CROSS REFERENCED TO RELATED APPLICATION
BACKGROUND OF THE INVENTION
This application claims priority from the USPTO provisional patent application entitled “An Apparatus and Method for Electrically Controlling Multiple Downhole Devices” by Jeffery Lee McDaniel, filed on Jan. 26, 2001, serial No. 60/264,364.
1. Field of the Invention
This invention relates generally to oilfield well operations and more particularly to an apparatus and method for electrically controlling multiple downhole devices.
2. Description of the Related Art
The control of oil and gas production wells constitutes an on-going concern of the petroleum industry due, in part, to the enormous monetary expense involved as well as the risks associated with environmental and safety issues.
It will be appreciated that relatively simple, timed intermittent operation of valves and the like are often not adequate to control either outflow from the well or injection to the well so as to optimize well production. As a consequence, sophisticated computerized controllers have been positioned at the surface of production wells for control of downhole devices such as motor valves.
Surface controllers are often hardwired to downhole sensors which transmit information to the surface such as pressure, temperature and flow. This data is then processed at the surface by the computerized control system.
While it is well recognized that petroleum production wells will have increased production efficiencies and lower operating costs if surface computer based controllers and downhole microprocessor controllers (actuated by external or surface signals) are utilized, current control systems nevertheless suffer from drawbacks and disadvantages. For example, reliability of surface to downhole signal integrity in a surface control system wherein a downhole microprocessor is actuated by a surface signal is a major concern. It will be appreciated that should the surface signal be in any way compromised on its way downhole, then important operations will not take place as needed.
Prior art surface control systems generally require a surface platform at each well for supporting the control electronics and associated equipment. However, in may instances, the well operator would rather forego building and maintaining a costly platform. Thus, a problem is encountered in that use of present surface controllers require the presence of a location for the control system, namely the platform.
- SUMMARY OF THE INVENTION
Disadvantages of present production well control systems involves the extremely high cost associated with implementing changes in well control and related workover operations. Presently, if a problem is detected at the well, the customer is required to send a rig to the wellsite at an extremely high cost (e.g., 5 million dollars for 30 days offshore work). The well must then be shut in during the workover causing a large loss in revenues (e.g., 1.5 million dollars for a 30 day period). Associated with these high costs are the relatively high risks of adverse environmental impact due to spills and other accidents as well as potential liability of personnel at the rig site. Of course, these risks can lead to even further costs. Because of the high costs and risks involved, in general, a customer may delay important and necessary workover of a single well until other wells in that area encounter problems. This delay may cause the production of the well to decrease or be shut in until the rig is brought in.
The present invention provides a production well control system for controlling multiple downhole devices, preferably, but not limited to, valves, separated by thousands of meters. This system allows for economic, reliable and reversible means of controlling a plurality of downhole devices.
In accordance with a first embodiment of the present invention, a surface control unit, downhole control module and interface unit are provided for selectively controlling downhole devices. An important feature of this invention is the ability to access individually, or as a group, multiple devices (e.g., valves) arranged in a distributed scheme. The number of downhole devices that can be controlled by this apparatus is only limited by the data address sizes, the power delivered and the power consumed. Additionally, the apparatus is inherently more reliable with each downhole device electrically coupled to an interface unit having a unique, stored address which must correspond to a surface transmitted address before actuation of the downhole device.
In accordance with a second embodiment of the present invention, comprising downhole sensors, downhole devices and a downhole control module whereby the control module automatically controls the downhole devices based upon a sensed downhole parameter or event. Therefore, using downhole sensors, the downhole control module will monitor actual downhole parameters (e.g., pressure, temperature, flow) and automatically execute control instructions to activate the downhole devices when parameters reach a preset limit or are outside of an optimum operating range.
In contrast to the first embodiment, well control systems which consist of a control module located wholly at the surface and a downhole computer system which requires an external initiation signal (as well as a surface control system), the downhole well production control system in the second embodiment automatically operates based on downhole conditions sensed in real time without the need for a surface or external signal. This important feature constitutes a significant advance in the field of production well control. Additional advantages of this system include elimination of the need for a surface platform and an even more reliable communication system since no surface to downhole actuation signal is required and the associated risk that such an actuation signal will be compromised is therefore rendered moot.
A power source provides energy to the downhole control unit in both embodiments described below. Power for the power source can be generated, preferably, at the surface or in the wellbore (e.g., by a turbine generator) or supplied by energy storage devices such as batteries (or a combination of one or more power sources). The power source provides electrical voltage and current to the downhole electronics, electromechanical devices and sensors in the wellbore.
BRIEF DESCRIPTION OF THE DRAWINGS
Examples of the more important features of the invention thus have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto.
For detailed understanding of the present invention, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein:
FIG. 1 is a schematic diagram of a production system that employs the apparatus of the present invention;
FIG. 2 is a block diagram showing an interface unit in accordance with the present invention;
FIG. 3 is a schematic diagram of the production system that employs an alternative embodiment of the present invention; and
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 4 is a block diagram showing a control unit of the alternative embodiment.
FIG. 1 is a schematic diagram of a production system 10, including a conventional derrick 11. A surface control unit 12 at the surface allows an operator to generate a command/request to be executed downhole. The operator may request downhole data or actuate one or more downhole devices by inputting a command into a communication terminal and display 16. The command is communicated by wire or wireless to a power and communication system 14.
The power and communication system 14 generates a command sequence and sufficient voltage to drive the selected downhole device. Specifically, the power and communication system 14 encodes the operator□s command as a command signal using a synchronized communication technique, preferably Manchester data encoding. The power and communication system 14 also generates a sufficiently high voltage to ensure that the command signal and activation voltage arrive at a downhole control module 30. The command signal and activation voltage are transmitted from the power and communication system 14 to the downhole control module 30 via twisted pair wiring housed in armored and shielded lines 22 extending downward from the surface 13 into the wellbore 20.
Upon receipt of the command signal and activation voltage, the downhole control module 30 interprets and reformats the command signal before transmitting a command serial data package and the activation voltage via armored and shielded lines 23, comprising a bi-directional four wire communication path comprising two wires for communicating power, one wire for communicating a clock pulse and one wire for communicating data. Power lines 24 and communication lines (e.g., clock pulse wire and data wire) 26, shown in FIG. 2, are connected to an interface unit 40 which is electrically coupled to at least one downhole device 41, preferably, but not limited to, a valve. Returning to FIG. 1, the downhole control module 30 may transmit the command signal and activation voltage to multiple interface units 40, 50, 60, 70, 80, 90 and 100 in a distributed control scheme.
As shown in FIG. 2, the interface unit 40, comprises a bi-directional communication transmitter and receiver or transceiver 42 which receives and transmits the data and clock pulse from communication line 26. The receiver/transmitter or transceiver 42 allows data to travel bi-directionally through the armored and shielded wire 23 in a half duplex manner. A programable logic unit 43, within the interface unit 40, decodes the address and clock and compares the transmitted address in the command serial stream to the local address stored in memory 45. The local address is either electrically programmed before or after the interface unit 40 is placed downhole or hardwired into the interface unit 40 prior to placement downhole.
If the transmitted address in the command serial stream and the stored address in the interface unit 40 are equivalent, and depending upon the operator Ds command/request, the downhole device drive circuit 44 will be energized and the downhole device 41 actuated (i.e., opens, closes, partially opens or closes) or data may be obtained from various downhole sensors including, but not limited to, a temperature sensor 46, pressure sensor 47, fluid sensor 48 and/or downhole device position sensor 49. This data is then transmitted to the downhole control module 30 and the surface control unit 12.
If the transmitted address in the command serial stream does not correspond to the stored address in the interface unit 40, the bi-directional transceiver 42 transmits the command serial stream to the next interface unit 50 downstream. Following this transmission, the transmitter portion of the transceiver 42 is de-energized and the receiver portion is energized. This process continues until the command serial stream reaches the appropriate interface unit containing the identical address as the transmitted address in the command serial stream.
FIG. 3 illustrates an alternative embodiment of the present invention. As in the first embodiment, the alternative embodiment includes a production system 10 comprising, in part, a conventional derrick 11. However, unlike the first embodiment, the alternative embodiment does not require transmission of surface commands since actuation of the downhole device or group of downhole devices is initiated upon the sensing of a preset downhole parameter (e.g., temperature, pressure, flow or change in position of the downhole device) or event.
Preferably, a power supply 12 is located at the surface to generate sufficient power to drive a downhole control unit 40 and at least one downhole device 41. The power from the supply 12 is transmitted via armored and shielded lines 22 extending downward from the surface 13 into the wellbore 20 to the downhole control unit 40 and at least one downhole device 41. However, it is contemplated that power for the power supply can be generated in the wellbore (e.g., by a turbine generator) or supplied by energy storage devices such as batteries (or a combination of one or more power sources).
FIG. 4 illustrates a block diagram of the downhole control unit 40, comprising a sensor device 46 and a drive circuit 44. As mentioned above, the downhole control unit 40 operates autonomously by sensing a preset downhole parameter, (i.e., temperature, pressure, flow, position or other area of interest) and actuating the downhole device 41. For example, in controlling flow through a valve which is prone to heat up or cool down due to pressure differences on either side of the valve, a silicone diode temperature switch or a bi-metal thermostat may be used as the sensing device 46. Upon sensing a preset temperature, the sensor device 46 switches from an open state to a closed state permitting power from lines 24 to reach the drive circuit 44 and activation (e.g., opening, closing, partially opening or partially closing) of at least one downhole device 41 (or multiple downhole devices) based upon the downhole parameter or event.
The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth are possible without departing from the scope and the spirit of the invention. It is intended that the following claims be interpreted to embrace all such modifications and changes.