Note: Descriptions are shown in the official language in which they were submitted.
CA Application
Blakes Ref. 25453/00001
METHOD, MEDIUM, TERMINAL AND DEVICE FOR EVALUATING LAYERED
WATER INJECTION EFFICIENCY OF OIL RESERVOIR
TECHNICAL FIELD
The present disclosure relates to the field of oil reservoir production, and
in particular to a
method, medium, terminal and device for evaluating a layered water injection
efficiency of an
oil reservoir.
BACKGROUND
Water injection is widely used in the secondary development stage of China's
onshore oil
reservoirs. With the expansion of the scope of the injected water, the flow
field in the reservoir
is constantly changing due to the influence of the heterogeneity of the
reservoir, resulting in
problems such as water channeling and dead oil zones. Accurately evaluating
the water
injection efficiency of each injection well is helpful to identify the
injection-production
correspondence between oil and water wells and determine a reasonable
injection-production
working system, which is the key basic work to increase the production and
efficiency of the
oil reservoir.
The commonly used water injection efficiency evaluation methods include
reservoir
engineering methods and numerical reservoir simulation methods. The
traditional reservoir
engineering methods are based on the physical data (permeability, height, well
spacing, etc.)
of the well point to calculate the splitting coefficients in each direction in
the well group as the
basis for calculating the water injection efficiency. These methods have been
practiced in mines
for a long time and have achieved good development results. However, since
they only consider
the static characteristics of the reservoir, there is a large error between
the calculated and actual
splitting coefficients, and the accuracy of the calculated water injection
efficiency is affected.
With the development of the numerical reservoir simulation technology,
streamline simulation
based evaluation methods have emerged. They can accurately calculate the
splitting coefficient
of each well, but have disadvantages such as complex modeling process and long
calculation
time.
SUMMARY
The present disclosure provides a method, medium, terminal and device for
evaluating a
layered water injection efficiency of an oil reservoir. The present disclosure
solves the above
technical problems such as inaccurate calculated water injection efficiency,
complicated
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calculation process and long calculation time.
To resolve the above problems, the present disclosure provides a method for
evaluating a
layered water injection efficiency of an oil reservoir, including the
following steps:
step 1: constructing an inter-well connectivity network model characterized by
two inter-
well connectivity parameters, namely conductivity and connected volume by
simplifying an
oil reservoir system into a network of interconnected nodes that considers
preset geological
characteristics, and correcting the inter-well connectivity parameters by
fitting an actual
production performance, so that the inter-well connectivity network model
conforms to an
actual reservoir connectivity relationship, where the preset geological
characteristics include
well point characteristics, water body characteristics and/or fault
characteristics;
step 2: calculating an injected water splitting coefficient of an injection
well to a
surrounding oil well in each layer according to the inter-well connectivity
network model and
a seepage theory, and calculating a water injection efficiency eik of each
injection well in each
layer and an average water injection efficiency exk of each layer according to
the injected
water splitting coefficient; and
step 3: comparing the water injection efficiency eik of the injection well in
each layer
with the average water injection efficiency exk of the same layer, and
determining that the
injection well needs to decrease injection in the layer if eik < exk,
otherwise determining that
the injection well needs to increase injection in the layer.
Further, each connected unit of the inter-well connectivity network model is
characterized
by two inter-well connectivity parameters, namely conductivity and connected
volume:
¨ ______________________________________________
u VR
1=1 j=1+1 u
0.0864kuVij
To =
Ito ,7S 12
LI]
where, N, represents the total number of wells connected to an i-th well; V
represents
a connected volume between the i-th well and a j-th well; VR represents the
total connected
volume of the reservoir; Tij represents a conductivity between the i-th well
and the j-th well;
represents an average porosity of a formation between the i-th well and the j-
th well;
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represents an average effective height of the formation between the i-th well
and the j-th well;
represents a spacing between the i-th well and the j-th well; kij represents
an average
permeability of the formation between the i-th well and the j-th well; [to
represents an in-situ
oil viscosity.
Further, the calculating an injected water splitting coefficient of an
injection well to a
surrounding oil well in each layer according to the inter-well connectivity
network model and
a seepage theory specifically includes:
S201: expressing a productivity index (PI) in the connected unit based on the
seepage
theory and the inter-well connectivity parameters:
in = 4Tiii t1
kAilk
j k [
,ln(0.51,iik/rik)+sik-0.751'
where, Jiik represents the PI between wells i and j in layer k, m3/(d=MPa);
kik represents a
mobility at a well point of well i, 10-3p,m2/(mPa.$); kiik represents a
mobility in the connected
unit of wells i and j in layer k, 10-3p,m2/(mPa.$); Liik represents a spacing
between wells i and j
in layer k, m; rik represents a wellbore radius of well i in layer k, m; sik
represents a skin factor
of well i in layer k; the superscripts n and n-1 represent n-th and (n-1)-th
time steps, respectively;
S202: determining the mobility in the connected unit by using an upstream
weighting
method by the mobility at nodes at both ends of the connected unit according
to a bottom hole
pressure and the PI:
= Kiik [Kro(S nw act) Krw(Swnik1)1 pi
n-1 n-1
= ktok ktwk
ifk iv:1¨ 1 = K..
ro(swnikl) K rw. (S wn ik1)1 pri < 19;1.-1
jk tjk
Pok ktwk
where, represents a
mobility at a well point of well j, 10-3p,m2/(mPa.$); Kiik
represents an average permeability between wells i and j in layer k, 10-3p,m2;
Swik represents
a water saturation of well i in layer k; Kro and Krw represent a relative
permeability of oil
and water respectively, 10-31-1m2; itok and ktwk represent a viscosity of oil
and water in layer
k respectively, mPa=s;
S203: calculating a total PI of well i according to the PI and the mobility in
the connected
unit:
= EkNiiEJ ii
ii N.w jnik;
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S204: calculating a longitudinal splitting coefficient of well i in layer k
according to the
total PI of well i:
in ( jiv j inik
Arilk = jn = r N j w
L'in
k=1 = 1 lik
where, Aik represents the splitting coefficient of well i in layer k; Jik
represents the total
PI of well i in layer k, m3/(d=MPa); Ji represents the total PI of well i,
m3/(d=MPa);
S205: obtaining a fluid flow in each connected unit, and calculating an
injected water
splitting coefficient of the connected unit to a surrounding oil well
according to the fluid flow
and the longitudinal splitting coefficient:
qinjk
=AJk Nw
En
j=1
giljk = Tijk(19I Pin
where, n represents a moment of the model; qiik represents an inflow (outflow)
in the
connected unit between the i-th well and the j-th well in the k-th layer; N,
represents the total
number of wells connected to the i-th well; Aiik represents the injected water
splitting
coefficient of the i-th injection well to the j-th well in the k-th layer;
Tiik represents an average
conductivity between the i-th well and the j-th well in the k-th layer; pi and
pi represent an
average pressure in a drainage area of the i-th well and the j-th well
respectively.
Further, the water injection efficiency eik and the average water injection
efficiency exk
of each injection well in each layer are calculated according to the injected
water splitting
coefficient as follows:
zinr. qprzik (1 _ fwnik)
eik = ________________
qink
ENi iz k fwni k)
e = ________________________________________________
xk EN1 i 1 ql
where, NI represents the total number of injection wells in the layer; eik
represents the
water injection efficiency of the i-th injection well in the k-th layer; exk
represents the average
water injection efficiency of the i-th injection well in the k-th layer; qik
represents an injection
volume of the i-th well in the k-th layer; fwik represents a water cut of the
j-th oil well
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connected to the i-th injection well in the k-th layer.
Further, in step 3, an injection volume to decrease or increase is calculated
according to a
preset injection increase/decrease equation:
new (= 1. wmax eik ¨ exk )(xl
qk [ I ii
,old
e. ¨ exk
min
[ exk eikcc] ,old
= 1 + '
exkii
emin
where, qiirw represents the injection volume of the water well in the layer
after
adjustment; qr represents the injection volume of the water well in the layer
before
adjustment; wmax represents a preset increase coefficient; wmin represents a
preset
decrease coefficient; emax represents the maximum water injection efficiency
of the water
well in the same layer; emin represents the minimum water injection efficiency
of the water
well in the same layer; a represents a weight change index, which is
determined according to
the average water injection efficiency of the single layer.
Further, wmax is maximally 0.5, wmin is minimally -0.5, and a=2.
A second aspect of the present disclosure provides a computer-readable storage
medium,
storing a computer program, where when the computer program is executed by a
processor, the
above method for evaluating a layered water injection efficiency of an oil
reservoir is
implemented.
A third aspect of the present disclosure provides a terminal for evaluating a
layered water
injection efficiency of an oil reservoir, including the above computer-
readable storage medium
and a processor, where when a computer program stored on the computer-readable
storage
medium is executed by the processor, the above method for evaluating a layered
water injection
efficiency of an oil reservoir is implemented.
A fourth aspect of the present disclosure provides a device for evaluating a
layered water
injection efficiency of an oil reservoir, including a model establishment
module, a calculation
module and a comparison and determination module, where
the model establishment module is configured to construct an inter-well
connectivity
network model characterized by two inter-well connectivity parameters, namely
conductivity
and connected volume by simplifying an oil reservoir system into a network of
interconnected
nodes that considers preset geological characteristics, and correct the inter-
well connectivity
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parameters by fitting an actual production performance, so that the inter-well
connectivity
network model conforms to an actual reservoir connectivity relationship, where
the preset
geological characteristics include well point characteristics, water body
characteristics and/or
fault characteristics;
the calculation module is configured to calculate an injected water splitting
coefficient of
an injection well to a surrounding oil well in each layer according to the
inter-well connectivity
network model and a seepage theory, and calculate a water injection efficiency
eik of each
injection well in each layer and an average water injection efficiency exk of
each layer
according to the injected water splitting coefficient;
the comparison and determination module is configured to compare the water
injection
efficiency eik of the injection well in each layer with the average water
injection efficiency
exk of the same layer, and determine that the injection well needs to decrease
injection in the
layer if eik < exk, otherwise determine that the injection well needs to
increase injection in the
layer.
The present disclosure provides a method, medium, terminal and device for
evaluating a
layered water injection efficiency of an oil reservoir. This method includes:
simplifying an oil
reservoir system into a network of interconnected nodes that considers a
series of complex
geological characteristics such as well points, water bodies and faults, and
constructing an
inter-well connectivity network model characterized by two inter-well
connectivity parameters
of conductivity and connected volume, thereby simplifying the reservoir into a
group of
connected units composed of single wells; and calculating an injected water
splitting
coefficient of an injection well in each layer, and increasing or decreasing
the injection
according to a water injection efficiency of the injection well in each layer
and an average water
injection efficiency of the same layer. The present disclosure reduces the
parameter dimension
required to be solved, and greatly reduces the calculation and fitting time.
The present
disclosure directly calculates the split volume and water injection efficiency
of the water well
in each connected unit, and has obvious advantages in evaluating the layered
water injection
efficiency of large oil reservoirs. Meanwhile, the present disclosure
alleviates the inter-layer
conflicts, realizes layered control of the separate injection wells, improves
the water injection
efficiency, and increases and stabilizes the production.
In order to make the above objectives, features and advantages of the present
disclosure
more understandable, the present disclosure is described in detail below with
reference to the
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preferred embodiments and accompanying drawings of the present disclosure.
BRIEF DESCRIPTION OF DRAWINGS
To describe the technical solutions in the embodiments of the present
disclosure more
clearly, the following briefly describes the accompanying drawings required
for describing the
.. embodiments. It should be understood that the following accompanying
drawings show merely
some embodiments of the present disclosure, and therefore should not be
regarded as a
limitation on the scope. A person of ordinary skill in the art may still
derive other related
drawings from these accompanying drawings without creative efforts.
FIG. 1 is a flowchart of a method for evaluating a layered water injection
efficiency of an
oil reservoir according to an embodiment.
FIG. 2 is a diagram of permeability distribution of an oil reservoir in
another embodiment.
FIG. 3a is a schematic diagram of inter-well connectivity parameters in layer
1 in another
embodiment.
FIG. 3b is a schematic diagram of inter-well connectivity parameters of layer
2 in another
embodiment.
FIG. 4 is a schematic diagram of longitudinal splitting in another embodiment.
FIG. 5 is a schematic diagram showing a longitudinal splitting change rule of
well W5 in
another embodiment.
FIG. 6 is a schematic diagram of splitting in a conceptual model in another
embodiment.
FIG. 7 is a schematic diagram of a water injection efficiency in the
conceptual model in
another embodiment.
FIG. 8 is a schematic diagram of the water injection efficiency of a single
well in a
sandstone section in another embodiment.
FIG. 9 is a schematic diagram of the water injection efficiency of a single
well in a
conglomerate section in another embodiment.
FIG. 10 is a schematic diagram of splitting of a Ti well group in another
embodiment.
FIG. 11 is a comparison diagram of a production performance of the Ti well
group in
another embodiment.
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FIG. 12 is a schematic diagram of splitting of a T6 well group in another
embodiment.
FIG. 13 is a comparison diagram of a production performance of the T6 well
group in
another embodiment.
FIG. 14 is a comparison diagram of optimization results in another embodiment.
FIG. 15 is a structural diagram of a device for evaluating a layered water
injection
efficiency of an oil reservoir according to an embodiment.
FIG. 16 is a structural diagram of a terminal for evaluating a layered water
injection
efficiency of an oil reservoir according to an embodiment.
DETAILED DESCRIPTION
To make the objectives, technical solutions and beneficial technical effects
of the present
disclosure clearer, the present disclosure is described in more detail below
with reference to
the accompanying drawings and specific implementations. It should be
understood that the
specific implementations described herein are merely intended to explain the
present disclosure,
rather than to limit the present disclosure.
FIG. 1 is a flowchart of a method for evaluating a layered water injection
efficiency of an
oil reservoir according to Embodiment 1 of the present disclosure. As shown in
FIG. 1, the
method includes the following steps:
Step 1: Construct an inter-well connectivity network model characterized by
two inter-well
connectivity parameters, namely conductivity and connected volume by
simplifying an oil
reservoir system into a network of interconnected nodes that considers preset
geological
characteristics, and correct the inter-well connectivity parameters by fitting
an actual
production performance, so that the inter-well connectivity network model
conforms to an
actual reservoir connectivity relationship, where the preset geological
characteristics include
well point characteristics, water body characteristics and/or fault
characteristics.
Step 2: Calculate an injected water splitting coefficient of an injection well
to a
surrounding oil well in a longitudinal direction and in each layer according
to the inter-well
connectivity network model and a seepage theory, and calculate a water
injection efficiency
eik of each injection well in each layer and an average water injection
efficiency exk of each
layer according to the injected water splitting coefficient.
Step 3: Compare the water injection efficiency eik of the injection well in
each layer with
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the average water injection efficiency exk of the same layer, and determine
that the injection
well needs to decrease injection in the layer if eik < exk, otherwise
determine that the injection
well needs to increase injection in the layer.
The above steps of the method are described in detail below through specific
embodiments.
Through the inter-well connectivity network model, the reservoir is simplified
into a group
of connected units composed of single wells. The properties of each connected
unit are
represented by the inter-well connectivity parameters (conductivity and
connected volume)
converted from the actual physical properties of the well point. In order to
explain the meaning
and calculation process of the basic parameters of the inter-well connectivity
network model,
the present disclosure establishes a conceptual model of five injection wells
and four
production wells. In this model, the spacing between the oil and water wells
is 200 m, and the
height of each layer is 10 m. The permeability ratio of layer 1 is 165.0 mD,
and the permeability
ratio of layer 2 is 171.6 mD. Assume that the initial oil saturation of the
reservoir is 0.8, the
viscosity of the formation water is 1 mPa.s, and the oil-water viscosity ratio
is 20, as shown in
FIG. 2. The initial values of the inter-well connectivity parameters are
calculated according to
Eqs. (1) and (2), and then the inter-well connectivity parameters are fitted
and corrected by
using an optimization theory based on the historical production data of the
reservoir, as shown
in FIG. 3. In the figure, three lines respectively indicate a dominant
connection direction, a
general connection direction and a poor connection direction between the
wells; the
conductivity and connected volume of each connected unit are indicated in the
parentheses in
turn. By comparing the distribution characteristics of the dominant connection
direction
between the wells with a high-permeability zone, the two have a high
consistency.
OutetiLii
= v,N v,Nw _________________________________ VR (1)
= 0.08641(1.111y
J1 j
In the Eqs., N, represents the total number of wells connected to an i-th
well;
represents a connected volume between the i-th well and a j-th well; VR
represents the total
connected volume of the reservoir; Tii represents a conductivity between the i-
th well and the
j-th well; Oij represents an average porosity of a formation between the i-th
well and the j-th
well; hii represents an average effective height of the formation between the
i-th well and the
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j-th well; Lii represents a spacing between the i-th well and the j-th well;
kij represents an
average permeability of the formation between the i-th well and the j-th well;
[to represents
an in-situ oil viscosity.
First, based on the seepage theory and the inter-well connectivity parameters,
a
productivity index (PI) in the connected unit is expressed:
I = __________ 4TillicAtilk
jk 1
(3).
,ln qi
In the Eq., Jijk represents the PI between wells i and j in layer k,
m3/(d=MPa); kik represents
a mobility at a well point of well i, 10-3p,m2/(mPa.$); kiik represents a
mobility in the connected
unit of wells i and j in layer k, 10-3p,m2/(mPa.$); Lk represents a spacing
between wells i and j
in layer k, m; rik represents a wellbore radius of well i in layer k, m; sik
represents a skin factor
of well i in layer k; the superscripts n and n-1 represent n-th and (n-1)-th
time steps, respectively.
Then, according to a bottom hole pressure and the PI, the mobility in the
connected unit is
determined by using an upstream weighting method by the mobility at nodes at
both ends of
the connected unit:
= [Kro(swni) Krw(Swnil n-1
P
ok ktw k
jk = (4).
yr-1 = K.. [Kro(swni7iZ) Krw(SwniTiZ)1 <
jk ijkj p1
ktok kiwk
In the Eq.,
represents a mobility at a well point of well j, 10-3p,m2/(mPa.$); Kiik
represents an average permeability between wells i and j in layer k, 10-3p,m2;
Swik represents
a water saturation of well i in layer k; Kro and Krw represent a relative
permeability of oil
and water respectively, 10-31-1m2; itok and kiwk represent a viscosity of oil
and water in layer
k respectively, mPa.s.
Then the total PI Jr of the i-th well is:
= EkNi i
ii N. jnik
A longitudinal splitting coefficient of the i-th well in the k-th layer is
determined by a ratio
of the sum of the PI of the i-th well in the k-th layer to the total PI of the
i-th well:
Ji finjk
v,N1 Nwko).
Jinjk
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Taking water well W5 as an example, the spacing between well W5 and each
production
well in the model is the same, and it is assumed that the perfection and the
borehole radius of
each well are the same. When the development of the reservoir starts, the
pressure of the water
well is high, and the mobility in the connected unit is consistent with the
mobility at the well
point of the water well. Therefore, the longitudinal splitting coefficient of
the injected water is
only related to the strength of the connection relationship between the layers
(the conductivity
between the wells). Eq. (6) is reducible to:
iik
Ana( = _________________________________ 1 v,Nw
n (7)=
Lk=1Lj,i Tijk
The sum of the conductivity of the connected units between well W5 and each
production
well is 0.339 m3/(d=MPa) in layer 1 of the conceptual model and 0.205
m3/(d=MPa) in layer 2
of the conceptual model. Accordingly, the splitting coefficient of well W5 is
0.623 in layer 1
and 0.377 in layer 2. As the reservoir continues to produce, the pressure of
each layer is
constantly changing. Due to differences in physical properties, production
systems and other
reasons, the pressure changes are not the same, which will lead to differences
in the longitudinal
split at different times, as shown in FIGS. 4 and 5.
In the conceptual model, the oil wells are produced with a fixed amount of
liquids, and the
working system of each well is shown in Table 1. The split volume of injected
water between
each pair of injection and production wells is calculated by Eq. (8):
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Table 1 Working system of single well
Volume of injection/production
Well No.
3,000 d 3,000 d later
W1 -W5 40 m3/d
P1 50 m3/d 80 m3/d
P2 50 m3/d 60 m3/d
P3 50 m3/d 40 m3/d
P4 50 m3/d 20 m3/d
qinjk = Tirlic(197 pin (8)
The fluid flow in each connected unit is calculated by Eq. (8). Since the
injection-
production ratio of the model is set to 1:1, the fluid flow in each connected
unit is the split
volume of the injected water in the connected unit, and then the injected
water splitting
coefficient of each connected unit can be obtained by Eq. (9). The injected
water splitting
coefficient reflects the direction and flow of the injected water, and is an
important indicator of
the interaction between oil and water wells.
Ak ¨ _________________________________ w (9)
qJk
In the Eq., n represents a moment of the model; qiik represents an inflow
(outflow) in the
connected unit between the i-th well and the j-th well in the k-th layer; N,
represents the total
number of wells connected to the i-th well; Auk represents the injected water
splitting
coefficient of the i-th injection well to the j-th well in the k-th layer;
Tiik represents an average
conductivity between the i-th well and the j-th well in the k-th layer; pi and
pi represent an
average pressure in a drainage area of the i-th well and the j-th well
respectively.
After the injected water splitting coefficient of the water well to the oil
well in each layer
is determined, the layered water injection efficiency of the water well can be
further solved,
that is, a ratio of the oil displacement of the water well to the surrounding
oil well in the layer
to the water injection of the layer. The ratio of the total oil production of
the oil wells in the
layer to the total water injection of the water wells in the layer is the
average water injection
efficiency of the layer.
fwjk
eik ¨ (10)
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ENt2,44 gA(1-filvilk) exk (11)
7N1 ,,n
ik
In the Eqs., NI represents the total number of injection wells in the layer;
eik represents
the water injection efficiency of the i-th injection well in the k-th layer;
exk represents the
average water injection efficiency of the i-th injection well in the k-th
layer; qik represents an
injection volume of the i-th well in the k-th layer; fwik represents a water
cut of the j-th oil
well connected to the i-th injection well in the k-th layer.
In the conceptual model, the water cut of each oil well in layer 1 is fwp"
=0.84,
f,p2,1 =0.67, f,p3,1 =0.81 and f,p4,1 =0.76, respectively. According to Eq.
(10), the water
injection efficiency of well W5 in layer 1 is ews,i =0.79. In the same way,
the water injection
efficiency of four water wells in layer 1 of the conceptual model is
calculated respectively, and
the average water injection efficiency of layer 1 is calculated as e1 =0.74 by
Eq. (11), as
shown in FIGS. 6 and 7.
The significance of evaluating the water injection efficiency of the injection
well is to
reduce the invalid water circulation and improve the overall water injection
efficiency of the
block by accurately adjusting the injection volume of different single wells.
The water injection efficiency of the water well in each layer is compared
with the average
water injection efficiency of the same layer. If the water injection
efficiency of the water well
eik < exk, the water well needs to decrease the injection in this layer;
otherwise, it needs to
increase the injection in this layer. The adjusted injection volume of the
water well in each layer
is calculated according to an injection increase/decrease equation:
qiikew = [1. wmax eik-exk )al old
qik (12)
emax-exk
___________________________________________ a
new = [1 - F winin exk-eik ) 1 old
= qik
exk-emin
In the Eqs., qr represents the injection volume of the water well in the layer
after
adjustment, m3/d; qr represents the injection volume of the water well in the
layer before
adjustment, m3/d. Due to the limitation of construction conditions, the
injection volume of the
water well is unlikely to change greatly, so the correlation coefficients in
the equations need to
be constrained. wmax represents an increase coefficient, usually 0 to 0.5;
wmin represents a
decrease coefficient, usually -0.5 to 0; emax represents the maximum water
injection
efficiency of the water well in the same layer; emin represents the minimum
water injection
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efficiency of the water well in the same layer; a represents a weight change
index, which is
determined according to the average water injection efficiency of the single
layer. According
to the change curve of a with a weight, in the present disclosure, a=2.
The adjustment in the injection volume of the five injection wells in the
conceptual model
is shown in Table 2.
Table 2 Adjustment in injection volume of injection wells
Injection well Layer Water injection efficiency Adjustment
(m3/d)
Li 0.70
Decrease by 5.3
W1
L2 0.79
Increase by 6.6
Li 0.86
Increase by 17.5
W2
L2 0.82
Increase by 20
Li 0.61
Decrease by 10.5
W3
L2 0.53
Decrease by 12
Li 0.73 Decrease by 2
W4
L2 0.81
Increase by 10
Li 0.79
Increase by 7.9
L2 0.75 Decrease by 2
The present disclosure is illustrated by an application example below.
In Xinjiang Oilfield, China, an edge-water glutenite reservoir controlled by
structure and
lithology has an oil-bearing area of 9.3 km2, an effective height of 26.3 m, a
porosity of 16.9%,
a permeability of 182.27x 10-3 pin2, a buried depth of 1,650 m, and a
geological reserve of
1530.70x 104 t. Since entering the secondary development stage in 2016, a
total of 213 new
wells have been deployed, with their average spacing reduced to 150 m, and a
geological
reserve of 1105.43x 104 t has been produced. As of the end of June 2018, the
daily liquid
production was 2,837 t, the daily oil production was 370 t, and the
comprehensive water cut
was 86.9%, indicating that the inefficient circulation of injected water was
serious.
As of the end of June 2018, 96 water wells and 133 oil wells had been opened
in the
reservoir. The reservoir is divided into an upper sandstone section and a
lower conglomerate
section, and separate injection and combined production techniques are used
between the
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different rock sections. According to the statistics of the layered water
injection efficiency of
the open injection wells, the average water injection efficiency in the
sandstone section is 0.09,
and the average water injection efficiency in the conglomerate section is
0.10. Layered
adjustment measures are taken for the different rock sections to increase the
injection of high-
efficiency injection wells and decrease the injection of low-efficiency
injection wells, as shown
in FIGS. 8 and 9.
The layered splitting coefficients of well Ti show that the production wells
P1 and P2 of
the same well group are the main splitting directions. As shown in FIG. 10,
the two wells in
the sandstone section split 45% and 27% of the injected water respectively; in
the conglomerate
section, the two wells split 32% and 42% of the injected water respectively.
The three wells
have good correspondence between injection and production. The tracer test
data of the Ti well
group, as shown in FIG. 11, shows that well P1 had the longest breakthrough
duration of tracer
(41 d) and the highest peak concentration of tracer (148.66 ng/ml). The tracer
breakthrough
duration of well P2 lasted 30 d and the peak concentration of tracer was
126.31 ng/ml. No
tracer reaction was detected in well P3. The tracer breakthrough duration of
well P4 lasted 36
d, and the peak concentration of tracer was 97.04 ng/ml.
Table 3 Tracer test results of Ti well group
Injection Breakthrough Peak
Breakthrough
Injection ty p e Monitoring Breakthrough period of
tracer concentration duration
well well date of tracer
and date (d) (ng/ml) (d)
P1 4/14/2019 26 148.66 41
Er
Ti P2 5/11/2019 54 126.31 30
3/19/2019
P4 5/19/2019 62 97.04 36
The water injection efficiency of well Ti is 0.12 in the sandstone section and
0.16 in the
conglomerate section, both of which are higher than the average water
injection efficiency in
the same rock section. According to Eq. 12, the increased injection volume of
well Ti in the
sandstone and conglomerate sections is 4.2 m3 and 7.5 m3, respectively.
The layered splitting coefficients of well T6 show that the production wells
P7 and P8 of
the same well group are the main splitting directions. The two wells split 36%
and 27% of the
injected water respectively in the sandstone section; in the conglomerate
section, the two wells
split 33% and 54% of the injected water respectively. The three wells have
good
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correspondence between injection and production. The tracer test data of the
T6 well group, as
shown in FIGS. 12 and 13, shows that well P7 had the longest breakthrough
duration of tracer
(26 d) and the highest peak concentration of tracer (97.01ng/m1). The two
tracers both broke
through in well P8; their breakthrough duration lasted 30 d and 21 d
respectively, and their
peak concentrations reached 52.4 ng/ml and 82.41 ng/ml respectively. No tracer
reaction was
detected in wells P3 and P4.
Table 4 Tracer test results of T6 well group
Breakthrough
Injection Peak Breakthrough
Injection type Monitoring Breakthrough period of
concentration duration
well well date of tracer tracer
and date (d) (ng/ml) (d)
Gd P8 5/9/2019 50 52.4 30
3/20/2019 P7 5/17/2019 58 97.01 26
T6
Sm
P8 4/25/2019 41 82.41 21
3/15/2019
The water injection efficiency of well T6 is 0.07 in the sandstone section and
0.16 in the
conglomerate section, and the water injection efficiency in the conglomerate
section is higher
than the average water injection efficiency in the same rock section.
According to Eqs. 12 and
13, the decreased injection volume of well T6 in the sandstone and
conglomerate sections is
3.5 m3 and 5 m3, respectively.
The adjustment in the injection volume of the injection wells in typical well
groups is
shown in Table 5.
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Table 5 Adjustment in injection volume of injection wells in typical well
groups
Injection well Rock section Water injection efficiency Adjustment
(m3/d)
Sandstone section 0.12 Increase by 4.2
Ti
Conglomerate section 0.16 Increase by 7.5
Sandstone section 0.07 Decrease by 3.5
T6
Conglomerate section 0.16 Increase by 5
Sandstone section 0.08 Decrease by 4.3
T10
Conglomerate section 0.11 Increase by 5.4
Sandstone section 0.13 Increase by 9.6
T15
Conglomerate section 0.07 Decrease by 6.7
Sandstone section 0.13 Increase by 9.7
T20
Conglomerate section 0.05 Decrease by 7.2
The injection volume adjustment schemes for the above five typical well groups
were
applied on site in August 2019. As of October 2019, the comprehensive water
cut of these five
well groups had been reduced by 2% compared to that before the injection
volume adjustment,
accompanied by a cumulative oil increase of 180 t.
There are a total of 20 injection wells in the adjustment area, some of which
have
developed dominant seepage channels, and have problems of too concentrated
splitting
directions and low water injection efficiency. The production performance of
the adjustment
area after two years of adjustment using the above injection volume adjustment
method is
predicted and compared with that without adjustment. According to the
prediction data, the oil
production rate of the block will increase by 60 m3/, the cumulative oil
production of the block
will increase by 4.24x104 m3, and the water cut of the block will reduce by
1.39%, as shown
in FIG. 14.
It should be understood that the serial number of each step in the above
embodiment does
not indicate the order of performing the process. The order of performing each
process is
determined by its function and internal logic, and should not limit the
implementation of the
embodiments of the present disclosure.
An embodiment of the present disclosure further provides a computer-readable
storage
medium. The computer-readable storage medium stores a computer program, and
when the
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computer program is executed by a processor, the above method for evaluating a
layered water
injection efficiency of an oil reservoir is implemented.
FIG. 15 shows a device for evaluating a layered water injection efficiency of
an oil
reservoir according to Embodiment 2 of the present disclosure. As shown in
FIG. 15, the device
includes a model establishment module 100, a calculation module 200 and a
comparison and
determination module 300.
The model establishment module 100 is configured to construct an inter-well
connectivity
network model characterized by two inter-well connectivity parameters, namely
conductivity
and connected volume by simplifying an oil reservoir system into a network of
interconnected
nodes that considers preset geological characteristics, and correct the inter-
well connectivity
parameters by fitting an actual production performance, so that the inter-well
connectivity
network model conforms to an actual reservoir connectivity relationship, where
the preset
geological characteristics include well point characteristics, water body
characteristics and/or
fault characteristics.
The calculation module 200 is configured to calculate an injected water
splitting
coefficient of an injection well to a surrounding oil well in each layer
according to the inter-
well connectivity network model and a seepage theory, and calculate a water
injection
efficiency eik of each injection well in each layer and an average water
injection efficiency
exk of each layer according to the injected water splitting coefficient.
The comparison and determination module 300 is configured to compare the water
injection efficiency eik of the injection well in each layer with the average
water injection
efficiency exk of the same layer, and determine that the injection well needs
to decrease
injection in the layer if eik < exk, otherwise determine that the injection
well needs to increase
injection in the layer.
In a preferred embodiment, the calculation module 200 specifically includes a
PI
expression unit, a mobility calculation unit, a total PI calculation unit, a
longitudinal splitting
coefficient calculation unit, an injected water splitting coefficient
calculation unit and an
efficiency calculation unit.
The PI expression unit 201 is configured to, based on the seepage theory and
the inter-well
connectivity parameters, express a PI in the connected unit:
4 Tit) k Artik 1
= _______________________________________________
k
,ln(0.51,iik/rik)+sik-0.751'
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In the Eq., Jiik represents the PI between wells i and j in layer k,
m3/(d=MPa); kik represents
a mobility at a well point of well i, 10-3p,m2/(mPa.$); kiik represents a
mobility in the connected
unit of wells i and j in layer k, 10-3p,m2/(mPa.$); Lk represents a spacing
between wells i and j
in layer k, m; rik represents a wellbore radius of well i in layer k, m; sik
represents a skin factor
of well i in layer k; the superscripts n and n-1 represent n-th and (n-1)-th
time steps, respectively.
The mobility calculation unit 202 is configured to determine the mobility in
the connected
unit by using an upstream weighting method by the mobility at nodes at both
ends of the
connected unit according to a bottom hole pressure and the PI,:
4 _ -1 Kok [Kro(swnik1) ^ Krw(Swn
n-1 n-1
PiPj
= L ktok ktwk
jfk K (Sn71) K (Sn71) 1)7.1.-1 = [ ro wik
^ rw prl n¨
"jk "tik P j
ktok ktwk
In the Eq., represents a
mobility at a well point of well j, 10-3p,m2/(mPa.$); Kiik
represents an average permeability between wells i and j in layer k, 10-3p,m2;
Swik represents
a water saturation of well i in layer k; Kõ and Kr, represent a relative
permeability of oil
and water respectively, 10-31-1m2; Yok and kiwk represent a viscosity of oil
and water in layer
k respectively, mPa.s.
The total PI calculation unit 203 is configured to calculate a total PI of
well i according to
the PI and the mobility in the connected unit:
in = EkNi i
ii N. jnik;
The longitudinal splitting coefficient calculation unit 204 is configured to
calculate a
longitudinal splitting coefficient of well i in layer k according to the total
PI of well i:
n uk = jinik
A ik = N N
lin r r w
Lk=iLf=iJifk
In the Eq., Aik represents the splitting coefficient of well i in layer k; uk
represents the
total PI of well i in layer k, m3/(d=MPa); Ji represents the total PI of well
i, m3/(d=MPa).
The injected water splitting coefficient calculation unit 205 is configured to
obtain a fluid
flow in each connected unit, and calculate an injected water splitting
coefficient of the
connected unit to a surrounding oil well according to the fluid flow and the
longitudinal
splitting coefficient:
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AJk qinjk
¨
j =1 tj k
qinjk = Tijk(197
In the Eq., n represents a moment of the model; qiik represents an inflow
(outflow) in the
connected unit between the i-th well and the j-th well in the k-th layer; N,
represents the total
number of wells connected to the i-th well; Auk represents the injected water
splitting
coefficient of the i-th injection well to the j-th well in the k-th layer;
Tiik represents an average
conductivity between the i-th well and the j-th well in the k-th layer; pi and
pi represent an
average pressure in a drainage area of the i-th well and the j-th well
respectively.
The efficiency calculation unit 206 is configured to calculate a water
injection efficiency
eik of each injection well in each layer and an average water injection
efficiency exk of each
layer according to the injected water splitting coefficient:
_ fwnik)
eik = ____________________________________________
qink
ENi 1EJN.w1gTik k (1 fn
wik)
exk = EiNllqink
In the Eqs., NI represents the total number of injection wells in the layer;
eik represents
the water injection efficiency of the i-th injection well in the k-th layer;
exk represents the
average water injection efficiency of the i-th injection well in the k-th
layer; qik represents an
injection volume of the i-th well in the k-th layer; fwik represents a water
cut of the j-th oil
well connected to the i-th injection well in the k-th layer.
An embodiment of the present disclosure further provides a terminal for
evaluating a
layered water injection efficiency of an oil reservoir. The evaluation
terminal includes the
computer-readable storage medium and a processor. When the computer program
stored on the
computer-readable storage medium is executed by the processor, the above
method for
evaluating a layered water injection efficiency of an oil reservoir is
implemented. FIG. 16 is a
structural diagram of the terminal for evaluating a layered water injection
efficiency of an oil
reservoir according to Embodiment 3 of the present disclosure. As shown in
FIG. 16, the
evaluation terminal 8 of this embodiment includes a processor 80, a readable
storage medium
81, and a computer program 82 stored in the readable storage medium 81 and
running on the
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processor 80. When the processor executes the computer program 82, the
processor 80
implements the steps in the above method embodiment, for example, steps 1 to 3
shown in FIG.
1. Alternatively, when the processor executes the computer program 82, the
processor 80
implements the functions of each module in the above device embodiment, for
example,
modules 100 to 300 shown in FIG. 15.
For example, the computer program 82 may be divided into one or more modules,
and the
one or more modules are stored in the readable storage medium 81 and executed
by the
processor 80 to complete the present disclosure. The one or more modules may
be a series of
instruction segments capable of completing specific functions in the computer
program, and
used to describe the execution process of the computer program 82 in the
evaluation terminal
8.
The evaluation terminal 8 may include, but is not limited to, a processor 80
and a readable
storage medium 81. Those skilled in the art should understand that FIG. 16 is
only an example
of the evaluation terminal 8 and is not intended to constitute a limitation to
the evaluation
terminal 8. It may include more or less components than shown in the figure,
or include a
combination of certain or different components. For example, the evaluation
terminal may also
include a power management module, an arithmetic processing module, an
input/output device,
a network access device, a bus, etc.
The processor 80 may be a central processing unit (CPU) or other general-
purpose
processor, a digital signal processor (DSP), an application specific
integrated circuit (ASIC), a
field-programmable gate array (FPGA) or other programmable logic device, a
discrete gate, a
transistor logic device, a discrete hardware component, etc. The general-
purpose processor may
be a microprocessor or any conventional processor.
The readable storage medium 81 may be an internal storage unit of the
evaluation terminal
8, such as a hard disk or a memory of the evaluation terminal 8. The readable
storage medium
81 may also be an external storage device of the evaluation terminal 8, such
as a plug-in hard
disk, a smart media card (SMC), a secure digital (SD) card and a flash card
equipped on the
evaluation terminal 8. Further, the readable storage medium 81 may also
include both an
internal storage unit and an external storage device of the evaluation
terminal 8. The readable
storage medium 81 is used to store the computer program and other programs and
data required
by the evaluation terminal. The readable storage medium 81 may also be used to
temporarily
store data that has been output or will be output.
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Those skilled in the art should clearly understand that, for convenience and
concise
description, only the division of the above functional units/modules is used
as an example for
illustration. In practical applications, the above functions may be
implemented by different
functional units/modules as required, that is, the internal structure of the
device is divided into
different functional units or modules to complete all or part of the above-
described functions.
The functional units/modules in the embodiments of the present disclosure may
be integrated
into one processing module, or each of the units may exist alone physically,
or two or more
units are integrated into one unit. The above integrated unit may be
implemented either in the
form of hardware or in the form of software functional units. In addition, the
specific names of
the functional units/modules are only for the convenience of distinguishing
each other, and are
not intended to limit the protection scope of the present disclosure. For the
specific working
process of the units/ modules in the above system, reference may be made to
the corresponding
process in the above method embodiment, which is not repeated here.
In the above embodiments, the description of the embodiments each has a focus,
and
portions not described or recorded in detail in one embodiment may refer to
the description of
other embodiments.
Those of ordinary skill in the art may be aware that the units and method
steps described
in the embodiments disclosed herein may be implemented by electronic hardware
or a
combination of computer software and electronic hardware. Whether these
functions are
implemented by hardware or software depends on the specific applications and
design
constraints of the technical solutions. Those skilled in the art may use
different methods to
implement the described functions for each specific application, but such
implementation
should not be considered to be beyond the scope of the present disclosure.
It should be understood that the device, terminal and method disclosed by the
embodiments
of the present disclosure may be implemented in other manners. For example,
the described
device/ terminal embodiment is merely an example. For example, the module or
unit division
is merely logical function division and may be other division in actual
implementation. For
example, a plurality of units or components may be combined or integrated into
another system,
or some features may be ignored or not executed. In other respects, the inter-
coupling or direct
coupling or communication connection shown or discussed may be indirect
coupling or
communication connection through some interfaces, devices, or units; or may be
implemented
in electrical, mechanical or other forms.
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The units described as separate parts may or may not be physically separate.
Parts
demonstrated as units may or may not be physical units, which may be located
in one position,
or may be distributed on a plurality of network units. Some or all of the
units may be selected
according to the actual needs to achieve the objectives of the solutions of
the embodiments.
In addition, the functional units in the embodiments of the present disclosure
may be
integrated into one processing unit, or each of the units may exist alone
physically, or two or
more units are integrated into one unit. The above integrated unit may be
implemented either
in the form of hardware or in the form of software functional units.
The present disclosure is not limited to those described in the specification
and
embodiments, and other advantages and modifications may be easily implemented
for those
skilled in the art. Therefore, without departing from the spirit and scope of
the general concept
defined by the claims and equivalent scope, the present disclosure is not
limited to the specific
details, representative devices, or illustrated examples shown and described
herein.
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