Method for quantitatively determining thermal recovery validity period of steam huff and puff well

Abstract

The invention discloses a method for quantitatively determining the thermal recovery validity period of a steam huff and puff well. The method comprises the steps that S1, production dynamic data are obtained; s2, calculating a steam huff and puff yield increase coefficient and reading a yield increase coefficient peak value within production time; s3, calculating the residual degree of the steam huff and puff synergistic effect; s4, a steam huff and puff synergistic effect residual degree-time curve is drawn, a thermal recovery failure interval is determined, and the starting time of the thermal recovery failure interval is recorded; s5, calculating the residual degree variance of the steam huff and puff synergistic effect; s6, drawing a steam huff and puff synergistic effect residual degree variance-production time relation curve; and S7, determining the validity period of steam huff and puff. The method can be quantified, is wide in application range, is suitable for steam huff and puff of different types of thickened oil, can also be used for hot water chemical composite huff and puff and steam chemical composite huff and puff of different types of thickened oil, and has important significance for guiding efficient development of a steam huff and puff well.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas field development, and particularly relates to a method for quantitatively determining the effective period of thermal recovery of steam soak wells. Background Art

[0002] Due to the high viscosity of formation crude oil in heavy oil reservoirs, the flowing ability of crude oil in the formation is poor. Conventional development has low productivity and poor economic benefits. By heating to reduce viscosity, the viscosity can be greatly reduced, thereby increasing the seepage ability of heavy oil in porous media. Development practices in domestic and foreign heavy oil fields over the years have shown that steam soak is one of the most effective heavy oil thermal recovery development technologies, which can greatly improve the recovery factor of heavy oil fields. Bohai Oilfield has successively practiced the technology of improving recovery factor by steam soak in such oilfields as Luda 27-2, Luda 21-2, and the north of Luda 5-2. After steam soak, the single-well productivity has been greatly improved, and many thermal recovery wells with a production of over 100 cubic meters have been achieved, obtaining good development results. Since the steam soak technology mainly relies on the heating and viscosity reduction effect of injected steam to improve the productivity of oil wells, a large amount of funds are required during the heat injection stage; and with the production and dissipation of the injected heat, the efficiency enhancement effect will gradually fail, and it is necessary to transfer to the next round of steam soak in a timely manner. Therefore, quantitatively determining the effective period of thermal recovery is of great significance for evaluating the economy of steam soak measures and determining the reasonable production time, etc.

[0003] Currently, for determining the effective period of steam soak wells, the commonly used methods are the flowing temperature method and the dimensionless specific oil production index method. By monitoring the flowing temperature and dimensionless specific oil production index of thermal recovery wells, when they are the same as those in the cold production stage, it is considered that the effective period of thermal recovery is reached. However, since most thermal recovery wells do not have a pre-existing cold production stage, it is difficult to obtain the flowing temperature and dimensionless specific oil production index in the cold production stage; at the same time, since steam soak is a depletion development, the static pressure shows a downward trend with the progress of production, but the static pressure test period of heavy oil reservoirs is long and it is difficult to obtain, so it is difficult to obtain the dimensionless specific oil production index in the production stage; in summary, the results obtained by these two methods usually have large errors and it is difficult to obtain the specific value of the effective period of steam soak. Currently, there is no mature technical solution in the industry to quantitatively obtain the effective period of steam soak of thermal recovery wells. Summary of the Invention

[0004] The present invention is proposed to solve the problem of quantitatively determining the effective period of thermal recovery of steam soak in the absence of cold production stage data and static pressure test data in the prior art, and its purpose is to provide a method for quantitatively determining the effective period of thermal recovery of steam soak wells.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for quantitatively determining the effective period of thermal recovery of steam soak wells, comprising the following steps:

[0007] S1. Obtain the production performance data after the blowdown and startup of the steam soak well;

[0008] S2. Calculate the daily steam soak production increase coefficient α during the production time of the steam soak well and read the peak value of the production increase coefficient during the production time, and record the peak value as the production increase coefficient peak value α0;

[0009] S3. Calculate the residual degree of the steam soak efficiency improvement effect on the i-th day during the production time of the steam soak well;

[0010] S4. Plot the curve of the residual degree of the steam soak efficiency improvement effect - time, determine the hot production failure interval, and record the start time of the hot production failure interval;

[0011] S5. Calculate the variance of the residual degree of the steam soak efficiency improvement effect;

[0012] S6. Plot the relationship curve of the residual degree of the steam soak efficiency improvement effect - production time;

[0013] S7. Determine the steam soak effective period.

[0014] In the above technical solution, the production performance data in step S1 includes the daily oil production of the oil well and the bottom-hole flowing pressure; the unit of the daily oil production of the oil well is m 3 / d or t / d; the unit of the bottom-hole flowing pressure is MPa or psi.

[0015] In the above technical solution, the calculation formula of the steam soak production increase coefficient is:

[0016] α = daily oil production of the oil well × bottom-hole flowing pressure

[0017] In the formula: α is the steam soak production increase coefficient, and the unit is m 3 ×MPa / d; the unit of the daily oil production of the oil well is m 3 / d; the unit of the bottom-hole flowing pressure is MPa.

[0018] In the above technical solution, the calculation formula of the residual degree of the steam soak efficiency improvement effect on the i-th day during the production time of the steam soak well is:

[0019] β i = α i / α0

[0020] In the formula: β i is the residual degree of the steam soak efficiency improvement effect on the i-th day during the production time of the steam soak well, which is a dimensionless quantity;

[0021] α i is the steam soak production increase coefficient on the i-th day during the production time of the steam soak well, and the unit is m 3 ×MPa / d;

[0022] α0 is the peak value of the production increase coefficient during the production time, with the unit of m 3 ×MPa / d;

[0023] The remaining degree β of the steam stimulation efficiency enhancement effect on the i-th day i In the calculation process, the denominator is not limited to the peak value of the production increase coefficient during the production time, and can also be the production increase coefficient on any day within the effective period.

[0024] In the above technical solution, the remaining degree-time curve of the steam stimulation efficiency enhancement effect takes time as the abscissa and the remaining degree of the steam stimulation efficiency enhancement effect as the ordinate; the thermal recovery failure interval is the flat section on the remaining degree-time curve of the steam stimulation efficiency enhancement effect; the starting time of the thermal recovery failure interval is the starting time of the flat section of the remaining degree-time curve of the steam stimulation efficiency enhancement effect. Generally, the remaining degree β of the steam stimulation efficiency enhancement effect i shows a gradually decreasing trend, representing the gradual deterioration of the thermal recovery effect.

[0025] In the above technical solution, the calculation method of the variance of the remaining degree of the steam stimulation efficiency enhancement effect is specifically as follows: Taking N days before the starting time t0 of the thermal recovery failure interval as the starting point, calculate the variance of the remaining degree of the steam stimulation efficiency enhancement effect in the previous N days for each time point.

[0026] In the above technical solution, the calculation method of the variance of the remaining degree of the steam stimulation efficiency enhancement effect includes the overall variance method, the standard deviation method or the mean square error method;

[0027] Taking the weighted average method as an example, the calculation formula is specifically as follows:

[0028]

[0029] In the formula: β i is the remaining degree of the steam stimulation efficiency enhancement effect on the i-th day during the production time of the steam stimulation well, which is a dimensionless quantity;

[0030] n is the time period for calculating the variance, corresponding to the time pushed forward, with the unit of d;

[0031] is the average value of the remaining degree of the steam stimulation efficiency enhancement effect within n days, which is a dimensionless quantity;

[0032] δ i is the variance of the remaining degree of the steam stimulation efficiency enhancement effect on the i-th day, which is a dimensionless quantity.

[0033] In the above technical solution, N is any integer between 30 and 60; in the calculation process of the residual degree variance of the steam huff and puff efficiency enhancement effect, the starting time t0 is pushed back N days, and the value range of N is generally recommended to be greater than 1 month (or 30 days) and less than 2 months (or 60 days); the larger the value of N, the higher the accuracy of the calculated validity period, but it will cause the production time after the validity period to be extended, affecting the oil well output; the smaller the value of N, the greater the impact of production fluctuations on the validity period, reducing the accuracy of the calculated validity period.

[0034] In the above technical solution, the relationship curve of the residual degree variance of the steam huff and puff efficiency enhancement effect - production time has time as the abscissa and the residual degree variance of the steam huff and puff efficiency enhancement effect as the ordinate, and the ordinate is plotted using a logarithmic coordinate system.

[0035] In the above technical solution, the specific method for determining the steam huff and puff validity period is: read the time t when the relationship curve of the residual degree variance of the steam huff and puff efficiency enhancement effect - production time first reaches the minimum value min , then t min - The time corresponding to N days is the steam huff and puff validity period, and the N here is the same value as the N for pushing back N days in the calculation of the residual degree variance of the steam huff and puff efficiency enhancement effect.

[0036] The beneficial effects of the present invention are:

[0037] The present invention provides a method for quantitatively determining the thermal recovery validity period of steam huff and puff wells. The steam huff and puff production increase coefficient is calculated by using the easily obtained daily oil production and bottom hole flowing pressure data of oil wells, and then the residual degree of the steam huff and puff efficiency enhancement effect is determined by the ratio of the steam huff and puff production increase coefficients. A curve is plotted with the residual degree of the steam huff and puff efficiency enhancement effect and time, and then the time range of steam huff and puff thermal recovery failure is determined. Finally, the steam huff and puff validity period is determined by the analysis of variance method; the method has the advantages of easy calculation, quantifiable, high precision, etc., and solves the problem of quantitative evaluation of the cycle validity period of steam huff and puff wells lacking cold production stage data and static pressure test data; the method is not only applicable to the effect evaluation of measures such as steam huff and puff and thermal composite huff and puff, but also applicable to the judgment of the reasonable cycle transfer time of measures such as steam huff and puff and thermal composite huff and puff, and has important significance for the efficient development of thermal recovery wells in heavy oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the flow chart of the method of the present invention;

[0039] Figure 2 is the curve graph of the residual degree of the steam huff and puff efficiency enhancement effect and production time in Embodiment 1 of the present invention;

[0040] Figure 3 is the curve graph of the residual degree variance of the steam huff and puff efficiency enhancement effect and production time in Embodiment 1 of the present invention;

[0041] Figure 4 It is the determination diagram of the effective period of thermal recovery of the target steam stimulation well in Embodiment 1 of the present invention;

[0042] Figure 5 It is the curve graph of the residual degree of steam stimulation efficiency increase and production time in Embodiment 2 of the present invention;

[0043] Figure 6 It is the curve graph of the variance of the residual degree of steam stimulation efficiency increase and production time of steam stimulation well B12H in Embodiment 2 of the present invention;

[0044] Figure 7 It is the determination diagram of the effective period of thermal recovery of steam stimulation well B12H in Embodiment 2 of the present invention.

[0045] For those of ordinary skill in the art, without creative efforts, other relevant drawings can be obtained based on the above drawings. Detailed implementation manners

[0046] In order to enable the personnel in the technical field to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the drawings in the specification and through specific implementation manners.

[0047] Embodiment 1

[0048] A method for quantitatively determining the effective period of thermal recovery of a steam stimulation well, as Figure 1 shown, includes the following steps:

[0049] S1. Obtain the daily oil production and bottom-hole flowing pressure data of the oil well. The specific operation is to obtain the daily oil production of the target oil well and the bottom-hole flowing pressure data at the corresponding time in days. The unit of daily oil production is m 3 / d or t / d, and the unit of bottom-hole flowing pressure is MPa or psi, as shown in Table 1;

[0050] Table 1 Example table of data of target steam stimulation well

[0051]

[0052]

[0053]

[0054] S2. Calculate the steam stimulation production increase coefficient α and read the peak value α0 of the production increase coefficient. The specific operation is to calculate the production increase coefficient according to the formula. The production increase coefficient α = daily oil production × bottom-hole flowing pressure; read the peak value α0 of the production increase coefficient. In the example, the peak value is reached at the production time of 9 days, and α0 = 727.28 (m 3 ×MPa) / d, as shown in Table 2;

[0055] Table 2 Calculation Example Table of Production Increase Coefficient of Target Steam Huff and Puff Wells (First 40 Days)

[0056]

[0057] S3. Calculate the residual degree βi of the steam huff and puff efficiency improvement effect at different times. The specific operation is to use the production increase coefficient on the i-th day of steam huff and puff production as the numerator and the peak production increase coefficient as the denominator to calculate the residual degree of the steam huff and puff efficiency improvement effect on the i-th day, denoted as β i , as shown in Table 3;

[0058] Table 3 Ratio β of Production Increase Coefficient of Target Steam Huff and Puff Wells i Calculation Example Table (First 40 Days)

[0059]

[0060]

[0061] S4. Plot the curve of the residual degree βi of the steam huff and puff efficiency improvement effect - time to determine the interval of thermal recovery failure. The specific operation is to use time as the abscissa and the residual degree β of the steam huff and puff efficiency improvement effect i as the ordinate to plot the change curve of the residual degree β of the steam huff and puff efficiency improvement effect i and the production time. The stable section on the curve represents the time interval of thermal recovery failure, and record the starting time t0 of the stable section. Such as Figure 2 ;

[0062] S5. Variance analysis of the residual degree of the steam huff and puff efficiency improvement effect. The specific operation is to use the starting time t of the stable section 0＝ 30 days before pushing 150 days forward as the starting point, and calculate the variance of the residual degree of the steam huff and puff efficiency improvement effect in the previous 30 days for each time point;

[0063] Table 4 Residual Degree β of Steam Huff and Puff Efficiency Improvement Effect of Target Steam Huff and Puff Wells i Calculation Example Table (150d - 189d)

[0064]

[0065] S6. Plot the relationship curve of the variance of the residual degree of the steam huff and puff efficiency improvement effect - production time. The specific operation is to use time as the abscissa and the variance of the residual degree of the steam huff and puff efficiency improvement effect as the ordinate, and the ordinate uses a logarithmic coordinate system to plot the relationship curve of the variance of the residual degree of the steam huff and puff efficiency improvement effect - production time, and the result is shown in Figure 3 ;

[0066] S7. Determine the effective period of steam huff and puff. The specific operation is to read the time t when the relationship curve of the variance of the residual degree β of the steam huff and puff efficiency improvement effect - production time first reaches the minimum value i ​min = 243d, then the time corresponding to (t min - 30) is the effective period of steam huff and puff, and the effective period of the target steam huff and puff well is 213d, see Figure 4 .

[0067] Through this method, the effective period of thermal recovery of steam huff and puff can be quantitatively determined on the basis of lacking data of cold production stage and static pressure test data. It provides a reference for the effect evaluation of measures such as steam huff and puff, thermal compound huff and puff, etc., and the judgment of the reasonable cycle conversion time of measures such as steam huff and puff, thermal compound huff and puff, etc., and guides the efficient development of steam huff and puff wells.

[0068] Example 2

[0069] A method for quantitatively determining the effective period of thermal recovery of steam huff and puff wells is adopted to determine the effective period of steam huff and puff for Well B12H in a certain steam huff and puff oilfield in the Bohai Sea. The process is as follows:

[0070] S1. Obtain the daily oil production and bottom hole flowing pressure data of the oil well. The specific operation is to obtain the daily oil production of the target oil well and the bottom hole flowing pressure data at the corresponding time in days. The unit of daily oil production is m 3 / d, and the unit of bottom hole flowing pressure is MPa, as shown in Table 5;

[0071] Table 5 Example table of production data of steam huff and puff well B12H

[0072]

[0073]

[0074] S2. Calculate the steam huff and puff production increase coefficient α and read the peak production increase coefficient α0. The specific operation is to calculate the production increase coefficient according to the formula. The production increase coefficient α = daily oil production × bottom hole flowing pressure; read the peak α0 of the production increase coefficient. Well B12H reaches the peak at the production time of 32d, and α0 = 756.72 (m 3 ×MPa) / d, as shown in Table 6;

[0075] Table 6 Example table of production increase coefficient calculation of steam huff and puff well B12H (the first 40 days)

[0076]

[0077]

[0078] S3. Calculate the residual degree of steam huff and puff efficiency enhancement effect at different times. The specific operation is to use the production increase coefficient on the i-th day of steam huff and puff production as the numerator and the peak production increase coefficient as the denominator to calculate the residual degree of steam huff and puff efficiency enhancement effect on the i-th day, denoted as β i , as shown in Table 7;

[0079] Table 7 Ratio β of production increase coefficient of steam soak well B12H i Calculation example table (first 40 days)

[0080]

[0081] S4. Plot the curve of the residual degree βi of steam soak production increase effect against time to determine the hot production failure interval. The specific operation is to use time as the abscissa and the residual degree β of steam soak production increase effect i as the ordinate to plot the curve of the residual degree β of steam soak production increase effect i against the production time. The stable section on the curve represents the time interval of hot production failure, and record the starting time t0 = 170d of the stable section. As Figure 5 ;

[0082] S5. Analysis of variance of the residual degree of steam soak production increase effect. The specific operation is to use the starting time t of the stable section 0＝ Push forward 30 days before 170d as the starting point, and calculate the variance of the residual degree of steam soak production increase effect for the first 30 days at each time point;

[0083] Table 8 Residual degree β of steam soak production increase effect of steam soak well B12H i Calculation example table (170d - 209d)

[0084]

[0085]

[0086] S6. Plot the relationship curve of the variance of the residual degree of steam soak production increase effect - production time. The specific operation is to use time as the abscissa and the variance of the residual degree of steam soak production increase effect as the ordinate. The ordinate uses a logarithmic coordinate system to plot the relationship curve of the variance of the residual degree of steam soak production increase effect - production time, and the result is shown in Figure 6 ;

[0087] S7. Determine the effective period of steam soak. The specific operation is to read the time t when the relationship curve of the variance of the residual degree of steam soak production increase effect - production time reaches the minimum value for the first time min = 229d, then the time corresponding to (t min - 30) is the effective period of steam soak. The effective period of the target steam soak well is 199d, as shown in Figure 7 .

[0088] Principle of the present invention:

[0089] The present invention introduces the concept of production increase coefficient (production increase coefficient = oil production × bottom-hole flowing pressure), uses the easily obtained production and flowing pressure data of oil wells to draw the decline curve of the production increase coefficient with production time, and obtains the time point when the production increase coefficient drops to stability through variance analysis. This time point represents that the effect of thermal recovery on improving production capacity has failed and can be used as the end time point of the effective period of steam stimulation, with strong operability.

[0090] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for quantitatively determining the effective period of thermal recovery in steam huff and puff wells, characterized in that: It includes the following steps: S1. Obtain the production dynamic data after the steam huff and puff well is put into production with blowdown; S2. Calculate the daily steam huff and puff incremental production coefficient during the production time of the steam huff and puff well and read the peak value of the incremental production coefficient during the production time, and record the peak value as the peak value of the incremental production coefficient; S3. Calculate the residual degree of the steam huff and puff efficiency improvement effect on the i-th day during the production time of the steam huff and puff well; S4. Plot the curve of the residual degree of the steam huff and puff efficiency improvement effect - time, determine the thermal recovery failure interval, and record the starting time of the thermal recovery failure interval; S5. Calculate the variance of the residual degree of the steam huff and puff efficiency improvement effect; S6. Plot the relationship curve of the variance of the residual degree of the steam huff and puff efficiency improvement effect - production time; S7. Determine the effective period of the steam huff and puff.

2. The method for quantitatively determining the effective period of thermal recovery in steam stimulation wells according to claim 1, characterized in that: The production dynamic data in step S1 includes the daily oil production of the oil well and the bottom hole flowing pressure.

3. The method for quantitatively determining the effective period of thermal recovery of steam stimulation wells according to claim 1, characterized in that: The calculation formula of the steam huff and puff incremental production coefficient is: α = daily oil production of the oil well × bottom hole flowing pressure Where: α is the steam stimulation incremental production coefficient, with the unit of m 3 ×MPa / d; the unit of the daily oil production of the oil well is m 3 / d; the unit of the bottom-hole flowing pressure is MPa.

4. The method for quantitatively determining the effective period of thermal recovery in steam huff and puff wells according to claim 1, characterized in that: The calculation formula of the residual degree of the steam huff and puff efficiency improvement effect on the i-th day during the production time of the steam huff and puff well is: β i ＝α i / α0 Where: β i is the residual degree of the enhanced steam stimulation effect on the i-th day during the production time of the steam stimulation well, which is a dimensionless quantity; α i is the steam stimulation incremental production coefficient on the i-th day during the production time of the steam stimulation well, with the unit of m 3 ×MPa / d; α0 is the peak value of the production increase coefficient during the production time, with the unit of m 3 ×MPa / d.

5. The method for quantitatively determining the effective period of thermal recovery in steam huff and puff wells according to claim 1, characterized in that: The curve of the residual degree of the steam huff and puff efficiency improvement effect - time takes time as the abscissa and the residual degree of the steam huff and puff efficiency improvement effect as the ordinate; the thermal recovery failure interval is the flat section on the curve of the residual degree of the steam huff and puff efficiency improvement effect - time; the starting time of the thermal recovery failure interval is the starting time of the flat section of the curve of the residual degree of the steam huff and puff efficiency improvement effect - time.

6. The method for quantitatively determining the effective period of thermal recovery in steam stimulation wells according to claim 1, wherein: The specific calculation method of the variance of the residual degree of the steam huff and puff efficiency improvement effect is: taking N days before the starting time t0 of the thermal recovery failure interval as the starting point, calculate the variance of the residual degree of the steam huff and puff efficiency improvement effect for the previous N days at each time point.

7. The method for quantitatively determining the effective period of thermal recovery in steam stimulation wells according to claim 6, characterized in that: The calculation method of the variance of the residual degree of the steam huff and puff efficiency improvement effect includes the overall variance method, the standard deviation method or the mean square error method.

8. The method for quantitatively determining the effective period of thermal recovery in steam stimulation wells according to claim 6, wherein: The N takes any integer between 30 and 60.

9. The method for quantitatively determining the effective period of thermal recovery of steam stimulation wells according to claim 1, characterized in that: The relationship curve of the variance of the residual degree of the steam huff and puff efficiency improvement effect - production time takes time as the abscissa and the variance of the residual degree of the steam huff and puff efficiency improvement effect as the ordinate, and the ordinate is plotted using a logarithmic coordinate system.

10. The method for quantitatively determining the effective period of thermal recovery of steam huff and puff wells according to claim 1, wherein: The specific method for determining the effective period of steam huff and puff is as follows: read the time t when the relationship curve of the residual degree variance of the steam huff and puff enhancement effect - production time reaches the minimum value for the first time min , then the time corresponding to t min - N days is the effective period of steam huff and puff.

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