Abstract:
A method for blending a well treatment fluid at a well site, including (1) providing centrifugal pumps for pumping components of the well treatment fluid into a pipe, (2) providing valves for controlling the flow of the components of the well treatment fluid into the pipe, and (3) controlling the pumps and the valves so as to control the ratio of the components of the well treatment fluid being delivered to the pipe.

Description:
BACKGROUND 
       [0001]    On-the-fly blending of well treatment fluids is not typically used for corrosive chemicals. Generally, blending corrosive chemicals, otherwise known as acids, or hazardous chemicals, is done at a location other than the well site, using batch mixing. The chemicals are mixed in a tank at a bulk chemical plant and then transported to the well site. The mixing and the transportation are costly. Specialized transports are required to transport the mix. Additionally, specially trained personnel are required. In addition to being costly, this can be undesirably time consuming. Further, any real-time change to the mix presents problems, as an entire new batch must be mixed and transported. While this occurs, the job must wait, which can be extremely costly. Further, batch mixing requires that the tank be emptied prior to changing the mix. It is difficult to anticipate the exact amount of mix that will be required for a given application. This generally leads to excess mix left in the tank at the end of a job, or at a change point. Proper disposal of this mix can be environmentally hazardous, costly, and dangerous. 
       SUMMARY 
       [0002]    The present invention relates generally to blending fluids and more specifically to an improved method of blending well treatment fluids at the well site. 
         [0003]    In one embodiment of the present invention a method for blending a well treatment fluid at a well site, comprises: providing a first centrifugal pump for pumping a first component of the well treatment fluid into a pipe; providing a first valve for controlling the flow of the first component of the well treatment fluid into the pipe; providing a second centrifugal pump for pumping a second component of the well treatment fluid into the pipe; providing a second valve for controlling the flow of the second component of the well treatment fluid into the pipe; and controlling the pumps and the valves so as to control the ratio of the first component of the well treatment fluid to the second component of the well treatment fluid being delivered to the pipe. 
         [0004]    In another embodiment of the present invention a system for blending a well treatment fluid at a well site, comprises: a first centrifugal pump for pumping a first component of the well treatment fluid into a pipe; a first valve for controlling the flow of the first component of the well treatment fluid into the pipe; a second centrifugal pump for pumping a second component of the well treatment fluid into the pipe; a second valve for controlling the flow of the second component of the well treatment fluid into the pipe; and means for controlling the pumps and the valves so as to control the ratio of the first component of the well treatment fluid to the second component of the well treatment fluid being delivered to the pipe. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a schematic view of a system for blending well treatment fluids at the well site. 
       
    
    
     DETAILED DESCRIPTION 
       [0006]    Referring now to  FIG. 1 , shown therein is an exemplary embodiment of a system for blending well treatment fluids at the well site. The system, designated generally by the numeral  100 , may be mounted on a trailer or skid (not shown). The system  100  blends various components of the well treatment fluid directly into a pipe  110 . This reduces or eliminates the need for standard mixing tanks or tubs. This may be accomplished using at least two centrifugal pumps  120  (shown as  120   a ,  120   b , and  120   c ). The centrifugal pumps  120  may each pump a different component of the desired well treatment fluid. For example, in an acid treatment, a first centrifugal pump  120   a  may pump a hazardous chemical such as hydrochloric acid (HCl), a second centrifugal pump  120   b  may pump water, and a third centrifugal pump  120   c  may pump a highly corrosive chemical such as Ammonium Bi-Fluoride (“AF”). While HCl, water, and AF are disclosed, it should be understood that the chemicals may include any acid, hazardous chemical, corrosive, or other fluid. 
         [0007]    The system  100  may also include a number of valves  140  (shown as  140   a ,  140   b , and  140   c ) for controlling the flow of the various components from the centrifugal pumps  120  into the pipe  110 . The valves  140  may be butterfly valves, or any other valve suitable for use with well treatment fluids. 
         [0008]    Between the centrifugal pumps  120  and the valves  140 , the system  100  may include pressure transducers  150  (shown as  150   a ,  150   b , and  150   c ) that act as a pressure controls on the centrifugal pumps  120 , preventing the centrifugal pumps  120  from pushing one another off line. Feedback from pressure transducers  150  may signal pressure set points in centrifugal pumps  120 , such that the centrifugal pumps  120  maintain a desirable balance. 
         [0009]    Between the valves  140  and the pipe  110 , the system  100  may additionally include flow meters  160  (shown as  160   a ,  160   b , and  160   c ) and check valves  162  (shown as  162   a ,  162   b , and  162   c ) to monitor and control flow rates from the pumps  140 . 
         [0010]    Liquid additives may also be introduced into the pipe  110 . The additives may be stored in liquid additive storage tanks (not shown), and pumped into the pipe  110  via one or more liquid additive pumps  130 . While the liquid additive pump  130  is shown as a hand pump, the liquid additive pump  130  may be any type of pump, including, but not limited to a positive displacement pump. One or more liquid additive valves (not shown) may be included to control the flow of liquid additives from the liquid additive pumps  130  into the pipe  110 . 
         [0011]    The well treatment fluid may be blended directly in the pipe  110 , without the use of any tank. The flow rate and pressure of any of the components may be controlled by controlling the pumps  120 ,  130  and the valves  140 . This allows for the ratio of the various components and additives of the well treatment fluid to be modified as necessary for the specific field conditions at any given time. This modification can take place in real-time, allowing the desired well treatment fluid mix to be pumped into the well as it is needed. 
         [0012]    Additionally, the system  100  may have a number of additional valves (not shown), with locations suitable for controlling flow in various ways as would be readily understood by one of ordinary skill in the art. For example, these additional valves may be butterfly valves, some of which are open and some of which are closed. 
         [0013]    A discharge flow meter  170  may be included in the system  100 . This may allow for adjustments to be made to the pumps  120  and valves  140 , such that the correct mix ratio is maintained without creating undesirable negative pressure in the system  100 . After the mix has passed through the discharge flow meter  170 , it may pass through another pump (not shown), which then pumps the mix downhole. 
         [0014]    Computer software may be used to control the mix ratio. The computer software may include a pressure control system, a rate control system, and/or a concentration control system. The pressure control system may control pressure by controlling the pumps  120 . The rate control system may control flow rate by controlling the valves  140 . The concentration control system may control the concentration by controlling the pumps  120 . 
         [0015]    The pressure control system may include a drive signal to the centrifugal pumps  120  and feedback from pressure transducers  150 . Each of the centrifugal pumps  120  may maintain a separate pressure set point. These pressure set points may be based on expected rate and resultant discharge pressure. The optimal pressure set point may place the valves  140  at a predetermined percentage open for each respective expected rate. 
         [0016]    The rate control system may include a drive signal to each valve  140  and feedback from the respective flow meter  160 . The valve  140  for a first (or master) component (e.g. water) may be set to 100% open and the rate may be set by the discharge rate, as measured by the discharge flow meter  170 . The rate set points for the remaining valves  140  may be set by the concentration control system. Thus as the requirements for concentrations change (even during a job), the operator has the ability to ramp up or down the concentration and/or liquid additives depending on the specific need. This may be a desirable alternative to the standard practice of mixing a new batch at the acid plant and transporting the mixture to the well site. 
         [0017]    The concentration control system may include the rate control system and the rate feedback from the master (e.g. water) rate, which may be measured by the corresponding flow meter  160 . Based on a predetermined well treatment fluid mix, the rate set points for the other components may be calculated from a concentration or parts per thousand of the master rate. As the master rate increases, the rate for the other components may also increase. The increasing rate of other components will slow the increasing master rate until the desired concentration is established. 
         [0018]    The system  100  may optionally include additional components. For example, as shown in  FIG. 1 , the system  100  may include a tank  180 . Due to the nature of the types of chemicals used, the tank  180  may be situated on the discharge side of the system  100 . The tank  180  may be used to prevent loss if something goes wrong and the job must be stopped. Additionally, the tank  180  may be useful in situations where the flow rates are very low. 
         [0019]    The system  100  may also optionally include a discharge recirculation pump  198 . The discharge recirculation pump  198  may serve two purposes. The first may be for recirculation. The second may be for discharge at very low flow rates. The recirculation pump  198  may be any type of pump for discharge recirculation (e.g. 120 HP pumps). 
         [0020]    This system  100  may be used for acid blending for acidizing wells, otherwise known as “Acid-On-the-Fly,” which involves blending two or more major hazardous chemical components into a pressurized piping system and injecting one or more liquid additives into that flow stream. This system  100  may alternatively be used for fracturing operations, in which case the treatment fluid would be a fracturing fluid. Additionally, this system  100  may be used for drilling operations, in which case the treatment fluid would be drilling mud. 
         [0021]    The ability to blend “On-the-Fly” may reduce the amount of blended chemicals requiring disposal upon completion of the process. It may also lower exposure of hazardous chemicals to personnel and the environment. Furthermore, it may decrease the number of personnel required for the process and decrease the amount of time hazardous chemicals would be in use. Additionally, by blending the chemicals as they are pumped downhole, there may be a significant reduction of waste that must be disposed of, and cost associated with that disposal process. Further, there may be a reduction in cost for transporting the mixed chemicals, since that would no longer be a requirement. Additionally, there may be a reduction of cost for buying and maintaining the highly regulated cargo tank motor vehicles. Additionally, there may be a reduction and/or elimination of the bulk chemical plants (otherwise known as acid plants) currently being used. By eliminating bulk acid plants, transports, and the physically handling of these types of chemicals the risk of personal and environmental exposure may be significantly reduced. 
         [0022]    Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. In addition, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.