Patent Application
20080099204
1. Field of the Invention
This invention, in various embodiments, relates generally to time delay apparatuses and, more specifically, to apparatuses comprising an electronic time delay assembly suitable for use in initiating explosives and propellants, as well as systems including an electronic time delay system and methods of operation thereof.
2. State of the Art
Perforating systems used for completing an oil or gas well are well known in the art. Well bores, which are drilled through earth formations for extracting hydrocarbons in the form of oil and gas, are conventionally lined by inserting a steel casing or liner into the well, and cementing at least a portion of the casing or liner in place to prevent migration of high pressure fluids up the well bore outside the casing or liner. The subterranean formation or formations having the potential to produce hydrocarbons are directly linked with the interior of the casing or liner by making holes, referred to as perforations, through the wall thereof, through surrounding cement and into the formation. Perforations are conventionally made by detonating explosive shaped charges disposed inside the casing at a location adjacent to the formation which is to produce the oil or gas. The shaped charges are configured to direct the energy of an explosive detonation in a focused, narrow pattern, called a “jet,” to create the holes in the casing.
Conventionally, well perforation systems include a firing head and a perforating gun, both of which are suspended from, and lowered into, a well on a conveyance device such as a tubular string which may comprise so-called “coiled tubing.” Well perforation systems also conventionally comprise various components including, for example, a packer, a firing pin, an explosive booster, and a time delay device. A time delay device is needed to provide an operator sufficient time between a pressurizing event and a subsequent perforation event in order to pressure balance a well for perforation to secure optimal flow of oil or gas flow into the well. Pressure balancing a well is an important procedure because failure to do so, or if the procedure is done incorrectly, may lead to equipment damage as well as possible injury to equipment operators if insufficient hydrostatic pressure is present in the casing or liner or, if too great a hydrostatic pressure is present, the producing formation exposed by the perforating operation may be contaminated or production compromised or prevented without remedial measures. Additionally, with a properly pressure-balanced well, producing formation fluid will immediately and rapidly flow upward through the interior of the tubular string and toward the earth's surface in an appropriate, controlled manner. Therefore, it is important that the timing delay device employed be reliable and accurate in order to allow for adequate time to pressure balance a well. Time delay devices currently used in the art employ pyrotechnic time delay fuses. As described below in greater detail, pyrotechnic fuse-based time delay devices have reliability and accuracy concerns, as well as time limitations which may eventually lead to greater complexity and increased costs for customers of the oil tool industry.
As mentioned above, conventional perforating systems may provide for a pyrotechnic time delay device 30 located within firing head 28. The pyrotechnic time delay device 30 provides for a time delay between the initiation of the firing head 28 and the subsequent firing of the shaped charges carried by the perforating gun 34 in order to, as described above, pressure balance the well 10 for optimal perforation. Pyrotechnic time delay devices as known in the art provide a maximum time delay of eight minutes. Therefore, in order to achieve longer delays, an operator is forced to string multiple pyrotechnic time delay devices together in a series formation. For example, additional delays may be coupled together so as to achieve a longer delay timer.
Due to the time and expense involved in perforating well bores and the explosive power of the devices used, it is essential that their operation be reliable and precise. Stringing together multiple pyrotechnic time delay devices diminishes the system's reliability and increases the system cost and complexity.
There is a need for methods and apparatuses to provide increased system reliability and flexibility of operation of well perforating systems. Specifically, there is a need for a time delay device used in a well perforating system to allow for adequate and precise timing of operation of a well perforating system in order to pressure balance a well for optimal perforation results. Such a time delay device would desirably exhibit a high level of reliability at a low level of cost and complexity of fabrication
An embodiment of the present invention comprises a time delay apparatus comprising an input assembly including an element positioned to be displaced to enable a power source connection. The time delay apparatus further includes an electronic time delay circuit operably coupled to the input assembly and configured to provide a time delay responsive to the enabled power source connection and initiate a fire command upon completion of the time delay.
Another embodiment of the present invention includes a well perforation system including a conveyance device, a perforating gun suspended from the conveyance device, a firing head suspended from the conveyance and operably coupled to the perforating gun, and a time delay apparatus within the firing head. The time delay apparatus includes an input assembly including an element positioned to be displaced to enable a power source connection, an electronic time delay circuit operably coupled to the input assembly and configured to provide a time delay responsive to an enabled power connection and initiate a fire command upon completion of the time delay.
Yet another embodiment of the present invention includes a method of using an electronic time delay apparatus within an explosive or propellant system. The method comprises applying an external force to an element to displace the element responsive to the external force, connecting a power source to an electronic time delay circuit responsive to the displacement of the element, providing an electronic time delay responsive to connection of the power source; and increasing a voltage from the power source to a predetermined, higher threshold firing voltage after the electronic time delay.
In the drawings:
The present invention, in various embodiments, comprises apparatuses and methods of operation for an electronic time delay assembly suitable for use within an explosive or propellant system configured, by way of nonlimiting example, as a well perforating system to address the reliability concerns, as well as the cost and complexity issues associated with conventional time delay devices.
In the following description, circuits and functions may be shown in block diagram form in order not to obscure the present invention in unnecessary detail. Conversely, specific circuit implementations shown and described are examples only and should not be construed as the only way to implement the present invention unless specified otherwise herein. Additionally, block definitions and partitioning of logic between various blocks is exemplary of a specific implementation. It will be readily apparent to one of ordinary skill in the art that the present invention may be practiced by numerous other partitioning solutions. For the most part, details concerning timing considerations and the like have been omitted where such details are not necessary to obtain a complete understanding of the present invention and are within the abilities of persons of ordinary skill in the relevant art.
In this description, some drawings may illustrate signals as a single signal for clarity of presentation and description. It will be understood by a person of ordinary skill in the art that the signal may represent a bus of signals, wherein the bus may have a variety of bit widths and the present invention may be implemented on any number of data signals including a single data signal.
In describing embodiments of the present invention, the systems and elements incorporating embodiments of the invention are described to facilitate an enhanced understanding of the function of the described embodiments of the invention as it may be implemented within these systems and elements.
The packer 132 provides a structure for sealing between the exterior of tubing string 136 and a wall 112 of casing 104 which may also be referred to as a casing bore wall or well bore wall 112. The resulting seal provides a well annulus 138 between the tubing string 136 and well bore wall 112 above the packer 132 and an isolated zone 116 of well 102 below packer 132. Perforating system 110 also includes a vent 140 located below the packer. Vent 140 allows for hydraulic communication between isolated zone 116 and tubing bore 142 to ensure fluid pressures within the tubing bore 142 and isolated zone 116 are substantially equal.
The perforating gun 124 is suspended from the tubing string 136 in the isolated zone 116 adjacent to the subsurface formation 120 which is to be perforated. The perforating gun 124 is configured to detonate and fire shaped charges to create holes, or perforations 122, in casing 104 and into the surrounding cement 106 and formation 120.
Also suspended from the tubing string 136 and located above the perforating gun 124 is the firing head 128. Firing head 128 includes, among other components, an electronic time delay assembly 126 according to an embodiment of the invention. As described in detail below, electronic time delay assembly 126 provides multiple safety features including various circuit and trigger isolation features as well as mechanical isolation features. Additionally, the electronic delay assembly 126 provides a time delay so as to allow an operator sufficient time to pressure balance well 102 for optimal perforation. Stated another way, the time delay allows time for an operator to alter the pressure in isolated zone 116 to the requirements of the formation fluids in formation 120. Electronic time delay assembly 126 provides this delay time capability by enabling longer, and more highly selectable, time delays in comparison to conventional pyrotechnic time delay uses. By way of example only, electronic time delay assembly 126 may provide a selected time delay duration of up to, for example, at least ten hours.
As illustrated in
Firing pin 301, which is disposed in firing pin bore 324, has a longitudinal axis L and may include a pin contact 306 located extending from at one end of firing pin 301. The opposite end 300 of firing pin 301 is configured to receive a firing stimulus from an external force, such as, for example only, hydraulic pressure in isolated zone 116 or an impact force from a dropped weight. As shown, firing pin 301 is configured for pressure actuation and includes an annular seal 336 disposed thereabout in annular groove 338. Sufficient external force acting on firing pin 301, and specifically on end 300, shears pins 710, 712 of shear pin assembly 302 and allows the firing pin 301 to be displaced to the right (as the drawing is oriented), or downwardly within well perforating system 110 (see
As described above, input module 206 acts as an electrical switch that requires an external force or stimulus in order to be activated. This configuration provides for a significant safety feature by isolating the battery 408 from the electronic time delay circuit 212 (
Electronic time delay device 500 comprises an oscillator 402 which oscillates at a selected frequency and is operably coupled with counter device 417. Oscillator 402 and counter device 417 are configured to count a desired time delay. By way of example, and not limitation, oscillator 402 may comprise a 75 KHz crystal oscillator. Counter device may comprise, by way of example only, a pair of CD4060B binary counter/divider devices 414, 415, offered by Texas Instruments of Dallas, Tex. Depending on the desired time delay, a single counter device may be used or multiple counter devices may be coupled together in series to achieve a longer delay. For example, if an eight-minute time delay is desired, a single eight-minute counter device may be used. Similarly, if a thirty-minute time delay is desired, a thirty-minute counter device may be use. On the other hand, if a thirty-minute counter device is unavailable, then a pair of counter devices, with a total delay time of thirty minutes may be coupled in series in an adder configuration to count the desired delay. For example only, one twenty-minute counter/divider device may be coupled with a ten-minute counter, or alternatively, two fifteen-minute counters may be coupled together to produce the desired thirty-minute delay. Alternatively, a pair of counter devices may be coupled in series in a multiplier configuration in order to achieve the desired time delay. For, example only, if a thirty-minute time delay is desired using a multiplier configuration, a first device would count up to fifteen minutes and upon completion of the fifteen minutes, a second device would increment to a value of one. Subsequently, the first device would again count up to fifteen minutes, and upon completion, the second device would increments to a value of two. Therefore, in a multiplier configuration example, with a 75 KHz oscillator, the first device is only required to count up to fifteen minutes (67,500,00 clock cycles) and the second device is only required to count to a value of two seconds (150,000 clock cycles).
As opposed to conventional pyrotechnic time delays, the embodiment of the invention may, for example only, provide time delays from a short duration such as eight minutes up to a much longer duration of, for example, a number of hours. This capability reduces cost and complexity and increases operational flexibility and reliability in comparison to conventional pyrotechnic se-type time delay devices because only one time delay unit and setting and only one detonation transfer event is required. Additionally, because of the high level of accuracy of electrical components, the timing accuracy and precision of an electronic time delay is improved over a conventional pyrotechnic time delay fuse, which may suffer from unpredictable burning rates.
As illustrated in
The operation of circuit 212 illustrated in
Trigger 406 provides a significant safety feature of the embodiment of the invention by isolating the initiator 418 from the circuit 212 which, in turn, provides isolation and safety from electrostatic discharge (ESD) and stray voltage which could result in premature detonation. As a further safety feature the oscillator 402 of circuit 212 may be configured to continue oscillating after the time delay has passed and after a voltage is applied at initiator 418. Therefore, any residual energy stored in battery 40S will be drained by the charging and de-charging oscillator. Additionally, one embodiment of the invention may comprise a resistor 522 operably coupled between battery 408 and a ground voltage VSS. Therefore, any residual energy stored in battery 408 may be drained to ground voltage VSS through resistor 522.
Whereas one embodiment of the electronic time delay circuit 212 is shown in
Returning to
Referring again to
While embodiments of the electronic time delay apparatus of the present invention have been described and illustrated as having utility with a well perforating system, it is not so limited. For example, the electronic time delay apparatus of the present invention may be employed, in various embodiments, to initiate other explosive or propellant systems within a well bore, such as tubing or casing cutters. In addition, it is contemplated that embodiments of the electronic time delay apparatus of the present invention will find utility in subterranean mining and tunneling operations, in commercial, industrial and military demolition operations, in military ordnance, and otherwise, as will be readily apparent to those of ordinary skill in the relevant arts.
Specific embodiments have been shown by way of example in the drawings and have been described in detail herein; however, the invention may be susceptible to various modifications and alternative forms. It should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
