WO2012125043A1

WO2012125043A1 - Method and device for cleaning drill cuttings

Info

Publication number: WO2012125043A1
Application number: PCT/NO2012/050042
Authority: WO
Inventors: Martin Gether STEINNES
Original assignee: Steinnes Martin Gether
Priority date: 2011-03-17
Filing date: 2012-03-15
Publication date: 2012-09-20
Also published as: NO20110409A1; GB201315305D0; NO336178B1; GB2501452B; GB2501452A; BR112013022408A2; US20130340791A1

Abstract

A method and a device for cleaning drill cuttings comprising cuttings and oil-based drilling mud, wherein a significant proportion of the drilling mud is removed from the drill cut- tings, and wherein the method comprises: - disposing the drill cuttings in a receptacle (1); - vibrating the receptacle (1) until particle fluidization of the drill cuttings takes place; - maintaining the drill cuttings in a particle- fluidized state during the subsequent treatment; - adding a soap to the drill cuttings; - allowing the soap to flow through the drill cuttings whilst the drill cuttings are particle- fluidized; - draining liquid from the receptacle (1); and - then emptying cleaned drill cuttings out of the receptacle (1).

Description

METHOD AND DEVICE FOR CLEANING DRILL CUTTINGS

This invention concerns a method for cleaning drill cuttings. More particularly, it concerns a method for cleaning drill cuttings, wherein the drill cuttings comprise cuttings and oil -based drilling mud, and wherein a significant proportion of the drilling mud is removed from the drill cuttings. The invention also comprises a device for carrying out the method.

During drilling operations in connection with petroleum recovery, significant amounts of oil -based drilling mud are used. The drilling mud flows to surface entraining cuttings from the drilling operation in the borehole.

A significant proportion of the drilling mud is immediately separated from the drill cuttings, whilst the drill cuttings with the remaining proportion of oil -based drilling mud is treated separately.

Relatively stringent statutory requirements prevent the drill cuttings from being discharged into the surroundings. It is known to reintroduce drill cuttings in a slurrified state into a borehole, but a significant proportion of the drill cuttings are shipped to treatment facilities for such

cuttings .

According to prior art, the drill cuttings are cleaned further via centrifuging, washing by means of chemicals, or via thermal treatment. Current statutory requirements require that the residual proportion of oil must be less than 10 g/kg of dry substance for allowing the cuttings to be disposed into the surroundings .

It is obvious, particularly when offshore drilling operations are involved, that transport and subsequent treatment of the drill cuttings are costly and environmentally dubious, insofar as transport and at least some of the known cleaning operations require significant amounts of energy.

The object of the invention is to remedy or to reduce at least one of the disadvantages of the prior art.

The object is achieved in accordance with the invention, and by virtue of those features disclosed in the following description and in the subsequent claims.

A method for cleaning drill cuttings comprising cuttings and oil -based drilling mud is provided, wherein a significant proportion of the drilling mud is removed from the drill cuttings, the method being characterized in that it

comprises :

- disposing the drill cuttings in a receptacle;

- vibrating the receptacle until particle fluidization of the drill cuttings takes place;

- maintaining the drill cuttings in a particle- fluidized state during the subsequent treatment;

- adding a soap to the drill cuttings;

- allowing the soap to flow through the drill cuttings whilst the drill cuttings are particle-fluidized;

- draining liquid from the receptacle; and

- then emptying cleaned drill cuttings out of the receptacle. Herein, particle fluidization (or soil liquefaction) implies a state in which relatively dry material is brought, by means of vibration, into a state within which it flows like a liquid. Hereinafter, the term fluidized is used to mean particle- fluidized .

Upon fluidizing the drill cuttings by means of vibration, the solid bodies of the drill cuttings, herein termed particles, will be brought into a wearing engagement with each other, thereby liberating a part of the oil -based drilling mud from the particles. Addition of soap to the fluidized drill cuttings contribute to the drilling mud releasing its bond to the particles. The process is described in more detail in the specific part of the document.

Normally, the soap is mixed with water in accordance with the supplier's user instructions. Soaps marketed under the trademarks "Safe Surfe Y" , "Safe Surfe E" and "Safe Surfe NS" from the firm M-I Swaco AS, as well as "Cleanwall WRC" from the firm Unitor AS, may prove applicable for the purpose.

The method may further comprise allowing the drill cuttings to compact in the receptacle before emptying. By so doing, the proportion of soap and drilling fluid is further reduced from the drill cuttings before emptying of the receptacle.

The method may further comprise separating the soap from the drained liquid for re-use. Upon carrying out such a process step, the consumption of soap may be reduced significantly.

The method may be carried out by means of a receptacle for treatment of drill cuttings, wherein the receptacle is connected to a frame structure and is provided with a supply of drill cuttings, and an outlet opening for treated drill cuttings, and wherein the receptacle is characterized in that it is restrictedly movable relative to the frame and is provided with at least one vibrator and also a soap supply.

The at least one vibrator may be dimensioned in a manner allowing it to vibrate the drill cuttings into a fluidized state .

The soap supply may comprise a distribution pipe having several outlet openings for allowing it to distribute the soap within the drill cuttings. The distribution pipe may be located in the lower portion of the receptacle, whereby the soap is prompted to flow upwards through the drill cuttings during the treatment. The vibration inflicted on the drill cuttings so as to bring the drill cuttings into the fluidized state, contributes to the soap rising up and out of the drill cuttings .

The receptacle may be connected to the frame structure by means of an elastic element. In some cases, the receptacle may be connected directly to a supporting structure without the presence of a separate frame structure. In such cases, and in context of the claims, the supporting structure is to be viewed as the frame structure.

The at least one vibrator may be comprised of e.g. an eccentric motor or a pneumatic vibrator. In some cases, an ultrasonic vibrator may be suitable.

The method and the device according to the invention allow drill cuttings to be cleaned to a purity which is better than the statutory requirements for disposal thereof. The device requires relatively little space and may, advantageously, be located at e.g. a drilling installation offshore. Hereinafter, an example of a preferred method and embodiment is described and is depicted in the accompanying drawings, wherein :

Fig. 1 shows a flow chart of a facility for practice of the invention, wherein also components known per se for pre-treatment of drill cuttings are shown; and

Fig. 2 schematically shows a section through a receptacle for treatment of drill cuttings.

In the drawings, reference numeral 1 denotes a receptacle for treatment of drill cuttings, which is connected to a frame structure 4 by means of elastic elements 2, see fig. 2.

The receptacle 1 is further provided with two vibrators 6 and a soap supply 8 connected to a distribution pipe 10 having openings 12. The distribution pipe 10 is disposed in a lower portion 14 of the receptacle 1. The soap supply 8 is

connected to a soap pump 16.

The receptacle 1, at an upper portion 18 thereof, is provided with a supply opening 20 for drill cuttings, and an outlet 22 for soap and drilling mud. This outlet 22 may be connected to a hose with a float (not shown) in the receptacle 1.

The receptacle 1, at the lower portion 14 thereof, is provided with a closable outlet opening 24. Herein, the outlet opening 24 is formed with a butterfly valve 26 operated by means of an actuator 28.

Fig. 1 schematically shows a treatment facility 30 which, besides the receptacle 1 with associated components, also shows other components for cleaning drill cuttings, the treatment facility of which constitutes, herein, a pre- treatment facility 32 within which the drill cuttings are treated before being led into the receptacle 1, see below.

The pre-treatment facility 32 comprises a drill cutting cleaner 34, typically in the form of a rotary screen being supplied drill cuttings via a supply 36. The treatment may comprise several successive phases of the same type. A first drill cutting pipe 38 connects the drill cutting cleaner 34 to a centrifuge 40 from which a second drill cutting pipe 42 extends to the supply 20 on the receptacle 1.

The drill cutting cleaner 34 ia provided with a first pump 44 which is connected, via a pipe 46, to a first separator 48 (or decanter) . A pipe 50 is connected between the centrifuge 40 and the pipe 46. The components 34, 40 and 48 constitute parts of the pre-treatment facility 32.

A third drill cutting pipe 52 extends between the first separator 48 and the second drill cutting pipe 42, whereas a first fluid pipe 54 is connected between the first separator 48 and an intermediate tank 56 for cleaning oil. A pipe 57 for water is also connected to the separator 48. A second pump 58 is connected, via a second fluid pipe 60, to the drill cutting cleaner 34. The intermediate tank 56 may be provided with a separation unit (not shown) in order to separate various oil types.

A third fluid pipe 62 having an outlet pump 63 extends from the outlet 22 on the receptacle 1 and onto a second separator 64, whereas an outlet pipe 66 is connected to the outlet opening 24 on the receptacle 1.

A fourth fluid pipe 68 extends from the second separator 64 and onto the intermediate tank 56, whereas a first soap pipe 70 extends from the second separator 64 and onto a soap tank 72, and an outlet 74 also emerges from the second separator The soap pump 16 on the soap tank 72 is connected, via a second soap pipe 76, to the soap supply 8 on the receptacle 1.

The treatment facility 30 is controlled by means of a control facility (not shown) . Energy supplies and control operations are known to a skilled person and are not described in further detail herein.

The drill cuttings to be cleaned, and which contain oil-based drilling mud, may contain approximately 20 % water and approximately 10 % oil when conveyed, via the supply 36, to the drill cutting cleaner 34. A significant proportion of the oil is located in pores and in a film surrounding the cutting particles .

In the first cleaning step, which is carried out in the drill cutting cleaner 34, cleaning oil from the intermediate tank 56 is supplied via the second pump 58 and the second fluid pipe 60. The cleaning oil may comprise base oil, diesel oil or vegetable oil. By so doing, the drill cuttings are washed in cleaning oil.

The drill cuttings are then conveyed via the first drill cutting pipe 38 onto the centrifuge 40 within which oil, in a second cleaning step, is separated from the drill cuttings until the drill cuttings contain approximately 5 % oil, the drill cuttings being conveyed onto the receptacle 1 via the second drill cutting pipe 42.

Oil and water separated from the drill cuttings flow onwards from the drill cutting cleaner 34 via the first pump 44 and the pipe 46, and also from the centrifuge 40 via the pipe 50, and onwards onto the first separator 48 from which oil is returned via the first fluid pipe 54 and onto the

intermediate tank 56, and drill cuttings are conveyed onto the receptacle 1 via the third drill cutting pipe 52, whereas water is drained via the pipe 57 and possibly via a filtering facility (not shown) .

When the drill cuttings are located in the receptacle 1, the third cleaning step is initiated by pumping-in soap from the soap tank 72 by means of the soap pump 16, and via the second soap pipe 76, the soap supply 8, the distribution pipe 10 and the openings 12.

In this step, vibration from the vibrators 6 brings the relatively dry drill cuttings into a fluidized state. Some enclosed droplet-shaped oil rises up between the particles.

In a fourth cleaning step, soap is circulated through the receptacle 1. This contributes to dissolve the oil film on the particles simultaneous with oil, which is released from pores and the surface of the particles, is being transported upwards and out of the receptacle 1. In this step, the particles rub against each other, the action of which is also thought to promote separation of oil -containing drilling mud from the drill cuttings. The higher density of the particles relative to that of the soap cause the drill cutting

particles to displace the soap and substantially remain in the lower portion 14 of the receptacle 1. Thus, the amount of particles entrained with the soap and the drilling mud so as to discharge via the outlet 22, is relatively modest.

In the fifth and last cleaning step, the supply of soap is closed. Residual soap and other fluids rise to the surface as the drill cuttings gradually compact in the lower portion 14 by means of vibration. This compacting further contributes to "squeeze" soap and drilling mud out of the drill cuttings. The reason for this is that smaller particles fill spaces between larger particles during compaction and, hence, reduce the available volume between the particles.

Upon having drained the fluid from the receptacle 1 by means of the outlet pump 63, the butterfly valve 26 is opened by means of the actuator 28, whereby cleaned drill cuttings may fall out of the receptacle 1 via the outlet pipe 66 .

The soa -oil -drilling mud mixture discharging from the receptacle 1 flows via the third fluid pipe 62 and onto a second separator 6 . Soap flows from the separator 64 onto the soap tank 72 via the first soap pipe 70, whereas oil flows onto the intermediate tank 56 via the fourth fluid pipe 68, and cleaned drill cuttings fall out via the outlet 74.

The amount of cleaned drill cuttings discharging via the outlet 74 is small relative to the discharge via the outlet 66.

Claims

P a t e n t c l a i m s

1. A method for cleaning drill cuttings comprising cuttings and oil-based drilling mud, wherein a significant

proportion of the drilling mud is removed from the drill cuttings, c h a r a c t e r i z e d i n that the method comprises :

- disposing the drill cuttings in a receptacle (1) ;

- vibrating the receptacle (1) until particle fluidization of the drill cuttings takes place;

- maintaining the drill cuttings in a particle-fluidized state during the subsequent treatment;

- adding a soap to the drill cuttings;

- allowing the soap to flow through the drill cuttings whilst the drill cuttings are particle- fluidized;

- draining liquid from the receptacle (1) ; and

- then emptying cleaned drill cuttings out of the

receptacle (1) .

2. The method according to claim 1, c h a r a c t e r i z e d i n that the method further comprises allowing the drill cuttings to compact in the receptacle (1) before emptying.

3. The method according to claim 1, c h a r a c t e r i z e d i n that the method further comprises separating the soap from the drained liquid for re-use.

4. A device for a receptacle (1) for treatment of drill

cuttings, wherein the receptacle (1) is connected to a frame structure (4) and is provided with a supply (20) of drill cuttings, and an outlet opening (24) for treated drill cuttings, and wherein the receptacle (1), which is restrictedly movable relative to the frame (4), is

provided with at least one vibrator (6) , c ha r a c t e r i z e d i n that the receptacle (1) is provided with a soap supply (8) .

5. The device according to claim 4, c h a r a c t e r i z e d i n that the vibrator (6) is dimensioned in a manner allowing it to vibrate the drill cuttings into a particle- fluidized state.

6. The device according to claim 4, c h a r a c t e r i z e d i n that the soap supply (8) comprises a distribution pipe (10) having several outlet openings (12) .

7. The device according to claim 6, c h a r a c t e r i z e d i n that the distribution pipe (10) is located in the lower portion (14) of the receptacle (1) .

8. The device according to claim 4, c h a r a c t e r i z e d i n that the receptacle (1) is connected to the frame (6) by means of an elastic element (2) .