CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to gas lift valve systems and particularly to replaceable gas lift valve system.
2. Description of the Prior Art
Gas lift systems have been used in oil wells to help increase production. In practice, a gas lift mandrel is permanently installed in the production line (either tubing or liners, for example). Once in place, the mandrel can be idle until such time as a gas injection program is desired. At that time, a hole is punched in the side of the gas lift mandrel and a gas lift valve is installed such that gas can be injected into the well between the casing and the production tubing, through the mandrel in to the gas lift valve, which is positioned to transfer the gas from the casing to the production tubing, where it mixes with the oil and aids in the flow of the oil through the production tubing. The main function of the gas lift valve is to meter the flow of gas into the production tubing to maximize the beneficial effects of the gas.
Over time, the gas lift valves corrode and have to be replaced. This operation can be done with current well technology. The major problem with this system is the mandrels are permanently installed. Because the gas and is highly corrosive, eventually, the mandrel fails. When this happens, the control of the flow of gas is eliminated and the gas flows freely into the production tubing, effectively stopping the flow of oil. There is no present way to repair the mandrel and after the mandrel fails, the well is typically shut in and it must be completely reworked to get production restarted. This is a very expensive solution for an aging well.
BRIEF DESCRIPTION OF THE INVENTION
The instant invention overcomes these difficulties. It is a replaceable gas lift valve system. In this system, the device is inserted into the production tubing, liner or other conduit (which is known as the gas producing zone) at a desired level. A hole is formed in the gas-producing zone to allow gas to be injected. The device is positioned adjacent to the opening. This allows gas to be pumped down the space between the casing and the production tubing, for example, as before. Because the tool is essentially fills the inside of the gas-producing zone, space is provided to allow almost normal production through the tool. Once in place, the device has a metering valve that allows the appropriate amount of gas or other fluid to enter the gas-producing zone to provide lift for the oil.
Over time, the corrosive effect will cause the valve to fail. Once this happens, the device can be quickly extracted using standard slick line techniques and a replacement unit quickly installed. Once installed, the replacement device allows resumed production. The recovered device can be dismantled, repaired and staged for another quick replacement where needed.
The difference here is that the entire unit, which consists of a mandrel and a valve, can be replaced. This capability allows gas injection to occur without ever having to shut in the well because of mandrel failure. Moreover, unlike the permanently installed gas lift mandrels, which are installed in fixed locations during the initial well completion, the instant device can be installed in any level desired within the well.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial cutaway view of the invention.
FIG. 2 is the partial cutaway view of FIG. 1 showing the flow of gas and fluid through the device.
FIG. 3 is a detail interior view of the device installed in a well.
FIG. 4 is the detail interior view of FIG. 3 showing the movement of gas.
FIG. 5 is the detail interior view of FIG. 3 showing the movement of oil and oil/gas mix.
FIG. 6 is an enlarged cross-sectional of the lift valve.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, a partial cutaway view of the invention 10 is shown. In this view, on the left is shown the outer shell 11 of the device 10, which is the mandrel. This mandrel is standard steel. On the right, the inner working of the device 10 are shown. At the center of the device is a gas lift valve 12. A gas mixing tube 13 allows the injected gas to mix with the production fluids (see e.g., FIG. 2). Production fluids travel through a flow pipe that has a lower unit 14 and an upper unit 15. Thus, once this device is installed production can continue while the gas is being injected.
FIG. 2 is the partial cutaway view of FIG. 1 showing the flow of gas and fluid through the device. In this view, injected gas (represented by the dashed lines labeled g) is pumped into the production tubing though the lift valve 12. The gas g exits the valve through tube 13, where it mixes with production fluids represented by the dashed line labeled p. After the gas and production fluids mix, they pass upwards through the device. This mixture is represented by the dashed lines labeled m.
FIG. 3 is a detail interior view of the device installed in a well. In this view, the outer casing 100. Within the outer casing 100 is a line of production tubing 101. Note that in this view, for the sake of illustration, production tubing is shown although the device can be installed in many other configurations and other pipes such as liners. Note also that the spacing shown is exaggerated for clarity. As shown, production tubing 101 is run within the casing 100. The device is installed in a line of patch tubing 102. As part of that string an upper mandrel portion 20 is threadably attached to a lower mandrel portion 21. At the junction of the upper and lower mandrel portions is a seal 22. Mandrel packers 103 are installed above and below the mandrel portions as shown. These ensure a seal between the production tubing and the patch tubing.
An entry port 23 is provided on the lower mandrel that allows for the entry of gas (see, FIG. 4), which is pumped down between the casing and the production pipe. The entry port is aligned with a hole in the production tubing as shown. The entry port is also in contact with the gas lift valve 24, which, as described above, is used to mix the gas with the production fluids in the well. The lift valve 24 is fitted between an upper seal sub 25 that has a seal 26 in it, and a lower seal sub 27 that has a seal 28 in it. At the base of the unit is a guide point 29. At the top of the unit is a fish neck 30. Note that there are seals 31 (see also FIG. 6) located on the gas lift valve that seal the valve to the lower housing when installed. A fish neck 30 allows the device to be set in a well and positioned where desired. When the lift valve fails, it can be retrieved by using the fish neck. The damaged unit can be pulled and quickly replaced with a new unit, thereby allowing the continued operation of the well. Another key feature, as discussed below is the production flow portion 32 in the gas lift valve, through which the production fluids continue to flow. Note that the installation within the production tubing can be at the location of a corroded existing permanently installed gas lift mandrel as well. The installation is the same. Unlike the case of a permanently installed gas lift mandrel, however, when the mandrel portions 20 or 21 corrode, the patch tubing string can be pulled and a new string with a new mandrel can be installed in its place. This is impossible in a standard oil well and is the biggest advantage that the instant invention has over the prior art.
FIG. 4 is the detail interior view of FIG. 3 showing the movement of gas and the pressure diagram. Here, the same view as in FIG. 3 is shown only in this view, the gas g is shown in the system as a series of dots. Note that the arrows show the pressures on the system imposed by the gas g.
FIG. 5 is the detail interior view of FIG. 3 showing the movement of oil and oil/gas mix. As before, this view reproduces that of FIG. 3 with the production fluids shown p shown as a dense pattern. Note too, as before, pressure is indicated by arrows on the figure. As note that one of the key features is the production flow portion 32 in the gas lift valve. As shown in FIG. 5, production fluids pass through the valve through this portion. It is this portion that allows the unit to be installed in a well as it is designed not to impede the flow of regular production fluids. It is important to remember that even though the production flow portion 32 is smaller that that of the regular production tubing, this unit is used in wells that are near the end of their operational life and, as such, regular production flows are generally considerably slower than normal flows. Thus, the installation of the unit is not an impediment to the flows in the well.
FIG. 6 is an enlarged cross-sectional of the lift valve. Here, the gas lift valve 24 is shown clearly showing the seals 31 and the production flow portion 32 in the valve.
In use, the well is prepared for gas injection as normal. However, instead of installing a permanent gas lift valve, the unit is positioned in place. Gas is then injected and production continues as normal. Eventually, the gas lift valve will corrode through and production will be curtailed. At this point, the unit is retrieved using common fish tools and a new unit is positioned in its place. In this way, a low production well can continue to produce for many years.
The present disclosure should not be construed in any limited sense other than that limited by the scope of the claims having regard to the teachings herein and the prior art being apparent with the preferred form of the invention disclosed herein and which reveals details of structure of a preferred form necessary for a better understanding of the invention and may be subject to change by skilled persons within the scope of the invention without departing from the concept thereof.
Patent Grant
9435181
