Patent Publication Number: US-2009223664-A1

Title: On-the-Fly Acid Blender with Sampling Equipment

Description:
BACKGROUND 
     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. 
     Moreover, it is important to monitor the properties of a treatment fluid to ensure proper performance. Traditionally, a valve and bucket approach is used to take a sample of the treatment fluid out of the system for testing and analysis. Specifically, the onsite personnel would have to open a valve and obtain a sample of the treatment fluid in a bucket for analysis. However, the traditional methods of retrieving samples have several drawbacks. The treatment fluid often comprises hazardous, corrosive or flammable material thereby posing a danger to the equipment, environment and the personnel taking the sample. Moreover, exposure to elements can compromise the sample properties leading to inaccurate results when analyzing the sample. 
    
    
     
       FIGURES 
       Some specific example embodiments of the disclosure may be understood by referring, in part, to the following description and the accompanying drawings. 
         FIG. 1  is a system for on-the-fly blending of treatment fluids with a sampling device in accordance with an exemplary embodiment of the present invention. 
         FIG. 2  is a system for on-the-fly blending of treatment fluids with a sampling device in accordance with another exemplary embodiment of the present invention. 
         FIG. 3  is an in-line sampling device in the closed position accordance with an embodiment of the present invention. 
         FIG. 4  is an in-line sampling device in the open position in accordance with an embodiment of the present invention. 
         FIG. 5  is a perspective view of a sampling device with a safety enclosure in accordance with an embodiment of the present invention. 
     
    
    
     While embodiments of this disclosure have been depicted and described and are defined by reference to example embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure. 
     SUMMARY 
     The present invention is directed to blending fluids. Specifically, the present invention is directed to improved methods and systems of blending and analyzing well treatment fluids at a well site. 
     In one embodiment, the present invention is directed to a method for blending a well treatment fluid at a well site, comprising: 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; 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; and providing a sampling device for analyzing the well treatment fluid. 
     In another embodiment, the present invention is directed to a system for blending a well treatment fluid at a well site, comprising: 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; 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; and a sampling device for monitoring the well treatment fluid. 
     The features and advantages of the present disclosure will be readily apparent to those skilled in the art upon a reading of the description of exemplary embodiments, which follows. 
     DESCRIPTION 
     The present invention is directed to blending fluids. Specifically, the present invention is directed to improved methods and systems of blending and analyzing well treatment fluids at a well site. 
     An improved method of blending the components of a well treatment fluid is disclosed in patent application Ser. No. 11/673,290, filed Feb. 9, 2007, which is incorporated herein by reference in its entirety. 
     Referring now to  FIG. 1 , an exemplary embodiment of a system for preparing and analyzing acids on-the-fly at a desired rate is depicted generally with reference numeral  100 . 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. 
     As would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure, more than two centrifugal pumps may be used to allow for more than two different components to be mixed together. For example, in one embodiment the system may include three centrifugal pumps for an acid treatment, where a first centrifugal pump may pump a hazardous chemical such as hydrochloric acid (“HCl”), a second centrifugal pump may pump water, and a third centrifugal pump 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. For instance, in another exemplary embodiment a non-aqueous fluid may be used as a primary flow stream. In one embodiment, the non-aqueous fluid may include diesel. 
     The system  100  may also include one or more 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. 
     Between the centrifugal pumps  120  and the valves  140 , the system  100  may include one or more pressure transducers  150  (shown as  150   a,    150   b,  and  150   c ) that act as 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. 
     Between the valves  140  and the pipe  110 , the system  100  may additionally include one or more flow meters  160  (shown as  160   a,    160   b,  and  160   c ) and one or more check valves  162  (shown as  162   a,    162   b,  and  162   c ) to monitor and control flow rates from the pumps  140 . 
     Additional 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 . 
     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  and  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. 
     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. In one exemplary embodiment, the additional valves may be used to address the mixing orders of some specific fluids by allowing a user to inject liquid additives into the raw product flow streams prior to entering the pipe  110 . 
     A discharge flow meter  190  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  190 , it may pass through another pump (not shown), which then pumps the mix downhole. 
     The system  100  may also optionally include a discharge recirculation pump  194 . The discharge recirculation pump  194  may serve two purposes. The first may be for recirculation. The second may be for discharge at very low flow rates. The recirculation pump  194  may be any type of pump for discharge recirculation (e.g., a 120 HP pump). 
     A sampling device  170  may be coupled to the system  100 . In one embodiment, the sampling device  170  may be coupled to the system in parallel to the discharge recirculation pump  194 . The sampling device may allow the operator to take samples of the fluid produced by the system  100  while protecting personnel from exposure to the material flowing through the pipe  110  which is often comprised of hazardous chemicals. 
       FIG. 2  depicts another exemplary embodiment of the present invention where the sampling device  170  is coupled to the pipe  110  just before the fluid enters the discharge flow meter  190 . 
     As would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure, in one embodiment (not shown) the sampling device  170  may be removably coupled to the system  100 . It may be desirable to attach the sampling device  170  to the system  100  when a sample is to be taken and remove it when the sampling process has been completed. One or more valves (not shown) may be used to control the fluid flow through the sampling device  170 . The valves may be closed when no sample is to be taken or when the sampling device  170  is not coupled to the system  100 . Once the operator decides to take a sample the valves may be opened to allow fluid flow through the sampling device  170 . 
     Shown in  FIG. 3  is an in-line sampling device in the closed position in accordance with an embodiment of the present invention denoted generally by reference numeral  300 . The in-line sampling device  300  allows fluid samples to be taken directly from the pipe  110  into a sampling container  302 . This ensures that a real-time sample is taken from the fluid stream and eliminates sample exposure while eradicating the health and safety risks to personnel who would otherwise be responsible for taking a sample. As would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure, a number of different methods may be used to couple the sampling device  300  with the pipe  110 . In one embodiment, the in-line sampling device  300  mounts onto the pipe  110  between two standard flanges  304 . 
     A sampling container  302  may be coupled at one end of the sampling device  300  and a lever  306  at the other. When a sample is not being taken, a valve spindle  308  may be pressed by a spring  310  against a soft seal  312 .  FIG. 4  depicts an in-line sampling device in accordance with an embodiment of the present invention in the open position. When the lever  306  is turned, the valve spindle  308  may be lifted from the soft seal  312 . The stroke of the lever  306  can be adjusted by a travel stop  314 . The valve spindle  308  allows a smooth and controlled sample flow into the sampling container  302  through an inlet  316 . As the sample fills the sampling container  302 , any displaced air vents through a ventilation outlet  318 . The ventilation outlet  318  may be coupled to a scrubber system when the samples taken include hazardous materials. The operation of scrubber systems is well know to those of ordinary skill in the art and will therefore not be discussed in detail herein. 
     Although the depicted sampling device  300  utilizes the lever  306 , in another exemplary embodiment a multi-turn hand wheel may be used to lift the valve spindle  308 . Although a multi-turn hand wheel allows accurate metering of the sample into a container, it is not fail-safe as the operator may mistakenly leave the sample valve open and overflow the sampling container  302 . In contrast, in a lever  306  operated design the spring  310  is used to create a spring loaded handle which will automatically close the valve when the operator releases the lever  306  handle. Thus, as would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure, a number of different mechanisms, including, but not limited to, a spring loaded lever, a multi-turn hand wheel, or any other device suitable for opening and/or closing a valve may be used to control the sampling process. 
     Different types of sampling containers  302  may be used in conjunction with the in-line sampling device  300 . In one embodiment, the sampling container  302  comprises a glass bottle which is threaded into the bottom of the sample device  300 . The bottle will then hold the sample as it is drawn from the pipe  110 . In order to minimize sample exposure and the possibility of spills, the sampling container  302  may be enclosed in a glove box  500  as depicted in  FIG. 5 . This allows the bottle to be capped inside the glove box thereby preventing the exposure of the sample taker to any fumes from the sample while minimizing sample exposure to outside elements. The glove box  500  may be any type of container suitable for containing spills and or fumes. 
     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 . 
     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. 
     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  190 . 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. 
     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. 
     The system  100  may optionally include additional components. For example, as shown in  FIG. 1 , the system  100  may include a tank  192 . Due to the nature of the types of chemicals used, the tank  192  may be situated on the discharge side of the system  100 . The tank  192  may be used to prevent loss if something goes wrong and the job must be stopped. Additionally, the tank  192  may be useful in situations where the flow rates are very low. As would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure, additional valves  196  may be used to control the flow of the fluid through the tank  192 . For example, these additional valves may be butterfly valves, some of which are open and some of which are closed. 
     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. Therefore, although the present invention is described in the context of acids, as would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure, the system and methods of the present invention may also apply to non-acids or other material requiring high-shear preparation on a single pass such as on-location preparation of emulsion based fracturing fluids, completion fluids, cementing fluids such as spacers, and drilling fluids. 
     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 physical handling of these types of chemicals, the risk of personal and environmental exposure may be significantly reduced. 
     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.