Patent Application
20140251619
1. Field
An apparatus and method for providing a time delay in injection of pressured fluid into a geologic formation. More specifically, it is a toe valve activated by fluid pressure that opens ports after a predetermined time interval to allow fluid to pass from a well casing to a formation.
2. Background
It has become a common practice to install a pressure responsive opening device at the bottom or toe of a casing string within a horizontal well bore. These devices are made up and run as an integral part of the casing string. After the casing has been cemented and allowed to solidify, the applied surface pressure is combined with the hydrostatic pressure and the pressure responsive valve is opened. The combination of hydrostatic and applied pressure is customarily used to overcome a number of shear pins or to overcome a precision rupture disc. Once communication with the well bore [i.e., area outside of the casing] is achieved, the well can be hydraulically fractured or the valve can be used as an injection port to pump down additional wire line perforating guns, plugs or other conveyance means such as well tractors. Other known methods of establishing communication with the cemented and cased well include tubing conveyed or coil tubing conveyed perforators. These are all common methods to achieve an injection point but require increased time and money.
An apparatus and method to provide time-delayed injection of pressurized fluid from a well casing to a geological formation, the apparatus comprising:
The method in broad aspect is the use and activation of the apparatus as described.
a is a plan view t of an apparatus of an embodiment of the invention.
b is a plan view of a cross section of an apparatus of an embodiment of the invention.
The present invention is an improved toe valve apparatus and method to allow fluid to be pressured through ports in an oil or gas well casing wall (and cement) into a geologic formation.
The apparatus provides time-delayed injection of pressurized fluid through opening in a well casing to a geological formation comprising:
The present invention represents several improvements over conventional pressure responsive devices—improvements that will be appreciated by those of ordinary skills in the art of well completions. The greatest limitation of current devices is that the sleeve or power piston of the device that allows fluid to flow from the casing to a formation (through openings or ports in the apparatus wall) opens immediately after the actuation pressure is reached. This limits the test time at pressure and in many cases precludes the operator from ever reaching the desired casing test pressure. The present invention overcomes that limitation by providing a hydraulic delay to afford adequate time to test the casing at the required pressure and duration before allowing fluid communication with the well bore and geologic formation. This is accomplished by slowly releasing a trapped volume of fluid through a hydraulic metering chamber that allows a piston covering the ports to move to a position where the ports are uncovered. This feature will become even more advantageous as federal and state regulators mandate the duration or dwell time of the casing test pressure. The metering time can be increased or tailored to a specific test requirement through manipulation of the fluid type, fluid volume and by altering the flow rate of the hydraulic liquid flow restrictor.
A second advantage of this invention is that two or more valves can be installed (run) as part of the same casing installation. This optional configuration of running two or more valves is made possible by the delay time that allows all of the valves to start metering before any of the valves are opened. The feature and option to run two or more valves in a single casing string increases the likelihood that the first stage of the well can be fracture stimulated without any well intervention whatsoever. Other known devices do not allow more than a single valve to operate in the same well since no further actuation pressure can be applied or increased after the first valve is opened.
A third significant advantage is that in the operation the valve, the ports are opened slowly so that as the ports are opened the liquid is injected to the cement on the outside of the casing in a high pressure jet, thus establishing better connection to the foundation. The jet begins as a highly effective pinpoint cutting jet and enlarges as the ports are opened to produce an effect of a guide-hole that is then enlarged.
Referring to the Figures,
The rupture disc 23 is the activation device that sets the valve opening operation in play. When ready to operate (i.e., open the piston), the casing pressure is increased to a test pressure condition. This pressurization process ruptures the rupture disc 23 and fluid at casing pressure (hydrostatic, applied or any combination) enters the chamber immediately below and adjacent to the piston 5. This entry of fluid causes the piston 5 to begin moving. This fluid movement allows the piston to move inexorably closer to an open position. In actual lab and field tests the piston movement of about 4.5 inches begins to uncover the openings 27-29 and 28. These openings are closed or sealed off from the casing fluid by the piston 28. As piston 28 moves toward the open and final position, the slots, 28, are uncovered allowing fluid to flow through openings 25, 26 and 27 through slots 28. Thus, the restrained movement of the piston allows a time delay from the time the disc is ruptured until the slots uncovered for fluid to pass. This movement continues until the piston has fully opened. As fluid pressure increases through port 14 it moves piston 5 into the fluid chamber 32. Piston 5 surrounds the inter wall of the apparatus 29. Hydraulic fluid in the fluid chamber restrains the movement of the piston. There is a hydraulic flow restrictor 22 that allows fluid to pass from chamber 32 to lower pressure chamber 34. This flow restrictor controls the rate of flow of fluid from chamber 32 to chamber 34 and thereby the speed of the movement of the piston as it moves to the full open position. Items 28 are the slots in the apparatus mandrel that will be the passageway for fluid from the casing to the formation.
In general the apparatus will be constructed of tool steel of about the same type used incasing.
A prototype apparatus had the general dimensions of 60 inches in lengths, with a nominal outside diameter of 6.5 inches and an inside diameter of 3.75 Inches. Other dimensions as appropriate for the well and operation in which the apparatus is intended to be used are intended to be included in the invention and may easily be determined by those skilled in the art.
In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification is, accordingly, to be regarded in an illustrative rather than a restrictive sense. Therefore, the scope of the invention should be limited only by the appended claims.
