Drilling mud dehydration system

Apparatus for dehydrating slurries such as water based drilling fluids heavily laden with drill cuttings and other earth solids comprising a rotating drum which is heated by combustion of a fuel air mixture to generate relatively large quantities of combustion products for heating in an enclosed chamber defined by said drum. The slurry to be dehydrated is injected into the interior of the drum or against the outer sidewall thereof for rapid exposure and substantially flash evaporation of the slurry liquids. An outer housing may be constructed around the drum and in one embodiment the drum is arranged inclined to the horizontal with the slurry introduced into the interior of the drum and the combustion chamber formed between the outer housing and the drum. In another embodiment the combustion chamber is formed on the interior of the drum and the evaporation chamber is formed between the drum and the outer housing. The exhaust flues for the evaporation chamber and the combustion chamber are interconnected to provide for induced flow of gases through a stack portion of one of the flues and to dilute the vapor flow stream to minimize the generation of condensation clouds or ice fogs during operations in cold environments.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention pertains to an indirect fired drying or dehydration 
apparatus particularly adapted for dehydrating well circulation fluids 
such as drilling muds containing substantial quantities of drill cuttings 
and similar solids. 
2. Background 
The continued and ever-increasing level of consciousness regarding proper 
handling of waste materials and disposal of such materials in an 
environmentally safe and acceptable manner has caused significant concern 
in the well drilling industry. The handling of well drilling circulation 
fluids or drilling muds which have become heavily contaminated with drill 
cuttings, including the disposal of the drill cuttings themselves, has 
typically been dealt with by digging a pit in the vicinity of the well 
drilling operation for collection of the drill cuttings and the quantities 
of fluids which cannot be entirely separated from these cuttings. 
In certain areas, such as off-shore drilling operations and operations in 
the Arctic, the disposal of drill cuttings and the quantities of fluids 
that cannot be entirely separated from the cuttings has required the 
transport of these substances to suitable on-shore sites, in the case of 
off-shore operations, and the construction of specially lined disposal 
pits. However, the construction of these pits in Arctic regions has been 
deemed undesireable for several reasons and new methods of disposal and 
dehydration of drill cuttings and drilling fluids have been sought. 
The disposal of well drilling cuttings or solid material generated in the 
drilling of a well should take into consideration the composition of the 
liquid base of the circulation fluid. In those instances where the liquid 
is primarily water, a suitable disposal method may be accomplished by 
indirect vaporization of the solids-laden fluids whereby substantially dry 
earthlike materials are then left for disposal and water or other 
evaporable or combustible substances may be treated in a manner whereby 
disposal into the atmosphere is acceptable. 
It is an object of this invention to provide an improved apparatus and 
method for treating drilling fluids which are laden with drill cuttings 
solids and other fluids generated in the drilling process whereby 
substantially dehydrated solid particles are provided which may be 
disposed of in various ways, including possibly use as a construction 
material. It is a further object of the present invention to provide a 
method and apparatus for treating drill cuttings whereby evaporable or 
combustible liquids may be subjected to high enough temperatures to cause 
complete vaporization and some oxidation so that resultant vapors, such as 
water vapor and carbon dioxide, may be discharged into the atmosphere 
directly after the dehydration process. 
SUMMARY OF THE INVENTION 
The present invention provides an improved apparatus and method for 
dehydrating slurries of such materials as well circulation fluids which 
include substantial quantities of borehole cuttings. In accordance with 
the invention, drill cuttings may be returned to the environment upon 
complete dehydration and oxidation of these substances which are possibly 
deleterious if otherwise disposed of, such as by discharge into open pits 
or into waterways or water reservoirs. 
In accordance with one aspect of the present invention, there is provided 
an indirect drying apparatus comprising a rotating drum, a combustion 
system for heating the drum and an arrangement for discharging a slurry of 
substantially water-based mud or like matter, including drill or borehole 
cuttings, onto a surface of the drum to rapidly dehydrate the solids in 
the slurry and to discharge the solids from the apparatus while conducting 
gaseous combustion products and liquid vapors out of the apparatus for 
discharge into the atmosphere through suitable filtration means, if 
necessary. 
In accordance with another aspect of the present invention, there is 
provided an apparatus for dehydrating slurry-like material comprised 
primarily of water, small amounts of hydrocarbons, siltlike materials and 
solid particles wherein the slurry is discharged onto a surface of a 
rotating drum and the dehydrated solid particles are allowed to be 
discharged primarily by gravity from one end of the drum. Gaseous 
combustion products generated during the heating or dehydration process, 
together with vapor or evaporated liquids, are discharged by convection 
flow through a flue and are preferably mixed in the flue to dilute the 
water vapor content of the flue gases. This last mentioned feature is 
particularly attractive for use of the apparatus in colder climates to 
minimize the production of ice fog in the atmosphere. 
In accordance with yet another aspect of the present invention, there is 
provided an apparatus which is adapted to dehydrate relatively large 
quantities of slurry-like materials such as drill cuttings and quantities 
of circulation fluids which have been disposed of in so-called reserve 
pits or holding tanks as a result of separation processes during well 
drilling operations. The apparatus is particularly economical to produce, 
is mechanically uncomplicated and is adapted to handle relatively large 
volumes of the slurry materials on a continuous basis. The apparatus is 
also configured to rely substantially on convection flow of air for 
combustion and for dehydration functions and is configured to provide for 
solids removal from the apparatus by gravity flow. Assistance in 
discharging solids material accumulating on the surface of the drum is 
provided by a scraper bar, or the like, and the drum is preferably rotated 
continuously during operation to distribute the slurry over the surfaces 
of the drum during the dehydration process. 
The present invention further contemplates an improved system for 
dehydrating slurries of water base drilling muds and the like which are 
particularly heavily laden with drill cuttings whereby, on a substantially 
continuous basis, the drilling mud/drill cuttings slurry is exposed to a 
high temperature environment by discharging the slurry on the surface of a 
rotating drum or the like. The improved system also contemplates the 
provision of relatively large, unobstructed flow paths for air for drying 
and conveying the vapors evaporated from the slurry and for discharging 
dehydrated solids to a collection point whereby the solids may be conveyed 
and distributed to a final disposal site. 
Those skilled in the art will recognize the above described advantages and 
features of the present invention, as well as additional superior aspects 
thereof upon reading the detailed description which follows in conjunction 
with the drawing.

DESCRIPTION OF PREFERRED EMBODIMENTS 
In the description which follows, like parts are marked throughout the 
specification and drawing with the same reference numerals, respectively. 
The drawing figures are not necessarily to scale and certain features of 
the invention may be shown in somewhat schematic form. Conventional 
elements and adaptations may also be illustrated in somewhat schematic 
form in the interest of clarity and conciseness. 
Referring to FIGS. 1 through 4, in particular, there is illustrated one 
embodiment of an improved apparatus for treating slurrylike materials, 
particularly slurries of subterranean well borehole cuttings produced 
during the drilling process. The apparatus illustrated is generally 
designated by the numeral 10 and is characterized by an elongated, 
cylindrical drum 12 which is supported for rotation on spaced apart 
supports, generally designated by the numerals 14 and 16, respectively, 
which comprise part of a support frame 18 for the apparatus. The drum 12 
is preferably made of alloy or stainless steel and is characterized as a 
substantially elongated cylindrical tube which is opened at its opposite 
ends 20 and 22, respectively, to provide a substantially unobstructed flow 
of air therethrough. The drum 12 includes spaced-apart generally 
cylindrical support flanges 24 and 26 which are engageable with respective 
sets of support rollers to provide for rotation of the drum about its 
central longitudinal axis 28. 
Referring to FIG. 2, for example, the support 16 is characterized by spaced 
apart upstanding members 30 extending from a base 32 of the frame 18, 
which members are interconnected by a transverse member 33. Adjustable 
support rollers 34 are mounted on the support 16 and engageable with the 
support flange 24 to support one end of the drum 12 for rotation about 
axis 28. The opposite end of the drum 12 is also supported on a set of 
rollers 38 and at least one drive roller 40. The rollers 38 may be 
configured to have somewhat V-shaped grooves and the flange 26 may be 
configured to have a somewhat V-shaped crown to control longitudinal 
excursion of the drum 12 and to increase the drive forces transmitted 
between the drive roller 40 and the flange 26. 
Referring to FIG. 3, also, the support 14 is characterized by spaced apart 
upstanding support members 46 interconnected by transverse members 48. The 
support rollers 38 and the drive roller 40 are mounted for adjustment 
generally vertically on the support members 46 whereby the angle formed by 
the axis 28 with respect to the horizontal or the frame base 32 may be 
adjusted to adjust the so-called pitch of the drum 12 with respect to the 
horizontal. The drive roller 40 is suitably connected to drive motor means 
41 mounted on a vertically adjustable transverse support bar 43. The motor 
means 41 may be fluid or electrically energized. Those skilled in the art 
will recognize that other means for rotating the drum 12 about its axis 28 
may be provided such as a chain or belt drive arrangement suitably 
engageable with the drum and supported on the frame 18. 
Referring to FIG. 1, the apparatus 10 is also provided with means for 
heating the drum 12 and in particular a dehydrating chamber 50 formed in 
the interior of the drum. The heating means comprises a generally 
cylindrical housing 52 disposed about the drum 12 and suitably supported 
for vertical adjustment with the drum 12 by means including spaced apart 
support members 54 and 56 on the frame 18. The housing 52 may typically be 
formed of opposed steel plate cylindrical half-sections 55 and 57 which 
are secured together along opposed mating flanges 58 and 60, see FIGS. 2 
and 3 also. The housing 52 includes opposed transverse end walls 62 and 64 
configured such that the drum 12 projects through both end walls as 
illustrated in FIG. 1. 
The housing 52, together with the drum 12, defines a generally annular 
combustion chamber 66, FIG. 1, having an outlet or exhaust conduit 68 for 
discharging combustion products from the chamber 66 and located generally 
at one end of the housing 52 adjacent to the end wall 62. The exhaust 
conduit 68 is connected to a combustion products flue conduit 70 
comprising a member which extends into a second exhaust stack or flue 72 
having a vertical stack portion 74 and a curved duct section 76, supported 
on the frame 18 for vertical adjustment with respect thereto on spaced 
apart support members 78. The duct section 76 is preferably supported by 
opposed trunnions 77, FIGS. 4 and 5, which are mounted for vertical 
adjustment along the channel shaped members 78 by fasteners 79, FIG. 5. 
The combustion chamber 66 is in communication with a gas fired burner 
assembly generally designated by the numeral 80 which is mounted at the 
end of the housing 52 adjacent the end wall 64. Referring to FIG. 2 also, 
the burner assembly 80 is preferably of a type commercially available and 
is adapted to be connected to a source of fuel such as natural gas or the 
like, not shown. The burner assembly may, for example, be of a type 
manufactured by Eclipse, Inc., Rockford, Ill., as their type 200 JIB-C-2 
Incinerator Burner. The burner assembly 80 is adapted to supply combustion 
air to the chamber 66 by an integral motor driven fan 81. 
The burner assembly 80 is mounted in such a way that a short injection 
conduit section 82 is provided for discharging a high velocity flow of 
burning gases and combustion air into the chamber 66 in such a way that a 
generally circular and somewhat helical flow of combustion gases 
progresses through the combustion chamber 66 toward the exhaust conduit 68 
to provide substantially uniform heating of the rotary drum 12. Suitable 
seals are provided between the transverse end walls 62 and 64 and the 
outer surface of the drum 12 to prevent all but an insignificant leakage 
flow of combustion gases from the combustion chamber 66 at opposite ends 
of the housing 52. The housing 52 is preferably a relatively thin walled 
steel structure having a suitable insulating blanket 53, FIG. 1, formed on 
the inner surface thereof to minimize heat losses through the housing 
itself. 
Referring again to FIGS. 1 and 4, the curved duct section 76 of the flue 72 
includes a generally cylindrical collar 86 which is fitted over the distal 
end 22 of the drum 12 and is stationary relative to the drum so that the 
flue 72 may receive the relatively large flow volume of vapor generated in 
the chamber 50 and the induced flow of air which enters the chamber 50 
through the open end 20 of the drum 12. As illustrated in the drawing 
figures, the longitudinal central axis 28 of the drum 12 is inclined 
slightly upwardly so that the end 22 is at a higher elevation than the end 
20. The support members for the rollers 38 and 40 are preferably 
vertically adjustable relative to the rollers 34 so that the angle of 
inclination of the axis 28 may be selectively adjusted. This angle of 
inclination of the drum 12 relative to the horizontal provides two major 
benefits in that the flow of vapor generated by heating a slurry 
introduced into the chamber 50 and a flow of ambient air into the open end 
20 progresses toward and through the end 22 of the drum 12 and up through 
the flue 72. Moreover, the dehydrated slurry solids which are discharged 
into the chamber 50 collect on the inner surface of the drum 12 and, with 
rotation of the drum, migrate toward the open end 20 and exit therefrom 
for collection and transportation to a suitable disposal site. 
Not only is the flow of vapor and the induced air flow through the chamber 
50 caused to flow through the flue 72 due to natural convection, but the 
discharge of combustion gases through the combustion products flue 70 also 
induces flow of air and vapor through the flue 72 by entrainment or the 
ejector effect. In this regard, the combustion products flue 70 has a 
discharge duct portion 71 which extends through the sidewall of the stack 
74 and has an outlet end 85 arranged to direct the combustion gas flow 
vertically upward in the stack 74 to mix with the relatively large flow 
volume of induced air flow, water vapor and other liquid vapors which have 
been generated in the chamber 50. This dilution of the concentration of 
water vapor is particularly advantageous in applications of the apparatus 
of the present invention in very low ambient temperatures such as are 
experienced in Arctic oil field operations whereby the generation of ice 
fogs at the outlet of the flue 72 is minimized. Referring to FIG. 1, the 
flue 72 may also be provided with a particle filter 88 disposed in the 
stack 74 to filter out any fines which may be induced to flow with the 
vapor flow stream exiting the drum 12 through the end 22. 
The slurry of well circulation fluid, drill cuttings and fluids mixed with 
the well circulation fluid during drilling operations is introduced into 
the chamber 50 through a conduit 90 which is suitably supported on the 
flue duct section 76 and includes an inlet end 92 extending through a 
bottom wall portion of the duct 76 and having an elongated discharge 
nozzle portion 94 extending substantially coaxially into the chamber 50 
and provided with a plurality of spaced apart nozzle orifices 96 formed 
thereon. The slurry injection conduit 90 is suitably supported in the duct 
76 so that the cantilever nozzle portion 94 is not required to be 
supported by the rotating drum 12. However, if necessary, the nozzle 
portion 94 could be extended farther toward the end 20 of the drum 12 and 
supported on suitable bearing means within the drum to permit rotation of 
the drum relative to the nozzle section. The slurry injection conduit 90 
is adapted to be connected to a source of slurry to be dehydrated, not 
shown, through suitable pump means, also not shown. 
Referring further to FIGS. 1 and 2, the drum 12 is also provided with means 
for continuously scraping the interior surface 13 of the drum 12 and 
comprising an elongated scraper bar 100 which extends into the chamber 50 
through the open ends of the drum and is supported by spaced apart support 
brackets 102 connected to the drum supports 14 and 16. One of the support 
brackets 102 extends through a suitable opening formed in the duct 76. 
Thanks to the scraper bar 100, any tendency for solid particles to collect 
on the surface 13 is minimized and the provision of the scraper bar 100 
aids in discharge of the solids which tend to collect in the chamber 50 as 
the drum 12 is rotated. The combination of the scraper bar 100 and the 
inclined attitude of the drum 12 assures relatively continuous migration 
of the dehydrated solids toward the open end 20 of the drum. 
In operation of the apparatus 10, the drum 12 is preferably continuously 
rotated at a selected speed which will assure complete dehydration of the 
solid particles which are injected in the slurry into the chamber 50 
through the conduit 90. This dehydration process is carried out largely 
through the process of heating the slurry injected into the chamber 50 
indirectly by the combustion of a gaseous or liquid fuel in the combustion 
chamber 66, preferably under a forced draft process utilizing the burner 
assembly 80. High velocity flow of the gaseous combustion products with an 
airflow substantially in excess of the stoichiometric ratio occurs in the 
chamber 66 and the flow of combustion products undergoes a somewhat 
helical flow path from the inlet to the housing 52 at the burner assembly 
to the combustion products exhaust outlet conduit 68. The rapid outflow of 
combustion products through the combustion products flue 70 into the flue 
72 also aids in inducing the flow of ambient air and vapors generated in 
the chamber 50 through the flue 72 whereby dilution of the vapors is 
enchanced by the induced air flow and by mixing with the combustion 
products to minimize the chance of the accumulation of large ice fog 
clouds when the apparatus 10 is being operated at ambient temperatures 
below 32.degree. F. 
As the slurry is injected into the chamber 50, it falls into contact with 
the drum wall 13 and in the presence of high temperature in the chamber 50 
the solid particles in the slurry are substantially dried and stripped of 
any deleterious substances such as traces of hydrocarbon fluids and the 
like by oxidation of these substances. The relatively large flow of 
ambient air through the chamber 50 from the end of the drum 20 to and 
through the end 22 assists in oxidizing any substances on the earth solids 
being dehydrated. Thanks to the inclination of the drum 12, the dehydrated 
solids migrate toward the open end 20 and are continuously scraped free 
from adherence to the drum wall 13 by the elongated scraper bar 100. 
Referring now to FIGS. 6 and 7, there is illustrated an alternate 
embodiment of the present invention, comprising a dehydration apparatus 
generally designated by the numeral 120. The apparatus 120 includes a 
generally cylindrical outer housing 122 having a substantially cylindrical 
insulated housing section 124, a somewhat frustoconical shaped dome 
section 126 and a generally vertical exhaust flue or stack portion 128. 
The housing 122 defines an interior slurry dehydration chamber 130 in 
which is disposed a generally cylindrical elongated hollow drum member 
132. The drum 132 defines an interior combustion chamber 134. The 
longitudinal central axis 135 of the drum 132 is inclined at a relatively 
steep angle to the horizontal, preferably vertical. For convenience, one 
end of the drum 132 is designated as the lower end 136 and the opposite 
end 138 is designated as the upper end. 
The lower end 136 of the drum 132 is substantially open to atmosphere and 
the upper end 138 is provided with a combustion products exhaust flue or 
stack 140. The stack 140 opens into the throat 131 of the chamber 130 just 
below the exhaust stack portion 128. The combustion products stack 140 may 
have a somewhat convergent nozzle configuration to increase the velocity 
of combustion gases exiting through the opening 141 into the interior of 
the stack 128 so as to induce the flow of slurry vapor and ambient air out 
of the chamber 130. The combustion chamber 134 is provided with a burner 
assembly 144 supported on a suitable conduit section 146. The burner 
assembly 144 may be provided with a multiport burner tube 148 arranged 
substantially transversely across the chamber 134 adjacent the lower end 
136 of the drum 132. The drum 132 includes spaced apart cylindrical 
flanges 149 and 150 which are journaled for rotation by respective sets of 
rollers 151 mounted on suitable supports 153 and 155. One of the rollers 
151 is operably connected to motor means 152 for driveably rotating the 
drum about the axis 135. The flange 150 is preferably shielded by a 
generally frustoconical shield 157 disposed about the drum 132. The shield 
157 is cut away to provide space for respective ones of the lower set of 
rollers 151. 
As illustrated in FIG. 6, relatively viscous slurry resulting from the 
separation of drill cuttings and the like from a drill circulation fluid 
may be pumped into the interior of the housing 122 through a plurality of 
vertically spaced apart injection nozzles 158 which are each connected to 
a supply manifold 160 in communication with suitable pump means, not 
shown, for supplying the slurry to the respective nozzles. The nozzles 158 
are adapted to direct a flow of slurry against the cylindrical wall 133 of 
the drum 132 whereupon the heated surface of the wall will act to 
dehydrate the relatively fine solids which are entrained in the slurry 
solution. Accumulation of dried or partially dried material on the drum 
wall 133 is prevented by a generally vertically extending scraper bar 162 
which is suitably supported in the interior chamber 130 by spaced apart 
support members 163 and is engageable with the wall 133 for removing any 
material which may tend to stick to the wall surface. The dehydrated 
solids will drop to the bottom of the chamber 130 and into an enlarged 
plenum area 139 defined in part by a rectangular support base 123 for the 
housing 122. The base 123 is preferably provided with a skirt 125 forming 
a suitable opening 127 to permit a substantial flow of air into the plenum 
139 and flow through the chamber 130 and the combustion chamber 134. 
Suitable means, not shown, may be employed for removing the accumulation 
of dried solids which fall into the plenum space 139 from the upper 
regions of the chamber 130. 
Operation of the apparatus 120 is similar to the apparatus 10 in that the 
drum 132 is continuously rotated during combustion of a mixture of air and 
fuel in the combustion chamber 134 to heat the chamber 130 and the outer 
surface of the wall 133 so that, upon spraying the slurry material into 
the chamber 130, the solids entrained in the slurry are rapidly dehydrated 
and allowed to fall into the plenum 139 for suitable removal. The large 
quantities of water vapor and other liquid vapors which are generated in 
the chamber 130 flow rapidly upwardly into the stack 128 and this flow is 
accelerated to some extent by the flow of combustion gases which exit 
through the nozzle 140 into the throat area 131 of the chamber 130 to 
assist in inducing the flow of vapors and induced air flow coming into the 
chamber 130 through the opening 127. As with the apparatus 10, operation 
in subfreezing environments may be carried out without the tendency to 
produce substantial clouds of condensed water vapor or ice fog at the 
outlet of the exhaust stack 128. In certain applications of the apparatus 
120, it may also be necessary to include suitable filtration means 166 
such as an electrostatic type precipitator or an impingement type filter 
interposed in the stack 128. 
Those skilled in the art will recognize that the dehydration apparatus 
described herein provides a unique and uncomplicated device for handling 
liquid-solids mixtures, particularly slurrylike remainders of water based 
drilling fluids in which substantial quantities of drill cuttings or other 
earth solids are disposed. 
Although preferred embodiments according to the present invention have been 
described herein, those skilled in the art will recognize that various 
substitutions and modifications may be made to the specific embodiments 
described without departing from the scope and spirit of the invention as 
recited in the appended claims.