US20070044672A1 - Methods and systems to activate downhole tools with light - Google Patents

Abstract

The present invention comprises a system and methods to actuate downhole tools by transmitting an optical signal through an optical fiber to the downhole tool. The optical signal can comprise a specific optical signal frequency, signal, wavelength or intensity. The downhole tool can comprise packers, perforating guns, flow control valves, such as sleeve valves and ball valves, samplers, sensors, pumps, screens (such as to expand), chemical cutters, plugs, detonators, or nipples.

Description

BACKGROUND
• The invention generally relates to the activation of downhole tools. More particularly, the invention relates to methods and systems used to activate downhole tools with light.
• Downhole tools are typically activated by mechanical, electrical, or hydraulic means. Each of these types of actuation have potential problems. Mechanically actuated tools normally rely on translation or torsion of the tube or cable connecting the tool to the surface. However, movement on the surface does not always translate into movement down-hole at the location of the tool. Furthermore, the movement of the tool may remove it from the position where the actuation is required. Electrically actuated tools need cables in which electrical insulation is required. The insulation is often bulky and compromises the strength of the cable. Electrical actuation is also sensitive to spurious currents and interference that could result in undesirable actuation. Hydraulically actuated tools also suffer from the risk of undesirable actuation or actuation at the wrong depth. The local pressure at the tool is difficult to control in some circumstances. All the above require complex control mechanisms to prevent undesirable activation.
• Moreover, reliability and safety are important when operating downhole tools, since a faulty tool can result in a substantial increase in costs and time for an operator and can also sometimes endanger the lives of workers. These issues are heightened when they relate to perforating guns, as these tools must have a very high level of reliability and safety.
• Thus, there exists a continuing need for an arrangement and/or technique that addresses one or more of the problems that are stated above.
SUMMARY
• The present invention comprises a system and methods to actuate downhole tools by transmitting an optical signal through an optical fiber to the downhole tool. The optical signal can comprise a specific optical signal frequency, signal, wavelength or intensity. The downhole tool can comprise packers, perforating guns, flow control valves, such as sleeve valves and ball valves, samplers, sensors, pumps, screens (such as to expand), chemical cutters, plugs, detonators, or nipples.
• Advantages and other features of the invention will become apparent from the following description, drawing and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows one embodiment of the activation system and methods.
• FIG. 2 shows a flow chart of the method used to activate downhole tools.
• FIGS. 3-7 illustrate different embodiments of the optical signal.
• FIG. 8 illustrates another embodiment of the activation system and methods.
• FIG. 9 shows a generic illustration of the receptor of the present invention.
• FIGS. 10-11 show different embodiments of the receptor.
• FIG. 12 shows another embodiment of the activation system and methods.
• FIGS. 13-14 illustrate different embodiments used to actuate multiple downhole tools.
• FIG. 15 illustrates an embodiment used to convert optical to electrical power for downhole tools.
• FIG. 16 illustrates an embodiment used to convert optical to chemical power for downhole tools.
• FIG. 17 illustrates an embodiment used to convert optical to mechanical power for downhole tools.
• FIGS. 18-19 show different embodiments of a perforating gun assembly activated by light.
• FIGS. 20-21 illustrate different embodiments of the firing device shown inFIG. 19.
• FIG. 22 shows another embodiment of the activation system and methods deployed with a casing collar locator.
DETAILED DESCRIPTION
• FIG. 1 shows one embodiment of this invention in which light is transmitted through an optical fiber to activate a downhole tool.FIG. 1 is a schematic of alogging system5 that can be used downhole. It includes anoptical fiber10 that may be deployed in aconduit12, with theconduit12 removably insertable in awellbore14 by way of areel16 loaded and transported in atruck18. Theoptical fiber10 is connected to a surface opto-electronic unit20 (with an optical transmitter) that transmits light into theoptical fiber10 and that also receives and analyzes light and reflections therefrom. Thelogging system5 includes at least onelogging tool15 and can also include at least onedownhole power source16, which can be a chemical battery, an optical to electrical power convertor, or a hydraulic turbine to electrical power convertor.Subcomponents17 of thelogging tool15 may be powered by thedownhole power source16 and may be connected to theconduit12.
• InFIG. 1, apacker150 andperforating gun152 are also connected toconduit12 and may be actuated via optical signals transmitted through theoptical fiber10. Thepacker150 may actuate to grip and seal against the wellbore walls, or thereafter, to ungrip and unseal from the wellbore walls. Also, perforatinggun152 may actuate to shoot theshaped charges155 and createperforations154 in the wellbore. Each of theperforating gun152 andpacker150 comprises adownhole tool2. Other downhole tools2 (not shown) may also be connected to theconduit12 and activated with an optical signal, including flow control valves, such as sleeve valves and ball valves, samplers, sensors, pumps, screens (such as to expand), chemical cutters, plugs, detonators, or nipples.
• The system illustrated inFIG. 1 is one way in which the present invention may be implemented in a wellbore. Instead of being part of an intervention orlogging system5 as shown inFIG. 1, the present invention may also be implemented on apermanent completion60, such as the one shown inFIG. 12. In this embodiment,production tubing62 may be deployed inwellbore14. Apacker50 maintainstubing62 in place in relation towellbore14. At least one downhole tool2 (as described above) is deployed onproduction tubing62, below or above thepacker50.Conduit12 is attached toproduction tubing62 typically by way of fasteners (not shown) and typically on the outside oftubing62.Optical fiber10 is inserted within theconduit12 and is in functional connection with theunit20.Optical fiber10 is also in functional connection with thetools2 which are meant to be activated byoptical signal40.
• Thedownhole tools2 described in the previous paragraphs may be activated by optical signals sent through theoptical fiber10. For instance, thedownhole tool2 may be functionally connected to theoptical fiber10 so that a specific optical signal frequency, signal, wavelength or intensity sent through theoptical fiber10 by theunit20 activates thedownhole tool2. Or, thedownhole tool2 may be functionally connected to theoptical fiber10 so that the presence of a certain amount of light in theoptical fiber10 activates thedownhole tool2.
• FIG. 2 shows the general sequence in which light is launched into an optical fiber at30 resulting in the activation of adownhole tool2 at32. In one embodiment and as previously disclosed, an optical signal with a specific characteristic is required to activate thedownhole tool2. In this case, which is beneficial for purposes of safety, therelevant downhole tool2 is configured so that it receives light from theoptical fiber10, but thedownhole tool2 is only activated if the light received comprises or includes a specific optical signal. The optical signal can have a variety of embodiments.
• As shown inFIG. 3,optical signal40 can comprise a certain intensity reached by the light traveling through the optical fiber. For instance,optical signal40 may comprise acontinuous lightwave42 whose intensity is raised up to a level “A”, at which point the relevantdownhole tool2 is activated.FIG. 4 is similar toFIG. 3, except that theoptical signal40 in this case is acontinuous lightwave42 whose intensity is lowered down to a level “A”, at which point the relevantdownhole tool2 is activated.
• FIGS. 5 and 6 are combinations of theoptical signals40 ofFIGS. 3 and 4. InFIG. 5, acontinuous lightwave42 begins at an intensity level “L”, is then raised at43 to an intensity level “H”, and is subsequently lowered at44 again to the intensity level “L”.Downhole tool2 is not activated until thecontinuous lightwave42 is lowered again to the intensity level “L” afterstep44. InFIG. 6, acontinuous lightwave42 begins at an intensity level “H”, is then lowered at43 to an intensity level “L”, and is subsequently raised again at44 to the intensity level “H”.Downhole tool2 is not activated until thecontinuous lightwave42 is raised again to the intensity level “H” atstep44.
• InFIGS. 5 and 6, it is the multiple intensity levels that trigger the activation; therefore, thedownhole tool2 would have components, such as a microprocessor, to monitor such transitions. Moreover, it is understood that a sequence of different intensities, regardless of whether they are as shown in the Figures, may be used as a triggering signal. For instance, inFIG. 5, after reaching level “H”, theoptical signal40 may comprise raising the intensity again to a level higher than “H”. Alternatively, inFIG. 6, after reaching level “L”, theoptical signal40 may comprise lowering the intensity again to a level higher than “L”. Such intensities need only be defined or pre-programmed as the specific triggering signal at thedownhole tool2.
• Theoptical signal40 ofFIG. 7 comprises at least onelight pulse46. Theoptical signal40 may also comprise a plurality oflight pulses46. In one embodiment, just the presence of apulse46 acts as theoptical signal40. In another embodiment, the presence of a train or a specific number ofpulses46 acts as theoptical signal40. Eachpulse46 may have a specific time duration as well as a specific characteristic (such as intensity and/or wavelength), such that only a pulse that lasts a specified amount of time and/or includes light of a specific intensity or wavelength is considered a valid, triggeringpulse46.
• In other embodiments, the presence of a signal (as previously disclosed) having a specific characteristic acts as theoptical signal40. The specific characteristic can comprise a specific frequency, wavelength, pulse code, or intensity. Specific wavelengths, for instance, may be keyed on by the use of at least one filter on theoptical fiber10. Alternatively, a specific intensity may be focused on by including a material on thefiber10 that ignites or deteriorates when exposed to such particular intensity.
• Also, in other embodiments, theoptical signal40 may comprise a combination of at least two of the previously disclosed signals.
• To enable the transmission of suchoptical signals40, the unit20 (as seen inFIG. 8) includes an optical transmitter which transmits theoptical signal40 through optical fiber10 (which is deployed in wellbore14). Depending on the type ofoptical signal40,unit20 may comprise a laser, such as a semiconductor laser, which is preferred at moderate power levels. However, certain embodiments require high powers for which other types of laser are especially appropriate, such as fibre lasers (e.g. based on Er-doped fibre) which are able to deliver significant intensity levels into an optical fibre. In certain embodiments other sources, such as light emitting diodes may be appropriate.
• To receive theoptical signal40, thedownhole tool2 includes areceptor50 which receives theoptical signal40 fromoptical fiber10. As shown inFIG. 9,receptor50 is functionally connected to theoptical fiber10.Receptor50 receives theoptical signal40, verifies it is the correct triggering signal, and subsequently activates or enables the activation of thedownhole tool2. The verification step may be performed by comparing the signal received to the correct triggering signal or by incorporating components that only function when exposed to the correct triggering signal.
• In one embodiment as shown inFIG. 10,receptor50 comprises amicroprocessor54 that processes theoptical signal40, determines whether theoptical signal40 matches a pre-programmed triggering signal, and, if there is a match, themicroprocessor54 activates or enables the activation of thedownhole tool2.Microprocessor54 may be functionally linked to astorage56 and acontroller58.
• Microprocessor54 may comprise an optical arrangement that may contain a combination of filters or lenses or other optical devices. It may comprise an analog or digital circuit. It could be a simple transistor or a complex digital microprocessor.Storage56 may comprise a programmable computer storage unit or an analog or digital circuit.Controller58 may comprise a mechanical trigger, a hydraulic valve, an explosive detonator, precursor chemical reaction, a thermal sensitive device, an element that bends or contracts or expands under light or light generated heat, an explosive, a pressurized vessel, a vacuum chamber, or a spring.
• The pre-programmed triggering signal may be stored instorage56 to enablemicroprocessor54 to access such pre-programmed triggering signal and compare it against the obtainedoptical signal40. If a match exists, themicroprocessor54 may activatecontroller58 which may actuatedownhole tool2. Themicroprocessor54 is, in one embodiment, powered by adownhole battery60. In other embodiments,microprocessor54 is powered by theoptical fiber10 or by an independent electrical line (not shown).
• In another embodiment as shown inFIG. 11,receptor50 comprises anactuator62 that actuates thedownhole tool2 directly upon reception of the correctoptical signal40, but does not compare the receivedoptical signal40 to a pre-determined signal (as is the case with the embodiment ofFIG. 10). Theactuator62 may, for instance, actuate thedownhole tool2 if theoptical signal40 includes a specific characteristic, as the term was previously described.
• In either embodiment ofFIG. 10 orFIG. 11, multipledownhole tools2 may be connected and actuated via theoptical fiber10. In one embodiment, each of thedownhole tools2 is functionally connected to theoptical fiber10. In another embodiment pursuant toFIG. 10, oneoptical fiber10 is functionally connected to a microprocessor54 (andstorage56 and controller58) which manages the actuation of the multipledownhole tools2 via thecontroller58. The triggering signals for eachdownhole tool2 are saved in thestorage56.Microprocessor54 compares theoptical signal40 obtained from theoptical fiber10 with the stored triggering signals from each of thedownhole tools2. If there is a match,microprocessor54, throughcontroller58, activates the relevantdownhole tool2.
• In an alternative embodiment, themicroprocessor54 andstorage56 can be replaced with a hard-wired recognition circuit (not shown), which may consist of an electrical circuit designed to pass only a specific characteristic of theoptical signal40 to activate acorresponding tool2. For instance, the characteristic may be a modulation frequency applied to the optical carrier.
• In another embodiment as shown inFIG. 13, optical filters64-70 may be used to selectively activate a plurality ofdownhole tools2 with a singleoptical fiber10. For instance, each optical filter64-70 may allow a specific wavelength to pass therethrough to the relevantdownhole tool2. The wavelength that passes through the relevant filter can therefore serve as theoptical signal40. As long as each of the filters64-70 passes a different wavelength, then thedownhole tools2 can be activated selectively.
• Similarly, in the embodiment shown inFIG. 14, optical couplers72-76 may be used to selectively activate a plurality ofdownhole tools2 with a singleoptical fiber10. For instance, each optical coupler72-76 may be selected so that only a specific wavelength is diverted to a specificdownhole tool2. The embodiment ofFIG. 14 is comparatively more efficient than that ofFIG. 13 since the optical power intended for a particular tool (ofFIG. 14) is passed to the relevant tool with low insertion loss. It may be desirable to insert additional filters in the embodiment ofFIG. 14 similar to those filters64-70 shown inFIG. 13 in order to improve the rejection of the couplers72-76.
• The light being transmitted through theoptical fiber10 may be converted at thedownhole tool2 into electrical energy, chemical energy (including explosive energy), or mechanical energy (including hydraulic energy). Each of these types of energy may then be utilized or harnessed to activate or to result in the activation of the relevantdownhole tool2.
• Optical energy may be converted to electrical energy by at least onephotodiode80 as shown inFIG. 15. Thephotodiode80 generally receives light from theoptical fiber10 and converts it to electrical energy which is then transmitted vialine82 to an initiator circuit (such as themicroprocessor54 ofFIG. 10 or its hard-wired equivalent).
• Optical energy may be converted to chemical energy by an opticallyreactive chemical chamber90 as shown inFIG. 16.Chamber90 includes an opticallyreactive substance92 as well as an environment to enable the reaction ofsubstance92 when it is subjected to light transmitted throughoptical fiber10. Once subjected to light,substance92 reacts (such as by heating, exploding, or deteriorating) which reaction causes or enables the activation of the relevantdownhole tool2. An explosion withinchamber90 can, for instance,sheer pin94 enablingpiston96 to move and activate downhole tool2 (such as the setting of a packer).
• Optical energy may be converted to mechanical energy by apiezoelectric stack100 as shown inFIG. 17. In this case, thestack100 may be placed in sequence after the at least onephotodiode80 as described inFIG. 15. Electrical energy converted by the at least onephotodiode80 is transmitted to thestack100, which stack100 then expands in size (as shown by dashed lines102) partaking in mechanical movement. The mechanical movement of thestack100 causes or enables the activation of the relevantdownhole tool2. For instance, movement of thestack100 may also cause movement ofarm104, which arm in the unexpanded state maintains a hydraulic circuit (not shown) closed but in the expanded state opens the circuit. The open hydraulic circuit then causes activation of thedownhole tool2.
• FIGS. 18 and 19 are two examples of downhole tools that may be activated using light as previously described. Although both of the examples are perforating guns, it is understood that other tools may also be activated using similar methods.
• FIG. 18 shows agun assembly200 including anoptical fiber202, afilter204, an optical toelectrical power converter206, anelectrical connection207, afiring circuit208, aprima cord210, and at least oneshaped charge212. Anoptical signal40 is transmitted throughoptical fiber202 to thegun assembly200.Filter204 can be added at the end of theoptical fiber202 to improve safety by preventing optical radiation of wavelength different from the one provided by the surface unit (such as20) controller by the operator from reaching theconverter206.Converter206, which for instance can be a 12 V photovoltaic power converter, receives the optical power and converts it into electrical power. The electric power is then transmitted throughelectrical connection207 to thefiring circuit208. Thefiring circuit208 then ignites theprima cord210 which then activates the shapedcharges212, as known in the field.
• FIG. 19 shows agun assembly220 including anoptical fiber222, afilter224, afiring device226, aprima cord228, and at least oneshaped charge230. Anoptical signal40 is transmitted throughoptical fiber222 to thegun assembly220.Filter224 can be added at the end of theoptical fiber222 to improve safety by preventing optical radiation of wavelength different from the one provided by the surface unit (such as20) controller by the operator from reaching thefiring device226.Firing device226 can contain amaterial227 that includes a high absorption for the wavelength provided by the light transmission unit controller by the operator. Thematerial227 is also designed to ignite at a certain optical power level. When exposed to the correct light characteristics transmitted throughoptical fiber222,firing device226 ignites theprima cord228 which then activates the shapedcharges230, as known in the field.
• FIG. 20 shows one embodiment of thefiring device226, in which thefiring device226 comprises a chamber252 havingoptical fiber222 as the input end and theprima cord228 as the output end.Material227 is located within the chamber252 so that it surrounds theoptical fiber222. In another embodiment as shown inFIG. 21,material227 is simply a layer applied to theoptical fiber222 within the chamber252. An explosive256 is located within the chamber252 so that it surroundsprima cord228. The remainder of the chamber252 is filled with asubstance254, such as a gas, that is conducive to the ignition of thematerial227. Ignition of the material227 results in ignition of the explosive256 which in turn ignites theprima cord228.
• Possible compositions ofmaterial227 include particles of silicon, iron oxide, coal, charcoal, phosphorous, gun powder, or starch; alternatively insulating materials such as ceramic wool or thermite may be used. In one embodiment, thematerial227 is porous thereby enabling thesubstance254 to be in contact with the material227 at as many places as possible including the area ofmaterial227 that is being heated by the light transmitted throughoptical fiber222. Possible compositions forsubstance254 include air or oxygen mixed with diethyl ether, ether, carbon disulphide, or n-pentane or hydrogen. In the case where the absorber is combustible (e.g. coal or starch particles) it may be sufficient for the surrounding medium merely to be a source of oxygen.
• In another embodiment, not shown, the gun assembly can include thereceptor50 illustrated and described in relation toFIG. 10.
• Use of optical signals to actuate perforating guns and other downhole tools increases safety since the optical fiber and signal will be immune to electromagnetic fields. Therefore, the detonation or activation can only occur when the light energy of the right wavelength is transmitted from a specific unit (such as a laser) from the surface. Moreover, in those embodiments in which no battery is used downhole, the method avoids the use of such potentially problematic components. As compared to mechanically activated systems, use of the optical signal to activate perforating guns avoids the use of ball or weight dropping to activate a percussion detonator and the concerns associated therewith.
• It is often times important to know the depth of thedownhole tool2 as thetool2 is deployed in awellbore14. This is to ensure that thetool2 is activated at the correct depth. For instance, iftool2 is a perforating gun, then the gun must be activated at the depth of the relevant hydrocarbon formation. Or, if thetool2 is a packer, then the packer must be activated above or below the relevant formations as required. As shown inFIG. 22, acasing collar locator250 can be used to determine the depth of atool2. In one embodiment, thecasing collar locator250 is electrically powered, by either a downhole battery or an electrical line from surface. In another embodiment, thecasing collar locator250 is a passive optical system which functions by changing the optical signal it reflects back to theunit20 whenever it passes a casing collar.
• The optical fiber used to transmit light for activation ofdownhole tool2 may be implemented in different ways. For instance, it may be housed within a conduit, as shown inFIGS. 1 and 12. It may also be incorporated into a slickline, wherein the slickline supports the weight of the relevantdownhole tool2 and optical fiber. It may also be incorporated into a wireline (or electrical line), wherein the wireline supports the weight of the relevantdownhole tool2 and optical fiber. The optical fiber may also be pumped into a conduit or a coiled tubing unit as described in U.S. Reissue Pat. 37,283.
• While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.

Claims (30)

1-109. (canceled)

110. A system to actuate downhole tools by light, comprising:

a downhole tool adapted to be deployed in a wellbore;

an optical transmitter optically connected to the downhole tool through an optical fiber;

the optical transmitter adapted to transmit an optical signal through the optical fiber; and

wherein the downhole tool is activated in response to reception of the optical signal.

111. The system ofclaim 110, wherein the optical signal comprises a specific number of optical pulses.

112. The system ofclaim 111, wherein the optical signal comprises at least one pulse with a specific time duration.

113. The system ofclaim 111, wherein the optical signal comprises at least one pulse of light at a specific intensity, frequency, wavelength, or amount.

114. The system ofclaim 110, wherein the downhole tool is selected from the group consisting of a packer, a perforating gun, a valve, a sampler, a sensor, a pump, a screen, a chemical cutter, a plug, a detonator, or a nipple.

115. The system ofclaim 110, wherein a receptor receives the optical signal, verifies the optical signal is a valid triggering signal, and subsequently enables the activation of the downhole tool.

116. The system ofclaim 115, wherein:

the receptor comprises a microprocessor, storage, and a controller;

the valid triggering signal is stored in the storage;

the microprocessor compares the optical signal to the valid triggering signal; and

the microprocessor activates the controller when the optical signal matches the stored valid triggering signal.

117. The system ofclaim 110, wherein a plurality of downhole tools are functionally connected to the optical fiber so that each of the downhole tools may be activated in response to the reception of the optical signal.

118. The system ofclaim 117, wherein a different optical signal activates different downhole tools.

119. The system ofclaim 117, further comprising at least one optical filter functionally connected to the optical fiber that allows only light at a specific wavelength to pass therethrough to activate a downhole tool.

120. The system ofclaim 117, further comprising at least one coupler functionally connected to the optical fiber that diverts only light at a specific wavelength towards a downhole tool to activate such downhole tool.

121. The system ofclaim 110, wherein:

the optical signal is received by at least one photodiode;

the at least one photodiode converts the optical signal into electrical energy; and

the electrical energy is transmitted to an initiator circuit to activate the downhole tool.

122. The system ofclaim 110, wherein:

the optical signal is transmitted into an optically reactive chemical chamber;

the chamber contains an optically reactive substance that chemically reacts when subjected to light; and

the chemical energy is transferred to activate the downhole tool.

123. The system ofclaim 122, wherein the chamber includes an environment conducive to chemical reaction of the substance to light.

124. The system ofclaim 122, wherein the reaction is one of heating, exploding, or deteriorating.

125. The system ofclaim 110, wherein:

the optical signal is converted into an electrical signal and is then transmitted into a piezoelectric stack that expands when exposed to electrical energy; and

the expansion of the stack is used to activate the downhole tool.

126. The system ofclaim 110, further comprising a casing collar locator used to determine the depth of the downhole tool.

127. A method to actuate downhole tools by light, comprising:

deploying a downhole tool in a wellbore;

optically connecting the downhole tool to an optical transmitter through an optical fiber;

transmitting an optical signal from the optical transmitter through the optical fiber;

activating the downhole tool in response to reception of the optical signal.

128. The method ofclaim 127, wherein the transmitting step comprises transmitting an optical signal including a specific number of optical pulses.

129. The method ofclaim 127, wherein the deploying step comprises deploying the downhole tool as part of a logging system.

130. The method ofclaim 127, wherein the deploying step comprises deploying the downhole tool as part of a permanent completion.

131. The method ofclaim 127, wherein the deploying step comprises deploying the downhole tool as part of a coiled tubing system.

132. The method ofclaim 127, further comprising functionally connecting a plurality of downhole tools to the optical fiber so that each of the downhole tools may be activated in response to the reception of the optical signal.

133. The method ofclaim 132, further comprising functionally connecting at least one optical filter to the optical fiber, the optical filter allowing only light at a specific wavelength to pass therethrough to activate a downhole tool.

134. The method ofclaim 132, further comprising functionally connecting at least one coupler to the optical fiber, the coupler diverting only light at a specific wavelength towards a downhole tool to activate such downhole tool.

135. The method ofclaim 127, further comprising:

receiving the optical signal at an at least one photodiode, the at least one photodiode converting the optical signal into electrical energy; and

transmitting the electrical energy to an initiator circuit to activate the downhole tool.

136. The method ofclaim 127, further comprising:

transmitting the optical signal into an optically reactive chemical chamber;

providing an optically reactive substance in the chamber that chemically reacts when subjected to light; and

transferring the chemical energy to activate the downhole tool.

137. The method ofclaim 127, further comprising:

converting the optical signal into an electrical signal;

transmitting the electrical signal into a piezoelectric stack that expands when exposed to electrical energy; and

utilizing the expansion of the stack to activate the downhole tool.

138. The method ofclaim 127, further comprising determining the depth of the downhole tool by using a casing collar locator.

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