Method for determining water injection rate of injection-production effective water-flooded well group

Abstract

The invention belongs to the technical field of oilfield development, and particularly relates to a method for determining the water injection rate of an injection-production effective water-flooded well group. The method comprises the steps that the real-time optimal daily water injection rate W of a target well group is determined according to the real-time produced water mineralization degree K of an effective well group in combination with a relation model of the optimal daily water injection rate W and the produced water mineralization degree K, and then the to-be-injected water rate of the effective well group is determined; the relation model of W and K is deduced according to the relation between K and water content fw, the relation between daily water storage rate Er and fw, the relation between daily water injection rate W'and daily water injection rate Qr and Er, the relation between fw and recovery degree R and the relation between daily injection-recovery ratio Zr and fw. By adopting the method, the optimal daily water injection rate of the effective well group can be accurately and quickly determined according to the mineralization degree of the produced water, and then the water injection rate of the effective well group is dynamically adjusted in real time according to the optimal daily water injection rate, so that the maximum oil production of the effective well group can be guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield development, and in particular relates to a method for determining the water injection volume of an effective water-flooded well group. Background Art

[0002] The main purpose of water injection in oil fields is, first, to maintain the energy of the oil layer so that the oil wells have sufficient production capacity; second, to continuously improve the water drive efficiency and sweep coefficient of various oil layers through the water injection effect, thereby improving the water drive recovery rate of the oil field. At present, more than 80% of my country's oil production comes from water injection development oil fields, and water injection is an important and main way of oil production in oil fields. The water injection development of oil fields maintains stable production and increased production, which is mainly reflected in the effective increase in oil production in the injection and production well groups. Through the dynamic adjustment of the water injection volume of water wells, the effective increase in oil production in the injection and production well groups will generally go through three stages: the low water content stage of effective oil production, the medium and high water content stage of effective stable production, and the high water content stage of effective production reduction. Therefore, the study of how to effectively adjust the water injection volume of the injection and production well group so that the well group can maintain a long period of stable production and increased production has attracted widespread attention.

[0003] In order to extend the stable production and increased production stage of the well group, reservoir management technicians have a variety of water well allocation methods based on the characteristics of the oil field and well group. For example, the adjustment water injection methods for relatively simple injection and production well groups include periodic water injection, pulse water injection, coupled water injection, variable intensity water injection, etc. These water injection adjustment methods can achieve the purpose of stable production and increased production under certain conditions. In general, no matter what method is used to adjust the water injection volume, it is determined based on the formation energy and the water content of the oil well output fluid. When the well group production increases and the water content rises, the water well injection volume will be reduced, and when the well group production decreases and the water content decreases, the water well injection volume will be increased. However, the adjustment of water injection volume when the daily liquid production of the well group increases and the water content rises, or the daily liquid production decreases and the water content decreases, cannot guarantee the stability or increase of the key indicator - daily oil production. In addition, in actual production, due to the immiscibility of oil and water, inter-formation outflow, discontinuous pumping and other reasons, the water content of the well group is not fixed, but varies dramatically within the same time period. The above-mentioned water adjustment method will lead to uncertainty in the adjustment of the water injection volume. It can only be done by continuous trial and error, and it is difficult to quickly find a clear optimal water injection volume. Summary of the invention

[0004] The purpose of the present invention is to provide a method for determining the water injection volume of a flooded well group for effective injection and production, so as to solve the technical problem that the method for adjusting the water injection volume in the prior art cannot find a clear optimal water injection volume, resulting in the inability to ensure the stability or increase of daily oil production.

[0005] In order to solve the above technical problems, the present invention provides a method for determining the water injection volume of an effective water-flooded well group, comprising the following steps:

[0006] According to the real-time produced water mineralization K of the effective well group, combined with the relationship model between the optimal daily water injection volume W of the effective well group and the produced water mineralization K, the real-time optimal daily water injection volume W of the target well group is determined, and the water volume to be injected of the effective well group is determined according to the real-time optimal daily water injection volume W of the effective well group; the relationship model between the optimal daily water injection volume W of the effective well group and the produced water mineralization K is based on the relationship between the produced water mineralization K and the water content f obtained based on the material balance principle. w The daily water storage rate E of the effective well group is obtained based on the definition of cumulative water storage rate and cumulative injection-production ratio. r With moisture content f w The relationship between the daily water injection volume W′ and the daily production water injection volume Q obtained based on the definition of water storage rate r and daily water storage rate E r The relationship between the water content f obtained based on reservoir engineering principles w Relationship with the recovery rate R and the daily injection-production ratio Z based on the definition of injection-production ratio r With moisture content f w The relationship between them is derived.

[0007] Its beneficial effects are: within the same time period, the mineralization of the well group's output fluid is relatively fixed, and at the same time, the size of the output fluid mineralization can reflect the degree of flooding of the effective layer, and the size of the mineralization decreases as the degree of flooding increases. Therefore, when the mineralization of the injected water is different from that of the formation water, the water injection amount of the water well can be reasonably determined according to the change in the size of the output water mineralization, thereby achieving the purpose of determining the optimal water injection amount for the effective flooded well group. The method of the present invention constructs a relationship model between the optimal daily water injection amount W of the effective well group and the output water mineralization K, and combines the real-time output water mineralization of the effective well group to accurately and quickly determine the real-time optimal daily water injection amount of the target well group, and then adjusts the water injection amount of the effective well group in real time and dynamically according to the optimal daily water injection amount, thereby ensuring the maximum oil production of the effective well group. In addition, the method of the present invention changes the determination of the water injection amount of the water well from the original qualitative to quantitative, making the injection and production management of the effective well group more accurate and more effective.

[0008] Preferably, the relationship model expression between the optimal daily water injection volume W of the effective well group and the salinity K of the produced water is:

[0009]

[0010] Where e is the base of the natural logarithm function, N p is the cumulative oil production, C is the geological reserves, R z is the ultimate recovery factor, Q 0 ′ is the maximum daily oil production, L p is the cumulative liquid production, Z s is the cumulative injection-production ratio, Ks is the formation water salinity, and Kz is the injected water salinity.

[0011] Preferably, the expression derived from the material balance principle includes:

[0012] Q w =Qf w =Q c +Q r ;Q w K=KsQ c +KZ r ;

[0013] In the formula, Q w is the daily water production, Q 0 is the daily oil production, Q c is the daily formation water production, Q r is the daily injected water volume, Ks is the formation water salinity, and Kz is the injected water salinity.

[0014] Preferably, the produced water mineralization K and water content f w The expressions of the relationship are:

[0015]

[0016] Preferably, the daily water storage rate E r With moisture content f w The expression of the relationship between is:

[0017]

[0018] In the formula, E r is the daily water storage rate, Z r is the daily injection-production ratio, Z s is the cumulative injection-production ratio, L p is the cumulative liquid production, N p is the cumulative oil production, Q 0 The daily oil production.

[0019] Preferably, the moisture content f w The expression of the relationship between the recovery degree R is:

[0020]

[0021] Where: R z is the ultimate recovery factor, and d is the water drive constant of the water drive reservoir.

[0022] Preferably, the daily injection-production ratio Z r With moisture content f w The expression of the relationship between is:

[0023]

[0024] In the formula, Q o Indicates daily oil production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the method steps of the present invention;

[0026] Figure 2 This is a schematic diagram of injection-production effective well group A. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] Example of method for determining water injection volume of effective flooded well group:

[0029] like Figure 1 As shown, the method for determining the water injection volume of the effective water-flooded well group of the present invention comprises the following steps:

[0030] Step 1: Obtain data such as fluid properties and production conditions of the target well group.

[0031] Based on the basic geological research data of the reservoir and the target well group, the characteristic parameters characterizing the adjustment of the water injection volume of the water well are determined, mainly including data such as geological reserves, production status and fluid properties, specifically the geological reserves of the effective water-flooded well group, cumulative water production, cumulative oil production, daily oil production, cumulative injection-production ratio, injected water mineralization, formation water mineralization, produced water mineralization and other data.

[0032] Step 2: Construct a relationship model between the injection volume of the target well group and the salinity of the produced water.

[0033] Based on the characteristic parameters and other required parameters required to determine the reasonable water injection volume obtained in step 1, a relationship model between the various parameters is constructed for the purpose of accurately determining the optimal water injection volume, and a relationship model between the water injection volume of the effective flooded well group and the mineralization of the produced water is established, and finally the optimal basis for dynamic adjustment of the water injection volume of the water wells is determined.

[0034] Step 2.1, construct a relationship model between the salinity and water content of the produced water of the effective well group and the daily injected water volume of the effective well group.

[0035] After the injection-production well group takes effect, the oil well output fluid is a mixture of produced water and produced oil. The produced water is a mixture of formation water and injected water. The mineralization of produced water includes two parts: the mineralization of formation water and the mineralization of injected water. Using the principle of material balance, we can get:

[0036]

[0037] Q w =Qfw =Q c +Q r (2)

[0038] Q w K=KsQ c +KZ r (3)

[0039] According to equations (2) and (3), the relationship model between daily injected water volume and daily water production can be further derived as follows:

[0040]

[0041] Combining equations (1) and (4), we can get the daily injected water volume Q r The relationship model with the produced water mineralization K is:

[0042]

[0043] In formula (1) to formula (5), Q is the daily liquid production, Q w is the daily water production, Q 0 is the daily oil production, Q c is the daily formation water production, Q r The amount of water injected into Nissan, f w is the water content, K is the produced water salinity, Ks is the formation water salinity, and Kz is the injected water salinity.

[0044] The constructed relationship model between produced water mineralization and water content (5) reflects the relationship between produced water mineralization and water content, daily water injection volume and daily oil production of a well group, thus providing a basis for constructing a relationship model between the optimal daily water injection volume and produced water mineralization of an effective well group.

[0045] Step 2.2, construct a relationship model between the daily water storage rate and water cut of the effective well group.

[0046] According to the known definitions of cumulative water storage rate and cumulative injection-production ratio, the relationship model expression between cumulative water storage rate and cumulative injection-production ratio can be obtained as follows:

[0047]

[0048] In formula (6), E S is the cumulative water storage rate, Z S is the cumulative injection-production ratio, N p is the cumulative oil production, L p Cumulative liquid production.

[0049] Using the relationship model (6), a relationship model between the daily water storage rate and water content of the effective well group is constructed.

[0050] In formula (6), the derivative of time t is:

[0051]

[0052] According to its physical meaning, is the daily water storage rate, symbolized by E r express, is the daily injection-production ratio, symbolized by Z r express, Q is the daily oil production 0 express, The daily liquid output is represented by Q. The relationship model between the daily water storage rate and water cut of the effective well group is as follows:

[0053]

[0054] In formula (7) to formula (8), E r is the daily water storage rate, Z r is the daily injection-production ratio, Z s is the cumulative injection-production ratio, E s is the cumulative water storage rate, L p is the cumulative liquid production, N p is the cumulative oil production, Q 0 is the daily oil production, f w is the moisture content.

[0055] From the relationship model between the daily water storage rate and water cut of the effective well group, it can be seen that the main factors affecting the determination of the daily water storage rate are the daily injection-production ratio, the cumulative injection-production ratio, the water cut of the well group, the cumulative liquid production, the cumulative oil production and the daily oil production.

[0056] Step 2.3: Construct a relationship model between the optimal daily water injection rate of the effective well group and the salinity of the produced water

[0057] In general, when the output water-oil ratio of the reservoir reaches 49 (that is, when the water content of the reservoir reaches 98%), the reservoir can be abandoned. The recovery degree at this time is the final recovery rate of the reservoir. According to the principles of reservoir engineering and the reservoir production data statistically compiled by Tong Xianzhang, a recognized petroleum engineer, the relationship model between water content and recovery degree can be expressed as:

[0058]

[0059] Where: R is the degree of recovery, R z is the ultimate recovery factor, f w is the water cut, and d is the water drive constant of the water drive reservoir.

[0060] Using the definition of water storage rate, we can get the daily water injection volume W′ and the daily injection water volume Q r and daily water storage rate E r The expression of the relationship model is:

[0061]

[0062] In the formula, Q r is the daily water injection volume, W′ is the daily water injection volume, E r is the daily water storage rate.

[0063] Using the definition of injection-production ratio, we can get:

[0064]

[0065] Where W is the optimal daily water injection volume, Q is the daily liquid production, and Z is the r is the daily injection-production ratio, Q 0 is the daily oil production, f w is the moisture content.

[0066] Combining equation (10) and equation (11), we can get

[0067] In the formula, Z r is the daily injection-production ratio, Q 0 is the daily oil production, f w is the moisture content, Q r The amount of water injected into Nissan, E r is the daily water storage rate.

[0068] Combining equations (5), (8), (9), (10) and (12), the expression of the relationship model between the optimal daily water injection volume of the effective well group and the salinity of the produced water can be derived as follows:

[0069]

[0070] In the expression of this model, K is the independent variable, W is the dependent variable, and other parameters are constants.

[0071] Where W is the optimal daily water injection volume, e is the base of the natural logarithm function, N p is the cumulative oil production, C is the geological reserves, R z is the ultimate recovery factor, Q 0 ′ is the maximum daily oil production, L p is the cumulative liquid production, N p is the cumulative oil production, Z s is the cumulative injection-production ratio, K is the produced water salinity, Ks is the formation water salinity, and Kz is the injected water salinity.

[0072] It can be seen from formula (12) that the smaller the produced water salinity K of the effective well group, the greater the optimal daily water injection volume.

[0073] Step three, measure the mineralization of the produced water of the effective well group in real time, and determine the real-time optimal daily water injection volume of the target well group based on the relationship model between the optimal daily water injection volume of the effective well group and the mineralization of the produced water, and determine the amount of water to be injected of the target well group based on the real-time optimal daily water injection volume of the target well group.

[0074] The produced water mineralization K can be obtained based on the sampling and testing results of the oil wells in the injection and production well group. The produced water mineralization K is input into the relationship model between the optimal daily water injection rate of the effective well group and the produced water mineralization to obtain the optimal daily water injection rate of the effective well group. Determine whether the water injection rate of the effective well group is optimal. If not, quantitatively adjust the water injection rate of the water well.

[0075] During the oil production process of the oil well, the mineralization degree K of the produced water is constantly decreasing. The size of the mineralization degree K of the produced water of the oil well is continuously monitored and input into the relationship model between the optimal daily water injection volume of the effective well group and the mineralization degree of the produced water to obtain the real-time optimal daily water injection volume of the effective well group. According to the real-time optimal daily water injection volume of the effective well group, the water injection volume of the water well is dynamically adjusted to achieve the goal of long-term stable production.

[0076] Taking the injection-production effective well group A as an example, the method of the present invention is verified. Figure 2 As shown, the well group is in the effective injection and production stage. The well group includes XX-1 and oil well XX-2. The output fluid of the water injection well is a mixture of produced water and produced oil. The produced water is a mixture of formation water and injected water. The mineralization of the produced water includes the mineralization of formation water and the mineralization of injected water. The maximum daily oil production of the well group is Q 0 ′ is 3.3 tons / day, the produced water mineralization K measured at time t is 17.5 mg / L, the formation water mineralization Ks is 31.2 mg / L, the injected water mineralization Kz is 11.5 mg / L, and the cumulative injection-production ratio Z s is 1.1, the cumulative oil production N p 8600 tons, with a total liquid production of L p The controlled geological reserves C of the injection-production well group are 24,900 tons, the recovery rate R = 0.86 / 2.49*100% = 34.5%, and the final recovery rate R z The actual daily water injection volume of the well group is 25 cubic meters. Substituting the above parameters into the relationship model between the optimal daily water injection volume and the salinity of the produced water of the effective well group, the optimal daily water injection volume of the effective well group A is 35.4 cubic meters. The actual water injection volume does not reach the optimal value, so the water injection volume of the water injection well XX-1 is increased to 35 cubic meters / day. By continuously monitoring the salinity of the produced water of the oil wells and dynamically adjusting the water injection volume of the water wells, the oil well XX-2 has achieved the goal of long-term stable production.

[0077] The method for determining a reasonable water injection amount for an effective water-flooded well group in the present invention is guided by the idea of ​​quantitatively and dynamically adjusting the water injection amount of the water well, takes the maximum oil production of the injection-production well group as the goal, establishes a relationship model between the water injection amount and the mineralization degree of the produced water, and forms a new method for determining the optimal water injection amount for an effective water-flooded well group. The method is invented for how to maintain stable and high production after the injection-production well group enters the effective water-flooding period. The method solves the problem of how to determine the optimal water injection amount well. Based on the changes in the mineralization degree of the produced water, the water injection amount of the water well is adjusted in a timely and quantitative manner to keep the well group in a production state with a high production rate. The method has strong practicality and universality, and provides a new method for reasonable dynamic allocation after the injection-production well group is effectively flooded.

Claims

1. A method for determining the water injection volume of a flooded well group with effective injection and production, It is characterized in that include: According to the real-time produced water mineralization K of the effective well group, combined with the relationship model between the optimal daily water injection volume W of the effective well group and the produced water mineralization K, the real-time optimal daily water injection volume W of the target well group is determined, and the water volume to be injected of the effective well group is determined according to the real-time optimal daily water injection volume W of the effective well group; the relationship model between the optimal daily water injection volume W of the effective well group and the produced water mineralization K is based on the relationship between the produced water mineralization K and the water content f obtained based on the material balance principle. w The daily water storage rate E of the effective well group is obtained based on the definition of cumulative water storage rate and cumulative injection-production ratio. r With moisture content f w The relationship between the daily water injection volume W′ and the daily production water injection volume Q obtained based on the definition of water storage rate r and daily water storage rate E r The relationship between the water content f obtained based on reservoir engineering principles w The relationship between the recovery rate R and the daily injection-production ratio Z obtained based on the definition of the injection-production ratio r With moisture content f w The relationship between them is derived.

2. The method for determining the water injection volume of a flooded well group according to claim 1, It is characterized in that The relationship model expression of the optimal daily water injection volume W of the effective well group and the salinity K of the produced water is: Where e is the base of the natural logarithm function, N p is the cumulative oil production, C is the geological reserves, R z is the ultimate recovery factor, Q 0 ′ is the maximum daily oil production, L p is the cumulative liquid production, Z s is the cumulative injection-production ratio, Ks is the formation water salinity, and Kz is the injected water salinity.

3. The method for determining the water injection volume of a flooded well group according to claim 1, It is characterized in that The expressions derived from the material balance principle include: Q w =Qf w =Q c +Q r ;Q w K=KsQ c +KzQ r ; In the formula, Q w is the daily water production, Q 0 is the daily oil production, Q c is the daily formation water production, Q r is the daily injected water volume, Ks is the formation water salinity, and Kz is the injected water salinity.

4. The method for determining the water injection volume of a flooded well group according to claim 3, It is characterized in that The produced water mineralization K and water content f w The expression of the relationship is:

5. The method for determining the water injection volume of a flooded well group according to claim 1, It is characterized in that Daily water storage rate E r With moisture content f w The expression of the relationship between is: In the formula, E r is the daily water storage rate, Z r is the daily injection-production ratio, Z s is the cumulative injection-production ratio, L p is the cumulative liquid production, N p is the cumulative oil production, Q 0 The daily oil production.

6. The method for determining the water injection volume of a flooded well group according to claim 1, It is characterized in that The moisture content f w The expression of the relationship between the recovery degree R is: Where: R z is the ultimate recovery factor, and d is the water drive constant of the water drive reservoir.

7. The method for determining the water injection volume of a flooded well group according to claim 1, It is characterized in that The daily injection-production ratio Z r With moisture content f w The expression of the relationship between is: In the formula, Q 0 Indicates daily oil production.

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