CA3108482C - Method, medium, terminal and device for evaluating layered water injection efficiency of oil reservoir - Google Patents

Abstract

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.

Description

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 24060664.1 1 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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;
24060664.1 2 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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;
24060664.1 3 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 24060664.1 4 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 24060664.1 5 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 24060664.1 6 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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.
24060664.1 7 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 24060664.1 8 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 24060664.1 9 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 24060664.1 10 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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):
24060664.1 11 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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) 24060664.1 12 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 24060664.1 13 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 L2 0.79 Increase by 6.6 Li 0.86 Increase by 17.5 L2 0.82 Increase by 20 Li 0.61 Decrease by 10.5 L2 0.53 Decrease by 12 Li 0.73 Decrease by 2 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 24060664.1 14 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 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 24060664.1 15 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 Sm P8 4/25/2019 41 82.41 21 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.
24060664.1 16 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 Conglomerate section 0.16 Increase by 5 Sandstone section 0.08 Decrease by 4.3 Conglomerate section 0.11 Increase by 5.4 Sandstone section 0.13 Increase by 9.6 Conglomerate section 0.07 Decrease by 6.7 Sandstone section 0.13 Increase by 9.7 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 24060664.1 17 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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' 24060664.1 18 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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:
24060664.1 19 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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 24060664.1 20 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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.
24060664.1 21 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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.
24060664.1 22 Date Recue/Date Received 2021-02-09 CA Application Blakes Ref. 25453/00001 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.
24060664.1 23 Date Recue/Date Received 2021-02-09

Claims (7)

What is claimed is:

1. A method for evaluating a layered water injection efficiency of an oil reservoir, comprising 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, wherein the preset geological characteristics comprise 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 elk 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 water injection in the layer if elk < exk , otherwise determining that the injection well needs to increase water injection in the layer, thereby obtaining an adjusted water injection volume of the injection well;
and the method for evaluating a layered water injection efficiency of an oil reservoir further comprising:
performing water injection on the injection well according to the adjusted water injection volume.

2. The method for evaluating a layered water injection efficiency of an oil reservoir according to claim 1, wherein each connected unit of the inter-well connectivity network model is characterized by two inter-well connectivity parameters, namely conductivity and connected volume:
wherein, Nw represents the total number of wells connected to an i-th well;
vii 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; 0,j represents an average porosity of a formation between the i-th well and the j-th well; 1111 represents an average effective height of the formation between the i-th well and the j-th well; L1 represents a spacing between the i-th well and the j-th well;
k,i represents an average permeability of the formation between the i-th well and the j-th well;
Ro represents an in-situ oil viscosity.

3. The method for evaluating a layered water injection efficiency of an oil reservoir according to claim 2, wherein 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 comprises:
expressing a productivity index (PI) in the connected unit based on the seepage theory and the inter-well connectivity parameters:
wherein, 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, 10-3Rm2/(mPa-s); Xuk represents a mobility in the connected unit of wells i and j in layer k, 10-3 m2/(mPa=s); Luk represents a spacing between wells i and j in layer k, m; rik represents a wellbore radius of well i in layer k, m; slk 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;
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:
wherein, Ajk represents a mobility hra well Vitit (51 well j, 10--).tm2/(mPa.$); Kijk represents an average permeability between wells i and j in layer k, 10-31=2;
Swik represents a water saturation of well i in layer k; Kõ and Krw represent a relative permeability of oil and water respectively, 10111112 ; Pok and liwk represent a viscosity of oil and water in layer k respectively, mPa.s;
calculating a total PI of well i according to the PI and the mobility in the connected unit:
calculating a longitudinal splitting coefficient of well i in layer k according to the total PI
of well i:
wherein, 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);
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:
wherein, n represents a moment of the model; qijk represents an inflow (outflow) in the connected unit between the i-th well and the j-th well in the k-th layer; Nw.
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; To represents an average conductivity between the i-th well and the j-th well in the k-th layer; p, and pi represent an average pressure in a drainage area of the i-th well and the j-th well respectively.

4. The method for evaluating a layered water injection efficiency of an oil reservoir according to claim 3, wherein the water injection efficiency elk 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:
wherein, N1 represents the total number of injection wells in the layer; elk 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; fwjk represents a water cut of the j-th oil well connected to the i-th injection well in the k-th layer.

5. The method for evaluating a layered water injection efficiency of an oil reservoir according to any one of claims 1 to 4, wherein in step 3, an injection volume to decrease or increase is calculated according to a preset injection increase/decrease equation:
wherein, qr represents tne 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; vvraõ represents a preset increase coefficient; wrma represents a preset decrease coefficient; en.. represents the maximum water injection efficiency of the water well in the same layer; emm 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.

6. The method for evaluating a layered water injection efficiency of an oil reservoir according to claim 5, wherein vvmax is maximally 0.5, vvram is minimally -0.5, and

7. A computer-readable storage medium, storing a computer program, wherein when the computer program is executed by a processor, the method for evaluating a layered water injection efficiency of an oil reservoir according to any one of claims 1 to 6 is implemented.