AU2007323801B2

AU2007323801B2 - Insulating fluid and methods for preparing and insulating concentric piping

Info

Publication number: AU2007323801B2
Application number: AU2007323801A
Authority: AU
Inventors: Sho-Wei Lo; Xiaoping Qiu
Original assignee: SHELL INT RESEARCH; Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2006-11-17
Filing date: 2007-11-15
Publication date: 2011-03-31
Anticipated expiration: 2027-11-15
Also published as: GB2456272A; WO2008064074A1; CA2669400C; AU2007323801A1; CA2669400A1; GB2456272B; US20100025615A1; GB0908297D0

Description

WO 2008/064074 PCT/US2007/084814 INSULATING FLUID AND METHODS FOR PREPARING AND INSULATING CONCENTRIC PIPING Field of Invention 5 The present inventions relate to an insulating fluid, a method for preparing the insulating fluid, and a method for insulating concentric piping using the insulating fluid. Background Annular fluids or packer fluids are liquids that are pumped into an annular 10 opening between a casing and a wellbore wall or between adjacent, concentric strings of pipe extending into a wellbore. The main functions of a packer fluid are to provide hydrostatic pressure in order to lower differential pressure across a sealing element, to lower differential pressure on the wellbore and casing to prevent collapse, and to protect metals in the completion from corrosion. Packer 15 fluids are prepared according to the requirements of the given completion. Generally, they should be of sufficient density to control the producing formation, solids-free and resistant to viscosity changes over long periods of time, and non corrosive to the wellbore and completion components. Special well conditions may require a packer fluid to also serve an 20 insulating function. In high temperature wells, hot fluid flowing inside the production tubing can cause the packer fluid to expand, rapidly building up pressure in the sealed annulus. In extreme circumstances, this build-up could potentially collapse the tubing or burst the casing, a result that would be catastrophic to the well. In addition, heat loss from the production tubing may 25 cause a variety of low-temperature problems including hydrate build-up, paraffin deposition, and precipitation of salts. Deepwater wells face a similar problem related to flow assurance. Undesired heat loss from production tubing to outer annuli can lead to the deposition of sludge, paraffin and asphaltene materials, the formation of gas 30 hydrates, and cause severe flow assurance problems and loss of productivity. In recent years, thermal insulation fluids have been successfully applied in wellbore and deepwater risers to prevent undesired heat loss. Other alternatives include 1 2 external insulation or injection of nitrogen gas for risers. Thus, many wells could benefit from the use of an insulating fluid capable of use in completions and risers. US Published Application 2004/0011990 Al (hereafter Dunaway) discloses a thermally insulating fluid comprising a glycol solvent for a viscosifier, a viscosifier, and optionally an aqueous 5 brine. The glycol may be selected from a propylene glycol, or under excessive heat temperatures, a butylene glycol, which can be used with or without a viscosifier. Viscosifiers can be selected from hydroxyl propyl methyl cellulose, xanthan and hydroxyl propyl guar and combinations thereof. The Dunaway fluid is not as insulating as is often desired. US Published Application 2005/0038199 Al (hereafter Wang) discloses a thermal insulating io fluid containing water and/or brine, a crosslinkable viscosifying polymer, a crosslinking agent and an optional set retarder. The composition is capable of inhibiting unwanted heat loss from production tubing or uncontrolled heat transfer to outer annuli. The viscosity of the composition is such as to reduce the convection flow velocity within the annulus. Although the insulating fluid in Wang exhibits low convection, the Wang fluid is not as insulating as is often desired. Is US Published Application 2004/0059054 (hereafter Lopez) discloses a thermal insulating fluid containing at least one water superabsorbent polymer and optionally water and/or brine, and a viscosifying polymer. The composition is capable of inhibiting unwanted heat loss from production tubing or uncontrolled heat transfer to outer annuli. The viscosity of the composition is sufficient to reduce the convection flow velocity within the annulus. One of the potential drawbacks of using the 20 fluid in Lopez is that when a workover is necessary, the Lopez fluid is not as insulating as is often desired. There is a need in the industry for the development of an insulating fluid that exhibits low thermoconductivity, low convection, and thermal stability. 25 Summary of the Invention In accordance with the present invention there is provided a method for insulating an annulus between concentric pipes comprising injecting into the annulus an insulating fluid comprising a non particulate viscosifying polymer selected from the group consisting of hydroxyl propryl guar, carboxymethyl hydroxypropyl and carboxymethyl-cellulose, a water or a brine, a cross-linking 30 agent, and a quantity of 0.1% to 30% by weight of insulating particulates selected from the group consisting of hollow glass bubbles and glass beads.

3 Brief Description of the Drawings The present invention is better understood by reading the following description of non limitative embodiments with reference to the attached drawings, which are briefly described as follows: s Figure 1 illustrates the test setup used for measuring the thermal conductivity of the insulating fluid. Figure 2 is a plot of the yield strength of the insulating fluid. Detailed Description 10 The invention relates to the application of a polymer-based fluid as an annular fluid (insulating fluid or packer fluid) for insulating production tubing or casing, insulating fluid during well treatment, or insulating fluid for risers for deepwater wells. This fluid is non-convective and exhibits low thermal conductivity and high thermal stability. The insulating fluid comprises a non-particulate viscosifying polymer, a water or brine, a cross-linking agent, and insulating particulates. Optionally, 15 the insulating fluid may further comprise a solvent. The density of the fluid is adjustable to fit the downhole pressure requirement for the wells. Preferred non-particulate viscosifying polymers are those having a high degree of molar substitution (MS) and are salt-tolerant. The hydroxyl groups enable better hydration in high concentration brines. Suitable non-particulate viscosifying polymers include cellulose, xanthan, 20 starch, guar gum and a derivatives thereof. Particularly suitable viscosifying polymer fluids include hydroxyl propryl guar, carboxymethyl hydroxypropyl, and carboxymethyl-cellulose. The non particulate viscosifying polymer is preferably present in a quantity of 0.1 % to 5 % by weight. The fluid can be crosslinked by metal ions such as Zr or Ti crosslinkers. Crosslinking generally increases viscosity, which in turn reduces eliminates WO 2008/064074 PCT/US2007/084814 convection. If desired, the crosslinking can be delayed to ensure pumpability of the fluid during mixing and for an amount of time thereafter. Suitable cross-linking agents include borate, zirconium, and organic complexed metals. The cross-linking agent is present in a quantity of 0.01 % to 5% by weight. 5 To lower the thermal conductivity and increase viscosity, particulates such as hollow glass bubbles, beads, or fibers are added to the mixture. The insulating particulates can be suspended in the mixture because of its high viscosity. Void spaces in the insulating particulates, if present, help reduce thermal conductivity of the mixture. The insulating particulates are preferably present in a quantity of 0.1% 10 to 30% by weight. Optionally, a solvent may be added to the insulating fluid to enhance the properties. Particularly suitable solvents include ethylene glycol ethers, propylene glycol ethers, and polyols.ethylene glycol ethers, propylene glycol ethers, and polyols. The solvent is preferably present in a quantity of 0.1% to 99.9% by weight. 15 Preferred methods for producing the present insulating fluids generally include: adding a non-particulate viscosifying polymer to a water or brine, adding a cross-linking agent; and adding insulating particulates. The insulating fluid may be mixed in the lab or in the field using a batch mixing method or continuous mixing method. The components of the insulating fluid may be mixed in any order. 20 Optionally a solvent may be added to the mix via batch mixing or continuous mixing. One preferred method of using the insulating fluid is for insulation of concentric piping, downhole tubulars, or similar situations where it is desirable to insulate the outside of a pipe. The insulating fluid may be injected into the annulus 25 between two or more concentric pipes or between a pipe and a wellbore or the like. Applications in which the present insulating fluids may be used include, but are not limited to, outside of production tubing casing, between casing and tubing, and around surface pipelines, subsea pipelines, or risers. Advantages of some embodiments of the invention include one or more of the 30 following: * Low thermal conductivity * Non-convection * High thermal stability 4 WO 2008/064074 PCT/US2007/084814 * Synergistic effect between cross-linking agent and insulating particulates * High pumpability (can be continuously mixed) * Easily broken to remove from the concentric piping with acids, peroxides, or other breakers 5 0 Environmentally safe EXAMPLES Example 1 In Example 1, the thermal conductivity of various formulations of the 10 insulating fluid were measured using a guarded heat flow meter. The guarded heat flow meter method is appropriate for measuring thermal conductivities in the range of 0.1 to 8 W-m- 1

-K-

1 in the temperature range from -120 to 300 0C with an accuracy of approximately ±6 %. This method is described in ASTM (American Society for Testing and Materials) Practice F 433, Standard Practice for Evaluating 15 Thermal Conductivity of Gasket Materials and in ASTM E 1530, Standard Test Method for Evaluating the Resistance to Thermal Transmission of Thin Specimens of Materials by the Guarded Heat Flow Meter Technique. A schematic diagram of the guarded heat flow meter is shown in Figure 1. The sample (a 2.0 inch diameter disk) was placed between two plates at different 20 temperatures, thus producing a heat flow through the sample. The hot-side heater temperature, Th, was controlled with a set-point controller; this parameter is used to set the mean temperature of the sample. The cold-side temperature and the guard temperature were controlled relative to the heater with differential controllers. The heat flow was measured with a heat flux transducer (a multi 25 junction thermopile across a thin sheet of insulation) contained in the lower plate. The sample was surrounded by a cylindrical guard which was maintained at a temperature close to the mean sample temperature to reduce lateral heat flow. Upper plate, lower plate, and guard temperatures were measured with type K (chromel/alumel) thermocouples. The sample was held between the plates of the 30 instrument with a piston pressure on the order of 20 psi. Four samples containing a base fluid, Zr as a cross-linking agent, hydroxyl propryl guar (HPG) as a non-particulate viscosifying polymer, and varying amounts of glass beads as insulating particulates were tested. Two of the four samples also 5 WO 2008/064074 PCT/US2007/084814 included a solvent (propylene glycol). Comparative sample (0419-1) contained no insulating particulates. Table 1 shows the compositions of the tested formulations: Table 1 Glass Glass Beads beads cross Polymer (g/100 linker Base Zr Sample wt% wt% mL) wt% HPG fluid cross-linker A 0.94 3.30 4.2 0.20 100# 10.5 ppg NaBr 2 gpt B 0.88 9.56 13 0.20 100# 10.5 ppg NaBr 2 gpt 50/50 2% KCI and propylene C 1.05 11.30 13 0.20 100# glycol 2 gpt 50/50 2% KC' and propylene D 1.20 0 0.0 0.20 100# glycol 2 gpt 5 Each sample was tested at two temperatures and the thermal conductivity data was recorded. The results of the tests are displayed in Table 2 below: Table 2 Thckness Temperature Conductivity Conductivity Saml () (W/m-K) BTU/(ft.h.*F) Sample (mm) (*C) (*F) A 10.4 4 39 0.433 0.250 23 73 0.457 0.264 B 9.84 5 41 0.341 0.197 23 73 0.342 0.198 C 11.0 5 41 0.304 0.176 23 74 0.299 0.173 D 10.3 5 41 0.393 0.227 23 74 0.389 0.225 10 Example 2 In Example 2, a sample was tested using a rheometer to determine thermal convection from yield strength (or gel strength) data. The standard paper used for natural convection of a viscous fluid in an annulus is G. Paul Willhite, "Over-all 15 Heat Transfer Coefficients in Steam and Hot Water Injection Wells," Journal of Petroleum Technology, May, 1967, which is hereby incorporated by reference. 6 7 There is an inverse correlation between gel strength and convection because insulating fluids can be modeled as Bingham materials. When a layer of Bingham material is subjected to a shear stress, it will not flow unless the shear stress exceeds the yield strength strength, To. Therefore a fluid with high yield strength will exhibit low convection. 5 In this example, the formulation of the sample was the same as that of sample A in Example 1. The experiments were performed at 1 Hz of frequency with an oscillation rheometer at a temperature of 44 0 C. A 1 mm sample was placed in between two plates. The bottom plate was fixed and the upper plate was oscillated. The torque required to oscillate the plate was measured and the yield strength of the sample. The results are shown Figure 2. The same test was io performed for a non-convective oil-based packer fluid. Sample A exhibits much higher yield point than the packer fluid, which suggests that the sample A is non-convective.

Claims

1. A method for insulating an annulus between concentric pipes, comprising injecting into the annulus an insulating fluid comprising a non-particulate viscosifying polymer selected from the group consisting of hydroxyl propryl guar, carboxymethyl hydroxypropyl, and carboxymethyl 5 cellulose, a water or brine, a cross-linking agent, and a quantity of 0.1% to 30% by weight of insulating particulates selected from the group consisting of hollow glass bubbles and glass beads.

2. The method of claim 1 wherein the pipes are production tubings, casings, surface pipelines, subsea pipelines, or risers.

3. The method of claim 1 or 2 wherein the cross-linking agent is selected from the group to consisting of borate, zirconium, titanium and organic complexed metals.

4. The method of any one of claims 1 to 3 wherein the insulating fluid further comprises a solvent.

5. The method of claim 4 wherein the solvent is an ether.

6. The method of claim 5 wherein the ether is selected from the group consisting of is ethylene glycol ethers, propylene glycol ethers, and polyols.

7. The method of any one of claims 1 to 6 wherein the cross-linking agent is present in a quantity of 0.01% to 5% by weight.

8. The method of any one of claims 1 to 7 wherein the non-particulate viscosifying polymer is present in a quantity of 0.1% to 5% by weight. 20

9. A method for insulating an annulus between concentric pipes, substantially as hereinbefore described with reference to any one of the examples and/or any one of the accompanying drawings. Dated 25 January, 2011 25 Shell Internationale Research Maatschapij B.V. Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON