Heater treater economizer system

An apparatus and method is disclosed for greatly increasing the efficiency of heater treater units, such as those used in heavy oil recovery, wherein exhaust air from the heater treater is circulated around incoming heavy oil lines from a freewater knockout unit to preheat the heavy oil reducing the required temperature increment provided by the heater treater to achieve a predetermined temperature for water/oil separation.

BACKGROUND OF THE INVENTION 
The present invention pertains to tertiary oil recovery processing and, 
more particularly, to improving the efficiency of heater treaters used in 
moisture removal for heavy oil. 
Presently, new oil wells are being drilled in remote areas and to greater 
depths. As such, new wells are becoming very expensive and the possibility 
of reworking old oil wells is increasingly attractive. 
In the past, oil wells were drilled and when natural pressure ceased 
forcing oil out of formations, the well was considered as nonproducing. In 
eariler wells, natural pressure diminished quickly since the majority of 
these wells were shallow. 
In most oil wells that are being reworked, the oil remaining is extremely 
heavy, having a density much closer to water than the oil originally 
produced. As a result, this oil may be suspended in water to the point 
where oil constitutes only thirty percent (30% ) of the solution. A good 
portion of this water is freewater and may be separated from an oil-water 
emulsion very easily by settling. 
The process for heavy oil recovery is fairly simple and well known in the 
prior art; however, for the sake of clarity, a brief outline will be 
presented. 
Heavy oil is forced from subsurface formations by the use of high pressure 
steam injection or by any one of many secondary or tertiary oil recovery 
methods currently in use in the art. In general, the heavy oil arrives at 
the surface in a slurry at approximately one hundred forty degrees 
Fahrenheit (140.degree. F.). This slurry may be greater than seventy 
percent (70%) water, primarily from ground water, although steam injection 
does add slightly to the water content, although most subsurface oil is 
significantly less dense than water and easily separates from the 
subsurface water. However, heavy oil of the type obtained in secondary or 
tertiary recovery has a density much closer to that of water and is more 
difficult to separate. 
As a result, chemical emulsion breakers, such as surfactants, are added to 
the water/oil mixture and the mixture is placed in a settling tank, 
sometimes referred to as the freewater knockout tank, for several hours. 
When the freewater has had an opportunity to settle, a water/oil emulsion 
along with the chemical coalescers are drawn off the top of the settling 
tank. Water is drained from the bottom of the tank. 
The water/oil emulsion is piped to a heater treater where the emulsion is 
heated from approximately one hundred to one hundred fifty degrees 
(100.degree.-150.degree.) to between two hundred and two hundred fifty 
degrees Fahrenheit (200.degree.-250.degree. F.). The emulsion has been 
reduced from approximately seventy percent (70%) water as it arrives from 
subsurface formations to approximately thirty-five percent (35%) water 
from the freewater knockout tank. After the emulsion is removed from the 
heater treater, water constitutes only about three percent (3%) which is 
acceptable for transport to a facility for further refining. 
The preshipment process comprising the freewater knockout tank along with 
the chemical surfactants and the heater treater add significant costs to 
the secondary and tertiary recovery of heavy oil. 
SUMMARY OF THE INVENTION 
The present invention discloses a method and apparatus for greatly 
increasing the efficiency of preshipment treatment facilities used in 
conjunction with secondary and tertiary heavy oil recovery systems. A 
pretreater is placed between a freewater knockout tank and a heater 
treater. The pretreater includes an opening for receiving the exhaust gas 
from the heater treater and a pipeline from the freewater knockout tank. 
The pipeline carries an oil/water emulsion through the preheater. The 
pipeline is run back and forth through the pretreater by having a 
plurality of one hundred eighty degree (180.degree. ) bends. The conduit 
used in the pipeline is configured to have heat transfer fins its entire 
length. Baffles are provided within the pretreater housing to direct flow 
of the exhaust gas from the heater treater.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, a heavy oil heater treater 12 is illustrated as 
receiving an input 14 of an oil-water emulsion from preheater 16 and 
having an exhaust output 18 supplying preheater 16 which has its own 
exhaust port 20. Preheater 16 receives an input of an oil/water emulsion 
22 from a freewater knockout tank 23. In freewater knockout tank 23, 
chemical coalescers, such as surfactants, have been added to the water/oil 
mixture to aid in the water/oil separation. Preheater 16 is mounted on a 
pipe support structure 24 comprised of pipe units 26 partially buried in 
base support structure 28 which may be the ground, a gravel pit, a cement 
slab, or the like. Preheater 16 is illustrated as having a conduit 30 
running from side 32 having input 22 to side 34 having output 36 in a 
serpentine manner. 
Heater treater 12 may be of any type currently in use in the art having a 
gas powered heater (not shown) for raising the temperature level of a 
heavy oil/water emulsion, such as that produced in secondary and tertiary 
oil recovery methods. Normally, heater treater 12 will have a gas powered 
flame heating the heavy oil/water emulsion prior to emulsion being placed 
in a settling portion of the heater treater having a variety of filters 
used to urge coalescence of water suspended in the heavy oil/water 
emulsion. 
Referring now to FIG. 2, a partially cut-away isometric view of pretreater 
16 is illustrated as having three levels of conduit 30 weaving back and 
forth from end 32 to end 34 starting at inlet 22 of end 32 and ending at 
outlet 36 at end 34. The portions of conduit 30 are illustrated as having 
heat conducting fins throughout to assure substantial heat transfer 
between the input exhaust gas and conduit 30. Intake 18 is illustrated as 
a Y having an emergency exhaust arm 38 which is normally closed and intake 
section 40 which is normally open. Arm 38 is normally closed by a movable 
vent which may be rotated to block off arm 40 in the event of repairs 
being required by preheater 16. At such time, the vent (not shown) may be 
rotated to prevent flow of exhaust air through arm 40 and to allow all 
exhaust gas to flow through arm 38. 
Under normal circumstances, arm 38 is blocked off and all exhaust air from 
heater treater 12 flows through preheater 16. The exhaust gas flowing 
through arm 40 may range from 600.degree. to 800.degree. F. Previously, 
this exhaust gas was being vented to the atmosphere resulting in 
tremendous amounts of waste heat. Through the use of the present 
invention, the exhaust air is provided to preheater 16 at end 34, 
circulates through preheater 16 and exhausts at exhaust port 20. The 
diameters of arm 38, arm 40, and exhaust port 20 are preferably all the 
same size to prevent any unnecessary back pressure to the burner of heater 
treater 20 while not allowing any expansion of the exhaust gas allowing it 
to cool and lose some of its heating properties. The diameters of arm 38, 
arm 40 and exhaust 20 are approximately 3-ft. However, any suitable 
diameter may be used as long as the general requirements as previously 
laid out are followed. The exhaust gas enters preheater 16 trhough arm 40 
and heats the water/oil emulsion contained in the sections of pipe 30 
between end plate 41 and baffle 42. The exhaust air travels toward baffle 
44 which extends down from the top of preheater 16. As indicated 
previously, conduits 30 contain a plurality of heat transfer fins to 
assure heat transfer between the exhaust gas and the fluid contained 
within conduits 30. 
Referring to FIG. 3, a sectional end view of FIG. 2 taken along lines 3--3 
is illustrated as having arm 38 equal and parallel to arm 40 of the 
exhaust of heater treater 12. Conduits 30 are illustrated as comprising 
three layers, each layer of which heat conducting fins 46 of conduits 30 
are in close proximity with each other having extremely slight clearances 
therebetween. It will be noted that there exists a space 48 and a space 50 
between layers of conduits 30. At the end of each horizontal roll of 
conduits 30, a baffle 52 is illustrated. Baffles 52 extend the entire 
length of preheater 16 to provide even heating of conduits 30 and avoiding 
hot spots caused by exhaust gas flow concentrating in small open areas. 
As illustrated in FIG. 4, exhaust gas enters through arm 40 rising along 
baffle 42 to an open area 56 above baffle 42. At this point, exhaust gas 
travels towards baffle 44 and is made to flow in a downward direction 
towards open area 58 below baffle 44. By using the construction 
illustrated in FIG. 5, the exhaust air rises and then is brought down to 
the bottom, allowed to rise again, brought down to the bottom again, and 
so on, throughout the length of preheater 16. In this manner, exhaust gas 
is circulated through preheater 16 in a serpentine manner til it exhausts 
at port 20 exhaust after heating the heavy oil/water emulsion flowing 
through conduits 30. 
As indicated previously, exhaust gas enters port 40 through arm 18 at a 
temperature between 600.degree. to 800.degree. F. After circulating 
through preheater 16, the exhaust gas exiting port 20 is approximately 
250.degree. F. The heavy oil/water emulsion entering conduit 30 at input 
22 is approximately 100.degree.-150.degree. F. The heavy oil/water 
emulsion exiting at output 36 has received an increase in temperature of 
approximately 30.degree. F. Thus, preheater 16 has utilized previously 
wasted exhaust gas from heater treater 12 to raise the temperature of the 
heavy oil/water emulsion arriving at heater treater 12 through input 14 to 
reduce the heating requirements of heater treater 12 making it more 
efficient. 
Referring now to FIG. 5, a side view of preheater 16 is illustrated. A 
housing 60 is comprised of two sections, 60a and 60b, a top half and a 
bottom half, respectively. Housing 60 is preferably made of steel covered 
with a fiberglass or asbestos insulation to prevent heat loss of exhaust 
gas from heater treater 12 entering through arm 18. Inlet 22 and outlet 36 
are preferably steel pipe having a diameter of three to six inches and 
also having insulation (not shown) similar to that for housing 60. 
The use of the present invention, preheater 16, permits the use of 
previously wasted exhaust gas from heater treater 12 having a temperature 
of 600.degree. to 800.degree. F. The exhaust gas is circulated through 
preheater 16 and forced over conduits carrying a heavy oil/water emulsion 
to raise the temperature of the emulsion approximately 30.degree. F. prior 
to entering heater treater 12. By providing preheater 16 a reduced demand 
is placed on heater treater 12 permitting it to be operated using less 
fuel. In addition, the gentle rolling action of the heavy oil/water 
emulsion in preheater 16 provides additional agitation and mixing of the 
emulsion aiding in the coalescing of the water portion. The additional 
agitation permits the use of lesser quantities of the chemical coalescers, 
such as surfactants, prior to freewater knockout tank 23. Thus, the use of 
preheater 16 reduces the fuel requirement for heater treater 12 and the 
surfactant requirement for the chemicals added prior to freewater knockout 
settling tank 23. The use of preheater 16 reduces the cost and thus 
improves the efficiency of the pretreatment system used in conjunction 
with secondary and tertiary heavy oil recovery systems. 
While the present invention has been illustrated by way of preferred 
embodiment, it is to be understood that it is not limited thereto but only 
by the scope of the following claims.