SYSTEMS AND METHODS IN WHICH COLLOIDAL SILICA GEL IS USED TO RESIST CORROSION OF A WELLHEAD COMPONENT IN A WELL CELLAR

Abstract

A system includes a well cellar, a wellhead and a colloidal silica gel. The well cellar includes a base and sidewalls extending from the base. The wellhead includes an aboveground region extending above the well cellar and a belowground region in the well cellar. The belowground region of the wellhead includes a wellhead component having an exterior surface. The colloidal silica gel occupies a volume extending from the base and sidewalls of the well cellar to the exterior surface of the wellhead component. The colloidal silica gel covers the exterior surface of the wellhead component.

Claims

1. A system comprising: a well cellar comprising a base and sidewalls extending from the base; a wellhead comprising an aboveground region extending above the well cellar and a belowground region in the well cellar, the belowground region of the wellhead comprising a wellhead component having an exterior surface; and a colloidal silica gel occupying a volume extending from the base and sidewalls of the well cellar to the exterior surface of the wellhead component, wherein the colloidal silica gel covers the exterior surface of the wellhead component.

2. The system of claim 1, wherein the colloidal silica gel substantially prevents water from passing through the colloidal silica gel to reach the exterior surface of the wellhead component.

3. The system of claim 1, further comprising a solid covering an upper surface of the polyacrylamide gel.

4. The system of claim 1, further comprising sand covering an upper surface of the colloidal silica gel.

5. The system of claim 1, wherein the wellhead component comprises a landing base.

6. The system of claim 1, wherein the wellhead component comprises a surface casing.

7. The system of claim 6, wherein the colloidal silica gel covers an exterior surface of an additional wellhead component.

8. The system of claim 7, wherein the additional wellhead component comprises a landing base.

9. The system of claim 1, wherein the system comprises a well selected from the group consisting of an oil well, a gas well and a water well.

10. The system of claim 1, wherein the base of the well cellar has an opening, and the wellhead comprises a plurality of casings that pass through and extend beneath the base of the well cellar.

11. The system of claim 1, wherein the plurality of casings comprise a surface casing that houses the other casings.

12. The system of claim 1, wherein the volume occupied by the gel is at least 1 ft.sup.3.

13. The system of claim 1, wherein the colloidal silica gel comprises at least 6.5 wt. % colloidal silica.

14. A method of reducing corrosion of an exterior surface of a wellhead component in a well cellar, the method comprising: disposing a composition within the well cellar, the composition comprising colloidal silica, water, an activator, an oxygen scavenger and a corrosion inhibitor; and allowing colloidal silica to precipitate from the composition to provide a colloidal silica gel, wherein the colloidal silica gel covers the exterior surface of the wellhead component and extends to a base and sidewalls of the well cellar.

15. The method of claim 14, wherein the activator is selected from the group consisting of NaCl and 1,6-hexanediol-diglycidyl-ether.

16. The method of claim 14, further comprising covering the colloidal silica gel with sand.

17. The method of claim 14, wherein the wellhead component is a landing base and/or a surface casing.

18. The method of claim 14, wherein the composition comprises: from 66 wt. % to 91.5 wt. % water; from 6.5 wt. % to 32 wt. % colloidal silica; from 0.2 wt. % to 4 wt. % NaCl; from 0.04 wt. % to 1 wt. % oxygen scavenger; and from 1 wt. % to 15 wt. % corrosion inhibitor.

19. The method of claim 14, wherein the composition comprises: from 66 wt. % to 91.5 wt. % water; from 6.5 wt. % to 32 wt. % colloidal silica; from 2.5 wt. % to 15 wt. % 1,6-hexanediol-diglycidyl-ether; from 0.04 wt. % to 1 wt. % oxygen scavenger; and from 1 wt. % to 15 wt. % corrosion inhibitor.

20. The method of claim 14, wherein the colloidal silica gel occupies a volume of at least 1 ft.sup.3.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0027] FIG. 1 is a schematic illustration of a system.

[0028] FIG. 2 is a schematic illustration of a system.

[0029] FIG. 3 is a schematic illustration of a system.

[0030] FIG. 4 is a schematic illustration of a system.

[0031] FIG. 5 is a schematic illustration of a system.

[0032] FIG. 6 is a photograph of a colloidal silica gel covered by an aqueous phase, which is, in turn covered by a low-density gel.

DETAILED DESCRIPTION

[0033] FIG. 1 schematically depicts a system 1000, which can, for example, be part of a well, such as an oil well, a gas well or a water well.

[0034] The system 1000 includes a well cellar 1010 having a bottom 1020 and sidewalls 1030. The uppermost surface 1012 of the well cellar 1010 substantially corresponds to the surface 1040 of the earth such that the well cellar 1010 is generally located belowground.

[0035] The system 1000 also includes a wellhead 1050 having an aboveground wellhead region 1060 that extends above the surface 1040 and a belowground wellhead region 1070 that extends below the surface 1040, through the well cellar 1010, and through an opening 1025 in the bottom 1020 of the well cellar 1010. Generally, the wellhead regions 1060 and 1070 have a variety of different components. As an example, as shown in FIG. 1, the aboveground wellhead region 1060 can include a water injection line flange 1062 and a crown adapter 1064, and the belowground wellhead region 1070 can include a landing base 1072 and a tubing spool 1074. The wellhead 1050 includes a surface casing 1076 having its exterior surface exposed within the well cellar 1010. The surface casing 1076 houses a plurality of nested casings that are exposed beneath the bottom 1020 of the well cellar 1010 (see FIGS. 2-4).

[0036] FIG. 2 schematically depicts a system 2000 including a wellhead 2050 having aboveground and belowground regions 2060 and 2070, respectively. The aboveground region 2060 includes a water injection valve 2062, a crown adapter 2064, an additional valve 2066 and a tubing bonnet 2068. The belowground region 2070 includes a landing base 2072 and a tubing spool 2074, which are disposed above a bottom 2020 of the well cellar. The belowground region 2070 also includes a plurality of nested casings housed within a surface casing (generally depicted at 2076) and extending below the bottom 2020 of the well cellar.

[0037] FIG. 3 schematically depicts a system 3000 including a wellhead 3050 having aboveground and belowground regions 3060 and 3070, respectively. The aboveground region 3060 includes a water flow pipe 3061 in fluid communication with a water injection valve 3062. In addition, the aboveground region includes a crown adapter 3064 and additional valves 3066 and 3067. The belowground region 3070 includes a landing base 3072 and a tubing spool 3074, which are disposed above a bottom 3020 of the well cellar. The belowground region 3070 further includes a surface casing and a plurality of nested casings (generally depicted at 3076) that extend through and below the bottom 3020 of the well cellar. In some embodiments, the injection line flange between the water flow pipe 3061 and the water injection valve 3062 can leak, for example, due to air exposure and continuous water flow. This can cause the leaking water to spill onto the sand covering the well cellar, which can result in corrosion of the surface casing 3076, the landing base 3072 and/or the tubing spool 3074.

[0038] FIG. 4 schematically depicts a belowground region of a wellhead 4050. Above a bottom 4020 of the well cellar, the wellhead 4050 includes a landing base 4072, a donut plate 4073 and a surface casing 4076. The surface casing 4076 extends through an opening 4025 in the bottom 4020 of the well cellar and into a conductor 4075. The surface casing 4076 houses a plurality of nested casings 4077, 4078 and 4079. In some embodiments, the bottom 4020 of the well cellar is made of cement. The integrity of the cement is sometimes low and cracks can develop in the cement, which can allow water penetration thereby inducing corrosion, for example, at the interface of the surface casing 4076 and the bottom 4020 of the well cellar. The colloidal silica gel can reduce, e.g., prevent, such corrosion.

[0039] Referring again to FIG. 1, the system 1000 also includes a colloidal silica gel 1080 that completely covers a portion of the exterior surface of the surface casing 1076 and the landing base 1072 and extends to the bottom 1020 and sidewalls 1030 of the well cellar 1010. Thus, the colloidal silica gel 1080 occupies a volume of space between the well cellar 1010, and the gel-covered exterior surfaces of the surface casing 1076 and the landing base 1072. A layer of sand 1090 is disposed on top of the colloidal silica gel 1080. With this arrangement, the colloidal silica gel 1080 acts as a barrier that, over a substantial period of time, can prevent water present in the sand 1090 from reaching the gel-covered exterior surfaces of the surface casing 1076 and the landing base 1072, thereby maintaining substantially dry conditions around the gel-covered exterior surface of the surface casing 1076 and the landing base 1072. As a result, over these periods of time, the colloidal silica gel helps to resist, and even completely prevent, corrosion of the gel-covered exterior surfaces of the surface casing 1076 and the landing base 1072.

[0040] FIG. 5 schematically depicts a system 5000 that includes a well cellar 5010 having a bottom 5020 and sidewalls 5030. The system 5000 also includes a wellhead 5050 having a belowground region 5070 that extends through the well cellar 5010, and through an opening 5025 in the bottom 5020 of the well cellar 5010. The system 5000 also includes a colloidal silica gel 5080 that completely covers a portion of the exterior surface of the belowground wellhead region 5070 and extends to the bottom 5020 and sidewalls 5030 of the well cellar 5010. In some embodiments, portion of the exterior surface of the belowground wellhead region 5070 covered by the colloidal silica gel includes a landing base. In some embodiments, portion of the exterior surface of the belowground wellhead region 5070 covered by the colloidal silica gel includes a surface casing. A layer of sand 5090 is disposed on top of the colloidal silica gel 5080. In some embodiments, the bottom 5020 layer below the colloidal silica gel 5080 includes cement. In some embodiments, the bottom 5020 layer below the colloidal silica gel 5080 includes sand.

[0041] In certain embodiments, the well cellar 5010 (or 1010) has a diameter of at least 1.25 (e.g. 1.36, at least 1.4, at least at least 1.5, at least 1.6, at least 1.7, at least 1.8, at least 1.9, at least 2.0) meters (m) and at most 5 (e.g. at most 4, at most 3) m.

[0042] In some embodiments, the well cellar 5010 (or 1010) has a depth of at least 4.5 (e.g. 4.54, at least 5, at least 6, at least 7, at least 8, at least 9) feet (ft) and at most 10 (e.g. at most 9, at most 8, at most 7, at most 6, at most 5) ft.

[0043] In general, the height of the colloidal silica gel is sufficient to at least partially (e.g., completely) cover the landing base. In some embodiments, the distance between the bottom of the well cellar and the highest part of the landing base is 10 feet. In certain embodiments, the height of the colloidal silica gel 5080 (or 1080) in the well is at least 1 (e.g. at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9) ft and at most 10 (e.g. at most 9, at most 8, at most 7, at most 6, at most 5, at most 4, at most 3, at most 2) ft.

[0044] In some embodiments, the volume occupied by the colloidal silica gel 5080 (or 1080) is at least 1 (e.g., at least 5, at least 10) cubic feet (ft.sup.3) and at most 30 (e.g., at most 25, at most 20) ft.sup.3.

[0045] In general, the colloidal silica gel 5080 (or 1080) has a density greater than that of water. In certain embodiments, the colloidal silica gel has a density of at least 1.13 (e.g. 1.14, 1.15, 1.3) g/ml and at most 2.5 g/mL.

[0046] In general, the colloidal silica gel 5080 (or 1080) is formed by precipitation from a composition that includes colloidal silica, water and an activator. As used herein, an “activator” is a species that promotes precipitation of the colloidal silica out of the composition. Examples of activators include NaCl and 1,6-hexanediol-diglycidyl-ether (Razeen® D7109). In some embodiments, the composition further includes a corrosion inhibitor (e.g., O-3670R) and/or an oxygen scavenger (e.g., sodium sulfite (Na.sub.2SO.sub.3), OXYGON™ or FE-20). In general, the corrosion inhibitor and/or oxygen scavenger prevent the water of the composition and/or dissolved oxygen from causing corrosion.

[0047] Generally, the composition is prepared by combining the components with mixing if desired. In general, the composition is then relatively quickly (e.g., immediately) disposed in the well cellar 5010 (or 1010). Typically, within a short time period (e.g., immediately), colloidal silica precipitates from the composition, resulting in formation of the colloidal silica gel 5080 (or 1080) and an aqueous layer on top of the colloidal silica gel 5080 (or 1080). The sand 5090 (or 1090) is disposed on top of the aqueous layer, and the sand absorbs the water from the aqueous layer.

[0048] In some embodiments, the composition contains at least 5000 (e.g. at least 6000, at least 7000, at least 8000) liters (L) of water and at most 11000 (e.g. at most 10000, at most 9000, at most 8000) L of water.

[0049] In certain embodiments, the composition contains at least 5000 (e.g. at least 6000, at least 7000) L of 20 weight percent (wt. %) colloidal silica solution and at most 11000 (e.g. at most 10000, at most 9000, at most 8000) L of 20 wt. % colloidal silica solution.

[0050] In some embodiments, the composition contains at least 100 (e.g. at least 200, at least 500, at least 600, at least 700) kilograms (kg) of NaCl and at most 1000 (e.g. at most 900, at most 800) kg of NaCl.

[0051] In certain embodiments, the composition contains at least 1000 (e.g. at least 1100, at least 1200, at least 1300, at least 1400) L of 1,6-hexanediol-diglycidyl-ether and at most 2100 (e.g. at most 2000, at most 1900, at most 1800) L 1,6-hexanediol-diglycidyl-ether.

[0052] In some embodiments, the composition contains at least 2.2 (e.g. at least 2.5, at least 3.0, at least 3.5, at least 4.0, at least 4.5, at least 4.8) kg of oxygen scavenger and at most 4.85 (e.g. at most 4.8, at most 4.5, at most 4.0, at most 3.5, at most 3.0, at most 2.5) kg of oxygen scavenger.

[0053] In certain embodiments, the composition contains at least 50 (e.g. at least 60, at least 70, at least 80, at least 90, at least 100, at least 105) kg of corrosion inhibitor and at most 110 (e.g. at most 105, at most 100, at most 90, at most 80, at most 70, at most 60) kg of corrosion inhibitor.

[0054] In certain embodiments, the composition contains at least 50 (e.g. at least 60, at least 70, at least 80, at least 90, at least 100, at least 105) L of corrosion inhibitor and at most 110 (e.g. at most 105, at most 100, at most 90, at most 80, at most 70, at most 60) L of corrosion inhibitor.

[0055] In some embodiments, the composition contains at least 6.5 (e.g., at least 10, at least 15) weight percent (wt. %) colloidal silica at most 32 (e.g., at most 25, at most 20) wt. % colloidal silica.

[0056] In certain embodiments, the composition contains at least 66 (e.g., at least 73, at least 78) wt. % water and at most 91.5 (e.g., at most 88, at most 83) wt. % water.

[0057] In some embodiments in which the activator is NaCl, the composition contains at least 0.2 (e.g., at least 0.5, at least 1, at least 2) wt. % NaCl and at most 4 (e.g., at most 3, at most 2) wt. % NaCl.

[0058] In certain embodiments in which the activator is 1,6-hexanediol-diglycidyl-ether, the composition contains at least 2.5 (e.g., at least 5, at least 7.5, at least 8) wt. % 1,6-hexanediol-diglycidyl-ether and at most 15 (e.g., at most 12.5, at most 10, at most 8) wt. % 1,6-hexanediol-diglycidyl-ether.

[0059] In some embodiments, the composition contains at least 0.04 (e.g., at least 0.07, at least 0.1) wt. % oxygen scavenger and at most 1 (e.g., at most 0.9, at most 0.8) wt. % oxygen scavenger.

[0060] In certain embodiments, the composition contains at least 1 (e.g., at least 5, at least 8, at least 10) wt. % corrosion inhibitor and at most 15 (e.g., at most 12) wt. % corrosion inhibitor.

[0061] Table 1 lists two exemplary compositions.

TABLE-US-00001 TABLE 1 1,6- Hexanediol- diglycidyl- OXYGON or O- CB17 NaCl ether FE-200 36670R Composition 54 wt % 2 wt % — 0.07 wt % 1 wt % 1 Composition 51 wt % — 8 wt % 0.07 wt % 1 wt % 2

[0062] In some embodiments, the colloidal silica gel 5080 (or 1080) contains only colloidal silica. However, in certain embodiments, the colloidal silica gel 5080 (or 1080) contains water, activator (e.g. NaCl or 1,6-hexanediol-diglycidyl-ether), oxygen scavenger and/or corrosion inhibitor. As an example, in some embodiments, the colloidal silica gel 5080 (or 1080) contains at least 6.5 (e.g., at least 10, at least 15) weight percent (wt. %) colloidal silica at most 32 (e.g., at most 25, at most 20) wt. % colloidal silica. As another example, in certain embodiments, the colloidal silica gel 5080 (or 1080) contains at least 66 (e.g., at least 73, at least 78) wt. % water and at most 91.5 (e.g., at most 88, at most 83) wt. % water. As a further example, in some embodiments, the colloidal silica gel 5080 (or 1080) contains at least 0.2 (e.g., at least 0.5, at least 1, a least 2) wt. % NaCl and at most 4 (e.g., at most 3, at most 2) wt. % NaCl. As an additional example, in certain embodiments, the colloidal silica gel 5080 (or 1080) contains at least 2.5 (e.g., at least 5, at least 7.5, at least 8) wt. % 1,6-hexanediol-diglycidyl-ether and at most 15 (e.g., at most 12.5, at most 10, at most 8) wt. % 1,6-hexanediol-diglycidyl-ether. As another example, in some embodiments, the colloidal silica gel 5080 (or 1080) contains at least 0.03 (e.g., at least 0.07, at least 0.1) wt. % oxygen scavenger and at most 1 (e.g., at most 0.9, at most 0.8) wt. % oxygen scavenger. As a further example, in certain embodiments, the colloidal silica gel 5080 (or 1080) contains at least 0.1 (e.g., at least 0.5, at least 1) wt. % corrosion inhibitor and at most 2 (e.g., at most 1.5) wt. % corrosion inhibitor.

[0063] In some embodiments, the colloidal silica gel silica gel is free from species that were not present in the composition from which the colloidal silica precipitated. As an example, in some embodiments, the colloidal silica gel is free of cement and/or non-aqueous-based fluid(s).

Examples

Forming a Colloidal Silica Gel

[0064] A composition that contained water, 20 wt. % CB17, and 2 wt. % NaCl was prepared in a container, and the colloidal silica gel was allowed to precipitate at room temperature for 2 minutes. FIG. 6 is a photograph of the colloidal silica gel that precipitated. From top to bottom, the three layers shown in FIG. 6 were a low-density gel (EXPANCEL WE40), an aqueous layer (2% NaCl brine) and the colloidal silica gel. The low-density gel was added to aid visualization of the aqueous layer.

Sample Calculations

[0065] A sample calculation was performed to determine the quantities of the constituents of Composition 1 for covering 10 feet (ft) above the bottom of the well cellar with Composition 1. The well cellar had a diameter of 3 m (9.84 ft). The colloidal silica gel formed by precipitation would cover only a portion of the space initially occupied by the composition. If the composition covered 10 ft, the precipitated colloidal silica layer would cover 2-3 ft above the bottom of the well cellar. The dimensions of the wellhead component(s) were not factored into the calculation. The relevant equations are shown below. The results are present in table 2.

[00001]$\begin{array}{c}\mathrm{Cellar}\mathrm{Volume}={\left(\frac{9.84}{2}\right)}^2*3.14*10=760{\mathrm{ft}}^3\\ \mathrm{To}\mathrm{Cover}10\mathrm{ft}\mathrm{of}\mathrm{the}\mathrm{Cellar}\frac{760{\mathrm{ft}}^3}{5.615{\mathrm{ft}}^3/\mathrm{bbl}}=135\mathrm{bbl}\\ 135\mathrm{bbl}*\frac{159L}{1\mathrm{bbl}}=21465L\\ \mathrm{Colloidal}\mathrm{silica}\mathrm{stock}(\mathrm{volume})=\frac{21465L}{2}=10732.5L\\ \mathrm{Water}(\mathrm{volume})=\frac{21465L}{2}=10732.5L\\ \mathrm{NaCl}\left(\mathrm{mass}\right)=10732.5*0.02=214.65\mathrm{kg}\\ \mathrm{Oxygen}\mathrm{scavenger}\left(\mathrm{mass}\right)=10732.5*\frac{0.07}{159}=4.725\mathrm{kg}\\ \mathrm{Corrosion}\mathrm{inhibitor}\left(\mathrm{volume}\right)=10732.5*0.01=107.325L\end{array}$

[0066] A corresponding sample calculation was performed to determine the quantities of the constituents in Composition 2 for covering 10 feet (ft) above the bottom of the well cellar with Composition 2. The well cellar had a diameter of 3 m (9.84 ft). The colloidal silica gel formed by precipitation would cover only a portion of the space initially occupied by the composition. If the composition covered 10 ft, the precipitated colloidal silica layer would cover 2-3 ft above the bottom of the well cellar. The dimensions of the wellhead component(s) were not factored into the calculation. The results are present in table 2.

TABLE-US-00002 TABLE 2 1,6-Hexanediol- OXYGON Water CB17 NaCl diglycidyl-ether or FE-200 O-36670R Composition 1 10732.5 L 10732.5 L 214.65 kg — 4.725 kg 107.325 L Composition 2 10732.5 L 10732.5 L — 1073.25 L 4.725 kg 107.325 L

Water Permeation Experiment

[0067] A layer of sand was placed in a container. 10 ml of Composition 1 was placed on top of the layer of sand, and colloidal silica was allowed to precipitate from the composition at room temperature for 2 minutes, thereby forming colloidal silica gel on the layer of sand, and an aqueous layer on top of the colloidal silica gel. An additional layer of sand was placed on top of the aqueous layer, and the sand absorbed the water in the aqueous layer. The container was subsequently filled with water, and the container was held at room temperature. Over the course of a day, a portion of the top layer of water evaporated. The top water layer was replenished daily to replace the evaporated water. Through visual inspection, after 7 days, the bottom layer of sand (beneath the colloidal silica gel) remained dry. Therefore, none of the water disposed on the topmost layer of sand penetrated through the colloidal silica gel. Thus, the experiment demonstrated that water was unable to penetrate through the colloidal silica layer. It is therefore believed that the colloidal silica gel can be used to reduce (e.g., prevent) water-induced corrosion in wellhead components present in a well cellar.

Other Embodiments

[0068] While certain embodiments have been disclosed, the disclosure is not limited to such embodiments.

[0069] As an example, while embodiments have been disclosed in which a layer of sand is disposed on top of the layer of colloidal silica gel, in some embodiments, a layer of sand is not present above the colloidal silica gel. As an example, in certain embodiments, the colloidal silica gel may be covered with a different material, such as but not limited to silica, alumina, or small gravel rocks. As another example, in some embodiments, the colloidal silica gel extends to the upper surface of the well cellar, i.e., the surface of the earth.