Wells – Automatic
Reexamination Certificate
1997-08-14
2001-06-05
Bagnell, David (Department: 3672)
Wells
Automatic
C166S372000, 36
Reexamination Certificate
active
06241014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the control of oil and gas wells using a plunger lift device and more particularly to adjustable control of such wells.
2. Background
Several technologies are used to assist the production of fluids from crude oil or natural gas wells. One of these involves the use of a plunger, a free moving rod or sealed tube with loose-fitting seals to prevent fluid bypassing between the plunger and the production tubing wall. The plunger is left at the bottom of the well until sufficient pressure has built up to allow the plunger to rise to the top of the well head, pushing the accumulated fluid ahead of the plunger. Movement of the plunger is normally controlled by opening a valve at the well head, connecting the tubing to an outlet line, such as the sales line or in some cases separation equipment used to separate oil, water, and gas. The principle of operation is based on the well slowly building up bottom hole pressure from fluids and gas passing from the formation into the well. When the sales valve is opened, the pressure in the sales line or separator is lower than the bottom hole pressure, so that the pressure differential causes the plunger to travel to the surface. In some instances it is desirable to leave the sales valve open for a period of time after the plunger has arrived at the surface. This time period is frequently referred to as “Afterflow.” There are several conditions under which it is desirable not to operate the sales valve for safety or production efficiency reasons. For example, the sales line pressure might be so high that one would not want to try to force more fluid or gas into an already loaded system.
History
The earliest devices which provided timing cycles for the sales valve were simple mechanical spring wound clock movements with pins or levers to open or close a pilot valve that would in turn operate a motor valve to operate the sales line. As technology advanced, these were superseded by battery-powered solid-state electronic timers such as the devices described in U.S. Pat. Nos. 4,150,721 and 3,445,746. These were then replaced by microprocessor-based units that could perform the same timing functions and also make limited changes in the time cycle based on outside influences. Such influences might include detecting the failure of the plunger to arrive in the expected time or observing high or low pressure limits through the use of external pressure switches such as the device described in U.S. Pat. No. 4,532,952. Further advances were made with the devices described in U.S. Pat. No. 5,146,991, which allowed production cycle changes based on the speed at which the plunger arrived at the well head.
SUMMARY OF THE PRESENT INVENTION
The present invention of a microprocessor based controller for oil or gas wells using a plunger lift device is addressed to an improved method for operating and controlling such an oil or gas well using the plunger system and procedures for assisted artificial lift of well fluids. Because of its flexibility and computational power, the modern microprocessor can perform a series of increasingly complex control algorithms as selected by the well operator. The controller can thus serve first as a manual control panel, performing operations on the oil or gas well only as directed by the human operator. The controller can serve as a simple low power timing device indicating elapsed times between various operations performed manually through the controller on the oil and gas well. The controller also may operate and control the well automatically, using the computational powers of the processor, changing various time intervals to adjust the ideal trip time set by the operator with changes in condition of the oil or gas well. In this mode the controller compares the actual trip time with the ideal trip time and changes Off time (the time after the trip is complete until the next trip) and/or Afterflow time by an exponential function of the difference between the actual trip time and the ideal trip time. Hence the change in the adjusted time will be large for large differences and small for small differences. Use of the exponential function calculation allows for rapid approach to the ideal trip time along a substantially asymptotic path while allowing correction on the next cycle for any overcompensation.
This microprocessor is preferably a battery-powered, solid-state electronic system with an associated set of program functions stored in nonvolatile memory connected by appropriate I/O to a well to permit improvement of the production efficiency of several different plunger lift applications. Additionally, the invention eases the human operator's burdens and improves safety of the equipment, environment, and personnel. Battery life may be extended with the addition of a photovoltaic panel, which may be mounted on top of the controller.
REFERENCES:
patent: 4352376 (1982-10-01), Norwood
patent: 5132904 (1992-07-01), Lamp
patent: 5146991 (1992-09-01), Rogers
Dees Ian
Drobnic Marina
Fields Chris
Majek Alfred
Bagnell David
Ostfeld David M.
Texas Electronic Resources, Inc.
Walker Zakiya
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