# Patent

## Title
Method of running DTS measurements in combination with a back pressure valve

## Abstract

A method of performing a wellbore operation at an oilfield comprises providing a bottom hole assembly comprising a backpressure valve on coiled tubing, deploying the bottom hole assembly into the wellbore with the coiled tubing, operating the backpressure valve to control a flow of fluid thereabove, and performing distributed temperature sensor measurements above the valve.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part application of application Ser. No. 12/135,682 entitled Backpressure Valve for Wireless Communication, filed on Jun. 9, 2008 now U.S. Pat. No. 7,793,732 and this application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 61/147,514, entitled A Method of Running DTS Measurements In Combination With A Back Pressure Valve filed on Jan. 27, 2008, the disclosures of each of which are incorporated herein by reference in their entirety.


FIELD
Embodiments described relate to coiled tubing for use in hydrocarbon wells. In particular, embodiments of coiled tubing are described utilizing a backpressure valve at a downhole end thereof to maintain a pressure differential between the coiled tubing and an environment in a well. Additionally, distributed temperature sensor (DTS) measurements may be taken in combination with a back pressure valve for improved accuracy and efficiency thereof.
BACKGROUND
Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years, well architecture has become more sophisticated where appropriate in order to help enhance access to underground hydrocarbon reserves. For example, as opposed to wells of limited depth, it is not uncommon to find hydrocarbon wells exceeding 30,000 feet in depth. Furthermore, as opposed to remaining entirely vertical, today's hydrocarbon wells often include deviated or horizontal sections aimed at targeting particular underground reserves. Indeed, it is not uncommon for a well to include a main vertical borehole with a variety of lateral legs stemming therefrom into a given formation.
While more sophisticated well architecture may increase the likelihood of accessing underground hydrocarbons, the nature of such wells presents particular challenges in terms of well access and management. For example, during the life of a well, a variety of well access applications may be performed within the well with a host of different tools or measurement devices. However, providing downhole access to wells of such challenging architecture may require more than simply dropping a wireline into the well with the applicable tool located at the end thereof. Thus, coiled tubing is frequently employed to provide access to wells of more sophisticated architecture.
Coiled tubing operations are particularly adept at providing access to highly deviated or tortuous wells where gravity alone fails to provide access to all regions of the wells. During a coiled tubing operation, a spool of pipe (i.e., a coiled tubing) with a downhole tool at the end thereof is slowly straightened and forcibly pushed into the well. This may be achieved by running coiled tubing from the spool and through a gooseneck guide arm and injector which are positioned over the well at the oilfield. In this manner, forces necessary to drive the coiled tubing through the deviated well may be employed, thereby delivering the tool to a desired downhole location.
As the coiled tubing is driven into the well as described, a degree of fluid pressure may be provided within the coiled tubing. At a minimum, this pressure may be enough to ensure that the coiled tubing maintains integrity and does not collapse. However, in many cases, the downhole application and tool may require pressurization that substantially exceeds the amount of pressure required to merely ensure coiled tubing integrity. As a result, measures may be taken to prevent fluid leakage from the coiled tubing and into the well. As described below, the importance of these measures may increase as the disparity between the pressure in the coiled tubing and that of the surrounding well environment also increases.
For example, it would not be uncommon for a low pressure well of about 2,000 PSI or so to accommodate coiled tubing at a vertical depth of over 10,000 feet. Due to the depth, if the coiled tubing is filled with a fluid such as water, hydrostatic pressure upwards of 5,000 PSI would be found at the downhole end of the coiled tubing. That is, even without any added pressurization, the column of water within the coiled tubing will display pressure at the end of the coiled tubing that exceeds the surrounding pressure of the well by over 3,000 PSI. Therefore, in order to prevent uncontrolled leakage of fluid into the well from the coiled tubing, a backpressure valve may be located at the terminal end of the coiled tubing. In this manner, uncontrolled leakage may be avoided, for example, to avoid collapse of the coiled tubing as noted above, and for a host of other purposes.
In many circumstances, downhole tools may be provided downhole of the backpressure valve. For example, a clean-out tool for cleaning debris from a lateral leg as described above may be disposed at the terminal end of the downhole assembly. Theoretically, a locating tool configured for locating a lateral leg stemming from the main borehole as described above may similarly be coupled to the backpressure valve above the clean-out tool. For such an application, an uninterrupted fluid path would be maintained between surface equipment and the locating tool. In this manner, the locating tool could communicate with surface equipment via pulse telemetry. That is, upon locating of a lateral leg, the tool may be configured to effect a temporary but discrete pressure change through the coiled tubing flow that may be detected by the surface equipment.
In an attempt to allow the pulse telemetry to be effectively employed, the backpressure valve above the locating tool may be opened when the tool is positioned downhole near the sought lateral leg. In theory, this would allow any pulse generated by the tool to make its way uphole through the coiled tubing and to the surface equipment. So, for example, where a surface equipment is employed to pump about 1 BPM of fluid through the coiled tubing to achieve a detectable pressure of about 5,000 PSI, the locating tool may be configured with an expandable flow-restrictor to effect a detectable pressure drop to about 4,500 PSI. That is, upon encountering the lateral leg, the flow-restrictor of the locating tool may expand in order to generate the detected pressure drop. With the lateral leg located, the clean-out tool would then be advanced thereinto for clean out of debris.
Unfortunately, the described technique of employing a pulse generating tool, such as the indicated locating tool, downhole of a backpressure valve, remains impractical. This is due to the fact that a conventional backpressure valve is subject to periodic throttling of the valve between open and closed positions with the closed position killing any signal from the locating tool. That is, once uphole pressure cracks open the backpressure valve, an equilibrium between pressure at either side of the valve is naturally sought, allowing the valve and seat to periodically open and close relative to one another in an uncontrolled manner. Thus, as a practical matter, where a pressure differential between the well and coiled tubing is significant enough to require use of a backpressure valve, hydraulic pulse communication from below the valve remains an unavailable option.
It is desirable to take DTS measurements within coiled tubing and to improve the accuracy and efficiency thereof.
SUMMARY
A method of performing a wellbore operation at an oilfield comprises providing a bottom hole assembly comprising a backpressure valve on coiled tubing, deploying the bottom hole assembly into the wellbore with the coiled tubing, operating the backpressure valve to control a flow of fluid thereabove, and performing distributed temperature sensor measurements above the valve. Providing may comprise providing at least one fiber optic line disposed within the coiled tubing. In an embodiment, performing comprises performing distributed temperature sensor measurements with the at least one fiber optic line. In an embodiment, providing further comprises attaching the fiber optic line to the bottom hole assembly. Providing may further comprise attaching the fiber optic line to the backpressure valve.
In an embodiment, operating comprises setting the backpressure valve to maximum overbalance. Setting may comprise setting the backpressure valve to control a flow of fluid thereabove at a predetermined wellbore depth. In an embodiment, the method further comprises opening the backpressure valve after performing distributed temperature sensor measurements above the valve. The method may further comprise performing distributed temperature sensor measurements above the valve after opening the backpressure valve. Opening may further comprise maintaining said opening in a substantially non-throttling manner with a pressure generating mechanism of the bottom hole assembly.
In an embodiment, opening comprises pumping fluid into the coiled tubing with a fluid pump at the oilfield. In an embodiment, the method further comprises transmitting a pressure pulse across the backpressure valve from a pressure pulse tool of the bottom hole assembly during said maintaining. In an embodiment, the method further comprises detecting the pressure pulse with a pressure detector coupled to the coiled tubing at the oilfield. In an embodiment, the method further comprising performing at least one well operation in the wellbore.
A method of employing a bottom hole assembly in a well at an oilfield, comprises providing a bottom hole assembly comprising a backpressure valve assembly on coiled tubing, the backpressure valve assembly comprising, a housing having an uphole portion for coupling to the coiled tubing and a downhole portion, a valve disposed within said housing at an interface of the uphole portion and the downhole portion, said the operable to open and close to provide fluid communication between the uphole and downhole portions, and a pressure generating mechanism disposed within the downhole portion for substantially avoiding throttling of the valve during the opening, deploying the bottom hole assembly into the wellbore with the coiled tubing, operating the backpressure valve assembly to control a flow of fluid thereabove, and performing distributed temperature sensor measurements above the valve assembly.
In an embodiment, the valve comprises a stationary valve, a moveable valve seat to interface said stationary valve, and a resistance mechanism coupled to said moveable valve seat for holding said moveable valve seat at the interface until a predetermined pressure is present in said uphole portion. In an embodiment, providing comprises providing at least one fiber optic line disposed within the coiled tubing and wherein performing comprises performing distributed temperature sensor measurements with the at least one fiber optic line.
In an embodiment, providing further comprises attaching the fiber optic line to the bottom hole assembly. In an embodiment, operating comprises setting comprises setting the backpressure valve assembly to control a flow of fluid thereabove at a predetermined wellbore depth. In an embodiment, the method further comprises opening the backpressure valve after performing distributed temperature sensor measurements above the valve performing at least one well operation in the wellbore.
A backpressure valve is provided to substantially maintain controlled pressure in coiled tubing disposed within a well. The valve may have a housing with an uphole portion for coupling to the coiled tubing and a downhole portion for coupling to a downhole tool. A valve is disposed within the housing at an interface of the uphole and downhole portions. The valve may be employed to open and close in order to provide pressure control as directed by an operator. Additionally, a pressure generating mechanism is disposed within the downhole portion to substantially prevent throttling of the valve when open.



BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
FIG. 1 is an oilfield overview depicting a bottom hole assembly within a well and employing an embodiment of a backpressure valve incorporating a pressure generating mechanism.
FIG. 2 is a partially sectional view of the bottom hole assembly of FIG. 1, revealing a valve assembly within the backpressure valve.
FIG. 3 is a cross-sectional view of the backpressure valve of FIGS. 1 and 2.
FIG. 4A is a side sectional view of the bottom hole assembly of FIG. 1 positioned at a first location in the well with the valve assembly of FIG. 2 closed.
FIG. 4B is a is a side sectional view of the bottom hole assembly of FIG. 1 positioned at the first location in the well with the valve assembly of FIG. 2 open.
FIG. 4C is a is a side sectional view of the bottom hole assembly of FIG. 1 positioned at a second location in the well with the valve assembly of FIG. 2 open.
FIG. 5 is a flow-chart summarizing an embodiment of employing a backpressure valve with a pressure generating mechanism incorporated therein in a coiled tubing operation.
FIG. 6 is a partial sectional schematic view of an embodiment of a bottomhole assembly comprising a fiber optic line.



DETAILED DESCRIPTION
Embodiments are described with reference to certain coiled tubing operations employing a downhole tool configured to communicate with surface equipment and the operator through the coiled tubing via pressure pulses. An embodiment of a backpressure valve with a pressure generating mechanism incorporated therein is coupled to the downhole tool that is of a configuration to allow pressure pulse communication therethrough. In the embodiments depicted herein, the downhole tool is a locating tool in the form of a multilateral tool for locating a horizontal or lateral leg off of a primary borehole. However, a variety of other locating tools or other tool types employing pressure pulse communication may be employed. Regardless, embodiments of the backpressure valve are configured to help ensure pressure signal communication between the tool and surface equipment at the oilfield may be permitted and maintained without signal interruption by throttling of the backpressure valve.
Referring now to FIG. 1, an overview of an oilfield 115 is depicted where coiled tubing 155 is employed to deliver a bottom hole assembly 101 to a well. More specifically, the coiled tubing 155 is employed to deliver the assembly 101 to a lateral leg 181 off of a main borehole 180 of the well. For example, in the embodiment depicted, the assembly 101 may include an application tool such as a clean-out nozzle 175 at an end thereof for removal of debris 193 clogging a production region 191 of the lateral leg 181.
As shown, the main borehole 180 traverses a variety of formation layers 197, 195, 190 and the overall architecture of the well is fairly sophisticated. For example, in addition to the lateral leg 181 noted above, another lateral leg 182 may stem from the main borehole 180 and include its own production region 192. As such, the bottom hole assembly 101 may be equipped with a pulse communication tool 170 in the form of a multilateral tool for locating the proper lateral leg 181 into which the assembly 101 is to be positioned. That is, given the sophisticated architecture of the well, positioning of the bottom hole assembly 101 for removal of the depicted debris 193 may involve a bit more than simply dropping the coiled tubing 155 into the main borehole 180 and pushing with surface equipment 150. Rather, a tool 170 and technique for proper positioning of the bottom hole assembly 101 as depicted may be employed as detailed further below.
Continuing with reference to FIG. 1, the bottom hole assembly 101 is delivered to the location depicted in order to perform a clean-out application as noted above. However, beyond merely locating the lateral leg 181, advancing of the assembly 101 through the horizontally oriented leg 181 presents a degree of challenge in and of itself. Therefore, the surface equipment 150 depicted at the oilfield 115 includes an injector assembly 153 supported by a tower 152. The injector assembly 153 may be employed to acquire the coiled tubing 155 from a rotating spool 162 and drive it through a blowout preventer stack 154, master control valve 157, well head 159, and/or other surface equipment 150 and into the main borehole 180.
Once the assembly is oriented within the lateral leg 181, the injector assembly 153 is configured to continue driving the coiled tubing 155 with force sufficient to overcome the deviated nature of the leg 181. For example, as depicted in FIG. 1, the coiled tubing 155 is forced around a bend in the leg 181 and to the horizontal position shown. The driving forces supplied by the injector assembly 153 are sufficient to overcome any resistance imparted on the coiled tubing 155 and the assembly 101 by the wall 185 of the leg 181 as the assembly 101 traverses the noted bend.
The above noted surface equipment 150 includes coiled tubing equipment 160 that is provided to the oilfield 115 by way of a conventional skid 168. However, a coiled tubing truck or other mobile delivery mechanisms may be employed for positioning of the equipment 160 at the oilfield 115. Regardless, the coiled tubing equipment 160 includes a fluid pump 164 for pumping fluid into the coiled tubing 155. Similarly, a hydraulic pressure detector 166 is provided to monitor a pressure of the fluid within the coiled tubing 155 during an operation.
In an embodiment, about 10,000 ft. of coiled tubing 155 may be present between the injector assembly 153 and the bottom hole assembly 101 with another 10,000 ft. between the injector assembly 153 and around the spool 162. Furthermore, the fluid pump 164 may be employed to generate a flow rate of about 1 BPM through the entire 20,000 ft. of coiled tubing 155 in order to provide an uninterrupted fluid channel therethrough. Depending on a variety of conditions, this may result in a hydrostatic pressure of say about 5,000 PSI detectable at the pressure detector 166. However, as detailed further below, a pressure pulse which is detectable by the pressure detector 166 may be transmitted from the borehole assembly 101 to the detector 166 upon changing downhole pressure conditions. Thus, changing conditions may be employed to communicate with an operator at the surface.
Continuing now with added reference to FIG. 2, the backpressure valve 100 is provided to the assembly 101 in order to ensure that sufficient fluid is maintained within the coiled tubing 155. For example, the well may be of low bottom hole pressure, say about 2,000 PSI, whereas the pressure at the end of the 10,000 ft. of substantially vertical coiled tubing 155 is likely to exceed about 5,000 PSI. Therefore, the backpressure valve 100 may be employed to help avoid fluid leakage into the well. Thus, an uninterrupted fluid channel through the coiled tubing 155 may be maintained as noted.
More specifically, as shown in FIG. 2, a valve assembly 200 of the backpressure valve 100 may be closed with a movable seat 250 positioned against a stationary valve 225 in order to limit fluid flow out of the coiled tubing 155 and into the well. However, as indicated above, hydraulic pressure pulse communication between the pulse communication tool 170 and the pressure detector 166 may be desirable at times. Thus, as detailed further below, the valve assembly 200 may be opened by application of sufficient hydraulic pressure. This may be initiated by an operator through the fluid pump 164 as the assembly 101 reaches a particular estimated downhole location. Furthermore, once cracked open, the valve assembly 200 may be configured to remain open without any significant throttling thereof. As such, pressure communication may reliably proceed between the tool 170 downhole of the backpressure valve 100 and the pressure detector 166 at the surface of the oilfield 115 without interference by the valve assembly 200. In one embodiment, the pressure pulse is generated as an angle between stationary 270 and arm 273 portions of the tool 170 is reduced by a predetermined amount. This manner of pressure pulse communication is described in greater detail below.
Continuing now with reference to FIG. 3, a detailed cross-section of the backpressure valve 100 is depicted, revealing a pressure generating mechanism that may be employed so as to substantially avoid throttling of the valve assembly 200 once opened. In the embodiment shown, the pressure generating mechanism includes a plurality of pressure generating flow-restrictors 300 positioned downhole of the valve assembly 200. However, a variety of alternative types of pressure generating mechanisms may be employed as noted below. Regardless, the pressure generating mechanism is disposed downhole of the valve assembly 200. Thus, pressure may be generated downhole of the valve assembly 200 once the interface 380 of the valve 225 and the seat 250 is opened as shown. In this manner, periodic throttling closure of the interface 380 may be avoided.
The above indicated throttling avoidance upon opening of the valve assembly 200 may be understood with reference to the fluid line through the backpressure valve 100. As shown in FIG. 3, the fluid line may be viewed as portions or chambers 310, 320 of the backpressure valve 100 at either side of the valve assembly 200. That is, an uphole chamber 310 is located uphole of the valve assembly 200 whereas a downhole chamber 320 is located downhole of the valve assembly 200. In the embodiment shown, the valve assembly 200 has been cracked open at the interface 380 allowing fluid communication between the chambers 310, 320. As a result of this communication an equilibrium of pressure between the chambers 310, 320 may be substantially achieved as a result of the pressure generating flow-restrictors 300 disposed within the downhole chamber 320. That is, a flow of fluid through the fluid line and the uphole chamber 310 may be employed to crack open the valve assembly 200. Subsequently, pressure within the downhole chamber 320 may be driven up by the presence of the flow-restrictors 300. As a result, pressure within the downhole chamber 320 may be driven up to a point of substantial equilibrium with the adjacent uphole chamber 310. In this manner, throttling of the valve assembly 200 may be substantially avoided as indicated above. Thus, once the backpressure valve 100 is opened, a pulse communication tool 170 may be effectively employed downhole of the backpressure valve 100. That is, wireless communication with a pressure detector 166 at the surface of the oilfield 115 may take place without significant concern over pressure pulse signals being killed by a throttling valve assembly 200 (see FIG. 1).
Continuing with reference to FIG. 3, with added reference to FIG. 1, the role of pressure between the chambers 310, 320 and at a spring 355 coupled to the valve seat 250 is described in greater detail. When the valve assembly 200 is in a closed position as depicted in FIG. 2, the backpressure valve 100 may be employed to maintain a column of fluid in the coiled tubing 155 as described above. Thus, leakage of fluid into the potentially low pressure well may be avoided. With reference to the scenario described above, about 5,000 PSI may be maintained within the uphole chamber 310 when the valve assembly 200 is closed. However, at this same time, the downhole chamber 320 may be open to the well sharing a common pressure therewith, for example about 2,000 PSI.
Given the 3,000 PSI disparity between the uphole 310 and downhole 320 chambers, a spring 355 is provided about a moveable mandrel 350 adjacent the valve seat 250 of the valve assembly 200. This spring 355 may be employed to hold the movable valve seat 250 in place keeping the valve assembly 200 closed until pressure conditions change. Alternative forms of resistance mechanisms other than a spring 355 may be employed for this purpose including belville washers or hydraulic resistance mechanisms. Regardless, in the scenario described above, the pressure in the downhole chamber 320 is about 3,000 PSI less than that of the uphole chamber 310. Therefore, the spring 355 may be configured to maintain 3,000 PSI or more of force on the movable valve seat 250 in order to keep the valve assembly 200 closed.
With about 3,000 PSI of force supplied by the spring 355, cracking open of the valve assembly may be achieved by the introduction of a pressure disparity between the chambers 310, 320 that is greater than 3,000 PSI. This increase in pressure may be directed by the fluid pump 164 at the surface of the oilfield 115. For example, in one embodiment, the fluid pump 164 may drive 1.5 barrels per minute (bpm) through the coiled tubing 155 and to the uphole chamber 310 increasing pressure therein to above 5,000 PSI. As such, a pressure disparity of greater than 3,000 PSI may be achieved, thereby overcoming the spring 355 to crack open the valve assembly 200 as depicted in FIG. 3.
Once the valve assembly 200 is cracked open, the uphole chamber 310 and the downhole chamber 320 are in direct communication through the interface 380. However, due to the configuration of the valve assembly 200 as detailed above, the tendency of the valve seat 250 to throttle relative to the valve 225 is avoided. More specifically, prevention of this throttling is achieved by the pressure generating mechanism disposed in the downhole chamber 320. In the embodiment shown, the pressure generating mechanism includes a plurality of flow restrictors 300 as described with an orifice 375 for regulating fluid passage therethrough.
The flow restrictors 300 serve to increase pressure in the downhole chamber 320 in response to an influx of fluid flow such as the 1.5 bpm noted above. As a result, periodic reduction in pressure in the downhole chamber 320 may be avoided, thereby allowing the valve assembly 200 to stay open. Pressure generation in this manner may be achieved through use of flow restrictors 300 as indicated. However, alternative forms of pressure generating mechanisms may be employed. For example, tubes or shafts of varying dimensions may be employed. In one embodiment, a shaft housing a plurality of washer shaped restrictors may be employed.
With reference to the particular embodiment of FIG. 3, the flow restrictors 300 may be about an inch in length with an outer diameter of about an inch matching the inner diameter of the downhole chamber 320. The orifices 375 of the flow restrictors 300 may be less than about 1.0 inches in diameter and of a tapered configuration. In such an embodiment, the introduction of about 1.5 bpm through the downhole chamber 320 may result in pressure generation of about 1,000 PSI at each of the four flow restrictors 300. The resulting 4,000 PSI increase would provide the downhole chamber 320 with a pressure of about 6,000 PSI (when accounting for the 2,000 PSI of well pressure). Thus, as indicated above, the pressure in the downhole chamber 320 is driven up to a level sufficient to keep the valve open (e.g. exceeding 5,000 PSI in the scenario as described above). As such, throttling of the valve assembly 200 may be avoided.
A variety of alternative sizing may be employed for the flow-restrictors 300 other than that described above. Indeed, sizing may change from one flow-restrictor 300 to the next with different restrictors 300 contributing a different predetermined percentage to the total pressure generation increase to the downhole chamber 320. Additionally, the number of flow-restrictors 300 employed may vary. However, in the embodiment shown, a sufficient number of restrictors 300 are employed so as to avoid the generation of vapor within the fluid, often referred to as cavitation. Such vapor would have a tendency to mask pressure pulse signals. However, with the principle of vena contracta in mind, a pressure drop at the orifice 375 that is roughly twice the pressure increase provided by any given restrictor 300 may be presumed and accounted for in determining the total number of flow restrictors 300 to be utilized. So, for example, with a starting pressure of about 2,000 PSI in downhole chamber 320 for the scenario described above, each restrictor 300 may be configured to contribute no more than about 1,000 PSI in response to 1.5 bpm as indicated. In this manner, a ‘vena contracta’ pressure drop of 2,000 PSI at the orifice 375 fails to result in a cavitation inducing pressure.
Continuing now with reference to FIGS. 4A-4C, a manner of employing the backpressure valve 100 in combination with a pressure pulse communication tool 170 is described. Cooperation between the backpressure valve 100 and the tool 170 may result in delivery of the entire borehole assembly 101 to the intended lateral leg 181 as depicted.
As shown in FIG. 4A, coiled tubing 155 is utilized to advance the bottom hole assembly 101 vertically through the main borehole 180. The arm 273 of the pressure pulse tool 170 is configured to flex about a hinge 475 of the tool 170 and toward the stationary portion 270 thereof. However, throughout most of the vertical downhole advancement of the assembly 101 the flexing of the arm 273 is substantially limited. This limitation on flexing is a result of the limited diameter of the borehole 180 which prevents further flexing and maintains an angle θ as depicted.
As the bottom hole assembly 101 is advanced downhole as depicted in FIG. 4A, the backpressure valve 100 may be closed. That is, the valve seat 250 may be closed against the valve 225 to prevent fluid leakage from the uphole chamber 310. The downhole chamber 320 may be in communication with the pressure pulse tool 170 and the well. However, at a time prior to searching for the lateral leg 181 or employing the clean-out nozzle 175, communication between the tool 170 and the uphole chamber 310 or other uphole equipment may be unnecessary.
Referring now to FIG. 4B, a locating operation may proceed wherein the pressure pulse tool 170 is employed to locate the lateral leg 181. For example, with added reference to FIG. 1, the fluid pump 164 may be employed to pump fluid through the coiled tubing 155 and crack open the interface 380 between the uphole 310 and downhole 320 chambers of the backpressure valve 100. The fluid pump 164 may be directed to open the interface 380 in this manner once the bottom hole assembly 101 has reached an estimated predetermined depth. For example, in one embodiment, the interface 380 is cracked open once the assembly 101 approaches to within about 20 feet of the estimated location of the lateral leg 181. With the interface 380 open in this manner, fluid may be pumped through the clean-out nozzle 175 as desired.
Continuing now with reference to FIG. 4C, opening of the backpressure valve 100 as indicated is achieved in a manner that avoids throttling closed of the interface 380 as detailed above. Thus, with added reference to FIG. 1, pressure pulse signals 400 emitted by the tool 170 may be transmitted all the way up the coiled tubing 155 and to the pressure detector 166 at the surface of the oilfield 115. In this manner an operator or automated equipment at the surface may be alerted as to the locating of the lateral leg 181 by the tool 170 as described below.
A variety of techniques may be employed for locating the lateral leg 181 with the tool 170. For example, it may be unlikely that the tool 170 would be initially oriented in line with the lateral leg 181 as depicted in FIGS. 4A-4B. Rather, the nozzle 175 may abut an opposite side of the borehole 180 relative to the lateral leg 181. As such, a series of advancing, retracting, and rotating of the bottom hole assembly 101 may proceed throughout a region where the lateral leg 181 is thought to be located. As the locating procedure is carried out, the backpressure valve 100 may be closed, for example, during periods of rotating the assembly 101 when encountering of the lateral leg 181 by the tool 170 is unlikely.
Regardless of the particular methodology employed for positioning and repositioning of the tool 170, once the arm 273 encounters the lateral leg 181, the effective diameter of the well increases. Thus, the arm 273 is able to increase its flex until encountering the wall 185 of the lateral leg 181. Stated another way, the angle θ at the hinge 475 is reduced. Reduction of the angle θ in this manner is utilized to set of a conventional pressure pulse mechanism within the tool 170. For example, this pressure pulse mechanism may act to increase the size of an orifice of the tool 170, thereby affecting a sudden pressure change on the fluid traveling therethrough. This sudden change in pressure may be transmitted uphole in the form of a pressure pulse 400. As noted above, due to the configuration of the backpressure valve 100 this pressure pulse 400 may be transmitted to a pressure detector 166 at the surface of the oilfield 115 without concern over the signal being killed by an intermittently throttling valve assembly 200 (see also FIG. 1).
Referring now to FIG. 5, a method of cooperatively employing a backpressure valve and pressure pulse communication tool as noted above is summarized in the form of a flow-chart. The backpressure valve, having a pressure generating mechanism therein, and the tool are part of the same bottom hole assembly that is coupled to coiled tubing. The coiled tubing may be closed off by the backpressure valve and filled with fluid at an oilfield as indicated at 510 and 520. The coiled tubing may then be employed to advance the entire bottom hole assembly into a main borehole as noted at 530.
As indicated at 540, the bottom hole assembly may be advanced to a predetermined location region of the main borehole. As noted above, this region may be within a given distance of the estimated location of a lateral leg off of the main borehole. Once the bottom hole assembly is positioned in this region, fluid may be pumped through the coiled tubing and to the backpressure valve in order to open it. Additionally, due to the pressure generating configuration of the backpressure valve as detailed above, opening of the valve may be achieved in a non-throttling manner as indicated at 550. Thus, once the lateral leg is located by the tool downhole of the backpressure valve as noted at 560, a pressure pulse may be sent from the tool to surface equipment at the oilfield as indicated at 570 without concern over the pulse being killed by a throttling valve.
With information on hand regarding the precise location of the lateral leg, an operator may direct the entire bottom hole assembly into the lateral leg as indicated at 580. As a result, an application may be performed on the lateral leg as noted at 590. The application may involve a clean-out of debris, stimulation, scale removal, perforation forming, water conformance applications, inflatable packer placement, or a host of other lateral leg procedures.
Embodiments described hereinabove include a bottom hole assembly that is equipped with a cooperatively acting pressure pulse tool and backpressure valve that allow for a pressure pulse signal to be transmitted through the backpressure valve without concern over a throttling valve assembly killing the pressure pulse signal. Thus, the pressure pulse tool may communicate with equipment at the surface of the oilfield. Furthermore, the noted throttling is avoided in a manner that also avoids cavitation of fluid within the backpressure valve. Thus, pressure pulse communication is not masked by the presence of any significant fluid vapor.
In an embodiment, Distributed Temperature Sensor(s) or DTS measurements may be taken while using the benefits of a bottom hole assembly comprising a back pressure valve, such as the bottom hole assembly 101 and the backpressure valve 100 shown in FIGS. 2 and 3, as will be appreciated by those skilled in the art.
In an embodiment, a fiber optic cable or line 600 is disposed within a length of coiled tubing, such as the 155 shown in FIGS. 1 and 2. The fiber optic line 600 in the coiled tubing 155 can be used to measure temperature (i.e. DTS measurements) along the well, such as the well or borehole 180, 181, and 182 shown in FIGS. 1, 4A, 4B, and 4C.
The fiber optic line 600 may be attached directly to the bottom hole assembly 101, such as to the backpressure valve 100 or at any suitable downhole location for taking downhole DTS measurements, such as to a fiber termination sub (not shown) in the coiled tubing string 155 or at another suitable location, as will be appreciated by those skilled in the art. The fiber optic line 600 may also be connected to suitable surface equipment, for processing DTS measurements such as surface equipment 150 or the like. Structures and methods for performing these DTS measurements can be found in U.S. Pat. No. 7,055,604, entitled “Use of Distributed Temperature Sensors during Wellbore Treatments”, filed on Jul. 28, 2003, the entirety of which is incorporated by reference. These DTS measurements may depend on the immediate environment surrounding the optical cable or fiber 600. Thus, a key to obtaining accurate DTS measurements within the coiled tubing 155 is to eliminate the dynamic effects inside of the coiled tubing 155 and movement of the coiled tubing 155 during the DTS measurements.
In low bottom hole pressure wells, the fluid from coiled tubing, such as the coiled tubing 155 shown in FIGS. 1 and 2, may start flowing from the coiled tubing 155 and into the well or borehole 180, 181, and 182 on its own due to the hydrostatic differential. Therefore, even if the coiled tubing 155 is stopped (i.e. is no longer moving downwardly in the well or borehole 180, 181, and 182), thermal equilibrium cannot be reached until the overbalanced induced flow stops flowing from the coiled tubing 155 into the well or borehole 180, 181, and 182 and/or the formation(s) 190, 195, or 197 and around the fiber optic line 600.
A back pressure valve, such as the backpressure valve 100 shown in FIGS. 2 and 3, may be installed on the coiled tubing 155 to reduce or alleviate {this problem} the flow from the coiled tubing 155 into the well or borehole 180, 181, and 182 and/or the formation(s) 190, 195, or 197. For example, with the fiber optic line 600 connected to and disposed above the backpressure valve 200, the valve 200 may be set at a setting equal to the maximum overbalance in the well. Such a setting will result in a no flow scenario whenever the coiled tubing 155 is stopped and distributed temperature measurements may be taken. That is, with the valve 200 closed, the flow of fluid within the coiled tubing 155 above the valve 200 is prevented and thus DTS measurements taken above the valve 200 are more accurate.
Maximum overbalance indicates that the backpressure valve 100 is set such that the settings of the valve 100, i.e., the number and size flow restrictors 300, the size of the orifice 375, the tension of the spring 355 or suitable resistance mechanisms, and the like, are selected such that at the anticipated depth that the bottom hole assembly will be deployed for DTS measurements, the backpressure valve 100 will remain closed and not allow flow from the uphole chamber 310 to the downhole chamber 320 until the pressure in the coiled tubing 155 and thus the uphole chamber 310 is increased to overcome the tension in the spring 355. Once the pressure in the uphole chamber 310 is increased and the valve 100 or valve assembly 200 is cracked open, a treatment operation may be conducted and, pressure pulse telemetry and/or the like may be performed as detailed hereinabove. After the valve 100 is opened, DTS measurements may again be taken. The backpressure valve 100 may then be closed (such as by reducing the pressure in the uphole chamber 310 by reducing flow within the coiled tubing 155 from the surface equipment 150) the flow of fluid within the coiled tubing 155 may be brought to an equilibrium, and DTS measurements taken again. Those skilled in the art will appreciate that the steps above may be repeated as often as required in order to complete a wellbore operation.
The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. For example, embodiments depicted herein reveal a pressure pulse communication tool in the form of a multilateral tool. However, other embodiments of pressure pulse communication tools may be employed such as a casing collar locator tool. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood as referring to the power set (the set of all subsets) of the respective range of values. Accordingly, the protection sought herein is as set forth in the claims below.

## Claims

1. A method of performing a wellbore operation at an oilfield, comprising:
providing a bottom hole assembly comprising a backpressure valve on coiled tubing;
deploying the bottom hole assembly into the wellbore with the coiled tubing;
operating the backpressure valve to control a flow of fluid thereabove; and
performing distributed temperature sensor measurements above the valve.

2. The method of claim 1 wherein providing comprises providing at least one fiber optic line disposed within the coiled tubing.

3. The method of claim 2 wherein performing comprises performing distributed temperature sensor measurements with the at least one fiber optic line.

4. The method of claim 2 wherein providing further comprises attaching the fiber optic line to the bottom hole assembly.

5. The method of claim 4 wherein providing further comprises attaching the fiber optic line to the backpressure valve.

6. The method of claim 1 wherein operating comprises setting the backpressure valve to a setting equal to a maximum overbalance in the wellbore.

7. The method of claim 6 wherein setting comprises setting the backpressure valve to control a flow of fluid thereabove at a predetermined wellbore depth.

8. The method of claim 1 further comprising opening the backpressure valve after performing distributed temperature sensor measurements above the valve.

9. The method of claim 8 further comprising performing distributed temperature sensor measurements above the valve after opening the backpressure valve.

10. The method of claim 8 wherein opening further comprises maintaining said valve in a substantially non-throttling manner with a pressure generating mechanism of the bottom hole assembly.

11. The method of claim 10 wherein opening comprises pumping fluid into the coiled tubing with a fluid pump at the oilfield.

12. The method of claim 10 further comprising transmitting a pressure pulse across the backpressure valve from a pressure pulse tool of the bottom hole assembly during said maintaining.

13. The method of claim 12 further comprising detecting the pressure pulse with a pressure detector coupled to the coiled tubing at the oilfield.

14. The method of claim 10 further comprising performing at least one well operation in the wellbore.

15. A method of employing a bottom hole assembly in a well at an oilfield, the method comprising:
providing a bottom hole assembly comprising a backpressure valve assembly on coiled tubing, the backpressure valve assembly comprising,
a housing having an uphole portion for coupling to the coiled tubing and a downhole portion;
a valve disposed within said housing at an interface of the uphole portion and the downhole portion, the valve operable to open and close to provide fluid communication between the uphole and downhole portions; and
a pressure generating mechanism disposed within the downhole portion for substantially avoiding throttling of the valve during the opening;

deploying the bottom hole assembly into the wellbore with the coiled tubing;
operating the backpressure valve assembly to control a flow of fluid thereabove; and
performing distributed temperature sensor measurements above the valve assembly.

16. The method of claim 15 wherein the valve comprises
a stationary valve;
a moveable valve seat to interface said stationary valve; and
a resistance mechanism coupled to said moveable valve seat for holding said moveable valve seat at the interface until a predetermined pressure is present in said uphole portion.

17. The method of claim 15 wherein providing comprises providing at least one fiber optic line disposed within the coiled tubing and wherein performing comprises performing distributed temperature sensor measurements with the at least one fiber optic line.

18. The method of claim 15 wherein providing further comprises attaching the fiber optic line to the bottom hole assembly.

19. The method of claim 15 wherein operating comprises setting the backpressure valve assembly to control a flow of fluid thereabove at a predetermined wellbore depth.

20. The method of claim 15 further comprising opening the backpressure valve after performing distributed temperature sensor measurements above the valve performing at least one well operation in the wellbore.