Quantitative determination method for pollution radius, acidification radius and unblocking acid liquid amount of under-injection well of sandstone reservoir

Abstract

The invention discloses a quantitative determination method for the pollution radius, the acidification radius and the unblocking acid liquid amount of an under-injection well of a sandstone reservoir. The quantitative determination method for the pollution radius comprises the steps that the daily injection allocation amount of the under-injection well or the daily actual injection amount of a selected date is obtained; pollution factors of the under-injection well and pollution coefficients a corresponding to the pollution factors are determined; calculating a conversion thickness h, an injection rate conversion coefficient b, an oil layer pressure conversion coefficient c and a communication direction coefficient gamma of the under-injection well; substituting the parameter values into a calculation formula to obtain a pollution radius r single-factor pollution radius corresponding to each pollution factor of the under-injection well; the calculation formula is as follows: r single factor pollution radius = gamma * a * (Q / h) 1 / 2 * ln (c / b); in the formula, Q is Q complex or Q choice; the problem that the existing method cannot rapidly, accurately and quantitatively calculate the pollution radius of the under-injection well of the sandstone reservoir is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development, and in particular to a method for calculating the plugging radius of a water injection well in a sandstone reservoir. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] The flow from the wellbore to the formation in a sandstone reservoir can be regarded as a stable planar radial flow, and the physical model is simple and easy to describe; however, the flow state of a carbonate reservoir is complex and the flow law is not easy to describe.

[0004] For sandstone reservoirs, conventional methods for determining the contamination radius of water injection wells can be divided into two types: experimental simulation method and well test method. The former uses artificial cores or natural cores to simulate the contamination of the water injection layer section of the block by blockages, calculates the blockage radius based on the core blockage law, and then determines the acidification radius. However, due to the water injection factors, small scale of indoor experiments, and reservoir heterogeneity, this method has poor single-well targeting and low effectiveness. Because the experimental simulation method is the result of indoor experiments, specifically the small-scale test results of a single small-sized core, it cannot fully simulate the specific well conditions of a single well. Therefore, a pollution radius range is given for the pollution status analysis of a single well, and a definite specific pollution radius value cannot be given.

[0005] The latter uses the skin coefficient, permeability and formation pressure obtained from the well test interpretation to calculate the contamination radius. This method requires well testing, which is less targeted, has high construction costs and takes up a long time in the well. The well test method requires the insertion of a pressure gauge during the well test, and a long pressure recovery test is performed. The calculation is based on the results. Affected by its own structure and downhole environment, it is easy to form ice, ice blockage, jamming and other production difficulties during the well test. These are some technical and human problems that are easy to occur during the well test.

[0006] Well testing is the most important means of reservoir engineering. The main well testing method is pressure testing. Traditional production generally adopts the extensive stable well testing method. Although the unstable well testing method (short well testing) has gradually replaced the previous traditional well testing method and can solve reservoir engineering problems more specifically, quickly and accurately, the analysis of well testing results is not perfect enough. It must be combined with other methods for effectiveness analysis to obtain a comprehensive understanding.

[0007] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may contain information that does not constitute prior art. Summary of the invention

[0008] In view of this, the present disclosure provides a method for quantitatively determining the contamination radius of an under-injection well in a sandstone reservoir, which solves the problem that the existing method cannot quickly and accurately quantitatively calculate the contamination radius of an under-injection well in a sandstone reservoir.

[0009] In addition, the present disclosure also provides a method for quantitatively determining the acidizing radius and acid volume of a water injection well in a sandstone oil reservoir.

[0010] In a first aspect, the method for quantitatively determining the contamination radius of an under-injected well in a sandstone reservoir comprises:

[0011] Get the daily injection volume Q of the under-injected well 配 Or the actual daily injection volume Q on the selected date 选 ;

[0012] Determine the pollution factors of the under-injection well and the pollution coefficient a corresponding to each pollution factor;

[0013] Calculating the converted thickness h, injection volume conversion coefficient b, reservoir pressure conversion coefficient c and connection direction coefficient γ of the under-injection well;

[0014] Substituting the above parameter values ​​into the calculation formula, we can obtain the pollution radius r corresponding to each pollution factor of the under-injection well. 单因素污染半径 ;

[0015] The calculation formula is: 单因素污染半径 =γ×a×(Q / h) 1 / 2 ×ln(c / b);

[0016] Where: Q is Q 配 or Q 选 .

[0017] In the present disclosure and possible embodiments, the method for determining the pollution coefficient a includes:

[0018] The injection water quality of the under-injection well is obtained, the pollution factors are determined according to the pollutant composition in the injection water quality, and the pollution coefficient a corresponding to each pollution factor is determined according to the blockage type included in the pollution factor.

[0019] In the present disclosure and possible embodiments, the blockage types are divided into mud, oil wax, mechanical impurities, clay and polymer blockages; the pollution coefficients a corresponding to each blockage type are: mud 0.15, oil wax 0.4, mechanical impurities 0.65, clay 0.85, polymer 0.95.

[0020] In the present disclosure and possible embodiments, the calculation formula for the converted thickness h is:

[0021] h=h 有效 +(1 / 4~1 / 2)×(h 射开 -h 有效 );

[0022] Where: h 射开 is the opening thickness, m; h 有效 is the effective thickness of the opening, m.

[0023] In the present disclosure and possible embodiments, the calculation formula of the injection amount conversion coefficient b is:

[0024] b=(Q 目前实注 / Q) 2 / 3 ;

[0025] Where: Q 目前实注 The current daily injection volume Q 目前实注 , m 3 ; If the daily actual injection volume is 0, the value is assigned to 1.

[0026] In the present disclosure and possible embodiments, the calculation formula of the oil layer pressure conversion coefficient c is:

[0027] c=[(P 目前油压+ H / 100-P 目前油层压力 ) / (P 初始油压+ H / 100-P 初始油层压力 )] 2 / 3 ;

[0028] Where: P 目前油压 is the current injection pressure, MPa; H is the reservoir depth, m; P 目前油层压力 is the current reservoir pressure, MPa; P 初始油压 is the initial injection pressure or the injection pressure on the selected date, MPa; P 初始油层压力 is the original formation pressure or the reservoir pressure on a selected date, MPa.

[0029] In the present disclosure and possible embodiments, the calculation formula of the connectivity direction coefficient γ is:

[0030] γ=(n / 6) -1 / 2 ;

[0031] Where: n is the number of connected wells.

[0032] In a second aspect, the method for quantitatively determining the acidizing radius of an under-injected well in a sandstone reservoir comprises:

[0033] Determine the contamination radius r corresponding to each contamination factor of the under-injection well according to the method of the first aspect. 单因素污染半径 ;

[0034] If the under-injected well is contaminated by a single factor, the deblocking acidizing radius R corresponding to the single factor contamination is 酸化半径 =r 单因素污染半径 +0.2m;

[0035] If the under-injected well is contaminated by two factors, the deblocking acidizing radius R corresponding to each contamination factor is 酸化半径 and the pollution radius r calculated based on the corresponding pollution factors 单因素污染半径 equal.

[0036] In a third aspect, the method for determining the amount of acid solution for plugging removal in an under-injected well in a sandstone reservoir comprises:

[0037] Determine the acidizing radius corresponding to each contamination factor of the under-injection well according to the method of the second aspect;

[0038] The amount of acid solution for unblocking corresponding to each pollution factor is calculated using the acidizing radius corresponding to each pollution factor, and the total amount of acid solution for unblocking the under-injection well is equal to the sum of the amount of acid solution for unblocking corresponding to each pollution factor.

[0039] In the present disclosure and possible embodiments, the formula used for calculation is:

[0040] Amount of acid for unblocking

[0041] Where: is the porosity, h is the converted thickness, m.

[0042] The present disclosure has the following beneficial effects:

[0043] The disclosed method for quantitatively determining the contamination radius of an under-injected well in a sandstone reservoir is designed to find out the main factors affecting the contamination radius of an under-injected well, utilize the historical dynamics of a single well and reservoir parameters, and classify and compare the current state and initial state of a single well, obtain a fitting formula for the contamination radius of an under-injected well through a big data experimental method, and then improve the calculation formula for the contamination radius of an under-injected well through dimensionalization and normalization correction. Since the disclosed determination method relies on the basic data and production history of the well and draws on the data of neighboring wells, the calculation results are highly targeted and reliable. Only the current reservoir pressure needs to be recorded or drawn on from neighboring wells, so the construction is simple and the well occupancy time is short. The data can be processed by programming, and the single well analysis speed is fast, which can be used for analysis and identification to determine the degree of contamination of different types of water injection wells. The data can be calculated on a large scale and can be quickly screened and analyzed, so as to be used for analysis of well selection and process guidance, thereby reducing work intensity. No on-site construction is required, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0045] Figure 1 It is a pressure variation curve during the acidizing construction of Well N in a certain oil field in the application example of the present disclosure. DETAILED DESCRIPTION

[0046] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts that are not described in detail, those skilled in the art can also fully understand the present disclosure.

[0047] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present disclosure, and the drawings are not actually drawn to scale.

[0048] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, the meaning is "including but not limited to".

[0049] Through research, the applicant found that water injection wells in sandstone oil reservoirs are affected and polluted by foreign fluids during the injection process, forming blockages near the wells, resulting in decreased permeability near the wells, increased injection pressure, decreased water injection volume, under-injection of water wells (under-injection wells) and insufficient energy replenishment of the oil layer.

[0050] Based on the above research results, the applicant first found out the main factors affecting the pollution radius of under-injection wells, and compared the historical dynamics and reservoir parameters of single wells, the current state and the initial state of single wells, and then used the dynamic data analysis method to obtain the fitting formula of the pollution radius of under-injection wells. Through dimensionalization and normalization correction, the calculation formula of the pollution radius of under-injection wells was improved; finally, by recording the pressure changes of the oil layer, combining the reservoir properties, specific characteristics of the single well, and the indoor experimental results of the block, the main influence radius of under-injection well pollution was calculated through the fitting formula. Specifically, the basic data, dynamic historical data, injection water type, and measured oil layer pressure of the under-injection wells were recorded, and the main influence radius of under-injection well pollution was calculated through the characteristics of the single well and its own evolution. At the same time, the radius parameters of the acidizing measures for under-injection wells can be further calculated through this method.

[0051] Example

[0052] Based on the above invention concept, the technical solution designed by the applicant is described through the following embodiments, which are as follows:

[0053] a. Record the basic data of under-injected wells, including the perforation thickness h 射开 、Effective opening thickness h 有效 , oil layer depth H, number of connected wells n, original formation pressure P 初始油层压力 (or reservoir pressure on a selected date).

[0054] The method of the embodiment of the present disclosure introduces the pollution state coefficient a, which represents the slope of the curve of the rapid decline of permeability at different radii in core experiments of different plugging types. According to the conventional technology and experience accumulation in this field, the reference values ​​of the pollution coefficient a are determined as follows: mud 0.15, oil wax 0.4, mechanical impurities 0.65, clay 0.85, polymer 0.95;

[0055] b. Record the historical dynamic data of under-injected wells, including the initial injection pressure P 初始油压 (or injection pressure on the selected date), current injection pressure P 目前油压 , daily injection volume Q 配 (or the actual daily injection volume Q of the selected date 选 ), current daily injection volume Q 目前实注 (If the daily actual injection volume is 0, the value is assigned to 1);

[0056] c. Measure the current reservoir pressure P of the well 目前油层压力 If this data is missing, refer to the reservoir pressure of adjacent wells;

[0057] d. Record the injection water quality of the under-injected well, and use the conventional technical means in this field to determine the pollution factors according to the main components of the injection water quality. Since the pollution factors correspond to the blockage types, the pollution coefficient a of the pollution factor is determined by the blockage type corresponding to each pollution factor;

[0058] e. Calculate the converted thickness h, h = h 有效 +(1 / 4~1 / 2)×(h 射开 -h 有效 );

[0059] In this formula, 1 / 4 is selected when the sandstone reservoir has medium-to-high permeability, 1 / 3 is selected when the permeability is low, and 1 / 2 is selected when the permeability is extremely low.

[0060] f. Calculate the injection volume conversion coefficient b, b = (Q 目前实注 / Q) 2 / 3 ; The injection volume conversion coefficient b is used to identify the changes in the water injection intensity plane of the oil layer, Q is Q 配 or Q 选 ;

[0061] g. Calculate the oil layer pressure conversion coefficient c, c = [(P 目前油压+ H / 100-P 目前油层压力 ) / (P 初始油压+ H / 100-P 初始油层压力 )] 2 / 3; The reservoir pressure conversion coefficient c represents the ratio of the completion injection degree coefficient to the reservoir pressure change coefficient; It should be noted that the initial data (reservoir pressure, injection volume, injection pressure) involved in steps f and g can be replaced with the data of the selected date, but each set of data must be at the same time point;

[0062] h. Calculate the connectivity direction coefficient, γ = (n / 6) -1 / 2 , the connectivity direction coefficient γ represents the number of connected wells;

[0063] i. Substitute the above values ​​into r 单因素污染半径 =γ×a×(Q / h) 1 / 2 ×ln(c / b) formula is used to calculate and determine the pollution radius under a single pollution factor.

[0064] j. The above method uses the fitting comparison between the current state and the initial state of a single well to determine the pollution radius of each factor. If the pollution of the under-injection well is affected by a single factor, the pollution radius of the single pollution factor can be determined using the formula in the above step i.

[0065] Furthermore, if the single factor pollution is unblocked, the acidification radius R 酸化半径 =r 单因素污染半径 +0.2m, amount of acid used for unblocking , where is the porosity.

[0066] k. If the pollution of the under-injected well is affected by two factors, the acidification radius of the two pollution factors is equal to the pollution radius of the corresponding pollution factors, that is, R 酸化半径 =r 单因素污染半径 .

[0067] Furthermore, because there are two main pollution factors, there will be two corresponding deblocking systems, and the two deblocking systems correspond to two acidification radii. Then, according to the method of step K, the acidification radius R corresponding to the two pollution factors is calculated respectively. 酸化半径1 and R 酸化半径2 .

[0068] Continue to use R 酸化半径1 and R 酸化半径2 Calculate the amount of acid Q used to remove the blockage corresponding to the pollution factor 酸1 and Q 酸2 Finally, the total amount of acid used to deblock the under-injected well is Q 酸 =Q 酸1 +Q 酸2 .

[0069] It can be seen from the above step description that the determination method described in the embodiment of the present disclosure is simple, has strong single-well specificity, does not require on-site operations, is low-cost, can batch and quickly screen wells in need of measures, and is suitable for the design of treatment radius parameters for various measure wells.

[0070] Application Examples

[0071] The determination method disclosed in the present invention is used to calculate the acidizing radius of N wells in a certain oil field, where N well is an under-injected well in a certain oil field. The specific calculation process is as follows:

[0072] a. Record the basic data of under-injected wells, including perforation thickness, effective perforation thickness, reservoir depth, connection direction, and original formation pressure; record the historical dynamic data of under-injected wells, including initial oil pressure, current oil pressure, daily injection volume, and current daily actual injection volume; measure the current reservoir pressure of the well. If this data is missing, refer to the reservoir pressure of the adjacent wells;

[0073] Among them, the perforation thickness of the well is h 射开 is 10.2m, the effective thickness of the opening is h 有效为 6.5m, porosity is 0.22, the oil layer depth H is 1200m, the number of connected wells n is 2, and the original reservoir pressure P 初始油层压力 =11.26MPa; initial injection pressure P 初始油压 =9.0MPa, daily injection volume Q 配 =50m 3 / d, current injection pressure P 目前油压 =13.5MPa, the current daily injection volume is Q 目前实注 =35m 3 / d, current formation pressure near the well P 目前油层压力 =10.55MPa.

[0074] b. According to the injection water quality of the well, dynamic analysis shows that the water pollution is mainly composed of mechanical impurities, so the blockage type is judged to be mechanical impurity blockage, and the pollution coefficient a corresponding to the mechanical impurity blockage type is 0.65.

[0075] c. Calculate the converted thickness h = h 有效 +1 / 4×(h 射开 -h 有效 )=7.43m;

[0076] d. Calculate the injection volume conversion coefficient b = 0.79;

[0077] e. Calculate the oil layer pressure conversion coefficient c = 1.33;

[0078] f. Calculate the connectivity direction coefficient γ = 1.73;

[0079] g. Substitute the above data into the formula r = γ × a × (Q 配 / h) 1 / 2 ×ln(c / b), the main influence radius is calculated to be 1.53m, the designed acidizing radius R=1.73m, and the amount of acid used is calculated to be 15.3m 3 , designed acid volume 16m 3 .

[0080] The actual amount of acid injected into the well is 16m 3 After the measures were taken, the initial injection pressure was 11.7MPa, and the daily injection volume was 50m 3 / d, pressure drop 1.8MPa, daily injection 13m 3 / d, which fully demonstrates that the measures have achieved good results.

[0081] Figure 1 is a pressure variation curve during the acidizing construction of a certain oil field well N in the application example of the present disclosure; Figure 1 As shown in the figure, with the continuous increase of acid injection volume, the wellhead injection pressure slowly drops to a stable value of 16, indicating that the acid has basically eliminated the blockage near the wellbore, and the acidizing effect will not increase significantly if the acid dosage continues to increase.

[0082] The pollution radius of the well was determined by the experimental simulation method described in the background technology. It was judged that the well was mainly blocked by mechanical impurities, and the pollution radius was 1.5-2.0m. After comprehensive consideration, the maximum pollution radius was adopted, the acidizing radius was designed to be 2.0m, and the acid dosage was designed to be 20.5m 3 Compared with the disclosed method, the amount of acid solution increased by 4.5m 3 , there is a problem of excessive acid design.

[0083] The above-described embodiments are only embodiments of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present disclosure. It should be noted that, for a person of ordinary skill in the art, without departing from the concept of the present disclosure, several variations, equivalent substitutions, improvements, etc. may be made, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the attached claims.

Claims

1. A method for quantitatively determining the contamination radius of an under-injected well in a sandstone reservoir, characterized in that: include: Get the daily injection volume Q of the under-injected well 配 Or the actual daily injection volume Q on the selected date 选 ; Determine the pollution factors of the under-injection well and the pollution coefficient a corresponding to each pollution factor; Calculating the converted thickness h, injection volume conversion coefficient b, reservoir pressure conversion coefficient c and connection direction coefficient γ of the under-injection well; Substitute the above parameter values ​​into the calculation formula to obtain the pollution radius r corresponding to each pollution factor of the under-injection well 单因素污染半径 ; The calculation formula is: 单因素污染半径 =γ×a×(Q / h) 1 / 2 ×ln(c / b); Where: Q is Q 配 or Q 选 .

2. The method for quantitatively determining the contamination radius of an under-injected well in a sandstone reservoir according to claim 1, characterized in that: The method for determining the pollution coefficient a includes: The injection water quality of the under-injection well is obtained, the pollution factors are determined according to the pollutant composition in the injection water quality, and the pollution coefficient a corresponding to each pollution factor is determined according to the blockage type included in the pollution factor.

3. The method for quantitatively determining the contamination radius of an under-injected well in a sandstone reservoir according to claim 2, characterized in that: The blockage types are divided into mud, oil wax, mechanical impurities, clay and polymer blockage; the pollution coefficients a corresponding to each blockage type are: mud 0.15, oil wax 0.4, mechanical impurities 0.65, clay 0.85, polymer 0.

95.

4. The method for quantitatively determining the contamination radius of an under-injection well in a sandstone reservoir according to any one of claims 1 to 3, characterized in that: The calculation formula of the converted thickness h is: h=h 有效 +(1 / 4~1 / 2)×(h 射开 -h 有效 ); Where: h 射开 is the opening thickness, m; h 有效 is the effective thickness of the opening, m.

5. The method for quantitatively determining the contamination radius of an under-injected well in a sandstone reservoir according to claim 4, characterized in that: The calculation formula of the injection volume conversion coefficient b is: b=(Q 目前实注 / Q) 2 / 3 ; Where: Q 目前实注 The current daily injection volume Q 目前实注 , m 3 ; If the daily actual injection volume is 0, the value is assigned to 1.

6. The method for quantitatively determining the contamination radius of an under-injected well in a sandstone reservoir according to claim 5, characterized in that: The calculation formula of the oil layer pressure conversion coefficient c is: c=[(P 目前油压+ H / 100-P 目前油层压力 ) / (P 初始油压+ H / 100-P 初始油层压力 )] 2 / 3 ; Where: P 目前油压 is the current injection pressure, MPa; H is the reservoir depth, m; P 目前油层压力 is the current reservoir pressure, MPa; P 初始油压 is the initial injection pressure or the injection pressure on the selected date, MPa; P 初始油层压力 is the original formation pressure or the reservoir pressure on a selected date, MPa.

7. The method for quantitatively determining the contamination radius of an under-injected well in a sandstone reservoir according to claim 6, characterized in that: The calculation formula of the connectivity direction coefficient γ is: γ=(n / 6) -1 / 2 ; Where: n is the number of connected wells.

8. A method for quantitatively determining the acidizing radius of an under-injected well in a sandstone reservoir, characterized in that: include: Determine the pollution radius r corresponding to each pollution factor of the under-injection well according to the method described in any one of claims 1 to 7 单因素污染半径 ; If the under-injected well is contaminated by a single factor, the deblocking acidizing radius R corresponding to the single factor contamination is 酸化半径 =r 单因素污染半径 +0.2m; If the under-injected well is contaminated by two factors, the deblocking acidizing radius R corresponding to each contamination factor is 酸化半径 and the pollution radius r calculated based on the corresponding pollution factors 单因素污染半径 equal.

9. A method for determining the amount of acid solution for unblocking an under-injected well in a sandstone reservoir, characterized in that: include: Determine the acidizing radius corresponding to each contamination factor of the under-injection well according to the method of claim 8; The amount of acid solution for unblocking corresponding to each pollution factor is calculated using the acidizing radius corresponding to each pollution factor, and the total amount of acid solution for unblocking the under-injection well is equal to the sum of the amount of acid solution for unblocking corresponding to each pollution factor.

10. The method for determining the amount of acid solution for unblocking under-injection wells in sandstone reservoirs according to claim 9, characterized in that: The formula used for the calculation is: Amount of acid for unblocking Where: is the porosity, h is the converted thickness, m.

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