CA2704561C - Heater string and process of well heating - Google Patents
Heater string and process of well heating Download PDFInfo
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- CA2704561C CA2704561C CA2704561A CA2704561A CA2704561C CA 2704561 C CA2704561 C CA 2704561C CA 2704561 A CA2704561 A CA 2704561A CA 2704561 A CA2704561 A CA 2704561A CA 2704561 C CA2704561 C CA 2704561C
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- FDDDEECHVMSUSB-UHFFFAOYSA-N sulfanilamide Chemical compound NC1=CC=C(S(N)(=O)=O)C=C1 FDDDEECHVMSUSB-UHFFFAOYSA-N 0.000 abstract description 2
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- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 2
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Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- G06Q30/00—Commerce
- G06Q30/02—Marketing; Price estimation or determination; Fundraising
- G06Q30/0207—Discounts or incentives, e.g. coupons or rebates
- G06Q30/0226—Incentive systems for frequent usage, e.g. frequent flyer miles programs or point systems
Abstract
A heater string for transmitting a heater fluid within a well, includes an inlet, an elongate tubular body and an inner tubular surface contiguous with the elongate body and contacting the heater fluid. The inner tubular surface includes a plasticized polyamide blend, allowing a reduction of the friction between the fluid and the string and thermal conductivity from the fluid toward the well, improving various functions of the string. The plasticizer may be a sulphonamide and include tougheners and reinforcement spines. Also, a hanger assembly for suspending the heater string includes an anchoring member, a nut mountable around the string and a connector body with a canalization communicating with the inlet of the string. The nut and connector body are securable together and abuttable against upstream-facing and downstream-facing surfaces of the anchoring member to enclose the anchoring member, allowing a secure hold on the heater string.
Description
HEATER STRING AND PROCESS OF WELL HEATING
FIELD OF THE INVENTION
The present invention generally relates to heating hydrocarbon recovery wells, and more specifically to heater strings and their application in hydrocarbon recovery wells.
BACKGROUND
In order to recover hydrocarbons from geological formations, it is often desirable or even necessary to provide heat. Heating a hydrocarbon well may increase hydrocarbon mobility, reduce formation of unwanted compounds, pre-condition the hydrocarbons prior to extraction, facilitate pumping, enable or improve various in situ recovery methods, generally improve the quality, quantity and economics of production.
It is well known that hydrocarbon wells are expensive endeavours, both in terms of capital and operating costs. Hydrocarbon wells vary widely in design and operating conditions, depending on their age, the composition of hydrocarbons that are present or recoverable within the formation, the presence of unwanted compounds in the formation, and their geographical location.
In natural gas wells, for instance, well heating is important due to the availability and composition of the gas, the above- and below-ground temperatures and the tendency of hydrate formation.
Though wells may be constructed in various ways, one construction includes a drilled wellbore that may have vertical, slanted or horizontal portions, a casing mounted within the wellbore, a production tube mounted within the casing, and other optional tubes mounted within the casing along the production tube to provide heat, fluids, chemical agents, steam, and wellbore accessories, etc., as the case may be.
One way of heating a well is by providing a heater string within the casing and along the production tube. Known heater strings have mainly provided heat using electricity, combustion, pyrolysis or heater fluids.
Heater strings that transmit heater fluids such as hot water or ethylene glycol have been used in the field and some designs have been described in United States patent Nos.
4,988,389 (Adamache et al), 3,627,047 (Leland et al), 3,207,219 (Mitchell), 2,705,535 (Waterman), and 2,914,124 (Ripley Jr).
Known heater strings for transmitting heater fluids are generally composed of steel, due to its mechanical and physical properties at low and high temperatures, its widespread use in the oil and gas industry, and its flow capacity, manufacturing sources and availability.
However, the use of steel in heater string applications presents a variety of disadvantages.
Heater strings are often desirable at profound depths, since heat is often needed far below the surface at or below the permafrost layer or at specific locations where the pressure-temperature conditions in the production tube may lead to a tendency toward undesirable hydrate "ice plug" formation. At such depths, steel heater strings are particularly fraught with drawbacks. Firstly, the friction coefficient of carbon and stainless steel often necessitates significant surface pressure in order to pump the heater fluid through the lengthy heater string. High surface pumping pressures require high capital cost pumps, increase operating costs and can be quite dangerous, also increasing the probability of ruptures, leaks and accidents.
Secondly, the thermal conductivity of steel leads to rapid heat transfer from the heater fluid to the well, which can be detrimental when heating is desired at great depths, since the heater fluid may be prematurely cooled by the time it reaches the desired heating location. This leads to higher energy costs - heating and pumping - necessary to transmit the heater fluid to the target zone. In order to avoid this premature cooling phenomenon, an operator may increase the fluid pressure, flow rate and temperature, which as mentioned above further exacerbates the disadvantages associated with high surface pumping pressures.
A section of the steel heater string may also rupture, crack or break-off. Break-off of a section of the heater string leads to further complications, including increased "fishing".
When a broken-off steel section falls down the wellbore at high speeds - sometimes reaching its terminal velocity - and then collides with the casing, the production tube or other well components, it fractures into many pieces that must be "fished" out of the well. Fishing can be very dangerous and results in shutdown time.
Thirdly, although steel may be relatively anti-corrosive compared to some other metals and alloys, in the harsh conditions of gas recovery wells, where highly corrosive compounds such as dissolved carbon dioxide and hydrogen sulphide are present, steel incurs unwanted chemical and physical wear. External corrosion can lead to accelerated deterioration, rupture Furthermore, given the capital costs associated with drilling a wellbore and installing the well components, there are often dimensional constraints which must be considered when The chemical nature of the formation, the hydrocarbons and the heater fluid also play a role in the functioning of heater strings. For instance, when sulphur, hydrogen sulphide or hydrate-forming compounds are present in the hydrocarbon stream, corrosion, sulphur deposition and In view of the above, it should be clear that there is a need for a technology that overcomes at least some of the disadvantages of the heater strings and well heating techniques that have been used up to now in the field.
The present invention responds to the above-mentioned need by providing a heater string, a hanger assembly, and a unique process of heating a well.
In one aspect of the present invention, there is provided a heater string for transmitting a heater fluid within a well, which includes a wellbore, a casing arranged within the wellbore and a production tube arranged within the casing. The heater string is mountable within the casing and adjacent to a portion of the production tube. The heater string includes an inlet for receiving the heater fluid, an elongate tubular body in fluid communication with the inlet and an inner tubular surface contiguous with the elongate body and contacting the heater fluid, and the inner tubular surface includes a plasticized polyamide blend.
The plasticized polyamide inner surface of the heater string allows a reduction of the friction between the heater fluid and the heater string and thermal conductivity of heat from the heater fluid toward the well, improving corrosion resistance, increasing the ductility, reducing the weight and reducing the likelihood of rupture, break-off and brittle fracturing. This enables improved heating at great depths by reducing the pressure required to pump the heater fluid as well as extending the heating capacity deep in to the well due to the insulation properties.
The plasticized polyamide enables advantages that are specific to heater string applications.
In optional embodiments, the heater string may be a one-piece tubular extrusion and the plasticizer may be a sulphonamide. The plasticized ployamide may optionally include tougheners and reinforcement members such as spines composed of aramid fiber.
In another aspect of the present invention, there is provided a process of heating a well having a wellbore, a casing arranged within the wellbore and a production tube arranged within the casing to define an annulus there between. The process includes:
providing a heater string comprising an inlet for receiving a heater fluid, an outlet for expelling the heater fluid, an elongate tubular body in fluid communication with the inlet and the outlet, and an inner tubular surface contiguous with the elongate body and contacting the heater fluid, the inner tubular surface comprising a plasticized polyamide blend;
mounting the heater string within the annulus;
providing the heater fluid at the inlet at a first pressure;
allowing the heater fluid to flow through the heater string to transfer heat to the production tube; and expelling the heater fluid from the outlet into the annulus.
FIELD OF THE INVENTION
The present invention generally relates to heating hydrocarbon recovery wells, and more specifically to heater strings and their application in hydrocarbon recovery wells.
BACKGROUND
In order to recover hydrocarbons from geological formations, it is often desirable or even necessary to provide heat. Heating a hydrocarbon well may increase hydrocarbon mobility, reduce formation of unwanted compounds, pre-condition the hydrocarbons prior to extraction, facilitate pumping, enable or improve various in situ recovery methods, generally improve the quality, quantity and economics of production.
It is well known that hydrocarbon wells are expensive endeavours, both in terms of capital and operating costs. Hydrocarbon wells vary widely in design and operating conditions, depending on their age, the composition of hydrocarbons that are present or recoverable within the formation, the presence of unwanted compounds in the formation, and their geographical location.
In natural gas wells, for instance, well heating is important due to the availability and composition of the gas, the above- and below-ground temperatures and the tendency of hydrate formation.
Though wells may be constructed in various ways, one construction includes a drilled wellbore that may have vertical, slanted or horizontal portions, a casing mounted within the wellbore, a production tube mounted within the casing, and other optional tubes mounted within the casing along the production tube to provide heat, fluids, chemical agents, steam, and wellbore accessories, etc., as the case may be.
One way of heating a well is by providing a heater string within the casing and along the production tube. Known heater strings have mainly provided heat using electricity, combustion, pyrolysis or heater fluids.
Heater strings that transmit heater fluids such as hot water or ethylene glycol have been used in the field and some designs have been described in United States patent Nos.
4,988,389 (Adamache et al), 3,627,047 (Leland et al), 3,207,219 (Mitchell), 2,705,535 (Waterman), and 2,914,124 (Ripley Jr).
Known heater strings for transmitting heater fluids are generally composed of steel, due to its mechanical and physical properties at low and high temperatures, its widespread use in the oil and gas industry, and its flow capacity, manufacturing sources and availability.
However, the use of steel in heater string applications presents a variety of disadvantages.
Heater strings are often desirable at profound depths, since heat is often needed far below the surface at or below the permafrost layer or at specific locations where the pressure-temperature conditions in the production tube may lead to a tendency toward undesirable hydrate "ice plug" formation. At such depths, steel heater strings are particularly fraught with drawbacks. Firstly, the friction coefficient of carbon and stainless steel often necessitates significant surface pressure in order to pump the heater fluid through the lengthy heater string. High surface pumping pressures require high capital cost pumps, increase operating costs and can be quite dangerous, also increasing the probability of ruptures, leaks and accidents.
Secondly, the thermal conductivity of steel leads to rapid heat transfer from the heater fluid to the well, which can be detrimental when heating is desired at great depths, since the heater fluid may be prematurely cooled by the time it reaches the desired heating location. This leads to higher energy costs - heating and pumping - necessary to transmit the heater fluid to the target zone. In order to avoid this premature cooling phenomenon, an operator may increase the fluid pressure, flow rate and temperature, which as mentioned above further exacerbates the disadvantages associated with high surface pumping pressures.
A section of the steel heater string may also rupture, crack or break-off. Break-off of a section of the heater string leads to further complications, including increased "fishing".
When a broken-off steel section falls down the wellbore at high speeds - sometimes reaching its terminal velocity - and then collides with the casing, the production tube or other well components, it fractures into many pieces that must be "fished" out of the well. Fishing can be very dangerous and results in shutdown time.
Thirdly, although steel may be relatively anti-corrosive compared to some other metals and alloys, in the harsh conditions of gas recovery wells, where highly corrosive compounds such as dissolved carbon dioxide and hydrogen sulphide are present, steel incurs unwanted chemical and physical wear. External corrosion can lead to accelerated deterioration, rupture Furthermore, given the capital costs associated with drilling a wellbore and installing the well components, there are often dimensional constraints which must be considered when The chemical nature of the formation, the hydrocarbons and the heater fluid also play a role in the functioning of heater strings. For instance, when sulphur, hydrogen sulphide or hydrate-forming compounds are present in the hydrocarbon stream, corrosion, sulphur deposition and In view of the above, it should be clear that there is a need for a technology that overcomes at least some of the disadvantages of the heater strings and well heating techniques that have been used up to now in the field.
The present invention responds to the above-mentioned need by providing a heater string, a hanger assembly, and a unique process of heating a well.
In one aspect of the present invention, there is provided a heater string for transmitting a heater fluid within a well, which includes a wellbore, a casing arranged within the wellbore and a production tube arranged within the casing. The heater string is mountable within the casing and adjacent to a portion of the production tube. The heater string includes an inlet for receiving the heater fluid, an elongate tubular body in fluid communication with the inlet and an inner tubular surface contiguous with the elongate body and contacting the heater fluid, and the inner tubular surface includes a plasticized polyamide blend.
The plasticized polyamide inner surface of the heater string allows a reduction of the friction between the heater fluid and the heater string and thermal conductivity of heat from the heater fluid toward the well, improving corrosion resistance, increasing the ductility, reducing the weight and reducing the likelihood of rupture, break-off and brittle fracturing. This enables improved heating at great depths by reducing the pressure required to pump the heater fluid as well as extending the heating capacity deep in to the well due to the insulation properties.
The plasticized polyamide enables advantages that are specific to heater string applications.
In optional embodiments, the heater string may be a one-piece tubular extrusion and the plasticizer may be a sulphonamide. The plasticized ployamide may optionally include tougheners and reinforcement members such as spines composed of aramid fiber.
In another aspect of the present invention, there is provided a process of heating a well having a wellbore, a casing arranged within the wellbore and a production tube arranged within the casing to define an annulus there between. The process includes:
providing a heater string comprising an inlet for receiving a heater fluid, an outlet for expelling the heater fluid, an elongate tubular body in fluid communication with the inlet and the outlet, and an inner tubular surface contiguous with the elongate body and contacting the heater fluid, the inner tubular surface comprising a plasticized polyamide blend;
mounting the heater string within the annulus;
providing the heater fluid at the inlet at a first pressure;
allowing the heater fluid to flow through the heater string to transfer heat to the production tube; and expelling the heater fluid from the outlet into the annulus.
In yet another aspect of the present invention, there is provided a hanger assembly for suspending a heater string within a well. The heater string may be constructed as one-piece tubular extrusion comprising a plasticized polyamide blend and having upstream and downstream ends and an inlet at the upstream end for receiving a heater fluid.
The hanger assembly includes an anchoring member secured to and extending radially outward from the upstream end of the heater string and having an upstream-facing surface and a downstream-facing surface. The hanger assembly also includes a nut mountable around the heater string and a connector body having an upstream section adapted to receive the heater fluid and a canalization in fluid communication with the inlet of the heater string. The nut and the connector body are securable together and abuttable against the upstream-facing surface and the downstream-facing surface of the anchoring member to enclose the anchoring member therebetween.
The hanger assembly allows a secure hold on a heater string while reducing or avoiding slippage or damage. The hanger assembly is preferably used for securing a heater string composed of a polymer material such as plasticized polyamide, as described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 is a side plan partial cross-sectional view of a well having a heater string therein, according to an optional embodiment of the present invention.
Fig 2 is a side plan partial cross-sectional view of a well having a heater string therein, according to another optional embodiment of the present invention.
Fig 3 is a cross-sectional view of a hanger assembly including part of a heater string, according to an optional embodiment of the present invention.
Fig 4 is a perspective view of the hanger assembly of Fig 3.
Fig 5 is a perspective partial transparent view of an outlet section of a heater string, according to another embodiment of the present invention.
Fig 6 is a transverse cross-sectional view schematic of a heater string showing embedded spines, according to an embodiment of the present invention.
The hanger assembly includes an anchoring member secured to and extending radially outward from the upstream end of the heater string and having an upstream-facing surface and a downstream-facing surface. The hanger assembly also includes a nut mountable around the heater string and a connector body having an upstream section adapted to receive the heater fluid and a canalization in fluid communication with the inlet of the heater string. The nut and the connector body are securable together and abuttable against the upstream-facing surface and the downstream-facing surface of the anchoring member to enclose the anchoring member therebetween.
The hanger assembly allows a secure hold on a heater string while reducing or avoiding slippage or damage. The hanger assembly is preferably used for securing a heater string composed of a polymer material such as plasticized polyamide, as described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 is a side plan partial cross-sectional view of a well having a heater string therein, according to an optional embodiment of the present invention.
Fig 2 is a side plan partial cross-sectional view of a well having a heater string therein, according to another optional embodiment of the present invention.
Fig 3 is a cross-sectional view of a hanger assembly including part of a heater string, according to an optional embodiment of the present invention.
Fig 4 is a perspective view of the hanger assembly of Fig 3.
Fig 5 is a perspective partial transparent view of an outlet section of a heater string, according to another embodiment of the present invention.
Fig 6 is a transverse cross-sectional view schematic of a heater string showing embedded spines, according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figs 1 and 2 illustrate wells 10 in which embodiments of the heater strings 12 may be installed. The illustrated wells 10 include a drilled vertical wellbore, although various embodiments of the present invention may be used in connection with slanted or horizontal wellbores or portions thereof. The well 10 further includes a casing 14 mounted within the wellbore, a production tube 16 mounted within the casing 14, and other tubes mounted within the casing. The outside of the production tube 16 and the inside of the casing 14 define an annulus 17 therebetween. It should be understood that the various tubes, strings and other components illustrated in Figs 1 and 2 are not to scale.
Referring to Fig 2, a chemical injection string 18 may also be installed within the annulus 17 to extend down the wellbore.
The heater string 12, chemical injection string 18 and production tube 16, each have a subsurface safety valve (SSSV). Figs 1 and 2 illustrate a SSSV control line 19 which may be arranged to a depth of about 50m. The chemical injection string 18 also has profiles 20 along its length.
Referring back to both to Figs 1 and 2, the production tube 16 also includes profiles 22 provided along its length. There may also be a packer 23 provided at a middle or lower portion of the well to provide isolation from the reservoir below.
Still referring to Figs 1 and 2, the heater string 12 is preferably installed to extend closely along an upper portion of the production tube 16 for providing heat to it. The heater string 12 is preferably suspended from a hanger assembly 24 at the top of the wellbore, and there may also be a string catcher 25 mounted below the heater string 12, in case of break off.
More particularly, the heater string 12 is installed for transmitting a heater fluid within the well 10. The heater fluid may be water, ethylene glycol or another type of heat transfer fluid or a combination thereof. Preferably, the heater fluid flows down the heater string and is expelled into the annulus 17 defined between the production tube 16 and the casing 14.
Also preferably, the heater fluid is then cycled back toward the surface and remains in a closed system. Spent heater fluid recovery and recycling equipment (not illustrated) may be provided at the surface of the well.
Referring briefly to Fig 6, the heater string 12 includes an elongate tubular body 26 and an inner tubular surface 27 contiguous with the elongate body 26 and contacting the heater fluid.
The inner surface defines a canalization having a preferred diameter between about 1/4 inch and about 2 inches. The tubular body may be generally cylindrical and the canalisation through which the heater fluid travels may also be generally cylindrical.
Alternatively, at least a portion of the wall or the canalization of the heater string may be tapered to provide specific fluid flow or heat transfer properties. The tapered portion may be, for instance, at the inlet or outlet of the string.
The inner tubular surface of the heater string 12 includes a plasticized polyamide blend. In one embodiment, the plasticized polyamide blend is provided as an internal liner and the elongate tubular body of the heater string is composed of a different material chosen from metals, rigid polymers or ductile polymers. Optionally, the heater string 12 may be manufactured by co-extruding polymers in contiguous melt-bonded layers.
In another embodiment, the entire heater string includes a plasticized polyamide blend and thus the elongate body and the inner surface form a one-piece tubular extrusion including the same plasticized polyamide blend. In this case, the heater string may be ductile and spoolable to facilitate transportation, storage and installation.
The heater string may comprise a plasticized polyamide blend produced by various methods.
The heater string may be extruded from pellets. The polyamide pellets may contain a variety of added components, such as plasticizer or a toughener or combinations thereof. In addition, thermal and oxidative stabilizers may be incorporated into the polymer as needed for the particular conditions of the heater string application. The pellet moisture content of the polyamide may be adjusted by drying or adding additional water. The polyamides used to produce the particles may be polyamide 11, 12, 6, 10, or 6,12. Other additives such as fillers and reinforcing agents may be incorporated into the pellets.
The heater string may be manufactured by using pellets as per the above general description, by forming the blend into a tubular shape. The heater string may be made of a polymer sold by DuPont under the trade name PipeIon . Alternatively, other plasticized polyamide blends may be employed in the production of the heater strings described herein.
For installation, the heater string 12 may be provided spooled around a coil tubing unit or reel.
The heater string is then uncoiled and fed down the wellbore to the desired depth, usually around to about 500-1500m depending on well flow properties.
Referring now to Fig 6, in one optional embodiment, the elongate body 26 may also include reinforcement members 28. The reinforcement members 28 may be spines embedded within the elongate body 26 and extending axially there along or in a spiral pattern at an angle from the longitudinal axis of body 26. The reinforcement members 28 may be up to 12 separate and discrete bundles consisting essentially of aramid fibres.
In another optional embodiment, the plasticized polyamide blend further includes at least one toughener. The tougheners may be grafted rubbers or ionic polymers or another suitable type, and may be anhydride-functionalized.
The heaters string 12 may also include one or more fibre optic cable 29. In the embodiment illustrated in Fig 6, the fibre optic cable 29 is embedded in the elongate body 26 of the heater string 12. The fibre optic cable 29 could alternatively be arranged inside the heater string after installation. The fibre optic cable 29 functions as a sensor and thus may be arranged according to the particular well flow properties and may be coupled with an automatic or manual control system (not illustrated) for modulating the well heating as desired. For example, when the sensor indicates that the temperature of a given portion of the well is near or has gone below a critical threshold of hydrate formation, the heater fluid temperature or inlet pressure may be increased as a counter measure.
Referring now to Fig 5, the elongate body is preferably generally linear and further includes an outlet for expelling the heater fluid the casing and the production tube.
The outlet may be flat, curved or have a mule-shoe shape or include modified outlet guide.
According to the illustrated embodiments, the heater string is non-branched, but various designs and alternative arrangements are possible.
The heater string may also include, upstream and proximate the outlet (0), at least one aperture (A) for expelling at least a portion of the heater fluid. In fact, there may be one or more apertures (A) provided along the heater string, for expelling a portion of the heater fluid at deliberate points along the heater string to prevent hydrate formation. The location of the apertures may be coordinated with the heater fluid inlet pressure and temperature to reduce the formation of hydrates at pre-determined or calculated locations along the production tube.
The heater sting embodiments according to the present invention may be used in a variety of applications for well heating. In one preferred application, the heater strings are used in natural gas wells. They may also be used in gas wells in general, condensate gas wells, crude oil wells with associated gas, and other wells. The heater strings are preferably used in applications requiring heat to prevent or mitigate the formation of hydrates.
In operation, the heater string is preferably used in conjunction with a process for well heating as will be further described below.
According to one aspect of the present invention, the process of heating a well includes step (a) of providing an embodiment of the heater string as described herein.
The process also includes step (b) of mounting the heater string within the annulus of the well. It should be understood that more than one heater string may be used, but in most cases a single heater string will be used as a replacement of an old steel version, thereby retrofitting an existing well. The heater string is mounted and arranged so as to heat exchange with the production. Optionally, the heater string may be suspended freely within the annulus.
The process also includes step (c) of providing the heater fluid at the inlet of the heater string at a first pressure. Optionally, the first pressure of the heater fluid is above about 0 MPa and below or equal to about 21 MPa. The heater fluid may be water, ethylene glycol, diesel, or a combination thereof, and the temperature of the heater fluid provided at the inlet may be between about 10 C and about 100 C. As will be explained hereinbelow, the pressure and temperature of the heater fluid may be controlled during the heating operation.
The process also includes step (d) of allowing the heater fluid to flow through the heater string to transfer heat to the production tube and step (e) of expelling the heater fluid from the outlet into the annulus. In some preferred embodiments of the process, the heat transfer mechanisms at work may include conduction and convection. More particularly, when the heater string is in direct physical contact with the production tube, conduction of heat occurs from the heater string's body through it contact surface with the production tube, which then heats the hydrocarbon stream within it. In addition, the heater fluid expelled from the outlet fills the annulus and flows upward, thereby heating the production tube on many if not all temperature and pressure conditions of the production tube so as to substantially reduce or avoid the formation of hydrates. The control may be based on pre-acquired measurements, modelling, experience, or real-time measurements on the particular wellbore location and depth parameters. For instance, the fibre optic cable or other sensors may be used with the The process may further include, in response to hydrate formation or an elevated risk of hydrate formation at a given location within the well, providing at least one aperture in the heater string for expelling a portion of the heater fluid at the given location. The apertures It is also preferable to cycle the heater fluid back up the annulus toward to the surface of the well to be recycled in a closed system.
Turning more particularly to the installation of various embodiments of the heater string 12, a hanger assembly 24 such as the one shown in Figs 3 and 4 may be employed. This hanger friction polymer material such as one composed of a plasticized polyamide blend. Such heater strings can be secured and suspended without slippage or damage.
More particularly, Fig 3 illustrates the hanger assembly 24 and its components. In describing the hanger assembly 24 it is useful to define the heater string 12 as including upstream 30 and downstream 32 ends and an inlet 34 at the upstream end for receiving a heater fluid. The hanger assembly 24 includes an anchoring member 36 secured to and extending radially outward from the upstream end of the heater string 12 and having an upstream-facing surface 38 and a downstream-facing surface 40. The anchoring member 36 may be, for example, a slip-type configuration, such as a LenzTM split ring on the outside surface of the heater string 12. The hanger assembly 24 also includes a nut 42 mountable around the heater string 12 and a connector body 44 having an upstream section 46 with outer threads 47. The upstream section 46 is adapted to receive the heater fluid. The connector body 44 also has a canalization 48 in fluid communication with the inlet 34 of the heater string 12. The nut 42 and the connector body 44 are securable together and abuttable against the upstream-facing surface 38 and the downstream-facing surface 40 of the anchoring member 36 to enclose the anchoring member 36 between them.
In one optional embodiment of the hanger assembly 24, the nut 42 may have a head 50 abuttable against the downstream-facing surface 40 of the anchoring member 36 and have a projection 52 extending upstream from the head 50. The connector body 44 may have a downstream section 54 opposite the upstream section 46, the downstream section comprising a neck 56 mountable around the heater string 12, abuttable against the upstream-facing surface 38 of the anchoring member 36 and securable to the projection 52 of the nut 42, in order to enclose the anchoring member 36. The projection 52 of the nut 42 is preferably secured around an outer surface of the neck of the connector body, and the projection and the outer surface are screwed together via cooperative threads.
The anchoring member 36 may also include an annular portion 58 secured to the heater string and a flange portion 60 extending outward from the annular portion 58, the flange portion 60 defining the upstream-facing 38 and downstream-facing 40 surfaces.
The annular portion 58 may be frustro-conical shaped tapering radially outward in the upstream direction.
The head 50 of the nut 42 may have an upstream-facing rim 62 abuttable against the downstream-facing surface 40 of the anchoring member 36, and an inner surface 64 having a frustro-conical shape corresponding to the annular portion 58 to abut thereagainst.
The connector body 44 may further include a peripheral edge 66 extending outward from the neck and being axially abuttable against the projection 52 of the nut 42. The neck of the connector body may also have inner annular grooves 68 and further comprising 0-rings 70 mounted within the inner annular grooves 68 and contacting the heater string.
The hanger assembly may also include a backup member 72 integrated into the connector body 44 and inserted into the inlet of the heater string. The backup member, he nut, the connector body and the anchoring member may all be composed of stainless steel.
It should be understood that "upstream-facing" and "downstream-facing" are meant for general reference and not to limit the geometry of the hanger assembly or heater string to mathematical exactitude. Thus, many angles and variations in orientation are possible for embodiments of the hanger assembly.
It should also be understood that the embodiments described herein are exemplary and are not meant to narrow or limit of what has actually been invented.
Figs 1 and 2 illustrate wells 10 in which embodiments of the heater strings 12 may be installed. The illustrated wells 10 include a drilled vertical wellbore, although various embodiments of the present invention may be used in connection with slanted or horizontal wellbores or portions thereof. The well 10 further includes a casing 14 mounted within the wellbore, a production tube 16 mounted within the casing 14, and other tubes mounted within the casing. The outside of the production tube 16 and the inside of the casing 14 define an annulus 17 therebetween. It should be understood that the various tubes, strings and other components illustrated in Figs 1 and 2 are not to scale.
Referring to Fig 2, a chemical injection string 18 may also be installed within the annulus 17 to extend down the wellbore.
The heater string 12, chemical injection string 18 and production tube 16, each have a subsurface safety valve (SSSV). Figs 1 and 2 illustrate a SSSV control line 19 which may be arranged to a depth of about 50m. The chemical injection string 18 also has profiles 20 along its length.
Referring back to both to Figs 1 and 2, the production tube 16 also includes profiles 22 provided along its length. There may also be a packer 23 provided at a middle or lower portion of the well to provide isolation from the reservoir below.
Still referring to Figs 1 and 2, the heater string 12 is preferably installed to extend closely along an upper portion of the production tube 16 for providing heat to it. The heater string 12 is preferably suspended from a hanger assembly 24 at the top of the wellbore, and there may also be a string catcher 25 mounted below the heater string 12, in case of break off.
More particularly, the heater string 12 is installed for transmitting a heater fluid within the well 10. The heater fluid may be water, ethylene glycol or another type of heat transfer fluid or a combination thereof. Preferably, the heater fluid flows down the heater string and is expelled into the annulus 17 defined between the production tube 16 and the casing 14.
Also preferably, the heater fluid is then cycled back toward the surface and remains in a closed system. Spent heater fluid recovery and recycling equipment (not illustrated) may be provided at the surface of the well.
Referring briefly to Fig 6, the heater string 12 includes an elongate tubular body 26 and an inner tubular surface 27 contiguous with the elongate body 26 and contacting the heater fluid.
The inner surface defines a canalization having a preferred diameter between about 1/4 inch and about 2 inches. The tubular body may be generally cylindrical and the canalisation through which the heater fluid travels may also be generally cylindrical.
Alternatively, at least a portion of the wall or the canalization of the heater string may be tapered to provide specific fluid flow or heat transfer properties. The tapered portion may be, for instance, at the inlet or outlet of the string.
The inner tubular surface of the heater string 12 includes a plasticized polyamide blend. In one embodiment, the plasticized polyamide blend is provided as an internal liner and the elongate tubular body of the heater string is composed of a different material chosen from metals, rigid polymers or ductile polymers. Optionally, the heater string 12 may be manufactured by co-extruding polymers in contiguous melt-bonded layers.
In another embodiment, the entire heater string includes a plasticized polyamide blend and thus the elongate body and the inner surface form a one-piece tubular extrusion including the same plasticized polyamide blend. In this case, the heater string may be ductile and spoolable to facilitate transportation, storage and installation.
The heater string may comprise a plasticized polyamide blend produced by various methods.
The heater string may be extruded from pellets. The polyamide pellets may contain a variety of added components, such as plasticizer or a toughener or combinations thereof. In addition, thermal and oxidative stabilizers may be incorporated into the polymer as needed for the particular conditions of the heater string application. The pellet moisture content of the polyamide may be adjusted by drying or adding additional water. The polyamides used to produce the particles may be polyamide 11, 12, 6, 10, or 6,12. Other additives such as fillers and reinforcing agents may be incorporated into the pellets.
The heater string may be manufactured by using pellets as per the above general description, by forming the blend into a tubular shape. The heater string may be made of a polymer sold by DuPont under the trade name PipeIon . Alternatively, other plasticized polyamide blends may be employed in the production of the heater strings described herein.
For installation, the heater string 12 may be provided spooled around a coil tubing unit or reel.
The heater string is then uncoiled and fed down the wellbore to the desired depth, usually around to about 500-1500m depending on well flow properties.
Referring now to Fig 6, in one optional embodiment, the elongate body 26 may also include reinforcement members 28. The reinforcement members 28 may be spines embedded within the elongate body 26 and extending axially there along or in a spiral pattern at an angle from the longitudinal axis of body 26. The reinforcement members 28 may be up to 12 separate and discrete bundles consisting essentially of aramid fibres.
In another optional embodiment, the plasticized polyamide blend further includes at least one toughener. The tougheners may be grafted rubbers or ionic polymers or another suitable type, and may be anhydride-functionalized.
The heaters string 12 may also include one or more fibre optic cable 29. In the embodiment illustrated in Fig 6, the fibre optic cable 29 is embedded in the elongate body 26 of the heater string 12. The fibre optic cable 29 could alternatively be arranged inside the heater string after installation. The fibre optic cable 29 functions as a sensor and thus may be arranged according to the particular well flow properties and may be coupled with an automatic or manual control system (not illustrated) for modulating the well heating as desired. For example, when the sensor indicates that the temperature of a given portion of the well is near or has gone below a critical threshold of hydrate formation, the heater fluid temperature or inlet pressure may be increased as a counter measure.
Referring now to Fig 5, the elongate body is preferably generally linear and further includes an outlet for expelling the heater fluid the casing and the production tube.
The outlet may be flat, curved or have a mule-shoe shape or include modified outlet guide.
According to the illustrated embodiments, the heater string is non-branched, but various designs and alternative arrangements are possible.
The heater string may also include, upstream and proximate the outlet (0), at least one aperture (A) for expelling at least a portion of the heater fluid. In fact, there may be one or more apertures (A) provided along the heater string, for expelling a portion of the heater fluid at deliberate points along the heater string to prevent hydrate formation. The location of the apertures may be coordinated with the heater fluid inlet pressure and temperature to reduce the formation of hydrates at pre-determined or calculated locations along the production tube.
The heater sting embodiments according to the present invention may be used in a variety of applications for well heating. In one preferred application, the heater strings are used in natural gas wells. They may also be used in gas wells in general, condensate gas wells, crude oil wells with associated gas, and other wells. The heater strings are preferably used in applications requiring heat to prevent or mitigate the formation of hydrates.
In operation, the heater string is preferably used in conjunction with a process for well heating as will be further described below.
According to one aspect of the present invention, the process of heating a well includes step (a) of providing an embodiment of the heater string as described herein.
The process also includes step (b) of mounting the heater string within the annulus of the well. It should be understood that more than one heater string may be used, but in most cases a single heater string will be used as a replacement of an old steel version, thereby retrofitting an existing well. The heater string is mounted and arranged so as to heat exchange with the production. Optionally, the heater string may be suspended freely within the annulus.
The process also includes step (c) of providing the heater fluid at the inlet of the heater string at a first pressure. Optionally, the first pressure of the heater fluid is above about 0 MPa and below or equal to about 21 MPa. The heater fluid may be water, ethylene glycol, diesel, or a combination thereof, and the temperature of the heater fluid provided at the inlet may be between about 10 C and about 100 C. As will be explained hereinbelow, the pressure and temperature of the heater fluid may be controlled during the heating operation.
The process also includes step (d) of allowing the heater fluid to flow through the heater string to transfer heat to the production tube and step (e) of expelling the heater fluid from the outlet into the annulus. In some preferred embodiments of the process, the heat transfer mechanisms at work may include conduction and convection. More particularly, when the heater string is in direct physical contact with the production tube, conduction of heat occurs from the heater string's body through it contact surface with the production tube, which then heats the hydrocarbon stream within it. In addition, the heater fluid expelled from the outlet fills the annulus and flows upward, thereby heating the production tube on many if not all temperature and pressure conditions of the production tube so as to substantially reduce or avoid the formation of hydrates. The control may be based on pre-acquired measurements, modelling, experience, or real-time measurements on the particular wellbore location and depth parameters. For instance, the fibre optic cable or other sensors may be used with the The process may further include, in response to hydrate formation or an elevated risk of hydrate formation at a given location within the well, providing at least one aperture in the heater string for expelling a portion of the heater fluid at the given location. The apertures It is also preferable to cycle the heater fluid back up the annulus toward to the surface of the well to be recycled in a closed system.
Turning more particularly to the installation of various embodiments of the heater string 12, a hanger assembly 24 such as the one shown in Figs 3 and 4 may be employed. This hanger friction polymer material such as one composed of a plasticized polyamide blend. Such heater strings can be secured and suspended without slippage or damage.
More particularly, Fig 3 illustrates the hanger assembly 24 and its components. In describing the hanger assembly 24 it is useful to define the heater string 12 as including upstream 30 and downstream 32 ends and an inlet 34 at the upstream end for receiving a heater fluid. The hanger assembly 24 includes an anchoring member 36 secured to and extending radially outward from the upstream end of the heater string 12 and having an upstream-facing surface 38 and a downstream-facing surface 40. The anchoring member 36 may be, for example, a slip-type configuration, such as a LenzTM split ring on the outside surface of the heater string 12. The hanger assembly 24 also includes a nut 42 mountable around the heater string 12 and a connector body 44 having an upstream section 46 with outer threads 47. The upstream section 46 is adapted to receive the heater fluid. The connector body 44 also has a canalization 48 in fluid communication with the inlet 34 of the heater string 12. The nut 42 and the connector body 44 are securable together and abuttable against the upstream-facing surface 38 and the downstream-facing surface 40 of the anchoring member 36 to enclose the anchoring member 36 between them.
In one optional embodiment of the hanger assembly 24, the nut 42 may have a head 50 abuttable against the downstream-facing surface 40 of the anchoring member 36 and have a projection 52 extending upstream from the head 50. The connector body 44 may have a downstream section 54 opposite the upstream section 46, the downstream section comprising a neck 56 mountable around the heater string 12, abuttable against the upstream-facing surface 38 of the anchoring member 36 and securable to the projection 52 of the nut 42, in order to enclose the anchoring member 36. The projection 52 of the nut 42 is preferably secured around an outer surface of the neck of the connector body, and the projection and the outer surface are screwed together via cooperative threads.
The anchoring member 36 may also include an annular portion 58 secured to the heater string and a flange portion 60 extending outward from the annular portion 58, the flange portion 60 defining the upstream-facing 38 and downstream-facing 40 surfaces.
The annular portion 58 may be frustro-conical shaped tapering radially outward in the upstream direction.
The head 50 of the nut 42 may have an upstream-facing rim 62 abuttable against the downstream-facing surface 40 of the anchoring member 36, and an inner surface 64 having a frustro-conical shape corresponding to the annular portion 58 to abut thereagainst.
The connector body 44 may further include a peripheral edge 66 extending outward from the neck and being axially abuttable against the projection 52 of the nut 42. The neck of the connector body may also have inner annular grooves 68 and further comprising 0-rings 70 mounted within the inner annular grooves 68 and contacting the heater string.
The hanger assembly may also include a backup member 72 integrated into the connector body 44 and inserted into the inlet of the heater string. The backup member, he nut, the connector body and the anchoring member may all be composed of stainless steel.
It should be understood that "upstream-facing" and "downstream-facing" are meant for general reference and not to limit the geometry of the hanger assembly or heater string to mathematical exactitude. Thus, many angles and variations in orientation are possible for embodiments of the hanger assembly.
It should also be understood that the embodiments described herein are exemplary and are not meant to narrow or limit of what has actually been invented.
Claims (26)
1. A heater string for transmitting a heater fluid within a well, the well comprising a wellbore, a casing arranged within the wellbore and a production tube arranged within the casing, the heater string being mountable within the casing and adjacent to a portion of the production tube, the heater string comprising an inlet for receiving the heater fluid, an elongate tubular body in fluid communication with the inlet and an inner tubular surface contiguous with the elongate body and contacting the heater fluid, the inner tubular surface comprising a plasticized polyamide blend.
2. The heater string of claim 1, wherein the elongate body comprises a plasticized polyamide blend.
3. The heater string of claim 2, wherein the elongate body and the inner surface form a one-piece tubular extrusion comprising the same plasticized polyamide blend.
4. The heater string of claim 3, wherein it has at least one tapered portion.
5. The heater string of claim 2 or 3, wherein it is generally cylindrical.
6. The heater string of any one of claims 2 to 5, further comprising one or more fibre optic cables embedded within or accommodated inside the elongate body.
7. The heater string of any one of claims 2 to 6, wherein the elongate body further comprises reinforcement members.
8. The heater string of claim 6, wherein the reinforcement members comprise spines embedded within the elongate body and extending axially or spirally therealong.
9. The heater string of claim 8, wherein the spines comprise or consist essentially of aramid fibres.
10. The heater string of any one of claims 2 to 9, wherein the plasticized polyamide blend further comprises at least one toughener.
11. The heater string of any one of claims 10, wherein the toughener includes grafted rubbers or ionic polymers.
12. The heater string of any one of claims 11, wherein the toughener includes an anhydride-functionalized toughener.
13. The heater string of any one of claims 1 to 12, wherein the inner surface defines a canalization having a diameter between about 3/4 inch and about 2 inches.
14. The heater string of any one of claims 1 to 13, wherein the elongate body is generally linear and further comprises an outlet for expelling the heater fluid between the casing and the production tube.
15. The heater string of claim 14, wherein the outlet has a mule-shoe shape or a modified outlet guide.
16. The heater string of claim 14 or 15, further comprising upstream and proximate the outlet at least one aperture for expelling a portion of the heater fluid.
17. The heater string of any one of claims 1 to 15, further comprising at least one aperture provided along the heater string for expelling a portion of the heater fluid.
18. A process of heating a well having a wellbore, a casing arranged within the wellbore and a production tube arranged within the casing to define an annulus therebetween, the process comprising:
(a) providing a heater string comprising an inlet for receiving a heater fluid, an outlet for expelling the heater fluid, an elongate tubular body in fluid communication with the inlet and the outlet, and an inner tubular surface contiguous with the elongate body and contacting the heater fluid, the inner tubular surface comprising a plasticized polyamide blend;
(b) mounting the heater string within the annulus;
(c) providing the heater fluid at the inlet at a first pressure and a first temperature;
(d) allowing the heater fluid to flow through the heater string; and (e) expelling the heater fluid from the outlet into the annulus to heat the production tube.
(a) providing a heater string comprising an inlet for receiving a heater fluid, an outlet for expelling the heater fluid, an elongate tubular body in fluid communication with the inlet and the outlet, and an inner tubular surface contiguous with the elongate body and contacting the heater fluid, the inner tubular surface comprising a plasticized polyamide blend;
(b) mounting the heater string within the annulus;
(c) providing the heater fluid at the inlet at a first pressure and a first temperature;
(d) allowing the heater fluid to flow through the heater string; and (e) expelling the heater fluid from the outlet into the annulus to heat the production tube.
19. The process of claim 18, wherein the first pressure of the heater fluid is above about 0 MPa and below or equal to about 21 MPa.
20. The process of claim 18 or 19, wherein the heater fluid comprises water, ethylene glycol, diesel, or a combination thereof, and the first temperature of the heater fluid provided at the inlet is between about 10°C and about 100°C.
21. The process of any one of claims 18 to 20, wherein the heater string is mounted so as to directly heat exchange with the production tube.
22. The process of any one of claims 18 to 21, wherein step (b) is performed by retrofitting an existing well.
23. The process of any one of claims 18 to 22, wherein steps (c) to (e) comprise controlling the flow of the heater fluid to maintain temperature and pressure conditions of the production tube so as to substantially avoid formation of hydrates therein.
24. The process of any one of claims 18 to 23, wherein the heater string is defined according to any one of claims 1 to 17.
25. The process of any one of claims 18 to 24, further comprising, in response to hydrate formation at a given location within the well, providing at least one aperture in the heater string for expelling a portion of the heater fluid at the given location.
26. The process of any one of claims 18 to 25, further comprising cycling the heater fluid back in a closed system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2809273A CA2809273C (en) | 2010-04-22 | 2010-05-18 | Hanger assembly and system including hanger assembly and heater string |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US32696810P | 2010-04-22 | 2010-04-22 | |
| US61/326,968 | 2010-04-22 |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2809273A Division CA2809273C (en) | 2010-04-22 | 2010-05-18 | Hanger assembly and system including hanger assembly and heater string |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2704561A1 CA2704561A1 (en) | 2011-10-22 |
| CA2704561C true CA2704561C (en) | 2014-10-21 |
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ID=44834916
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2809273A Active CA2809273C (en) | 2010-04-22 | 2010-05-18 | Hanger assembly and system including hanger assembly and heater string |
| CA2704561A Active CA2704561C (en) | 2010-04-22 | 2010-05-18 | Heater string and process of well heating |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2809273A Active CA2809273C (en) | 2010-04-22 | 2010-05-18 | Hanger assembly and system including hanger assembly and heater string |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA2809273C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103739895B (en) * | 2013-12-20 | 2016-03-02 | 柳州日高汽车减振技术有限责任公司 | Hanger bracket assembly sizing material and after-processing technology |
| CN105604512A (en) * | 2016-03-14 | 2016-05-25 | 中国石油集团西部钻探工程有限公司 | Dual-row-type prestressed well cementation ground anchor assembly |
| CN105604511B (en) * | 2016-03-14 | 2018-03-02 | 中国石油集团西部钻探工程有限公司 | Thermal production well earth anchor |
-
2010
- 2010-05-18 CA CA2809273A patent/CA2809273C/en active Active
- 2010-05-18 CA CA2704561A patent/CA2704561C/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CA2809273A1 (en) | 2011-10-22 |
| CA2704561A1 (en) | 2011-10-22 |
| CA2809273C (en) | 2014-10-21 |
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