1. Field of the Invention
The present invention relates generally to the use of electromechanical cable, typically logging cable, in the treatment of wells for enhanced production of petroleum products, such as crude oil, natural gas, distillate and other petroleum constituents. More particularly, the present invention concerns the use of logging cable to accomplish precision location within wells of the various well tools that are employed for well servicing activities. Even more specifically, the present invention concerns one or more processes that are employed to prepare an electromechanical logging cable so that its permanent stretch characteristic is substantially eliminated and permitting a well tool connected with the logging cable to be more precisely located within a well simply by calculating the elastic stretch of the cable.
2. Description of the Prior Art
It is well known in the well drilling and completion industry that wells being drilled must be logged periodically to determine the characteristics of the earth formation and to confirm the location of the drill bit in the earth formation at any point in time. Well logging is typically accomplished by connecting a logging tool to an electromechanical cable, typically referred to as a logging cable, and running the logging tool into the wellbore. In order to accurately locate the logging tool within the wellbore and with respect to the formation various factors must be calculated including the stretch of the logging cable.
Electromechanical cable is typically manufactured with an inner armor having a left hand lay, which is encompassed by an outer armor having a right hand lay. Newly manufactured electromechanical cable typically has elastic stretch characteristics which can be easily calculated, but also has permanent stretch characteristics which are quite difficult to calculate. Each time the electromechanical cable is run down-hole for logging or other well service activities the permanent stretch characteristics change to some extent and adversely affect precision use of the cable, especially for well logging. Consequently, newly manufactured electromechanical cable is not acceptable for accurate well logging since it is difficult to precisely confirm the location of a logging tool within a well. For well logging activities well drilling organizations typically rely on the use of “seasoned” electromechanical cable, i.e., cable that has been run into a deep well and recovered to a spool 10 to 15 or more times.
During each cable run within a deep well a percentage of the permanent stretch characteristics of the cable is depleted and this percentage changes with each cable run. After the cable has been repeatedly run into a deep well and recovered to a cable spool a predetermined number of times, most of the permanent stretch characteristics has been depleted and the cable will have become “seasoned” to the point that only the elastic stretch of the cable need be calculated in order to accurately position a logging tool within a wellbore. Some well drilling companies maintain a deep non-productive well solely for seasoning newly manufactured electromechanical cable. The newly manufactured electromechanical cable must be transported to the designated well and run into the well and retrieved a number of times, for example 10 to 12 times before being transported to a well drilling site for use. Obviously, running and retrieving an electromechanical cable multiple times while doing no income producing work is a time consuming and expensive proposition. Yet, some well drilling organizations maintain a deep well, such as having a depth of 25,000 feet or more, for the sole purpose of facilitating the seasoning of new electromechanical cable to make it ready for accurate well logging and other well service activities.
It is desirable therefore, to provide a method or process and apparatus having the capability of accomplishing accurate and effective seasoning of newly manufactured electromechanical cable in one or more cable processing runs, thus minimizing the time and costs of cable seasoning activities in designated non-productive wells.
It is a principal feature of the present invention to provide a novel method and apparatus for applying controlled stretching and working of a newly manufactured electromechanical cable to remove or dissipate a sufficient amount of the permanent stretch characteristics of the cable to render it suitable for accurate well logging activities.
It is another feature of the present invention to provide a novel method and apparatus for processing electromechanical cable by application of controlled tension for cable stretching and controlled application of heat to the cable to temporarily soften polymer insulation of the typically 7 conductors of the cable and permit relative movement of the metal strands of the inner and outer armor. During tension and heat processing the cable is worked by passing it through the multiple cable grooves of a driven capstan and a braking capstan.
Briefly, the various objects and features of the present invention are realized through the provision of a powered or driven capstan and a braking capstan that are located in spaced relation. Each of the capstans has a pair of spaced sheaves, such as 36″ diameter sheaves, each having an external spiral cable groove receiving multiple wraps, for example 10 to 12 wraps of cable, which prevent slippage of the cable as forces are applied to stretch the cable and remove its characteristics of permanent stretch. The spiral grooves of the capstans has a geometric configuration that is designed to precisely fit the cross-sectional dimension and configuration of the electromechanical cable that is being processed. This feature also prevents slippage of the cable during its processing. The electromechanical cable is withdrawn from a supply spool that is mounted on a turntable that is rotated to loosen the outer armor of the cable prior to application of force to stretch the cable. The supply spool or let-off is oriented in spaced relation with the first of the capstans and is recovered by a take-up spool that is also oriented in spaced relation with the capstans. The take-up spool is also mounted on a turntable that is rotated to re-tighten the outer armor of the cable after the cable has been stretched.
Between the spaced sheaves of the first of the capstans is located a cable heating device through which the electromechanical cable passes during its processing. The cable heater is arranged and controlled to accomplish controlled heating of a predetermined length of the cable to a predetermined temperature while the cable is under controlled tension. This feature relaxes the frictional resistance of the polymer insulation with the metal conductor strands and permits movement of the metal conductors relative to the polymer insulation. The cable heater device may be powered electrically for application of radiant heat to the cable that is moving through the cable heater. Alternatively, the cable heater may be gas fired and arranged to apply radiant heat to the moving cable.
After passing through the cable heater the cable is stretched and is then permitted to cool to ambient temperature so that the polymer insulation returns to its hardened state. If desired, the heated cable may be moved through a cooler device, such as a water cooler or refrigerated cooler, so that cooling and hardening of the electromechanical cable will occur more rapidly.
So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the preferred embodiment thereof which is illustrated in the appended drawings, which drawings are incorporated as a part hereof.
It is to be noted however, that the appended drawings illustrate only a typical embodiment of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
In the Drawings:
Referring now to the drawings and first to
The power driven capstan 22 has a pair of spaced capstan drums 23 and 24, which, like the braking capstan 17, define multiple closely spaced cable grooves 25 that define multiple passes or wraps of cable within the grooves and about the spaced capstan drums as is evident in
Since substantially continuous application of capstan braking generates considerable heat, the drums 18 and 19 of the braking capstan 17 are of hollow construction, each defining a coolant compartment that contains a volume of coolant fluid such as water. A coolant supply and a coolant receptacle are in heat controlling communication with the coolant compartment and are controlled to ensure that heating of the braking capstan drum or drums is maintained within a predetermined range of temperature. Coolant to and from the internal coolant compartment is provided by passages that are located centrally of the drum bearings 23 and are connected with a coolant supply manifold 32.
A drive belt 33 is driven by a motor 34, such as a rotary electric motor, pneumatic motor or rotary hydraulic motor, and is received by drive pulleys 35 and 36 for driving the drums 23 and 24 of the powered capstan. The drums 23 and 24 of the powered capstan also have multiple cable grooves to establish multiple wraps of cable that extend about the drums and prevent slippage of the cable. The cable leaving the power driven drum 23 extends upwardly to a sheave 37 that is supported by a sheave support structure 38 and is then directed to move downwardly for collection by a take-up spool 39. The take-up spool is mounted for rotation by a turntable 40 which is rotated in a direction for tightening the outer armor of the electromechanical cable 14 and returning the cable to the same conditions as when it is removed from the let-off or cable supply drum 12. The driven capstan 30 is also provided with a braking system that is similar or identical, as compared with the braking system of the capstan shown in
Referring again to
As mentioned above, heating of the electromechanical cable 14 while it is maintained under predetermined tension is also an important aspect of the present invention. A predetermined length of the cable is heated to soften the polymer insulation of the conductors so that relative movement of the conductors can occur in response to the tension being applied to the cable by the braking and driven capstans, thereby causing most if not virtually all of the permanent stretch characteristics of the cable to be dissipated, leaving the cable in seasoned condition and ready for use during well logging activities. The cable heater 20 is supported between the rotary cable drums of the braking capstan as shown in
The treated electromechanical cable 14 is then passed about a return sheave 37 that is rotatably supported by a sheave support structure 38. The take-up reel or drum 39 is rotatably supported by a turntable 40 and serves to receive the treated and seasoned electromechanical cable 14. Starting and end portions of the cable will not have been adequately treated by application of tension and heat and thus will need to be discarded or electronically marked so that the treated and seasoned section of the cable can be easily identified as the cable is used for well logging and many other activities where the tensile strength and permanent stretch characteristics must be taken into consideration.
Electromechanical cable for well logging and for other purposes are manufactured in many different forms.
In
In
A length of electromechanical cable is provided on a supply reel or drum 12 that is mounted for rotation by a turntable 13. As the cable is pulled from the supply drum 12 upwardly about the cable direction sheave the turntable 13 is rotated in a direction for loosening the outer armor. The outer cable armor which is composed of multiple wires that are wrapped in spiral fashion about the insulation or other wires of the cable with the spiral having a right hand lay. After the cable has been retrieved from the supply reel and loosened by rotation of the turntable 13, multiple wraps of the cable are positioned within the external cable grooves of the spaced drums of a braking capstan. As the last wrap of electromechanical cable is pulled from the first cable drum of the braking capstan a cable heater located between the drums of the braking capstan heats a section of the cable to sufficient temperature for softening of the polymer insulation of the conductors of the cable. The braking action of the braking capstan and the pulling force of the power driven capstan cause this predetermined section of the cable to be subjected to tension, thus subjecting the loosened cable to stretching activity to remove substantially all of the permanent stretch characteristics of the cable. Loosening of the electromechanical cable together with the application of controlled heating in the loosened condition of the cable enhances the cable stretching capability. Subsequent cooling of the heated section of cable will permit the polymer insulation to harden to its original condition, thus stabilizing the stretched cable so that the resulting treated cable will remain with its characteristic of permanent stretch removed. The multiple external cable grooves of each pair of spaced cable drums of the braking and power driven capstans effectively prevents slippage of the cable during the precisely controlled cable stretching process.
The cable is loosened to start the tension and heat responsive seasoning process. The electromechanical cable is supplied on a let-off drum that is mounted for rotation by being supported by a rotary turntable. As the electromechanical cable is paid out from the let-off or cable supply drum the turntable is rotated in a direction for loosening the spiral wound outer armor of the cable and for tightening the oppositely wound inner armor. The leading end of the electromechanical cable is contacted by a tension control sheave and is looped about a return sheave and is connected to a take-up reel or drum. The electromechanical cable is also passed through or in close proximity with a heater unit that is located between the drums of the braking capstan and may also be passed through or in close proximity with a cable cooling unit the is located downstream from the heater unit. The cable remains torque balanced during the stretching or seasoning process so that the torque characteristics of the finished cable are substantially the same as when the cable seasoning process is started.
With the brake of the braking capstan set for application of predetermined tension to the electromechanical cable and with the heater unit in operation, the driven capstan is actuated to move the cable substantially continuously and to apply predetermined tension to the cable as it is moved through or in close proximity with the heater unit to soften the polymer insulation of the conductors and permit relative movement of the conductors with respect to the polymer insulation surrounding the conductors. The application of heat and tension to the cable causes the permanent stretch characteristics of the cable to be virtually dissipated, leaving the cable seasoned for accurate and efficient use during well logging activities.
Though a pair of double drummed capstans are preferably employed for applying controlled tension to the electromechanical cable during processing for dissipation of the permanent stretch characteristics of the cable, it is to be understood that the present invention is not restricted or limited to this particular arrangement of cable stretching apparatus. The present invention is practiced by employing any suitable apparatus for application of controlled tension to the electromechanical cable and by applying predetermined heat to the cable while it is under tension to thus permit cable stretching for the purpose of removing or dissipating the permanent stretch characteristics of the cable. controlled movement of the cable conductors relative to the polymer coating that is present and then causing hardening of the polymer coating while the cable is maintained under tension. As the cable is being processed the torque characteristics of the cable remains balanced. As the cable seasoning process is completed the cable is passed about tension control and return sheaves and is then recovered to a take-up spool or drum, thus readying the cable for shipment to a site for use in well logging or other well servicing activities.
In view of the foregoing it is evident that the present invention is one well adapted to attain all of the objects and features hereinabove set forth, together with other objects and features which are inherent in the apparatus disclosed herein.
As will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its spirit or essential characteristics. The present embodiment is, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within the meaning and range of equivalence of the claims are therefore intended to be embraced therein.