CA2694811C

CA2694811C - Separator for separating liquid hydrocarbons, solids and fluid from a slurry

Info

Publication number: CA2694811C
Application number: CA2694811A
Authority: CA
Inventors: Timothy Macartney
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-03-04
Filing date: 2010-03-04
Publication date: 2016-11-22
Anticipated expiration: 2030-03-04
Also published as: CA2694811A1

Abstract

A separator for separating liquid hydrocarbons, solids and fluid from a slurry, such as a drilling fluid used in a drilling operation. The separator has a first separator tank, and a first centrifugal separator fed by the first separator tank that removes at least a portion of the solids from the first separator tank. An agitator foams the liquid hydrocarbons in the first separator tank. One or more settling tanks are connected in series to the first separator tank. Each settling tank has a baffle that extends below a top surface of the slurry between the inlet and the outlet to prevent foamed liquid hydrocarbons in the slurry from passing through the outlet. There is a base fluid that is substantially the same as the fluid in each of the first separator tank and the one or more settling tanks.

Description

TITLE
[0001] Separator for separating liquid hydrocarbons, solids and fluid from a slurry FIELD

[0002] This relates to a separator for separating liquid hydrocarbons, solids, and fluid from a sluiTy, such as separating cuttings and oil from a drilling fluid that has been used in a drilling operation.
BACKGROUND

[0003] Drilling fluids are used during a drilling operation to cool a drill bit and to flush out the cuttings. In hydrocarbon wells, the most common drilling fluids are water-based or hydrocarbon-based. When drilling a hydrocarbon-producing well, the cuttings will often be oily cuttings. A shale shaker is used to remove some of the liquid from the cuttings, but the result is a slurry of cuttings, liquid hydrocarbons and drilling fluid that must be disposed of.
-United States patent no. 5,093,008 (Clifford, III) entitled "Process and apparatus for recovering reusable water from waste drilling fluid" describes how water may be recovered from the drilling fluid.
SUMMARY

[0004] There is provided a separator for separating liquid hydrocarbons, solids and fluid from a slurry. The fluid may be a drilling fluid used in a chilling operation and the solids may be cuttings. The separator comprises a first separator tank that has an inlet for receiving the slimy and an outlet. A first centrifugal separator is fed by the first separator tank and removes at least a portion of the solids from the slurry and returns the shiny to the first separator tank.
An agitator foams the liquid hydrocarbons in the first separator tank. One or more settling tanks is connected in series to the first separator tank. Each settling tank has an inlet that receives the slurry, and an outlet that outputs the sluiTy. The settling tank has a baffle that extends below a top surface of the slurry between the inlet and the outlet.
The baffle prevents foamed liquid hydrocarbons in the sluny from passing through the outlet. There is a base fluid that is substantially the same as the fluid in each of the first separator tank and the one or more settling tanks. The slurry is deposited into the base fluid.

[0005] According to an aspect, there may be a circulation pump for circulating the fluids in a circulation conduit from the last settling tank to the first separation tank. The agitator may comprise a pressurized outlet into the first separation tank from the circulation conduit.
The circulation conduit comprises an outlet for collecting separated fluid.
The circulation conduit may comprise an injection port for injecting a flocculant for flocculating fine particles. There may be a vacuum line having multiple valves connecting the first centrifugal separator and the circulation pump to more than one tank, such that the first centrifugal separator and the circulation pump each draw from a selected tank.

[0006] According to another aspect, the fluid and the base fluid may be water-based or may be hydrocarbon-based.

[0007] According to another aspect, there may be a second separator tank connected between the one or more settling tanks and the first separator tank. There may be a second centrifugal separator, where each of the first and second centrifugal separators draws the slurry from one or both of the first and second separator tanks.

[0008] According to another aspect, there may be multiple fluid connections between the settling tanks and the first and second separator tanks that define more than one flow path from the first separation tank to the last settling tank.

[0009] According to another aspect, there is provided a method of separating liquid hydrocarbons, solids and fluid from a slurry, such as a drilling fluid used in a drilling operation containing cuttings. The method comprises the steps of: providing a first separator tank and one or more settling tanks containing a base fluid that is substantially the same as the fluid, the settling tank comprising an inlet, an outlet, and a baffle that restrains a top layer of fluid from transferring from the inlet to the outlet; transferring the slurry into the first separator tank; using a centrifugal separator connected to the first separator tank, separating at least some of the solids from the slurry; using an agitator, agitating the slurry to cause at least some of the liquid hydrocarbons to foam; transferring the slurry and the foamed liquid hydrocarbons from the first separator tank to the at least one settling tank and allowing at least some of the solids to settle; and removing the foamed hydrocarbons from the top of the settling tank and the settled solids from the bottom of the settling tank.

[0010] According to another aspect, the method may further comprise the step of circulating the slurry from the last settling tank to the first separation tank using a circulation pump. Agitating the slurry in the first separator tank may comprise using a pressurized outlet fed by the circulation pump. A vacuum line having multiple valves may connect the first centrifugal separator and the circulation pump to more than one tank, such that the first centrifugal separator and the circulation pump each draw from a selected tank

[0011] According to another aspect, the method may further the step of collecting a portion of the separated fluid circulated by the circulation pump for reuse in, for example, a drilling operation. The method may comprise the step of injecting a flocculant into the first separator tank for flocculating fine particles.

[0012] According to another aspect, the method may further comprise the step of transferring the slurry from the first separator tank to a second separator tank prior to transferring the slurry to at least one settling tank. The method may comprise the step of using a centrifugal separator connected to the first separator tank to separate at least some of the solids from the slurry. The method may also comprise the step of varying the flow path between the first separation tank and the last settling tank.
BRIEF DESCRIPTION OF THE DRAWINGS

[0013] These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:
FIG. 1 is a top plan view of a separator.
FIG. 2 is a side elevation view of the separator.
DETAILED DESCRIPTION

[0014] A separator for separating liquid hydrocarbons, solids and fluid from a slurry, such as a drilling fluid used in a drilling operation, generally identified by reference numeral 10, will now be described with reference to FIG. 1 and 2.
Structure and RelationshiP of Parts:

[0015] Separator 10 is intended to be used in separating the different components in a slurry that contains liquid hydrocarbons, solids, and fluid. For example, separator 10 is useful in separating components in a used drilling fluid, such as water or hydrocarbon based drilling fluids. As the drilling fluids exit a wellbore, there will be cuttings, such as sand or other products from the drilling operation, which may be coated in oil. Oil may also be entrained with the drilling fluid without being coated on the cuttings. Separating the components allows the cuttings to be disposed of more easily and also allows the drilling fluid to be reused. In industry, the drilling fluid is first passed over a standard rig shaker, which generally uses screens and vibration to remove some of the larger cuttings from drilling fluid.
Separator 10 described below is preferably located after the rig shaker to receive the fluids after the larger cuttings have been removed.

[0016] In the desciipfion below, separator 10 is discussed with reference to used drilling fluids. However, it will be understood that separator 10 may be used for other slurrys, such as those that exist in tailings ponds, which are made up of hydrocarbons, suspended solids, and water.

[0017] Referring to FIG. 1, separator 10 has a first separator tank 12 that has an inlet 14 for receiving the used drilling fluid and an outlet 16. As shown, inlet 14 is a screen 15 or a shaker that removes the open top of tank 12, although it rnay take other forms. Screen 15 is fed from a trough 17 connected to a rig shaker 19, which removes a portion of the drilling fluid. In the depicted embodiment, separator 10 is fed by the solids stream that are output from rig shaker 19, and as such there may be more solids than drilling fluid in the used drilling fluid stream input into separator 10. Screen 15 is used to remove large objects that are easily removed., but may be difficult to process by separator 10.
Furthermore, as the solid stream from rig shaker 19 is intended to be treated by separator 10, rig shaker 19 may use a tighter mesh, which keeps out finer solids, but also results in more drilling fluid passing into trough 17.

=

[0018] There is a first centrifugal separator 20 fed by first separator tank 12 that removes at least a portion of the solids from the used drilling fluid and returns the used drilling fluid to first separator tank 12. Preferably, separator 10 also has a second separator tank 18 adjacent 5 to separator tank 12 and a second centrifugal separator 22. Centrifuges 20 and 22 may be connected by valves 24, 26 and 28 to tanks 12 and 18, such that they may be fed by one or both. Referring to FIG. 2, the fluid in tank 12 is preferably drawn off the bottom of tank 12 through a vacuum line 30, as there will generally be a larger concentration of solids toward the bottom. The separated fluids may be returned at any convenient height.
Referring to FIG. 1, tank 18 is also connected by a vacuum line 30 to centrifuge 22.

[0019] Referring to FIG. 1, first separator tank 12 has an agitator 32 that causes the liquid hydrocarbons present in the drilling fluid to foam. This method works with drilling fluids that generally do not foam. As depicted, agitator 32 is the pressurized outlet 34 in a circulation conduit 36 that is fed by a high volume pump 38, such as a Mission Tm pump.

[0020] Down stream of first and second separator tanks 12 and 18 are one or more settling tanks. As shown, there are four settling tanks 40, 42, 44 and 46 connected in series.
Each settling tank 40, 42 and 44 has an inlet 48 that receives the used drilling fluid from the next tank upstream, and an outlet 50 that outputs the used drilling fluid.
Each settling tank 46 is also connected to a vacuum line 30, for example as shown in FIG. 2 as an outlet to feed pump 38. Preferably, settling tanks 40, 42, 44 and 46 are designed such that there is a minimal amount of disturbance to allow solids to settle. Referring to FIG. 2, settling tanks 42, and 44 have a baffle 49 that extends below a top surface of the used drilling fluid between inlet 48 and outlet 50. While not shown, at least settling tank 40 will also have baffle 49. As settling tank 46 is not connected to another tank, and the only outlet is at the bottom, baffle 49 is unnecessary in tank 46. Baffle 49 prevents foamed liquid hydrocarbons in the used drilling fluid from passing through outlet 50, and allows them to be skimmed from the top of each tank.

[0021] Referring to FIG. 2, it can be seen that each tank 12, 42 and 44 is connected to vacuum line 30. While not shown, tanks 18, 40 and 46 are similarly connected to a vacuum line 30. Referring to FIG. 1, these two parallel vacuum lines 30 are connected before centrifuges 20 and 22 at one end of apparatus 10, and are also connected before pump 38 at the other end of apparatus 10. Referring to FIG. 1 and 2, a series of valves 47 and 52 are provided that allow the flow to be directed, while valves 24, 26 and 28 direct flow among centrifuges 20 and 22. Valves 47 control the flow between tanks, and valves 52 control what tanks are drawn upon by pump 38 or centrifuges 20 and 22. For example, by selectively opening and closing certain valves 52, pump 38 may be used to draw fluid from settling tank 42 instead of tank 44 or 46. Alternatively, centrifuge 20 may draw fluid from tank 42 rather than tank 12. Centrifuge 20 is used to remove solids from the system as it draws from various tanks, and then recirculates the fluid in the system. It will be understood that the actual configuration of vacuum lines and valves may vary depending on the preferences of the user.

[0022] Referring to FIG. 1, before receiving the drilling fluids, the various tanks in separator 10 are filled with a base fluid that is substantially the same as the drilling fluid in each of the first separator tank and the one or more settling tanks, the used drilling fluid being deposited into the base fluid. The tanks may not be entirely filled to leave sufficient room for the anticipated volume of drilling fluids.

[0023] As mentioned above, there is a circulation pump 38 that circulates fluids through circulation conduit 36 from last settling tank 46 to first separation tank 12, which also allows fluids in separation tank 12 to be agitated, although other types of agitators may also be used.
As depicted, fluids are circulated through separator 10 to be treated continuously. Circulation conduit 36 may also include an injection port 54 to be that allows flocculants to be injected into the system. The flocculant encourages the fine particles in the cuttings to be agglomerate, making them easier to remove. In addition to circulating fluid to tank 12, circulation pump 38 may have a second outlet 56, or circulation conduit 36 may have a separate outlet that can be used to capture the separated drilling fluid and used to replenish the drilling fluid being used in the drilling operation, or to provide a relatively clean fluid to wash the rig shaker and prevent a build-up of cuttings in its collection trough.
Preferably, circulation conduit 36 has an additional line 58 that is used to flush trough 17 to fluidized the used drilling fluids coming from rig shaker 19 sufficiently to cause them to flow into tank 12, or to prevent build-up in trough 17 of the cuttings. While not shown, it will be understood that screen 15 as well as centrifuges 20 and 22 will output the captured solids or cuttings into a waste stream to be properly disposed of.

[0024] In a preferred embodiment, six tanks are used ¨ two separator tanks 12 and 18 and four settling tanks 40, 42, 44 and 46. Preferably, each tank is connected to more than one other tank. As shown, each tank is connected to the other adjacent two or three tanks. By controlling the flow between inlets and outlets with valves or gates 47, the flow path through separator 10 may be changed. For example, it may be that second separator tank 18 is not required because the cuttings are relatively clean, easy to separate, or the volume of drilling fluid being received is low. In that case, the flow path may include tanks 12, 42, 44 and 46.
Alternatively, the flow path may include both separator tanks 12 and 18, but only settling tanks 42 and 46. Other flow paths may also be defined by including additional flow lines and flow valves not shown. For example, second separator tank 18 may also be used to receive the slurry from the rig shaker 19 with additional flow and valves.
Operation:

[0025] Separator 10 is intended to be used at a drilling site.
Accordingly, it is preferably skid-mounted for ease of transport. Referring to FIG. 1, each tank 12, 18, 40, 42, 44, and 46 are initially filled with a base fluid that is the same, or substantially the same, as the drilling fluid used in the drilling operation. Referring to FIG. 1 and 2, valves 47 and 52 are set to handle the anticipated load. The slurry of drilling fluid, oil and cuttings are deposited from the rig shaker (not shown) into the base fluid in first separator tank 12. The mixture is agitated by fluid being pumped by circulation pump 38 through pressurized outlet 34 to cause the oil to foam. At the same time, first centrifuge 20 draws fluid out of first separator tank 12 through vacuum line 30 (shown in FIG. 2) to remove solids from the fluid, and returns the fluid to tank 12. As tank 12 fills, it will over flow into second separator tank 18, where second centrifuge 22 removes more solids from the fluid. First and second centrifuges 20 and 22 may be set to draw from one or both of tanks 12 and 18 in different proportions using valves 24, 26 and 28, depending on the preferences of the user and the composition of the slurry. If second centrifuge 22 is not used to process fluid in second tank 18, the corresponding vacuum line 30 may be used to draw off settled solids instead from a settling tank. From second tank 18, fluid moves through settling tanks 40, 42, 44 and 46 as the upstream tank overflows into the next. As discussed above, the actual flow path through the various tanks may be changed by selectively opening and closing gates 47. In each settling tank 40, 42 and 44, the foamed oil will float to the top where it is captured by baffle 49, while the solids settle to the bottom. Generally, the heavier solids will be removed by centrifuges, while settling tanks 40, 42, and 44 target the fines. The settling solids fall toward the sloped bottom, where they are removed by having centrifuge 20 or 22 draw from that tank. Baffle 49 allows the fluids from the center of the tank to move on to the next. From tank 46, the fluid is recycled back to first separation tank 12 to agitate the newly deposited drilling fluids, with a flocculant added through injection port 54 to help remove the fmes, and some fluid drawn off through outlet 56 to replace drilling fluid used in the drilling operation and to wash out the rig shaker. The process is therefore a continuous process that is driven by the newly deposited used drilling fluids, while diluting those drilling fluids in the base fluid and the separated, recirculated fluid.

[0026] Cuttings removed by centrifuges 20 and 22 are more easily disposed of relative to traditional methods as they are drier and contain less oil. At the same time, additional drilling fluid may be recovered, which reduces the amount of new drilling fluid that needs to be introduced into the drilling operation.

[0027] In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

[0028] The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope of the claims. The illustrated embodiments have been set forth only as examples and should not be taken as limiting the invention. It is to be understood that, within the scope of the following claims, the invention may be practiced other than as specifically illustrated and described.

Claims

What is Claimed Is-

1. A separator for separating liquid hydrocarbons, solids and a carrier fluid from a slurry, the separator comprising:
a first separator tank that has an inlet for receiving the slurry and an outlet;
a first centrifugal separator fed by the first separator tank that removes at least a portion of the solids from the slurry and returns the liquid hydrocarbons and carrier fluid to the first separator tank, an agitator that foams the liquid hydrocarbons m the first separator tank;
one or more settling tanks connected in series to the first separator tank, each settling tank having an inlet that receives the slurry, and an outlet that outputs the slimy, the settling tank having a baffle that extends below a top surface of the slurry between the inlet and the outlet, the baffle preventing foamed liquid hydrocarbons in the slurry from passing through the outlet, and a base fluid in each of the first separator tank and the one or more settling tanks, the base fluid being substantially the same as the carrier fluid, the slurry being deposited into the base fluid.

2. The separator of claim 1, wherein the carrier fluid in the slurry is used drilling fluid, and the solids are cuttings.

3. The separator of claim 1, further comprising a circulation pump for circulating the carrier fluid in a circulation conduit from the last settling tank to the first separation tank.

4. The separator of claim 3, wherein the agitator comprises a pressurized outlet into the first separation tank from the circulation conduit.

5. The separator of claim 3, wherein the circulation conduit comprises an outlet for collecting separated earner fluid.

6. The separator of claim 3, wherein the circulation conduit comprises an injection port for injecting a flocculant for flocculating fine particles.

7. The separator of claim 2, wherein the drilling fluid and the base fluid are water-based

8. The separator of claim 2, wherein the drilling fluid and the base fluid are hydrocarbon-based.

9. The separator of claim 1, further comprising a second separator tank connected between the one or more settling tanks and the first separator tank.

10. The separator of claim 9, further comprising a second centrifugal separator, each of the first and second centrifugal separators drawing the slurry from one or both of the first and second separator tanks

11 The separator of claim 9, comprising multiple fluid connections between the settling tanks and the first and second separator tanks that define more than one flow path from the first separation tank to the last settling tank.

12. The separator of claim 3, further comprising a vacuum line having multiple valves connecting the first centrifugal separator and the circulation pump to more than one tank, such that the first centrifugal separator and the circulation pump each draw from a selected tank.

13. A method of separating liquid hydrocarbons, solids and carrier fluid from a shiny, comprising the steps of:
providing a first separator tank and one or more settling tanks containing a base fluid that is substantially the same as the carrier fluid in the slurry, the settling tank comprising an inlet, an outlet, and a baffle that restrains a top layer of fluid from transferring from the inlet to the outlet;
transferring the slurry into the first separator tank;
using a centrifugal separator connected to the first separator tank, separating at least some of the solids from the slurry;
using an agitator, agitating the slurry in the first separator tank to cause at least some of the liquid hydrocarbons to foam;
transferring the carrier fluid, remaining solids and the foamed liquid hydrocarbons from the first separator tank to the at least one settling tank and allowing at least some of the solids to settle; and removing the foamed hydrocarbons from the top of the settling tank and the settled solids from the bottom of the settling tank.

14. The method of claim 13, wherein the carrier fluid is a used drilling fluid, and the solids are cuttings.

15. The method of claim 13, further comprising the step of circulating the carrier fluid from the last settling tank to the first separation tank using a circulation pump.

16. The method of claim 15, wherein agitating the slurry in the first separator tank comprises using a pressurized outlet fed by the circulation pump.

17. The method of claim 15, further comprising the step of collecting a portion of the separated carrier fluid circulated by the circulation pump

18. The method of claim 13, further comprising the step of injecting a flocculant into the first separator tank for flocculating fine particles.

19. The method of claim 14, wherein the drilling fluid and the base fluid are water-based

20. The method of claim 14, wherein the drilling fluid and the base fluid are hydrocarbon-based

21. The method of claim 13, further comprising the step of transferring the slurry from the first separator tank to a second separator tank prior to transferring the slurry to at least one settling tank.

22. The method of claim 21, further comprising the step of using a centrifugal separator connected to the first separator tank to separate at least some of the solids from the slurry

23. The method of claim 19, further comprising the step of varying the flow path between the first separation tank and the last settling tank

24. The method of claim 14, further comprising a vacuum line having multiple valves connecting the first centrifugal separator and the circulation pump to more than one tank selected from the first separator tank and one or more of the settling tanks, such that the first centrifugal separator and the circulation pump each draw from a selected tank.