CN107145987B - Early warning method for monitoring development of cross flow channel between polymer flooding injection and production wells - Google Patents

Early warning method for monitoring development of cross flow channel between polymer flooding injection and production wells Download PDF

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CN107145987B
CN107145987B CN201710396186.0A CN201710396186A CN107145987B CN 107145987 B CN107145987 B CN 107145987B CN 201710396186 A CN201710396186 A CN 201710396186A CN 107145987 B CN107145987 B CN 107145987B
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梁丹
康晓东
唐恩高
王旭东
陈文娟
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CNOOC Research Institute Co Ltd
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Abstract

The invention discloses an early warning method for monitoring the development of a cross flow channel between polymer flooding injection wells, which comprises the following steps: 1) searching an alarm source, and searching influence factors and specific performance characteristics of a cross flow channel formed in a reservoir based on dynamic and static data and monitoring data of a target oil field; 2) analyzing warning signs, determining main control factors influencing polymer flooding and channeling by using a grey correlation analysis method, and forming a polymer flooding and channeling early warning index system; 3) judging the alarm degree, and establishing a gathering and channeling early warning evaluation model by utilizing a fuzzy comprehensive judgment model; 4) predicting the alarm degree, wherein the polymer flooding and channeling early warning index system determined in the step 2) consists of a static index and a dynamic index, and the development trend of a later-stage channeling channel is predicted by predicting the dynamic index. The early warning method can provide theoretical guidance for implementation of optimal adjustment measures in the polymer flooding stage, so that the polymer flooding efficiency is improved and enhanced, and the used reserves are increased to the maximum extent.

Description

Early warning method for monitoring development of cross flow channel between polymer flooding injection and production wells
Technical Field
The invention relates to an early warning method for monitoring the development of a cross flow channel between polymer flooding injection wells and polymer flooding production wells, and belongs to the technical field of dynamic parameter monitoring in the development process of oil and gas fields.
Background
Because the oil and gas reservoir is influenced by the deposition environment, diagenesis and tectonic action in the forming process, the spatial distribution and internal properties (such as porosity, permeability, porosity mechanism and the like) of the oil and gas reservoir are all heterogeneous, and the oil and gas reservoir is an important factor influencing the movement of underground oil, gas and water and the recovery ratio of oil and gas. After years of water injection development, fine particles are moved and sand is produced from the stratum due to long-term erosion of injected water, and a water flow channeling channel is formed between an injection well and an oil production well, so that the heterogeneity of the stratum is increased. After the channeling channel is formed, injected water is easy to burst along the channeling channel to generate the channeling phenomenon, the medium and low permeable layers absorb little water, the longitudinal sweep coefficient is difficult to improve, and the injected water is in ineffective circulation in the stratum, so that the water drive development effect and the whole benefit of oil field development are seriously influenced. The same channeling problem also exists for oil reservoirs developed by polymer flooding, so that individual oil wells are prematurely gathered, the mass concentration of polymers in produced liquid is high, the development effect of the polymer flooding is influenced, and the treatment difficulty of the produced liquid is increased.
Mastering the development condition of a channeling channel in a reservoir is an important basis for formulating oil and water stabilizing and controlling measures such as profile control, water shutoff and the like. The existing identification method for the cross flow channel mainly comprises the steps of dynamic production monitoring, well testing identification, tracer monitoring, well logging data identification and the like, a large amount of test data is needed in the methods, the acquisition period is long, the cost is high, the oil field production is influenced, only one time point can be identified, and early warning cannot be carried out on the later development trend.
Disclosure of Invention
Aiming at the problems, the invention aims to provide an early warning method for monitoring the development of the channeling channel between the polymer flooding injection and production wells, which can judge the development position and degree of the channeling channel at the current stage, can predict the development condition of the channeling channel at the later stage, and provides theoretical guidance for optimization and adjustment in the development process of the polymer flooding oil field, thereby improving and enhancing the polymer flooding efficiency and maximally improving the utilization reserve.
In order to achieve the purpose, the invention adopts the following technical scheme: an early warning method for monitoring the development of a cross flow channel between polymer flooding injection wells is characterized by comprising the following steps:
1) finding police sources
On the basis of the dynamic and static data and the monitoring data of the target oil field, carrying out statistical analysis on various parameter values of an oil well, a polymer injection well and a well group, and searching for influence factors and specific performance characteristics of a cross flow channel formed in a reservoir stratum;
2) analysis warning sign
Aiming at the influence factors of the cross flow channel counted in the step 1) and each parameter of the specific representation characteristic, determining main control factors influencing the polymer flooding cross flow by using a grey correlation analysis method, and forming a polymer flooding cross flow early warning index system by the main control factors;
3) degree of recognition
Establishing a gathering and channeling early warning evaluation model by using a fuzzy comprehensive evaluation model;
4) prediction of the degree of alarm
The polymer flooding channeling early warning index system determined in the step 2) consists of a static index and a dynamic index, wherein the dynamic index changes along with the production process, and therefore the development trend of a later-stage channeling channel is predicted by predicting the dynamic index.
The influencing factors and the specific expression characteristics for forming the channeling channel in the step 1) are reservoir static parameters and production dynamic characteristic parameters in a polymer flooding area of the target oil field, and the influencing factors and the specific expression characteristics comprise: permeability grade difference, accumulated injection quantity, accumulated liquid production quantity, dimensionless visible aggregation time, aggregation production concentration change rate, liquid production index change rate, apparent water absorption index change rate, injection-production connectivity and polymer flooding channeling strength factor;
wherein, the change rate of the apparent water absorption index refers to the ratio of the initial apparent water absorption index to the current apparent water absorption index;
the strength factor of the polymer flooding channeling is used for representing the strength of the polymer flooding channeling, the symbol is expressed by M, and the calculation formula is as follows:
M＝Qp×Vp×ω (1)
in the formula: qpThe dimensionless amount of produced polymer is equal to the amount of produced polymer of the oil well divided by the amount of split polymer; vpThe polymer breakthrough rate, equal to the well spacing divided by the time to coalescence; ω is an effect factor, and when the time of onset is earlier than the effect time, ω is the effect time/(effect time-time of onset), when the time of onset is equal to the effect time, ω is 1, and when the time of onset is later than the effect time, ω is the time (time of onset-time of onset)/time of onset.
The specific process for establishing the polymer flooding cross-flow early warning index system in the step 2) is as follows:
① using the polymer flooding channeling intensity factor calculated in the step 1) as a reference sequence;
② using the rest dynamic and static parameters in the step 1) as comparison sequences;
③, calculating the degree of association between the comparison sequence and the reference sequence by a grey correlation analysis method, wherein the greater the degree of association, the more consistent the change situation of the comparison sequence and the reference sequence is, normalizing the degree of association on the basis, and if the degree of association between the comparison sequence and the reference sequence is more than 0.7, the correlation can be used as a main control factor to form a polymer flooding cross-flow early warning index system.
The specific process of establishing the channeling early warning evaluation model in the step 3) is as follows:
①, establishing typical numerical simulation models of different basic permeability according to relevant parameters of the target oil field;
②, respectively simulating the variation trend of the water content reduction amplitude of the polymer flooding under different permeability level differences under the condition of different injected polymer flooding solution volumes by using the established typical numerical simulation model to obtain the limit values of each main control factor in the polymer flooding cross-flow early warning index system determined in the step 2):
according to the change trend of the permeability level difference and the water content descending amplitude of the polymer flooding in a typical numerical simulation model, establishing a water content descending amplitude change curve of the polymer flooding under different permeability level differences by taking the permeability level difference as a horizontal axis and the water content descending amplitude as a vertical axis, defining the corresponding permeability level difference as a gathering observation limit when the water content descending amplitude of the polymer flooding begins to descend, and defining the corresponding permeability level difference as a gathering development limit when the water content descending amplitude exceeds 1.2%; obtaining the threshold value of each main control factor under the condition of different injected polymer flooding solution volumes according to the boundary definitions of different polymer flooding degrees;
③ applying control variable method to each main control factor parameter value in the polymer flooding cross-flow early warning index system, i.e. single main control factor parameter value is changed according to + 10% and-10%, applying formula (1) to calculate corresponding cross-flow factor, different main control factors have different influence degrees on polymer cross-flow, obtaining weight symbol A of each index through sensitivity analysis and normalization processingiRepresents:
Figure BDA0001307045910000031
in the formula: | Δ MiI is the absolute value of the change of the corresponding channeling factor after the single index parameter value is changed by + 10% and-10%; n is the number of main control factors in the polymer flooding cross-flow early warning index system; i is any main control factor of a polymer flooding cross flow early warning index system;
④, finally substituting the determined threshold values and weights of the main control factors in the polymer flooding channeling early warning system into the fuzzy comprehensive evaluation model to establish a gathering channeling early warning evaluation model, further respectively judging the gathering channeling development, the gathering channeling observation and the gathering channeling-free condition of each well, drawing a gathering channeling judgment result graph on a well bitmap, and visually seeing the distribution of the gathering channeling on the well bitmap.
The specific calculation process for establishing the channeling early warning evaluation model in the step ④ is as follows:
i) determining a comment set, generally setting the comment set as three levels of scurrying development, scurrying observation and no scurrying in a scurrying early warning model, and recording the comment set as:
V＝{v1,v2,v3} (3)
in the formula: v is a comment set; v. of1Representing that the oil well is in a channeling development state; v. of2Representing that the oil well is in a channeling observation state; v. of3Representing that the oil well has not been subjected to gathering;
ii) determining a factor set influencing the comment set, namely the polymer flooding cross-flow early warning index system determined in the step 2), wherein the factor set is recorded as:
U＝{u1,u2,…,un} (4)
in the formula: u represents a polymer flooding cross flow early warning index system; u. of1,u2,…,unCorresponding to each main control factor in the polymer flooding cross flow early warning index system one by one; n is the number of main control factors;
iii) obtaining an evaluation matrix after the threshold values of the main control factors in the polymer flooding cross-flow early warning index system determined in the step ② are processed by a normalization method:
Figure BDA0001307045910000041
in the formula, ri＝(ri1,ri2,ri3) An evaluation matrix corresponding to any master control factor; i is any main control factor, i is 1, 2, … …, n;
iv) establishing a weight set according to the weight of each main control factor in the polymer flooding cross-flow early warning index system determined in the step ③, wherein the weight set is recorded as:
A＝{a1,a2,…,an} (6)
in the formula: a represents a weight set; a isiIs the weight of any index, i ═ 1, 2, … …, n;
v) applying the synthesis operation of fuzzy transformation to obtain a comprehensive judgment result:
B＝A×R＝{b1,b2,b3} (7)
in the formula: b is a comprehensive judgment result; b1Corresponding to v in comment set1The evaluation results of (1); b2Corresponding to v in the comment set2The evaluation results of (1); b3Corresponding to a commentLanguage set v3The evaluation results of (1);
in the comprehensive evaluation result, b1、b2Or b3And if the numerical value is large, the oil well is in a corresponding gathering state in the comment set, so that the gathering condition is judged.
The specific process for predicting the development trend of the later stage channeling channel in the step 4) is as follows:
①, firstly, selecting one or more of a numerical simulation method, a support vector machine method and a gray prediction method to be combined, and predicting the numerical value of the dynamic index T + n time point in the polymer flooding cross-flow early warning index system in the step 2);
②, substituting the predicted numerical value into the gathering and fleeing early warning evaluation model established in the step 3) to obtain the gathering and fleeing development condition of the T + n time point, and drawing a gathering and fleeing prediction result graph on a well map, wherein the result graph can visually see the gathering and fleeing development condition.
By adopting the technical scheme, the invention has the following advantages: the early warning method can monitor the channeling situation in the polymer flooding process in real time and predict the later-stage channeling development trend, has strong operability, high prediction precision and accurate and reliable calculation result, and can provide theoretical guidance for implementing optimization adjustment measures in the polymer flooding stage.
Drawings
FIG. 1 is a schematic overall flow diagram of the present invention;
FIG. 2 is a well location profile for a J-field polymer flooding zone;
FIG. 3 is a water content decrease curve of a polymer flooding at different permeability level differences;
FIG. 4 is the cross-gathering judgment result after 4 years of gathering in the J oil field;
FIG. 5 is a gathering early warning result after 5 and a half years of gathering of the J oil field;
fig. 6 is the actual judgment result of the gathering after the gathering of the J oil field for 5 and a half years.
Detailed Description
The invention is described in detail below with reference to the figures and examples.
The invention provides an early warning method for monitoring the development of a cross flow channel between polymer flooding injection wells, which comprises the following steps:
1) finding police sources
Based on the dynamic and static data and the monitoring data of the target oil field, the parameters of the oil well, the polymer injection well and the well group are statistically analyzed, and the influence factors and the specific performance characteristics of the cross flow channel formed in the reservoir stratum are searched.
Obtaining reservoir static parameters and production dynamic characteristic parameters in a polymer flooding area of a target oil field, wherein the parameters comprise: permeability grade difference, accumulated injection quantity, accumulated liquid production quantity, dimensionless visible aggregation time, aggregation production concentration change rate, liquid production index change rate, apparent water absorption index change rate, injection-production connectivity and polymer flooding channeling strength factor.
Wherein, the change rate of the apparent water absorption index refers to the ratio of the initial apparent water absorption index to the current apparent water absorption index.
The strength factor of the polymer flooding channeling is used for representing the strength of the polymer flooding channeling, the symbol is expressed by M, and the calculation formula is as follows:
M＝Qp×Vp×ω (1)
in the formula: qpThe dimensionless amount of produced polymer is equal to the amount of produced polymer of the oil well divided by the amount of split polymer; vpThe polymer breakthrough rate, equal to the well spacing divided by the time to coalescence; ω is an effect factor, and when the time of onset is earlier than the effect time, ω is the effect time/(effect time-time of onset), when the time of onset is equal to the effect time, ω is 1, and when the time of onset is later than the effect time, ω is the time (time of onset-time of onset)/time of onset.
2) Analysis warning sign
Aiming at the influence factors of the cross flow channel counted in the step 1) and each parameter of the specific representation characteristic, determining main control factors influencing the polymer flooding cross flow by using a grey correlation analysis method, and forming a polymer flooding cross flow early warning index system by the main control factors.
The specific process for establishing the polymer flooding cross flow early warning index system comprises the following steps:
① using the polymer flooding channeling intensity factor calculated in the step 1) as a reference sequence;
② using the rest dynamic and static parameters in the step 1) as comparison sequences;
③, calculating the degree of association between the comparison sequence and the reference sequence by a grey correlation analysis method, wherein the greater the degree of association, the more consistent the change situation of the comparison sequence and the reference sequence, and normalizing the degree of association on the basis, generally considering that the degree of association between the comparison sequence and the reference sequence is more than 0.7 can be used as a main control factor, and can be correspondingly adjusted according to the actual situation to form a polymer flooding channeling early warning index system.
3) Degree of recognition
The method comprises the following steps of establishing a gathering and channeling early warning evaluation model by using a fuzzy comprehensive evaluation model, and quantitatively evaluating a channeling channel formed in a polymer flooding process according to the gathering and channeling early warning evaluation model, wherein the specific process comprises the following steps:
①, establishing typical numerical simulation models according to the relevant parameters of the target oil field, generally speaking, for an actual oil field, the permeability distribution range is wider, and the standards of the channeling channels are judged to be different in different permeability ranges, so that the typical numerical simulation models with different basic permeability can be established according to different permeability ranges;
②, respectively simulating the variation trend of the water content reduction amplitude of the polymer flooding under different permeability level differences under the condition of different injected polymer flooding solution volumes by using the established typical numerical simulation model to obtain the limit value of each main control factor in the step 2):
according to the change trend of the permeability level difference and the water content reduction range of the polymer flooding in a typical numerical simulation model, establishing a water content reduction range change curve of the polymer flooding under different permeability level differences by taking the permeability level difference as a horizontal axis and the water content reduction range as a vertical axis, defining the corresponding permeability level difference as a gathering observation limit when the water content reduction range of the polymer flooding begins to reduce, and defining the corresponding permeability level difference as a gathering development limit when the water content reduction range rapidly reduces (the reduction speed exceeds 1.2%); obtaining the limit value corresponding to each main control factor in the polymer flooding cross-flow early warning index system in the step 2) under the condition of different injected polymer flooding solution volumes according to the limit definitions of different polymer flooding degrees;
③ applying control variable method to the parameter values of each main control factor in the polymer flooding cross-flow early warning index system, i.e. changing the parameter values of single main control factor according to + 10% and-10%, calculating the corresponding cross-flow factor by applying formula (1), obtaining the weight symbol A of each index through sensitivity analysis and normalization processingiRepresents:
Figure BDA0001307045910000061
in the formula: | Δ MiI is the absolute value of the change of the corresponding channeling factor after the single index parameter value is changed by + 10% and-10%; n is the number of main control factors in the polymer flooding cross-flow early warning index system; i is any main control factor of a polymer flooding cross flow early warning index system;
④, finally, substituting the determined threshold values of the main control factors and the weights of the main control factors in the polymer flooding channeling early warning system into a fuzzy comprehensive judgment model to establish a gathering channeling early warning evaluation model, further, judging the conditions of gathering channeling development, gathering channeling observation and no gathering channeling of each well respectively, drawing a gathering channeling judgment result graph on a well bitmap, wherein the result graph can visually see the distribution of the gathering channeling on the well bitmap, and the specific calculation steps are as follows:
firstly, determining a comment set, wherein the comment set is generally defined as three levels of scurrying development, scurrying observation and no scurrying in a scurrying early warning model, and the comment set can be recorded as:
V＝{v1,v2,v3} (3)
in the formula: v is a comment set; v. of1Representing that the oil well is in a channeling development state; v. of2Representing that the oil well is in a channeling observation state; v. of3Representing that the oil well has not been subjected to gathering;
secondly, determining a factor set influencing the comment set, namely the polymer flooding cross-flow early warning index system determined in the step 2), wherein the factor set can be recorded as:
U＝{u1,u2,…,un} (4)
in the formula (I); u represents a polymer flooding cross flow early warning index system; u. of1,u2,…,unCorresponding to each main control factor in the polymer flooding cross flow early warning index system one by one; n is the number of main control factors;
according to the threshold values of the main control factors in the polymer flooding cross-flow early warning index system determined in the step ②, and after the threshold values are processed by a normalization method, an evaluation matrix is obtained:
Figure BDA0001307045910000071
in the formula, ri＝(ri1,ri2,ri3) An evaluation matrix corresponding to any master control factor; i is any main control factor, i is 1, 2, … …, n;
establishing a weight set according to the weight of each main control factor in the polymer flooding cross-flow early warning index system determined in the step ③, wherein the weight set can be recorded as:
A＝{a1,a2,…,anin the formula (6), A represents a weight set; a isiIs the weight of any main control factor, i is 1, 2, … …, n;
and finally, applying the synthesis operation of fuzzy transformation to obtain a comprehensive evaluation result:
B＝A×R＝{b1,b2,b3} (7)
in the formula: b is a comprehensive judgment result; b1Corresponding to v in comment set1The evaluation results of (1); b2Corresponding to v in the comment set2The evaluation results of (1); b3Corresponding to v in comment set3The evaluation results of (1);
in the comprehensive evaluation result, b1、b2Or b3And if the numerical value is large, the oil well is in a corresponding gathering state in the comment set, so that the gathering condition is judged.
4) Prediction of the degree of alarm
The polymer flooding channeling early warning index system determined in the step 2) consists of a static index and a dynamic index, wherein the dynamic index changes along with the production process, so that the development trend of a later-stage channeling channel is predicted by predicting the dynamic index, and the specific process is as follows:
①, firstly, selecting one or more of a numerical simulation method, a support vector machine method and a gray prediction method to be combined, and predicting the numerical value of the dynamic index T + n time point in the polymer flooding cross-flow early warning index system;
②, substituting the predicted numerical value into the gathering and fleeing early warning evaluation model established in the step 3) to obtain the gathering and fleeing development condition of the T + n time point, and drawing a gathering and fleeing prediction result graph on a well map, wherein the result graph can visually see the gathering and fleeing development condition.
Example (b):
taking an early warning method for development of a cross-flow channel between Bohai sea J oil field polymer flooding injection and production wells as an example, a well pattern (shown in figure 2) of a polymer injection region of the J oil field is provided with 28 wells in the region, wherein 8 polymer injection wells and 20 oil production wells. The specific steps are as follows:
1) the static parameters of a reservoir in a polymer injection region and the production dynamic characteristic parameters after 4 years of polymer injection are counted, a flow-through intensity factor of an oil well is calculated, the relation between the flow-through intensity factor and the static parameters of the reservoir and various production dynamic characteristic parameters is analyzed, and because the static parameters and the production dynamic characteristic parameters are more, only partial analysis results are displayed below.
TABLE 1J statistical results of production dynamic characteristic parameters of oil field partial polymer injection well
Polymer injection well Cumulative injection amount (Wanfang) Apparent water absorption index change rate (decimal)
J9 154.19 0.58
J7 221.45 0.31
J5 92.64 0.75
J3 154.82 0.52
J1 206.22 0.42
Under the condition that the reservoir property is not changed, the water absorption index of the polymer injection well is stably changed, and after the flow channel is formed, the bottom hole pressure is reduced when the daily water injection amount is not changed, and the apparent water absorption index is increased. The possibility of the occurrence of the channeling is tracked by comparing the change of the current apparent water absorption index relative to the initial apparent water absorption index, after the channeling is gathered, the change rate of the apparent water absorption index is less than 1, and the smaller the value of the change rate is, the more the channeling is. From the statistical results in table 1, it can be seen that the larger the cumulative injection amount of the well, the smaller the change rate of the water absorption index, the more severe the flushing, the easier the formation of the cross flow channel, and the increased water absorption capacity.
Table 2 shows the statistics of the water storage rate and the communication rate of the partial well groups at the initial stage of polymer injection and after 4 years of polymer injection.
TABLE 2J statistical results of dynamic characteristic parameters of production of partial well groups in oil field
Well group Initial water storage rate Water storage rate after 4 years Initial connectivity rate Connectivity after 4 years
J1 0.68 0.57 0.58 0.76
J3 0.77 0.62 0.52 0.68
J5 0.85 0.71 0.75 0.79
J7 0.53 0.46 0.63 0.68
J9 0.79 0.72 0.61 0.67
As can be seen from the statistical results in Table 2, after 4 years of polymer injection and the formation of the channeling channel, the formation water storage rate is reduced due to the direct production of a large amount of injected water, and meanwhile, the channeling channel directly connects the oil-water well, so that the injection-production relevance is very strong, the injection-production connectivity is very obvious, and the channeling characteristic is obvious.
And Table 3 shows the statistical results of the production dynamic characteristic parameters of the J oil field part of the production wells.
TABLE 3J statistical results of production dynamics characteristic parameters of oilfield partial production wells
Number of well Cross flow intensity factor Water content (%) Current concentration of aggregation (mg/L)
J8 1.49 70.55 221.8
J10 1.00 65.95 232.8
J6 0.89 66.99 180.3
J4 0.42 46.22 103.4
J12 1.66 82.51 602.4
J14 1.78 86.72 600.4
J19 1.81 82.43 498.4
J24 2.83 72.81 484.7
J27 0.23 65.89 169.6
J16 0.87 74.99 203.8
J23 2.33 70.94 551.8
J18 1.56 82.14 277.0
J22 0.52 50.78 202.3
J26 1.14 56.44 516.7
J28 0.46 69.05 123.0
J2 0.81 40.82 247.5
J21 0.68 83.02 384.1
J25 0.13 20.48 132.6
As can be seen from the statistical results in Table 3, the water content and the polymer concentration of the well with the higher polymer flooding channeling strength factor are higher, and the well has obvious channeling characteristics, which indicates that the polymer flooding channeling factor can be used as an important parameter for representing the channeling condition.
2) And calculating the correlation between the static parameters and the dynamic production indexes of the reservoir and the channeling intensity factor by using a grey correlation analysis method to obtain indexes which are closely compared with the channeling intensity factor, such as permeability grade difference, accumulated injection quantity, accumulated liquid production quantity, dimensionless accumulation time, accumulation concentration, liquid production index change rate, apparent water absorption index change rate, accumulation concentration change rate and injection-production connectivity.
3) The permeability was classified as 250 × 10 by statistical analysis of the J field permeability data-3μm2、500×10-3μm2、1000×10-3μm2Three grades basic permeability of 250 × 10 was established-3μm2、500×10-3μm2、1000×10-3μm2Respectively simulating the channeling conditions under the conditions of 1, 2, 5, 8, 10, 12 and 15 of permeability level differences to obtain the water content reduction range of the polymer flooding under different permeability level differences (as shown in figure 3).
As can be seen from fig. 3, at the same level difference, the polymer precipitation amplitude decreases continuously as the base permeability increases; for the same basic permeability, the polymer precipitation amplitude rises first and then falls as the grade difference increases. According to the water content descending range, the gathering and channeling limit is calibrated, the level difference that the water content descending range begins to descend is a gathering and channeling observation area, the level difference that the water content descending range rapidly descends is a gathering and channeling serious area, and the specific limit of each index is shown in a table 4.
TABLE 4 channeling index limit calibration of different level difference models
Figure BDA0001307045910000101
On the basis of a typical numerical simulation model, the weight of the channeling index is researched by a control variable method. Under the condition of single index value change, namely, the values of all parameters are changed according to + 10% and-10%, the variable quantity of the channeling intensity factor is calculated, the influence degree of different indexes on the channeling is obtained, and therefore the weight of each index is obtained and shown in a table 5.
TABLE 5 weight of fleeing evaluation index
Serial number Index (I) Weight of
1 Difference in permeability grade 0.19
2 Cumulative injection amount 0.08
3 Cumulative fluid production 0.08
4 Concentration of produced polymer 0.06
5 Apparent water absorption index change rate 0.15
6 Dimensionless time to gather 0.14
7 Rate of change of fluid production index 0.05
8 Rate of change of concentration of produced polymer 0.17
9 Injection and production connectivity 0.08
And (3) establishing a gathering channeling judgment model by using a fuzzy comprehensive judgment method, judging the channeling condition of each well in the area, wherein the judgment result is shown in figure 4.
4) And performing arithmetic mean on the dynamic production indexes predicted by the gray prediction model and the support vector machine model, determining the numerical values of all the evaluation indexes after focusing for 5 and a half years, and substituting the obtained predicted values of all the evaluation indexes into the clustering recognition model, so as to predict the clustering development condition after the focusing for 5 and a half years, wherein the prediction result is shown in fig. 5. And substituting the actual values of the evaluation indexes after 5 and a half years into the gathering recognition model, and calculating to obtain the actual development condition of the gathering after 5 and a half years, wherein the calculation result is shown in figure 6.
From the comparison of fig. 4 and fig. 5, it is found that as the injection time is prolonged, the channeling area is enlarged, and the number of wells in the channeling development area is increased from 6 to 8 and the number of wells in the channeling observation area is increased from 4 to 11. Comparing fig. 5 with fig. 6, it is found that the total 4 wells with different early warning and actual results, 28 production wells in the whole area, and the prediction accuracy is 86%.
The present invention is described only by the above embodiments, and the selection method of each step and each parameter can be changed, and on the basis of the technical solution of the present invention, the improvement and equivalent transformation of the value of each step or each parameter according to the principle of the present invention should not be excluded from the protection scope of the present invention.

Claims (5)

1. An early warning method for monitoring the development of a cross flow channel between polymer flooding injection wells is characterized by comprising the following steps:
1) finding police sources
On the basis of the dynamic and static data and the monitoring data of the target oil field, carrying out statistical analysis on various parameter values of an oil well, a polymer injection well and a well group, and searching for influence factors and specific performance characteristics of a cross flow channel formed in a reservoir stratum;
2) analysis warning sign
Aiming at the influence factors of the cross flow channel counted in the step 1) and each parameter of the specific representation characteristic, determining main control factors influencing the polymer flooding cross flow by using a grey correlation analysis method, and forming a polymer flooding cross flow early warning index system by the main control factors;
3) degree of recognition
Establishing a gathering and channeling early warning evaluation model by using a fuzzy comprehensive evaluation model;
4) prediction of the degree of alarm
The polymer flooding channeling early warning index system determined in the step 2) consists of a static index and a dynamic index, wherein the dynamic index changes along with the production process, so that the development trend of a later-stage channeling channel is predicted by predicting the dynamic index;
the influencing factors and the specific expression characteristics for forming the channeling channel in the step 1) are reservoir static parameters and production dynamic characteristic parameters in a polymer flooding area of the target oil field, and the influencing factors and the specific expression characteristics comprise: permeability grade difference, accumulated injection quantity, accumulated liquid production quantity, dimensionless visible aggregation time, aggregation production concentration change rate, liquid production index change rate, apparent water absorption index change rate, injection-production connectivity and polymer flooding channeling strength factor;
wherein, the change rate of the apparent water absorption index refers to the ratio of the initial apparent water absorption index to the current apparent water absorption index;
the strength factor of the polymer flooding channeling is used for representing the strength of the polymer flooding channeling, the symbol is expressed by M, and the calculation formula is as follows:
M＝Qp×Vp×ω (1)
in the formula: qpThe dimensionless amount of produced polymer is equal to the amount of produced polymer of the oil well divided by the amount of split polymer; vpThe polymer breakthrough rate, equal to the well spacing divided by the time to coalescence; ω is an effect factor, and when the time of onset is earlier than the effect time, ω is the effect time/(effect time-time of onset), when the time of onset is equal to the effect time, ω is 1, and when the time of onset is later than the effect time, ω is the time (time of onset-time of onset)/time of onset.
2. The early warning method for monitoring the development of the cross flow channel between the polymer flooding injection well and the production well according to claim 1, wherein the specific process for establishing the polymer flooding cross flow early warning index system in the step 2) is as follows:
① using the polymer flooding channeling intensity factor calculated in the step 1) as a reference sequence;
② using the rest dynamic and static parameters in the step 1) as comparison sequences;
③, calculating the degree of association between the comparison sequence and the reference sequence by a grey correlation analysis method, wherein the greater the degree of association, the more consistent the change situation of the comparison sequence and the reference sequence is, normalizing the degree of association on the basis, and if the degree of association between the comparison sequence and the reference sequence is more than 0.7, the correlation can be used as a main control factor to form a polymer flooding cross-flow early warning index system.
3. The early warning method for monitoring the development of the cross flow channel between the polymer flooding injection well and the production well according to claim 2, wherein the specific process for establishing the cross flow early warning evaluation model in the step 3) is as follows:
①, establishing typical numerical simulation models of different basic permeability according to relevant parameters of the target oil field;
②, respectively simulating the variation trend of the water content reduction amplitude of the polymer flooding under different permeability level differences under the condition of different injected polymer flooding solution volumes by using the established typical numerical simulation model to obtain the limit value of each main control factor in the step 2):
according to the change trend of the permeability level difference and the water content descending amplitude of the polymer flooding in a typical numerical simulation model, establishing a water content descending amplitude change curve of the polymer flooding under different permeability level differences by taking the permeability level difference as a horizontal axis and the water content descending amplitude as a vertical axis, defining the corresponding permeability level difference as a gathering observation limit when the water content descending amplitude of the polymer flooding begins to descend, and defining the corresponding permeability level difference as a gathering development limit when the water content descending amplitude exceeds 1.2%; obtaining the threshold value of each main control factor under the condition of different injected polymer flooding solution volumes according to the boundary definitions of different polymer flooding degrees;
③ applying control variable method to each main control factor parameter value in the polymer flooding cross-flow early warning index system, i.e. single main control factor parameter value is changed according to + 10% and-10%, applying formula (1) to calculate corresponding cross-flow factor, different main control factors have different influence degrees on polymer cross-flow, obtaining weight symbol A of each index through sensitivity analysis and normalization processingiRepresents:
Figure FDA0002522007190000021
in the formula: | Δ MiI is the absolute value of the change of the corresponding channeling factor after the single index parameter value is changed by + 10% and-10%; n is the number of main control factors in the polymer flooding cross-flow early warning index system; i is any main control factor of a polymer flooding cross flow early warning index system;
④, finally substituting the determined threshold values and weights of the main control factors in the polymer flooding channeling early warning system into the fuzzy comprehensive evaluation model to establish a gathering channeling early warning evaluation model, further respectively judging the gathering channeling development, the gathering channeling observation and the gathering channeling-free condition of each well, drawing a gathering channeling judgment result graph on a well bitmap, and visually seeing the distribution of the gathering channeling on the well bitmap.
4. The early warning method for monitoring the development of the cross flow channel between the polymer flooding injection well and the production well according to claim 3, wherein the specific calculation process for establishing the cross flow early warning evaluation model in the step ④ is as follows:
i) determining a comment set, and setting the comment set as three levels of scurry gathering development, scurry gathering observation and scurry gathering-free in a scurry gathering early warning model, wherein the comment set is marked as:
V＝{v1,v2,v3} (3)
in the formula: v is a comment set; v. of1Representing that the oil well is in a channeling development state; v. of2Representing that the oil well is in a channeling observation state; v. of3Representing that the oil well has not been subjected to gathering;
ii) determining a factor set influencing the comment set, namely the polymer flooding cross-flow early warning index system determined in the step 2), wherein the factor set is recorded as:
U＝{u1,u2,…,un} (4)
in the formula: u represents a polymer flooding cross flow early warning index system; u. of1,u2,…,unCorresponding to each main control factor in the polymer flooding cross flow early warning index system one by one; n is the number of main control factors;
iii) obtaining an evaluation matrix after the threshold values of the main control factors in the polymer flooding cross-flow early warning index system determined in the step ② are processed by a normalization method:
Figure FDA0002522007190000031
in the formula, ri＝(ri1,ri2,ri3) An evaluation matrix corresponding to any master control factor; i is any main control factor, i is 1, 2, … …, n；
iv) establishing a weight set according to the weight of each main control factor in the polymer flooding cross-flow early warning index system determined in the step ③, wherein the weight set is recorded as:
A＝{a1,a2,…,an} (6)
in the formula: a represents a weight set; a isiIs the weight of any index, i ═ 1, 2, … …, n;
v) applying the synthesis operation of fuzzy transformation to obtain a comprehensive judgment result:
B＝A×R＝{b1,b2,b3} (7)
in the formula: b is a comprehensive judgment result; b1Corresponding to v in comment set1The evaluation results of (1); b2Corresponding to v in the comment set2The evaluation results of (1); b3Corresponding to v in comment set3The evaluation results of (1);
in the comprehensive evaluation result, b1、b2Or b3And if the numerical value is large, the oil well is in a corresponding gathering state in the comment set, so that the gathering condition is judged.
5. The early warning method for monitoring the development of the cross flow channel between the polymer flooding injection well and the production well according to claim 1, wherein the specific process for predicting the development trend of the later-stage cross flow channel in the step 4) is as follows:
①, firstly, selecting one or more of a numerical simulation method, a support vector machine method and a gray prediction method to be combined, and predicting the numerical value of the dynamic index T + m time point in the polymer flooding cross-flow early warning index system in the step 2);
② substituting the predicted numerical value into the gathering and fleeing early warning evaluation model established in the step 3) to obtain the gathering and fleeing development condition at the time point of T + m, and drawing a gathering and fleeing prediction result graph on a well map, wherein the result graph can visually see the gathering and fleeing development condition.
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