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PRODUCING OIL FROM TAR SAND by injecting a fluid such as water or steam into the formation through the injection well to the production
r> A ni/nnni Txnr» rwc The raucwnnw Wel1' tnen a fluid> e-g-> steam. is passed through the pas
BACKGROUND OF THE INVENTION sag£way from ^ ... ^ prodlfction ^
1. Field of the Invention 5 thus entraining bituminous fluids with which the hot
This invention relates to a process for producing bitu- flowinJS flJuid c0TMes contact The mixture of bitumi
minous fluid from bituminous sand formations. nou* fluids and h(* fluids's then Produced from the
production well and the bituminous fluids are recov
2. Prior Art ered therefrom.
In view of the increasing rate of energy usage in the 10 In sti» another Patent ^.S. Pat. No. 3 554,285 to world today, it is becoming clear that methods must be Meldau) a process is described which is also useful m found to recover energy values from all available fossil a formation comprising less water permeable oilsources of fuel, especially those heretofore relatively beann8 sand overlying a more water permeable oil undeveloped unconventional sources such as tar sands. beanng sand zone- This Process ls/ery similar to the It has been known for many years that large deposits of 15 Durie Process> above> except that after communication tar sands exist in the world, such as those in the Edna 1S established between the injection and production and Sisquoc regions in California, regions in Venezu- wells in the more permeable zone, the formation is ela, and regions in Alberta, Canada, especially along heated t0 more than 550 F by injecting steam or an oxthe Athabasca and Peace Rivers. In the Athabasca ygen containing gas to establsih a combustion front, River area alone anywhere from 200 to 1,500 billion 20 then heating is terminated to allow oil of decreased visbarrels of oil may be present. However, only a small cosity t0 flow int0 the permeable zone. This oil is then percentage of the oil is economically recoverable by displaced towards the production well by again mjectthe now operable Great Canadian Oil Sands process, ing the oxygen containing gas or steam, then the oil is wherein the tar sands are surface mined and the tar sep- pumped up from the well.
arated from the tar sands so mined. It is clear that, if the 25 lt has now been found that m a bituminous fluidenergy values are to be recovered from the vast major- bearing formation characterized by having a relatively ity of the tar sand deposits, they must be recovered in water-impermeable zone lying above and adjacent a situ. The process of this invention provides a new and water-permeable zone, if steam is injected into the perparticularly effective means of obtaining energy values meable zone and maintained there at a high temperafrom tar sands, particularly the tar sands in the Peace 30 ture and pressure, to decrease the viscosity of the bituRiver area. minous fluid, in both zones, the bituminous fluid can It has been proposed to mine the tar sand and to re- later be produced by reducing the pressure in the percover oil from the mined sands by various operations meable zone by increasing the flow of fluids through a requiring mechanical preparation followed by washing production well and oil can then be recovered from and heating. Such a process is described in U.S. Pat. 5 these fluids. By this method oil recovery can be as No. 3,401,110 to P. H. Floyd et al. The cost of these much as 75 percent of the oil in place in the formation operations on a commercial scale is excessive both in s° treated.
terms of capital investment and operating expenses, es- SUMMARY OF THE INVENTION pecially for deep deposits. And, as pointed out before,
if the majority of the energy values are to be recovered This invention is a process for recovering bituminous from the tar sands, the values will have to be recovered fluid from a bituminous sand formation which contains using in situ methods. at least one water-permeable zone and at least one adMany attempts have been made in the past to apply jacent, preferably overlying, water-impermeable zone secondary and tertiary oil recovery methods to recover and which has been penetrated by at least one injection tar from tar sand formations. Although these recovery well and at least one production well both of which methods are of interest, the technology is not always communicate with a water-permeable zone. The proeconomically applicable to the treatment of tar sands. cess comprises
Various attempts have been made using soaks, drives, a. injecting a hot aqueous fluid, preferably steam, in situ combustion, and combinations thereof, but to .„ into the permeable zone to establish a hot, waterdate there has yet to be commercial production. Exam- permeable channel between the injection and producples of some of the in situ methods used in attempting tion wells, preferably so that the bituminous fluid in the to recover hydrocarbons from tar sand and viscous oil- channel has a mobility of at least 15 millidarcies/cenbearing formations include the following: U.S. Pat. No. tipoise;
2,825,408 to Watson; U.S. Pat. No. 3,040,809 to 55 b. continuing the injection of said hot aqueous fluid
Helser; U.S. Pat. No. 2,881,838 to Morris; U.S. Pat. at a rate sufficient to maintain the desired mobility
No. 3,221,813 to Closmann; U.S. Pat. No. 3,396,791 to level of the bituminous fluid in the channel and suffi
Van Meurs et al; U.S. Pat. No. 3,091,292 to Kerr; Ca- cient to increase the mobility of the bituminous fluid in
nadian Pat. No. 679,222 to Muskat; and Venezuelan the bulk of the formation to at least 15 millidarcies per
patents 631/72 and 632/72. 60 centipoise;
Another method is discussed in U.S. Pat. No. c. reducing the pressure in said formation by increas
3,439,742 to Durie which is useful in a formation ing the production of fluids at the production well, and wherein the permeability of the tar sand varies from
being relatively water impermeable in the upper zone d. recovering bituminous fluids from the fluids proof the tar sand formation but relatively water permea- 65 duced.
ble in the lower regions of the formation. In that pro- Preferably steam is initially injected into a produc
cess, a passageway is established between injection and tion well at very high injection rates while at the same
production wells in the lower regions of the formation time water is produced from an injection well and the
