparatus also includes a line, the line configured to move the reaction housing from the surface to the wellbore, wherein the line contains a plurality of electric cables, each of the plurality of electric cables being configured to transmit a signal to and from the reaction apparatus, and a reel, the reel configured to guide the line into and out of the wellbore. 
     In certain aspects of the present invention, the reaction apparatus further includes a settling area in the mixing chamber, the settling area configured to collect non-gaseous by-products from the reaction. In certain aspects of the present invention, the settling area includes a dump valve, the dump valve configured to release the non-gaseous by-products into the wellbore, wherein the dump valve is in electrical communication with at least one of the plurality of electric cables. In certain aspects of the present invention, the reaction apparatus further includes a first port in the first passage, the first port configured to allow the first reactant to pass from the first reactant cell to the mixing chamber at a predetermined mark, and a second port in the second passage, the second port configured to allow the second reactant to pass from the second reactant cell to the mixing chamber at the predetermined mark, where the first port and the second port are in electrical communication with at least one of the plurality of electric cables. In certain aspects of the present invention, the first reactant is NH 4 Cl and the second reactant is NaNO 2  and the generated gas is nitrogen. In certain aspects of the present invention, the reaction apparatus further includes a temperature gauge, the temperature gauge in electrical communication with at least one of the plurality of electric cables, and a pressure gauge, the pressure gauge in electrical communication with at least one of the plurality of electric cables. In certain aspects of the present invention, the reaction apparatus further includes a density gauge mounted externally to the reaction apparatus, the density gauge being in electrical communication with at least one of the plurality of electric cables to transmit the density of the fluid in the wellbore to the surface. 
     In a second aspect of the present invention, a method for providing reactants that undergo a reaction to produce a generated gas in situ in a wellbore to affect a density of a fluid in the wellbore is provided. The method includes the steps of positioning a reaction housing into the wellbore using a line, the line including a plurality of electric cables, each of the plurality of electric cables being configured to transmit a signal to and from the reaction housing, the reaction housing including a first reactant cell, the first reactant cell containing a first reactant, a second reactant cell, the second reactant cell containing a second reactant, a mixing chamber, the mixing chamber in fluid communication with the first reactant cell through a first passage, the first passage including a first port, the mixing chamber in fluid communication with the second reactant cell through a second passage, the second passage including a second port, and an outlet, the outlet positioned in the mixing chamber. The method further including the steps of opening the first port in the first passage at a predetermined mark to allow the first reactant to pass from the first reactant cell into the mixing chamber, opening the second port in the second passage at the predetermined mark to allow the second reactant to pass from the second reactant cell into the mixing chamber, allowing the first reactant and the second reactant to react in the mixing chamber to generate gas, where the generated gas increases a reaction pressure, increasing the reaction pressure in the mixing chamber until the reaction pressure exceeds a wellbore pressure in the wellbore, and opening the outlet when the reaction pressure exceeds the wellbore pressure, where opening the outlet releases the generated gas into the wellbore such that the generated gas mixes with the fluid in the wellbore and affects the density of the fluid. 
     In certain aspects of the present invention, the first reactant reacting in the mixing chamber is NH 4 Cl and the second reactant reacting in the mixing chamber is NaNO 2  and the generated gas is nitrogen. In certain aspects of the present invention, the method further includes the step of accumulating non-gaseous by-products from the reaction in a settling area in the mixing chamber situated below the outlet. In certain aspects of the present invention, the method further includes the step of dumping the non-gaseous byproducts into the wellbore through a dump valve, where the dump valve is in electrical communication with at least one of the plurality of electric cables. In certain aspects of the present invention, the method further includes the steps of measuring a temperature using a temperature gauge, and measuring a pressure using a pressure gauge, where the temperature gauge and the pressure gauge being in electrical communication with at least one of the plurality of electric cables. In certain aspects of the present invention, the method further includes the step of measuring the density of the fluid in the wellbore using a density gauge mounted externally to the reaction housing, the density gauge being in electrical communication with at least one of the plurality of electric cables to transmit the density of the fluid in the wellbore to a surface. 
     In a third aspect of the present invention, a method for reversing a well kill operation using a kill fluid in a wellbore is provided. The method including the steps of placing a reaction housing into the wellbore using a line, the line including a plurality of electric cables, each of the plurality of electric cables being configured to transmit a signal to and from the reaction housing, the reaction housing including a first reactant cell, the first reactant cell containing a first reactant, a second reactant cell, the second reactant cell containing a second reactant, a mixing chamber, the mixing chamber in fluid communication with the first reactant cell through a first passage, the first passage including a first port, the mixing chamber in fluid communication with the second reactant cell through a second passage, the second passage including a second port, and an outlet, the outlet positioned in the mixing chamber. The method further including the steps of opening the first port in the first passage at a predetermined mark to allow the first reactant to pass from the first reactant cell into the mixing chamber, opening the second port in the second passage at the predetermined mark to allow the second reactant to pass from the second reactant cell into the mixing chamber, allowing the first reactant and the second reactant to react in a reaction in the mixing chamber to produce a generated gas, wherein the generated gas increases a reaction pressure, increasing the reaction pressure in the mixing chamber until the reaction pressure exceeds a wellbore pressure in the wellbore, opening the outlet when the reaction pressure exceeds the wellbore pressure, wherein opening the outlet releases the generated gas into the wellbore, and altering a density of the kill fluid in the wellbore, wherein the density of the kill fluid is altered by mixing with the generated gas, such that the kill fluid rises up from the wellbore. 
     In certain aspects of the present invention, the first reactant reacting in the mixing chamber is NH 4 Cl and the second reactant reacting in the mixing chamber is NaNO 2  and the generated gas is nitrogen. In certain aspects of the present invention, the method further includes the step of accumulating non-gaseous byproducts from the reaction in a settling area at the bottom of the mixing chamber situated below the outlet. In certain aspects of the present invention, the method further includes the step of dumping the non-gaseous byproducts into the wellbore through a dump valve, wherein the dump valve is in electrical communication with at least one of the plurality of electric cables. In certain aspects of the present invention, the method further includes the steps of measuring a temperature using a temperature gauge and measuring a pressure using a pressure gauge the temperature gauge and the pressure gauge being in electrical communication with at least one of the plurality of electric cables. In certain aspects of the present invention, the method further includes the step of measuring the density of the fluid in the wellbore using a density gauge mounted externally to the reaction housing, the density gauge being in electrical communication with at least one of the plurality of electric cables to transmit the density of the fluid in the wellbore to a surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood with regard to the following descriptions, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention&#39;s scope as it can admit to other equally effective embodiments. 
         FIG. 1  is a schematic of an embodiment of the present invention. 
         FIG. 2  is a sectional perspective view of an embodiment of the present invention. 
         FIG. 3  is a sectional perspective view of an alternate embodiment of the present 
         FIG. 4  is a sectional perspective view of an alternate embodiment of the present 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the invention will be described with several embodiments, it is understood that one of ordinary skill in the relevant art will appreciate that many examples, variations and alterations to the apparatus and methods described herein are within the scope and spirit of the invention. Accordingly, the exemplary embodiments of the invention described herein are set forth without any loss of generality, and without imposing limitations, on the claimed invention. 
     Referring to  FIG. 1 , a schematic view of an embodiment of reaction apparatus  100  is provided. Reaction housing  102  attached to line  104  is positioned in wellbore  106  using reel  110  stationed on surface  108 . Surface  108  is any location from which drilling operations are conducted. Surface  108  can include the earth&#39;s surface or a platform surface. Line  104  can be any line, cable, wire, or tubing capable of moving reaction housing  102  from surface  108  into wellbore  106 . Line  104  can be single-strand or multistrand. Line  104  can be braided. In some embodiments of the present invention, line  104  is a slickline. In some embodiments of the present invention, line  104  is a wireline. 
     In at least one embodiment of the present invention, line  104  contains electric cables. The electric cables connect elements of reaction housing  102  to monitoring systems, process control systems, electricity sources, or combinations thereof. The electric cables transmit signals between systems at surface  108  to reaction housing  102 . 
     Wellbore  106  is any wellbore in connection with a reservoir where a kill operation was performed. In at least one embodiment of the present invention, the kill operation was performed as a necessary as part of the overall hydrocarbon production plan. 
     Reel  110  is any device that stores, transports, spools, and unspools line  104 . In some embodiments, reel  110  includes equipment necessary to communicate electronically with reaction housing  102 . In some embodiments of the present invention, the electric cables of line  104  connect elements of reaction housing  102  to reel  110 . 
     Reaction housing  102  can be positioned at any point in wellbore  106  in consideration of the configuration of wellbore  106 , the reservoir, and the properties of the kill fluid. Reaction housing  102  can be any material that can maintain structural integrity under the temperature and pressure in wellbore  106  and is non-reactive with the kill fluid, the generated gas, and the hydrocarbons in the reservoir. The dimensions of reaction housing  102  are dictated by the internal components, described with reference to  FIG. 2  herein and by the diameter (size) of wellbore  106 . Dimensions, as used herein includes measurements for size and volume, i.e., length, height, width, depth, thickness, and also shape. 
     In at least one embodiment of the present invention, reaction housing  102  is connected to coiled tubing, with the coiled tubing connected to a supply source on surface  108 . 
     With reference to  FIG. 1  as described above,  FIG. 2  provides a cross-sectional perspective view of reaction housing  102  according to one embodiment of the present invention. As provided in  FIG. 2 , reaction housing  102  includes first reactant cell  10  and second reactant cell  12 , the reactant cells. First reactant cell  10  is configured to contain the first reactant. Second reactant cell  12  is configured to contain the second reactant. In at least one embodiment of the present invention, the reactant cells isolate the reactants from each other. In some embodiments of the present invention, first reactant cell  10  and second reactant cell  12  are two separate chambers. In at least one embodiment of the present invention, first reactant cell  10  and second reactant cell  12  are separated by a partial partition (not shown) that does not extend the full height of the reactant cells. First reactant cell  10  is fully enclosed within reaction housing  102 . Second reactant cell  12  is fully enclosed within reaction housing  102 . The dimensions of first reactant cell  10  and second reactant cell  12  are determined by the quantity or volume of the reactants and by the diameter (size) of wellbore  106 . Alternately, the diameter (size) of the production tubing can be used to size reaction housing  102 . In one embodiment of the present invention, the reactant cells are sloped to channel the reactants to a place within the reactant cell. The reactant cells are designed to withstand the pressure and temperature of wellbore  106 . In some embodiments of the present invention, first reactant cell  10  and second reactant cell  12  are the same in size, shape, and configuration. In at least one embodiment of the present invention, first reactant cell  10  and second reactant cell  12  are different in size, shape, and configuration. In at least one embodiment of the present invention, the exterior of first reactant cell  10  and second reactant cell  12  forms part of reaction housing  102 . In at least on embodiment of the present invention, the exteriors of the reactant cells contact the interior of reaction housing  102 . The materials of construction for the reactant cells are chosen for compatibility with the reactants. 
     The first reactant and the second reactant, the reactants, are chosen to react together to generate gas as at least one of the reaction products. The reactants can be salts, acids, or combinations thereof. The generated gases can include nitrogen, hydrogen, carbon dioxide, and combinations thereof. The first reactant and the second reactant can be solid, liquid, gas, or combinations thereof. In at least one embodiment of the present invention, the reactants are solids. The reaction of the present invention can produce non-gaseous by-products. 
     In accordance with one embodiment of the present invention, the first reactant is ammonium chloride (NH 4 Cl), the second reactant is sodium nitrite (NaNO 2 ). The reactants react according to the following equation:
 
NH 4 Cl+NaNO 2 →NaCl+2H 2 O+N 2  
 
     The generated gas is nitrogen (N 2 ) and the non-gaseous by-products are sodium chloride (NaCl) and water (H 2 O). 
     In accordance with one embodiment of the present invention, the first reactant is sodium bicarbonate (NaHCO 3 ), the second reactant is acetic acid (CH 3 CO 2 H). The reactants react according to the following equation:
 
NaHCO 3 +CH 3 CO 2 H→C 2 H 3 NaO 2 +H 2 O+CO 2  
 
     The generated gas is carbon dioxide (CO 2 ) and the non-gaseous by-products are sodium acetate (C 2 H 3 NaO 2 ) and water (H 2 O). 
     In at least one embodiment, a third reactant is included in mixing chamber  50 . In at least one embodiment of the present invention, the third reactant is a catalyst. 
     Reaction housing  102  further includes first passage  30  and second passage  32 . First passage  30  connects passing side  20  of first reactant cell  10  with mixing chamber  50 . Second passage  32  connects passing side  22  of second reactant cell  12  with mixing chamber  50 . First passage  30  and second passage  32  can be connected to induce contact of the reactants prior to mixing chamber  50 , as shown in accordance with  FIG. 2 . In at least one embodiment of the present invention, first passage  30  and second passage  32  are not connected, such that the reactants pass directly from the reactant cells to mixing chamber  50  without first coming into contact, as shown in accordance with  FIG. 3 . One of skill in the art will appreciate that the physical dimensions, including the shape and length, and the interconnectedness of first passage  30  and second passage  32  can be configured to accommodate the need for contact prior to mixing chamber  50 , the composition of the reactants, or for any reason as desired within the scope of the invention. 
     First passage  30  is configured to allow the first reactant to pass from first reactant cell  10  to mixing chamber  50 . First passage  30  can be in any configuration that allows a material to pass from first reactant cell  10  to mixing chamber  50 . Exemplary configurations for first passage  30  include a length of pipe, a length of tubing, or a machined chute. First passage  30  can be at any angle between passing side  20  and mixing chamber  50 . The diameter, or width, of first passage  30  can be configured to limit the rate at which the first reactant passes from first reactant cell  10  to mixing chamber  50 . In at least one embodiment of the present invention, passing side  20  and first passage  30  are designed such that the first reactant passes from first reactant cell  10  to mixing chamber  50  due to gravity. In at least one embodiment of the present invention, reaction housing  102  is in the absence of first passage  30 , such that the first reactant passes directly from passing side  20  to mixing chamber  50 . 
     Second passage  32  is configured to allow the second reactant to pass from second reactant cell  12  to mixing chamber  50 . Second passage  32  can be in any configuration that allows a material to pass from second reactant cell  12  to mixing chamber  50 . Exemplary configurations for second passage  32  can be a length of pipe, a length of tubing, or a machined chute. Second passage  32  can be at any angle between passing side  22  and mixing chamber  50 . The diameter, or width, of second passage  32  can be configured to limit the rate at which the second reactant passes from second reactant cell  12  to mixing chamber  50 . In at least one embodiment of the present invention, passing side  22  and second passage  32  are designed such that the second reactant passes from second reactant cell  12  to mixing chamber  50  due to gravity. In at least one embodiment of the present invention, reaction housing  102  is in the absence of second passage  32 , such that the second reactant passes directly from passing side  22  to mixing chamber  50 . 
     First passage  30  includes first port  40 . First port  40  controls the passage of the first reactant from first reactant cell  10  to mixing chamber  50 . First port  40  is configured to allow the passage of the first reactant at the predetermined mark. The predetermined mark can be a physical location within wellbore  106 , a measure of time after reaction housing  102  is positioned within wellbore  106 , or at a predetermined wellbore pressure in wellbore  106 . Exemplary devices for use as first port  40  include valves, nozzles, swing arms, gates, or combinations thereof. First port  40  can be electrically controlled, pneumatically controlled, pressure controlled, or combinations thereof. First port  40  can be manually controlled or can be controlled by a process control loop, wherein the occurrence of one state triggers an action in first port  40 . One of skill in the art will appreciate that the design of first port  40  depends on the state of the first reactant and the configuration of first passage  30  and mixing chamber  50 . In some embodiments of the present invention, first port  40  is connected to an electric cable which is connected to reel  110  on surface  108 . 
     Second passage  32  includes second port  42 . Second port  42  controls the passage of the second reactant from second reactant cell  12  to mixing chamber  50 . Second port  42  is configured to allow the passage of the second reactant at the predetermined mark. Second port  42  can be any device that can control the passage of second reactant from second reactant cell  12  to mixing chamber  50 . Exemplary devices for use as second port  42  include valves, nozzles, swing arms, or gates. Second port  42  can be electrically controlled, pneumatically controlled, or pressure controlled. Second port  42  can be manually controlled or can be controlled by a process control loop, wherein the occurrence of one state triggers an action in second port  42 . One of skill in the art will appreciate that the design of second port  42  depends on the state of the second reactant and the configuration of second passage  32  and mixing chamber  50 . In some embodiments of the present invention, second port  42  is connected to an electric cable which is connected to reel  110  on surface  108 . 
     Mixing chamber  50  provides space for the reaction between the first reactant and the second reactant. As the reaction proceeds, the generated gas pressurizes mixing chamber  50  to the reaction pressure. Mixing chamber  50  is designed to maintain structural integrity under the pressure and temperature of wellbore  106 . Mixing chamber  50  is designed to maintain structural integrity under the reaction pressure of the generated gas. The materials of construction selected from mixing chamber  50  are chosen to be compatible with the reaction products. The dimensions of mixing chamber  50  are designed to facilitate the reaction between the reactants, to build up the pressure of the generated gas, and to provide a space for the non-gaseous byproducts to accumulate. 
     Outlet  54  allows the generated gas to escape from mixing chamber  50  into wellbore  106 . Mixing chamber  50  includes at least one outlet  54 , alternately one outlet  54 , alternately two outlets  54 , alternately three outlets  54 , alternately four outlets  54 , alternately more than four outlets  54 . Exemplary devices for use as outlet  54  include valves, nozzles, swing arms, and gates. Outlet  54  can be electrically, mechanically, or pneumatically controlled. Outlet  54  can be automatically controlled by a process system or require manual manipulation. In at least one embodiment of the present invention, outlet  54  is a pressure relief valve. In at least one embodiment of the present invention, mixing chamber  50  includes two outlets  54 . Outlet  54  can be located in any part of mixing chamber  50 , which allows the generated gas to escape into wellbore  106 . In accordance with one embodiment of the present invention, outlet  54  is a check valve that can be controlled mechanically or electrically. In an alternate embodiment, outlet  54  is a relief valve rated for the pressure at which the relief valve is to open. 
     In at least one embodiment of the present invention, mixing chamber  50  includes settling area  52 . Settling area  52  collects the non-gaseous by-products from the reaction of the reactants. Settling area  52  can have any configuration that allows for the collection of nongaseous by-products. In at least one embodiment of the present invention, settling area  52  has sloped sides (not shown). Settling area  52  can be configured to hold the non-gaseous by-products or to expel them. In some embodiments of the present invention, settling area  52  is located so that none of non-gaseous by-products are expelled through outlet  54 . In at least one embodiment of the present invention, dump valve  56  is located in settling area  52 . Dump valve  56  provides the egress for the non-gaseous by-products from mixing chamber  50 . Exemplary devices for use as dump valve  56  include valves, swing arms, and gates. Dump valve  56  can be electrically controlled, pneumatically controlled, pressure controlled, or combinations thereof. Dump valve  56  can be manually controlled or can be controlled by a process control loop, wherein the occurrence of one state triggers an action in dump valve  56 . In one embodiment of the present invention, dump valve  56  opens to wellbore  106 , such that the non-gaseous by-products are expelled into wellbore  106 . 
     It will be appreciated by one skill in the art that other configurations of first reactant cell  10 , second reactant cell  12 , mixing chamber  50 , first passage  30 , and second passage  32  can be considered to accommodate the reactants, the reaction, and the reaction products. In at least one embodiment of reaction apparatus  100 , as shown with reference to  FIG. 4  and with reference to elements described herein, reaction housing  102  contains only first reactant cell  10  and second reactant cell  12 . First reactant cell  10  contains the first reactant and second reactant cell  12  contains the second reactant. First passage  30  allows the first reactant to pass from passing side  20  through first port  40  into second reactant cell  12 . 
     Reaction housing  102  includes sensors for pressure, temperature, and density. The sensors are connected to the electric cables in line  104 . In one embodiment of the present invention, the electric cables transmit signals from the sensors to reel  110  on surface  108 . The signals transmitted through the electric cables can be used in a process control system to control the functions of reaction housing  102  and reaction apparatus  100 . In some embodiments of the present invention, reaction housing  102  includes a pressure gauge externally mounted to reaction housing  102 . In some embodiments of the present invention, a density gauge is externally mounted to reaction housing  102 . In some embodiments of the present invention, a temperature gauge is externally mounted to reaction housing  102 . In some embodiments of the present embodiments of the present invention, a pressure gauge is internally mounted in mixing chamber  50 . In some embodiments of the present invention, a pressure gauge with an orifice is installed to capture flow rate measurements through outlet  54 . 
     A method is herein provided. In a first step, reaction housing  102  is loaded with the first reactant in first reactant cell  10  and the second reactant in second reactant cell  12 . First port  40  and second port  42  are closed to prevent the passage of the first reactant and the second reactant into mixing chamber  50 . In at least one embodiment of the present invention, first reactant cell  10  and second reactant cell  12  are pressurized to a pressure commensurate with the pressure of wellbore  106 . 
     Once loaded, reaction housing  102  is positioned within wellbore  106 . In accordance with one embodiment of the present invention, line  104  is unspooled from reel  110  to lower reaction housing  102  into wellbore  106 . Reaction housing  102  is positioned within wellbore  106  at the predetermined mark. The predetermined mark can be a physical location within wellbore  106 , such as a depth from surface  108  or a distance from the terminal point of wellbore  106 . The predetermined mark can be a measure of time, such that reaction housing  102  is moved within wellbore  106  until the measure of time is reached. The predetermined mark can be a wellbore pressure within wellbore  106  as measured by a pressure gauge externally mounted to reaction housing  102 . 
     When the predetermined mark is reached, first port  40  in first passage  30  is opened. Opening first port  40  allows the first reactant to enter first passage  30  and pass into mixing chamber  50 . Second port  42  in second passage  32  is opened. In one embodiment of the present invention, each port, first port  40  and second port  42 , opens upon reaching the predetermined mark. In one embodiment of the present invention, first port  40  opens, then second port  42  opens after first port  40  is opened, but prior to first reactant cell  10  being empty of the first reactant. In an alternate embodiment of the present invention, first port  40  opens, then second port  42  opens after first port  40  closes. In at least one embodiment of the present invention, second port  42  opens before first port  40  opens. 
     After both first reactant cell  10  and second reactant cell  12  are empty or substantially empty of the reactants, first port  40  and second port  42  close. The first reactant and the second reactant are both in mixing chamber  50 . The first reactant and second reactant react in mixing chamber  50  and generate the generated gas. The generated gas increases the reaction pressure in mixing chamber  50 . 
     When the reaction pressure exceeds the wellbore pressure, outlet  54  opens and releases the generated gas into wellbore  106  where the generated gas mixes with the fluid in wellbore  106 . In some embodiments, outlet  54  continuously allows the generated gas to escape from mixing chamber  50  into wellbore  106 . In some embodiments of the present invention, outlet  54  is designed and controlled to allow intermittent releases of the generated gas from mixing chamber  50 . An intermittent release of the generated gas can be based on the reaction pressure in mixing chamber  50 , a length of time, or any other factor. The mixing of the generated gas and the fluid decreases the density of the fluid. A decrease in the density of the fluid causes a decrease in the hydrostatic pressure exerted by the fluid in wellbore  106 . Once enough generated gas has mixed with the fluid, the density will be decreased enough to lift the fluid from wellbore  106  to surface  108 . In at least one embodiment of the present invention, the fluid is the kill fluid. 
     In at least one embodiment of the present invention, the mixing of the generated gas with the fluid in wellbore  106  reduces the density of the fluid with a negligible effect on the viscosity. In at least one embodiment of the present invention, the generated gas mixes with the fluid in wellbore  106  in the absence of reservoir or formation fluids. 
     The method described herein can be repeated at the same predetermined mark, or at a second predetermined mark within wellbore  106 , until the fluid has been removed from the wellbore  106 . In at least one embodiment of the present invention, reaction housing  102  is reloaded. 
     Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereupon without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents. 
     The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise. 
     Optional or optionally means that the subsequently described event or circumstances can or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur. 
     Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range. 
     Throughout this application, where patents or publications are referenced, the disclosures of these references in their entireties are intended to be incorporated by reference into this application, in order to more fully describe the state of the art to which the invention pertains, except when these references contradict the statements made herein. 
     As used herein and in the appended claims, the words “comprise,” “has,” and “include” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps. 
     As used herein, terms such as “first” and “second” are arbitrarily assigned and are merely intended to differentiate between two or more components of an apparatus. It is to be understood that the words “first” and “second” serve no other purpose and are not part of the name or description of the component, nor do they necessarily define a relative location or position of the component. Furthermore, it is to be understood that that the mere use of the term “first” and “second” does not require that there be any “third” component, although that possibility is contemplated under the scope of the present invention.

Summary:
A reaction apparatus for providing reactants from a surface to a wellbore to create a generated gas when the reactants undergo a reaction in situ to affect the density of a fluid in the wellbore, the reaction apparatus comprises a reaction housing, the reaction housing comprises a first reactant cell configured to contain a first reactant, a second reactant cell configured to contain a second reactant, a mixing chamber, configured to allow the first reactant and the second reactant to mix, a first passage configured to allow the first reactant to pass from the first reactant cell to the mixing chamber, a second passage configured to allow the second reactant to pass from the second reactant cell to the mixing chamber, an outlet configured to allow the generated gas from the reaction to escape the mixing chamber, a line comprising a plurality of electric cables, and a reel.