Injection Apparatus and Method

Abstract

The invention relates to an injection apparatus for injecting a chemical additive into a fluid mixture flowing in a well-bore. The invention also relates to a corresponding injection method. A particular application of the invention relates to the oilfield industry, for example in cementing operation

1 . An injection apparatus for injecting a chemical additive into a fluid mixture flowing into an annulus of a well-bore comprising a body defining an internal chamber receiving a valve arrangement, wherein the body comprises:
 a) at least one port for coupling to a reservoir containing the chemical additive, and   b) at least one injection nozzle for injecting the chemical additive into the fluid mixture flowing into the annulus, wherein the valve arrangement has a closed position and an open position defined as a function of the fluid flow-rate of the fluid mixture flowing through the valve arrangement, such that:
 ι) in a closed position, the valve arrangement closes communication between a reservoir and the injection nozzle, the injection apparatus delivering a non-activated fluid mixture, and 
 ιι) in an open position, the valve arrangement puts in communication the reservoir with the injection nozzle, the injection apparatus injecting the chemical additive into the fluid mixture flowing into the annulus. 
   
   
   
       2 . The injection apparatus according to  claim 1 , wherein the valve arrangement comprises:
 a) a main sleeve comprising an internal conduit forming a venturi and a peripheral groove forming a communication chamber, and   b) an indexer sleeve coupled to the main sleeve and the body defining the position of the main sleeve as a function of fluid flow-rate of the fluid mixture flowing through the main sleeve, such that:
 ι) in the closed position, the main sleeve closes the communication between the reservoir and the injection nozzle, and 
 ιι) in the open position, the main sleeve puts in communication the reservoir with the injection nozzle through the communication chamber. 
   
   
   
       3 . The injection apparatus according to  claim 1 , wherein the body further comprises at least one coupler at one extremity of the body for coupling the injection apparatus to a pipe. 
   
   
       4 . The injection apparatus according to  claim 1 , wherein the reservoir is contained in a casing joint. 
   
   
       5 . The injection apparatus according to  claim 1 , wherein the injection nozzle is located at a lower extremity of the body, above a port. 
   
   
       6 . The injection apparatus according to  claim 1 , wherein the internal chamber is filled with a clean fluid. 
   
   
       7 . The injection apparatus according to  claim 2 , wherein a peripheral groove is isolated from the injection nozzles by a seal in the closed position. 
   
   
       8 . The injection apparatus according to  claim 1 , wherein the valve arrangement further comprises a compression spring positioned inside the internal chamber, pushing against a first and second shoulder of the body and the main sleeve, respectively. 
   
   
       9 . The injection apparatus according to  claim 8 , wherein the compression spring characteristic determines a threshold flow-rate that triggers the main sleeve from the open position to the closed position, and vice-versa. 
   
   
       10 . The injection apparatus according to  claim 8 , wherein the indexer sleeve is positioned between the second shoulder and a third shoulder of the main sleeve, the indexer sleeve rotating around the main sleeve under limitation of an indexer pin secured to the body. 
   
   
       11 . The injection apparatus according to  claim 10 , wherein the indexer pin is engaged in a groove in an external wall of the indexer sleeve, the groove having a plurality of ‘J-slot’ shape around the indexer sleeve. 
   
   
       12 . The injection apparatus according to  claim 1 , wherein the valve arrangement further comprises a compensating piston positioned on top of the main sleeve for compensating the pressure between the internal chamber and the fluid mixture flowing through the injector apparatus. 
   
   
       13 . An injection method for injecting a chemical additive into a fluid mixture flowing into an annulus of a well-bore, wherein the method comprises the following steps:
 a. running an injection apparatus at a proper location in the well-bore, the injection apparatus comprising a body defining an internal chamber receiving a valve arrangement, at least one injection nozzle for injecting a chemical additive contained in a pressurized reservoir into the fluid mixture flowing into the annulus, the valve arrangement being in a closed configuration,   b. letting flow the fluid mixture at a first flow-rate into the well-bore through the injection apparatus, and   c. triggering the valve arrangement to an open position by letting flow the fluid mixture at a second flow-rate into the well-bore through the injection apparatus, so as to put in communication the injection nozzles with the reservoir and letting flow the chemical additive into the annulus of well-bore through injection nozzles.   
   
   
       14 . The injection method according to  claim 13 , wherein the triggering step comprises sequentially raising the fluid flow-rate of the fluid mixture above a threshold flow-rate then lowering said flow-rate under the threshold flow-rate. 
   
   
       15 . The injection method according to  claim 14 , wherein the method further comprises the step of triggering the valve arrangement back to the close position by sequentially raising the fluid flow-rate of the fluid mixture above the threshold flow-rate then lowering said flow-rate under the threshold flow-rate, so as to stop putting in communication the injection nozzles with the reservoir. 
   
   
       16 . The injection method according to  claim 13 , wherein the chemical additive in the reservoir is at a pressure substantially identical as a pressure of the fluid mixture inside of the casing, which is higher than a pressure of the fluid mixture in the annulus. 
   
   
       17 . The injection method according to  claim 13  wherein the triggering step is remotely controlled through a pumping arrangement of a surface equipment.