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Патент USA US3093204

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June II,_ 1963
D. L. HOYT
3,093,190
METHOD OF IMPROVING PRODUCTION OF PETRQLEUM
FROM AN UNDERGROUND RESERVOIR
Filed April 11, 1960
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June 11, 1963
D. |_. HOYT
3,093,190
METHOD OF‘ IMPROVING PRODUCTION OF PETROLEUM
FROM AN UNDERGROUND RESERVOIR
Filed April 11, 1960
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June 11, 1963
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METHOD OF IMPROVING PRODUCTION OF PETROLEUM‘
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United States Patent O?lice
1
3,093,190
Patented June 11, 1963
2
3,093,190
METHOD OF
ROVENG PRODUCTHUN 0F
PETROLEUM FROM AN UNDERGROUND
RESERVOIR
Donald L. Hoyt, Houston, Tex., assignor to Texaco Inc,
New York, N.Y., a corporation of Delaware
Filed Apr. 11, 1960, Ser. No. 21,485
5 Claims. (Cl. 166-9)
More particularly, it has been discovered that the petro
leum production from an underground, elongated, sub
stantially elliptical, petroleum-producing formation, which
is under the in?uence of a water drive, is improved by
disposing the production wells penetrating the formation
substantially in line along the major axis of the forma
tion.
Still more particularly, in accordance with this inven
tion, it has been discovered that the production of petro
This invention relates generally to the recovery of petro— 10
leum from an underground, elongated, substantially ellip
tical, water drive petroleum-producing formation is im
this invention relates to a method for improving the re
proved
by disposing the production Wells producing the
covery of petroleum from an underground petroleum
formation so that ‘as many of the production wells as
proclucing reservoir. In a speci?c embodiment, this in
vention is directed to the production of petroleum from 15 practicable are disposed substantially in line along (i.e.
on or near) the major axis of the formation.
an underground petroleum-producing formation which is
As indicated hereinbefore, the practice of this inven
under the in?uence of an adjacent, e.g. underlying, water
tion is applicable particularly to improving the recovery
producing formation or aquifer.
of petroleum from elongated, substantially elliptical, water
In the production of petroleum from underground for
drive
petroleum-producing formations. More particu
mations, it has been the practice heretofore to penetrate 20
larly, improved results are obtained in accordance with
the petroleum-producing formation ‘with a plurality of
the practice of this invention when the elongated, sub~
Wells arranged in a grid pattern, the petroleum being pro
stantially
elliptical, petroleum-producing formation has a
duced from the formation via these Wells. It has been
major axis at least four times greater than the minor axis,
observed particularly when the petroleum-producing for
a ratio of major axis to minor axis in the range of
mation is a so-called water drive formation, i.e. under 25 e.g.
about 4.5-10.0 to 1.0.
_
the in?uence of a water-producing formation which tends
Referring
now
to
the
accompanying
drawings, particu
to displace the petroleum from the petroleum-producing
larly to FIG. 1 thereof, there is illustrated schematically
formation via the production wells, that the wells around
leum from underground reservoirs. More particularly,
the periphery of the producing formation relatively quick
ly produce an excessive amount of water and must be
abandoned before substantially all of the petroleum in
that zone of the formation under the in?uence of these
peripheral wells has been produced.
Accordingly, it is an object of this invention to pro
therein an elongated, substantially elliptical water drive
petroleum-producing formation ‘wherein the major axis
thereof has a length about 4.5 times greater than the
minor axis. The periphery of this reservoir is delineated
by ellipse 10. Penetrating the elliptical reservoir 10‘ is a
plurality of production wells P, for a total of 34 produc
vide a method for improving the production or recovery 35 ‘tion Wells. Of these production wells, 12 or 35 percent
or" the total number are disposed in line along the major
of petroleum from an underground petroleum-producing
axis of the formation and equidistant from each other.
formation.
The remaining production wells, P, 22 in number, are
Another object of this invention is to provide an im
proved method for the production and recovery of petro
leum from an elongated, substantially elliptical, petro
leum-producing formation which is under the in?uence
of an adjacent water-producing formation.
Another object of this invention is to provide a method
for increasing the amount of oil which is recovered from
disposed, as indicated, in a grid-like pattern with respect
to the aforementioned production wells disposed in line
along the major axis of the formation. Laboratory tests
on a model simulating the above-described elliptical reser
voir indicated that when all the wells are produced simul
taneously, there is ultimately swept about 86.4 percent
of the oil in place in the reservoir, i.e. during production
an underground, water drive, petroleum-producing forma 45 of this reservoir via the 34 production wells, 86.4 percent
tion.
'
of the reservoir formation was swept by the displacing
Still another object of this invention is to provide an
?uid (water).
improved method for producing a ‘water drive petroleum
On the other hand, tests conducted on the same reser
producing formation during primary depletion as well as
voir having a total of 46 production wells, 12 or 26 per
during secondary recovery operations.
50 cent of which are disposed in line along the major axis
How these and other objects of this invention are
thereof, as illustrated in accompanying FIG. 2, indicated
accomplished will become apparent from the following
that only 86.4 percent of the reservoir was swept. Upon
description when read in conjunction with the accom
comparison of the results obtained with the petroleum
panying drawings wherein FIGS. 1, 2, 3 and 4 schemati
production techniques as disclosed in FIGS. 1 and 2, it is
cally illustrate the distribution of petroleum-producing
seen that the 12 additional wells employed in connection
vwells producing an elongated petroleum-producing forma
with FIG. 2 did not contribute to any additional produc
tion of petroleum from the reservoir and represented, in
fact, a substantially needless expenditure.
achieved respectively by conventional practice and by
FIG. 3 represents the same reservoir again having a
practice of this invention.
‘
,
60 total of 46 production wells, but this time 16V or about 35
In accordance with this invention, it has been dis
percent of which are disposed substantially in line along
covered that the production of petroleum from an under
the major axis thereof. Tests carried out in connection
with the production wells disposed in the manner illus
ground petroleum-producing formation is improved by
trated in FIG. 3 indicated that 90.7 percent of the pe
disposing the production wells producing the formation
tion.
-
FIGS. 5 and 6 are graphical showings of results
substantially in line along the length of the producing
formation.
65
troleum-producing formation would have been swept,
with resulting increase in the production of petroleum.
Further, since the total number of ‘wells has been in
3,093,190
3
4
FIG. 5 is a chart of part of this data, where it can be
seen that there is no de?nite break in the curve. There is
also some scatter, particularly in the lower values of N,
where an increase in N sometimes results in a decrease
in R.
creased, it is possible to deplete the reservoir in a much
shorter period of time along with the substantial increase
in petroleum production.
Finally, the same water drive petroleum-producing for—
mation was again simulated and this time all the produc
FIG. 6 is a plot of R versus 11 which produces a much
smoother curve than that disclosed in FIG. 5 and has no
tion wells, a total of 12 in number, were disposed in line
along the major axis of the formation. The laboratory
tests carried out in connection with the well arrangement
set forth in FIG. 4, wherein all the production wells are
instance of a decrease in R for an increase in it.
There
appears to be a break in the curve where the value of n
is aqual to 6 or 7 and a levelling off at about )1 equals 25
disposed in line along the major axis of the formation,
showed that such an elongated, elliptical water drive
(and R equals 95 percent). Beyond this value, the curve
will still approach 1100 percent as it approaches in?nity
but the slope is very small. Measurement of the slope
formation would be produced to the extent of 88.1 per
cent thereof by these '12 wells alone, i.e. 88.1 percent of
the formation would be swept. Although the rate at which
petroleum is produced from such a formation is less than
of the curve ‘for values of n greater than 25 shows that
the slope can be less than 3/2 percent per well, so that
additional data points would not be reliable enough to
Warrant the time required for further study.
the rate of production from the same formation by em
ploying a larger number of production wells in the manner
The data in Table I for R, N ‘and It indicates quite
indicated in FIGS. 1 through 3, still the overall recovery
clearly that the sweep-out ‘is not nearly so dependent
is high, and higher than that exhibited by the tests carried
on N as on 11. Tests which utilize the same number of
out with respect to the well arrangements illustrated in 20 axial wells tend to have the same or nearly the same
FIGS. 1 and 2, so that substantially less capital expendi
sweep, even though the total number of wells may dif
ture is required to exploit a petroleum-producing forma
fer considerably. This is true especially for the higher
tion in accordance with the well arrangement of FIG. 4.
values of n. The plot in FIG. 6 when weighed in con
The problem of optimum well density, or spacing, to
junction with other factors, helps to determine the best
deplete a producing ?eld has many facets. It is only 25 number of axial wells to use. Sweep-out of ‘approxi
natural that a. producer would wish to get the greatest
mately 95 percent of the areal extent of the reservoir
possible volume of oil from his various reservoirs and also
may be achieved with as few as 25-30 wells.
to do it with the least possible number of wells. Assum
It is recognized that when a ?eld is discovered, a cer
ing that recovery is proportional to the area swept out,
tain number of development wells will always be re
30
any curve of recovery versus the number of wells is in
quired in order to delineate ?eld boundaries and ob
?uenced by such factors as:
tain necessary information. It is recognized further that
the maximum well potential and the total ?eld produc
(1) The shape of the ?eld.
tion requirement will establish a minimum number of
(2) Source and type of drive.
wells to be in operation. In other words, the principles
(3) Types of production and injection well patterns.
described above, when applied to a producing ?eld will
(4) Permeability distributions.
tend to yield the optimum sweep-out of a typical elon
(5 ) Gravitational forces.
(6) Field production practices.
gated ?eld.
Although in the practice of this invention, particular
In an investigation concerning these tabulated factors, it
emphasis has been placed on the exploitation of elon
is obvious that an increase in sweepout will not be a
linear function of the number of wells. Somewhere on
gated, substantially elliptical, water drive reservoir, the
production techniques of this invention are also applicable
the slope of any curve showing the plot of these variables,
there will begin a decrease and probably very sharply.
To include an evaluation of the relative effects of all of
the factors mentioned above would require a tremendous
amount of time and effort, so that certain logical starting
points and assumptions for a study are required. As an
example, the shape of a ?eld may be assumed as an ideal
to so-oalled gas-drive reservoirs and indeed are gen
erally applicable to large, elongated reservoirs wherein
the ratio (NW) of the length (l) to the width (w)
thereof is greater than 4. The elongated reservoir ap
plicable in the practice of this invention need not be
substantially elliptical in shape but may be curved, angled
er serpentine in con?guration, provided the ratio of the
model, to be uniformly thick, nearly ?at and elliptical,
such type of ?eld occurring in the petroleum producing
formations adjacent the Persian Gulf. Further, perme
ability variations need not be considered since their effect
overall length to the overall or average width of the
formation (l/w) is at least greater than 4.
As will be apparent to those skilled in the art, in the
light of the accompanying disclosure, many changes,
would be present for each value of the total number of
alterations and substitutions are possible in the prac
wells investigated and would tend to cancel each other.
55
tice of this invention without departing from the ‘spirit
A study of the sweep-out (R) versus the number of
wells (N) in the ?eld yielded the data listed in Table I,
and scope thereof.
below, showing the measured values of R versus N, to
I claim:
gether with the number of wells on the axis (n).
1. A method of producing petroleum from a uni
Number
of wells
Percent
svrept
Wells on
axis
Number
of wells
N
R
n
N
formation, elongated and substantially elliptical in shape
with the ratio (a/ b) of the major axis (a) of said forma
tion to the minor axis (b) thereof being greater than
four, which comprises penetrating said formation with a
Percent Wells on
swept
axis
n
65
l1
12
13
4
5
6
7
26. 6
39. 9
51. 5
12. 0
32.6
59. 7
53.1
1
2
3
U
1
4
3
17
19
23
25
28
31
34
72.0
76. 6
77. 3
79. 6
83. 3
84. 2
86.4
5
7
7
9
10
11
12
8
9
10
1 12
13
48. 8
67.4
G2. 4
88.1
71. 2
2
5
4
12
5
40
46
46
69
88. 3
86. 4
90.7
95. 4
14
12
16
25
1 No pattern; wells only on axis.
formly thick, nearly ?at, underground petroleum-bearing
60
Table I
plurality of production wells, and producing petroleum
from said formation via said production wells, the num
ber of said production Wells disposed substantially in
line along said major axis of said formation varying from
5 to 30.
70
2. A method in accordance with claim 1, wherein the
production wells disposed substantially in line along said
major ‘axis are substantially equidistant from each other.
3. A method in accordance with claim 1, wherein all
the production wells penetrating said formation are dis
r posed substantially in line along the major axis.
5
3,093,190
4. A method in accordance with claim 1 wherein
the number of production wells disposed substantially
by Water, volume HI, Reinhold Publishing Corporation,
in line along ‘the major axis of said formation is at least
330 West 42d St, N.Y., 1947 (pages 241, 242 relied on).
Muscat, Morris: Physical Principles of Oil Production,
5. A method in ‘accordance with claim 1 wherein said
formation is under the in?uence of and in contact with
a Water-producing formation.
P. 818 relied on.
the majority thereof.
References Cited in the ?le of this patent
Jones, Park J.: Petroleum Production, Oil Production 10
?rst edition, McGraW-Hill Book Co., Inc, N.Y., 1949.
Uren, L. C.: Petroleum Production Engineering, ‘fourth
edition, published by MoGraW-Hill Book Co., Inc, N.Y.,
1956. (Pp. 50 and 51 relied on.)
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