Abstract:
Methods and systems for deliquification of fluid loaded, packed wells with sub-surface safety valves (“SSSVs”) utilizing timed and tailored chemical treatments. A flow meter measures the flow rate of the well and an intermitter initiates shut in of the well when a particular flow rate is reached. A chemical treatment is applied and allowed to penetrate the length of the well before production is restarted. Predetermined combinations of chemical treatments and production cycles are utilized based on past experience and well data, and the entire process can be automated through the use of a computer system.

Description:
[0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 60/854,481, filed on Oct. 26, 2006, entitled METHODS AND SYSTEMS FOR GAS WELL DELIQUIFICATION, the entire content of which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    This invention pertains to the deliquification of gas wells, and particularly to methods and systems for deliquification of fluid loaded, packed wells with sub-surface safety valves (“SSSVs”) utilizing timed and tailored foamer treatments with cyclical, repeating sequences of shutin, batch and fall applications, and flow back. 
         [0003]    The accumulation of water and liquid hydrocarbons in well bores is a problem both in natural-gas production and underground gas storage. Siphons and accompanying equipment, such as gas-lift valves and timing devices, probably are the most logical choices to relieve this problem where water production is profuse. However, such systems are expensive and often are not justified for marginal wells or those that produce only a little water. The number of such wells is large and is increasing rapidly, particularly in underground gas-storage projects where water accumulates only after extended withdrawal periods and only to a limited extent. Although bailing and swabbing usually will remove the liquids from such wells, these practices are relatively expensive and time consuming. 
         [0004]    There are many other approaches to the deliquification of gas wells. These approaches include: velocity strings, plunger lift, pump jacks, compression. submersible pumps, foaming and swabbing. Each of these technologies has applications in which they perform best. For instance, high gas to liquid ratio wells with high well pressure are well-suited for plunger lift applications. Also, high water flow rates are well suited for submersible pump applications. 
         [0005]    A widespread method for removing water from well bores is the use of foaming agents. The method is rapid, relatively inexpensive, and generally more cost effective. Furthermore, only a lubricator or small pump is required for the treatment. Foaming agents form a light foam column when properly mixed with the water or brine in the well bore and agitated by even a small amount of gas from the formation. This lightened column is lifted from the well by gas pressure that is too low to lift a column of water. Furthermore, the foam is rigid and, by capturing gas in the form of small bubbles, prevents the gas from bypassing water in large casings. 
         [0006]    A subsurface safety valve (“SSSV”) is a safety device installed in a well below the wellhead with the design function to prevent uncontrolled well flow when actuated. These devices can be installed and retired by wireline and/or pump down methods or be an integral part of the tubing. Most offshore gas wells that are loaded with SSSVs are presumed to need a capillary string that will extend below the SSSV to inject foamer to maintain gas well unloading. That type of capillary string technology is very expensive. The total cost is perhaps in the range of $100,000 to $200,000 per well. The use of capillary string technology in conjunction with SSSVs is complicated, and therefore expensive, because running a capillary string through the length of the tubing interferes with the ability to shut the SSSVs. Instead, the capillary tubing has to be modified to provide for retractable sections that bridge the SSSVs and can be mechanically retracted when the SSSVs need to be shut. 
         [0007]    Another option for deliquification of gas wells having SSSVs is the use of foam sticks. First, the well must be shut in. Then a foam stick has to be physically dropped through the length of the tubing with the SSSVs open. Materials in the foam stick then act to create foam which can be removed from the well. The use of foam sticks is very labor intensive and therefore undesirable. 
         [0008]    What is needed, therefore, is a method for deliquifying gas wells loaded with SSSVs that is low in cost and risk. 
         [0009]    The present invention relates generally to the field of gas and oil wells. In particular, this invention pertains to methods and systems for removing liquid from gas wells using repeated and cyclical sequences of shutin, batch and fall foamer application, and flow back. 
         [0010]    Generally, the current invention pertains to a method for deliquification of fluid loaded, packed gas wells with SSSVs. The method utilizes shut in and production intervals. Production cycles follow the shut in cycles during the unloading phase. Once the unloading phase ends and normal production begins, the same method can be followed to tailor treatment cycles to maintain optimum production. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  shows a general schematic of a gas well deliquification system; and 
           [0012]      FIG. 2  shows a graph comparing how a gas well could perform during single batch treatments vs. cyclical batch treatments. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0013]    The present invention relates to a method for the deliquification of gas wells. In particular, the method involves the timed application of foamer treatments during sequential shut in cycles. The gas well can be modified with a flow meter and an intermitter to control the shut in and production cycles. 
         [0014]    One aspect of the present invention is the use of a flow meter or pressure monitor and an intermitter in the deliquification of a gas well. A flow meter measures any kind of liquid that is preset by the user. With appropriate flow controlling software that is commercially available and sold in conjunction with the flow meter, the flow meter can be used to monitor the gas flow in a gas well. Some commercially available flow meters include TOTALFLOW EFMs (ABB, Zurich, Switzerland). Preferably, the flow meter and associated software is configured to register a selected flow rate or pressure of gas, such as the minimum flow rate or pressure that is allowed before the need for a deliquification treatment. Once this particular flow rate or pressure is measured by the flow meter or pressure monitor, a signal is sent to the intermitter. An intermitter is a manual or automated flowline valve control with appropriate safety controls to allow for automated shut in and restart. Some commercially available intermitters include those made by Ferguson Beauregard (Tyler, Tex.). Once the signal is received, based on the flow rate or pressure measured by the flow meter or pressure monitor, the intermitter then shuts in the gas well for deliquification treatment. 
         [0015]    An additional aspect of the present invention is a method for the deliquification of gas wells that have been shut in through the use of a flow meter and intermitter. Preferably, a chemical treatment is applied to the shut in well and allowed to penetrate the length of the tubing. The chemical treatment can be stored in a tank having a pump and a tube that travels to an injection point at the wellhead. When the pump is engaged at the appropriate time, subsequent to shut in of the well, the chemical treatment is applied to the fluid in the well. The shut in interval should last long enough for the chemical treatment to penetrate the entire fluid level. For example, a fall rate of 2000 ft/hr should be taken into consideration. If the well is 10,000 feet deep, then it must be shut in for 5 hours to allow the chemical treatment to penetrate. Weighted foamers are also useable with this method to allow faster penetration once the foamer gets to the fluid level. 
         [0016]    Preferably, the same software and computer system that measures the flow rate of the well and engages the intermitter to shut in the well also controls the pump and the chemical treatment. In that way, the entire deliquification process can be carried out simultaneously using one system. When the appropriate flow rate is measured, the intermitter is engaged to shut in the well, and the appropriate amount of a chemical treatment is applied to the well. After a preset period of time, which allows the chemical treatment to take affect, the intermitter is again engaged by the computer system and software to open the well again. 
         [0017]    A further aspect of the present invention is the selection of an appropriate chemical treatment to use for deliquification while the well is shut in. An appropriate foamer must be selected. Suitable foamers include non-ionic, anionic, cationic, amphoteric, and other chemical foamers, or mixtures thereof. Some foamers are available with additional components, such as scale inhibitors and corrosion inhibitors. An appropriate foamer can be selected according to individual preference and personal experience. Commercially available foamers include those made by MultiChem Group, LLC (Sonora, Tex.). 
         [0018]    Preferably, the flowmeter and intermitter are used to tailor the shut in/treatment and production intervals to maximize gas production overall. While the well is shut in and is undergoing treatment, it is not producing gas. However, the deliquification treatments during this unloading phase are necessary to maintain a productive flow of gas. Ideally, a series of different interval schemes are utilized and tested to determine which results in maximum production over time. Each well will react differently depending on the amount of water present and the flow rate, so one specific interval scheme cannot be adopted for every case. Anyone of skill in the field is capable of varying the treatment intervals and monitoring the results in order to determine a scheme that is ideal for a particular well. In some cases, these different treatment schemes can be done manually until the ideal settings are worked out. Then the system for deliquification utilizing the software, the intermitter, and the chemical pump can be configured to apply these ideal settings automatically. In some cases, the first unloading treatment may bring the well to the normal production cycle, whereas in some cases the unloading cycle will take multiple treatments. 
         [0019]    In an optional step, during the shut in interval, the well can also be pressurized with high pressure gas, such as methane, compressed or solid carbon dioxide, or nitrogen gas. Pressurization of the well results in the dissolving of both the methane gas and the pressurized gas in water. Preferably, the pressurized gas is carbon dioxide because it has more solubility in water. Nitrogen gas is also usable. Although compressed air could be utilized, the corrosiveness of oxygen makes it less than ideal. The production of foam in the shut in well is increased by injecting the pressurized gas into the well. The use of pressurized gas in conjunction with the shut in/treatment cycle is typically used with “dead wells,” or wells that have become so loaded with water that they are no longer producing a significant amount of gas, or any gas at all. 
         [0020]      FIG. 1  shows a general schematic of how the gas well deliquification system  10  could work in conjunction with a gas well  20  having at least one sub surface safety valve (“SSSV”)  25 . An output line  30  of the gas well  20  is equipped with a gas pressurizing stub  32 , a flow meter  34 , and an intermitter  36 . A chemical pump  42  works in conjunction with the intermitter  36  to inject an appropriate chemical treatment into the gas well  20  after shut in is initiated by the intermitter  36 . The intermitter  36  can use a flowline valve control  44  to allow the automated shut in and restart of the gas well  20 . The gas flow monitoring software and hardware  46  works in conjunction with the flow meter  34  to measure the gas flow rate and determine when shut in of the gas well  20  should be initiated. Optionally, the gas pressurizing stub  32  also injects pressurized gas during shut in of the well. This injection of pressurized gas can be carried out in conjunction with an inlet valving system  48  having appropriate safety controls. 
       Example 1 
       [0021]      FIG. 2  shows a graph comparing how a gas well could perform during single batch treatments versus cyclical batch treatments. During the first couple of weeks of gas production, at the left of the graph, the gas well has first been unloaded using single batch treatments. These single batch treatments could be single foam sticks or single batches of liquid foamer that are applied to the well without retreating it. Single treatments such as these remove large batches of water and result in the sharp peaks that are visible at the left side of the graph. Once the cyclical treatment begins, there are initially some large peaks, but eventually only small amounts of water are being removed each time. Thus, the graph levels out and becomes more cyclical.