Method and device for identifying energy supplement timing for carbonate rock reservoirs

Abstract

The present invention provides a method for identifying the energy replenishment timing for carbonate rock reservoirs, which includes: collecting the energy change data of a target well during the flowing well period and the stable production stage, and drawing an energy indication curve of the target well based on the energy change data; calculating the energy coefficient of the target well during the flowing well period, and combining the energy change data to obtain the classification result of the natural energy level of the target well according to the energy strength classification standard; dividing the production stage of the target well according to the change trend of the energy indication curve, calculating the energy coefficient corresponding to each production stage, and determining the energy replenishment timing in combination with the natural energy level classification result. On the basis of fully evaluating the mutual relationship between the bottom hole flowing pressure and the cumulative production during the production process of the oil well, through the analysis of the energy indication curves of a large number of production wells on site and in combination with the characteristics of the production dynamic curves, the present invention divides the boundaries of the energy indication curves of oil wells under different natural energy conditions indicating the weakening of the oil well energy and the boundaries for taking effective energy replenishment measures.

Description

Technical Field

[0001] The present invention relates to the technical field of unconventional oil and gas reservoir energy development, and more specifically, to a method and device for identifying the timing of energy replenishment for carbonate oil reservoirs. Background Art

[0002] During the development process of an oil reservoir, it is necessary to consider the pressure maintenance situation, production changes, and the law of water cut increase to diagnose the current development status of oil wells, and consider tapping the development potential by means of water injection or gas injection. An important criterion for determining the timing of water injection and gas injection is to judge the strength of energy, and then identify the timing of energy replenishment.

[0003] In the prior art, to evaluate the elastic energy of an oil reservoir, based on data such as reservoir, fluid properties, and actual production dynamic data, the dimensionless elastic production ratio N pr and the formation pressure drop D for every 1% of geological reserves produced pr can be used to make a quantitative evaluation. Among them, N pr reflects the ratio of the actual elastic production to the theoretical elastic production under closed conditions. The larger this value, the more sufficient the elastic energy replenishment. D pr reflects the sufficiency of the elastic energy of the oil reservoir. The smaller this value, the more sufficient the elastic energy of the oil reservoir.

[0004] However, the prior art has the following problems:

[0005] First, production dynamic data cannot intuitively reflect the energy change characteristics of the oil reservoir.

[0006] In the prior art, based on the analysis of the characteristics and variation laws of on-site production dynamic curves, and by comprehensively considering data such as oil production, water cut, oil wellhead pressure, casing pressure, and flowing pressure tests, the change of working system and the law of production decline can be dynamically identified. For carbonate oil reservoirs, due to the interference of production measures, it is difficult to directly reflect the strength of energy change from the curves of production or water cut changing with time. At the same time, the size of the formation energy of carbonate oil reservoirs determines the mutual relationship between production and pressure during the actual production process of oil wells.

[0007] Second, the existing energy grading and quantification standards rely heavily on the calculation of geological reserves.

[0008] In the prior art, using the commonly used elastic energy evaluation indexes on site to judge the strength of energy requires the calculation of relatively accurate geological reserves. However, the reservoir space in fractured-vuggy carbonate oil reservoirs is complex, and the oil-water distribution law is different from that of conventional sandstone oil reservoirs. It is difficult to accurately determine each parameter during the calculation of geological reserves. Therefore, the geological reserves calculated by different methods vary greatly, and it is impossible to meet the calculation of energy evaluation parameters such as dimensionless elastic production ratio and the grading of energy.

[0009] Third, there is a lack of a method for identifying the energy replenishment timing that takes into account the differences in the natural energy of the near-wellbore formations of individual wells at the well site.

[0010] Generally speaking, differences in the reservoir body types and distributions of fractured-vuggy carbonate rock reservoirs, as well as the original oil and gas filling conditions, etc., result in different natural energies near each well. In the prior art, when using a unified standard to identify the energy replenishment timing, it is difficult to balance the energy fluctuation differences caused by different natural energy levels, and thus it is impossible to objectively reflect the true timing when an oil well needs to replenish energy.

[0011] Therefore, the present invention provides a method and device for identifying the energy replenishment timing for carbonate rock oil reservoirs. Summary of the Invention

[0012] To solve the above problems, the present invention provides a method for identifying the energy replenishment timing for carbonate rock oil reservoirs, and the method includes the following steps:

[0013] Step 1: Collect the energy change data of the target well during the flowing well period and the stable production stage, and draw an energy indicator curve of the target well based on the energy change data;

[0014] Step 2: Calculate the energy coefficient of the target well during the flowing well period, and combine the energy change data to obtain the classification result of the natural energy level of the target well according to the energy strength classification standard;

[0015] Step 3: Divide the production stage of the target well according to the change trend of the energy indicator curve, calculate the energy coefficient corresponding to each production stage, and determine the energy replenishment timing in combination with the classification result of the natural energy level.

[0016] According to an embodiment of the present invention, the energy change data includes cumulative production data and bottom-hole flowing pressure data, and the energy indicator curve is drawn with the cumulative production data as the horizontal axis and the bottom-hole flowing pressure data as the vertical axis.

[0017] According to an embodiment of the present invention, the following steps are specifically included in Step 2:

[0018] Statistical cumulative production data of the target well during the flowing well period, and determine the production level of the target well according to the production level standard in the energy strength classification standard.

[0019] According to an embodiment of the present invention, the following steps are specifically included in Step 2:

[0020] Perform curve fitting on the energy indicator curve of the target well during the flowing well period to obtain a fitting curve during the flowing well period;

[0021] Take the slope of the fitting curve during the flowing well period as the energy coefficient during the flowing well period;

[0022] Based on the energy coefficient during the natural flow period, determine the energy coefficient level of the target well according to the coefficient standard in the energy strength classification standard.

[0023] According to an embodiment of the present invention, the specific steps in step two include the following steps:

[0024] Based on the production level and the energy coefficient level, combine the energy strength classification standard to obtain the classification result of the natural energy level.

[0025] According to an embodiment of the present invention, the specific steps in step two include the following steps:

[0026] Judge whether both the production level and the energy coefficient level point to the same natural energy level;

[0027] If the judgment result is yes, use the current natural energy level as the classification result of the natural energy level of the target well.

[0028] According to an embodiment of the present invention, the specific steps in step three include the following steps:

[0029] Perform curve fitting on the energy indication curve corresponding to each production stage to obtain a fitting curve corresponding to each production stage one by one;

[0030] Calculate the slope of the fitting curve of each production stage as the energy coefficient corresponding to each production stage.

[0031] According to an embodiment of the present invention, the specific steps in step three include the following steps:

[0032] Calculate the difference between the energy coefficient of the latter production stage and the energy coefficient of the previous production stage to obtain a difference result;

[0033] Based on the difference result and the energy coefficient during the natural flow period, calculate a supplementary timing coefficient;

[0034] Based on the supplementary timing coefficient and the classification result of the natural energy level, combine the supplementary timing standard to determine the energy supplementary timing.

[0035] According to an embodiment of the present invention, the specific steps in step three include the following steps:

[0036] Use the difference result as the dividend and the energy coefficient during the natural flow period as the divisor to perform a division operation, and use the obtained quotient as the supplementary timing coefficient.

[0037] According to another aspect of the present invention, there is also provided an energy supplementary timing identification device for a carbonate rock reservoir, and the device includes:

[0038] The first module is used to collect the energy change data of the target well during the natural flow period and the stable production stage, and draw an energy indicator curve of the target well based on the energy change data;

[0039] The second module is used to calculate the energy coefficient of the target well during the natural flow period, and combine the energy change data to obtain the classification result of the natural energy level of the target well according to the energy strength classification standard;

[0040] The third module is used to divide the production stage of the target well according to the change trend of the energy indicator curve, calculate the energy coefficient corresponding to each production stage, and determine the energy supplement timing in combination with the natural energy level classification result.

[0041] The energy supplement timing identification method and device for carbonate reservoirs provided by the present invention are based on a full evaluation of the mutual relationship between the bottom hole flowing pressure and the cumulative production during the production process of the oil well. Through the analysis of the energy indicator curves of a large number of production wells on site and in combination with the characteristics of the production performance curves, the boundaries of the energy indicator curves of different oil wells under different natural energy conditions indicating that the energy of the oil well weakens and effective energy supplement measures need to be taken are divided. The energy attenuation law of the oil well is indicated by the change rate of the energy indicator curve, the production characteristics of different energy strength stages of the oil well are indicated by the cumulative production during the evaluation stage, and the energy supplement timing identification method determined by the comprehensive constraint of the cumulative production and the slope of the energy indicator curve can effectively evaluate the change of the energy strength of the oil well, and then determine the energy supplement timing in combination with the production performance analysis.

[0042] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the structures specifically pointed out in the specification, the claims, and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0044] Figure 1 Shows a flow chart of a method for identifying the energy supplement timing for a carbonate reservoir according to an embodiment of the present invention;

[0045] Figure 2 Shows a flow chart of a method for determining the energy coefficient level of a target well according to an embodiment of the present invention;

[0046] Figure 3 Shows a flow chart of a method for determining the energy supplement timing according to an embodiment of the present invention;

[0047] Figure 4 shows an energy indication curve with a relatively slow energy decline according to an embodiment of the present invention;

[0048] Figure 5 shows an energy indication curve with a relatively fast energy decline according to an embodiment of the present invention;

[0049] Figure 6 shows a schematic diagram of energy grading boundaries according to an embodiment of the present invention;

[0050] Figure 7 shows the energy indication curve of Well TH10346 according to an embodiment of the present invention;

[0051] Figure 8 shows the energy indication curves of each stage of Well TH10346 according to an embodiment of the present invention;

[0052] Figure 9 shows the structural block diagram of an energy replenishment timing identification device for carbonate rock reservoirs according to an embodiment of the present invention. Detailed implementation manners

[0053] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the embodiments of the present invention in detail with reference to the accompanying drawings.

[0054] In the prior art, to evaluate the elastic energy of an oil reservoir, based on data such as reservoir, fluid properties, and actual production dynamic data, the dimensionless elastic production ratio N pr and the formation pressure drop D for every 1% of geological reserves produced pr can be used to make a quantitative evaluation. Among them, N pr reflects the ratio of the actual elastic production to the theoretical elastic production under closed conditions. The larger this value is, the more sufficient the elastic energy replenishment is. D pr reflects the sufficiency of the elastic energy of the oil reservoir. The smaller this value is, the more sufficient the elastic energy of the oil reservoir is. Its definition formula is as follows:

[0055]

[0056]

[0057] Among them, N pr represents the dimensionless elastic production ratio, N p represents the cumulative oil production, B 0 represents the formation oil volume factor, N represents the geological reserves, B oi represents the oil volume factor under original conditions, C t represents the total compressibility, P i represents the original formation pressure, Pc represents the critical pressure, D pr represents the formation pressure drop per 1% of the geological reserves produced.

[0058] In the prior art, the evaluation of the elastic energy of the reservoir is shown in Table 1 below:

[0059] Table 1 Evaluation of the elastic energy of the reservoir

[0060] Energy classification <![CDATA[N pr > <![CDATA[D pr / MPa]]> Energy level I ＞30 ＜0.2 Adequate II 10-30 0.2-0.8 Relatively adequate III 2-10 0.8-2.5 With a certain amount of energy Ⅳ ＜2 ＞2.5 Insufficient

[0061] In the prior art, the evaluation indexes (D pr , N pr ) of the elastic energy of the fracture-cavity unit in the Tahe Oilfield have the following boundary values as shown in Table 2:

[0062] Table 2 Boundary values of the evaluation indexes (D pr , N pr ) of the elastic energy of the fracture-cavity unit in the Tahe Oilfield

[0063]

[0064] In view of the problems in the prior art that the production performance data cannot intuitively reflect the characteristics of reservoir energy change, the energy grading and quantification standard in the prior art depends greatly on the calculation of geological reserves, and there is a lack of a method for identifying the energy replenishment timing considering the natural energy differences in the near-well formations of single wells on site, the present invention proposes a method and device for identifying the energy replenishment timing for carbonate reservoirs. The present invention can form an energy replenishment timing identification considering the characteristics of natural energy differences in the near-well formations of wells and is applicable to fracture-cavity type carbonate reservoirs, and is used in field practice and is easy to promote.

[0065] Figure 1 shows a flow chart of a method for identifying the energy replenishment timing for carbonate reservoirs according to an embodiment of the present invention.

[0066] As Figure 1 shown, in step S101, the energy change data of the target well during the flowing well period and the stable production stage is collected, and an energy indicator curve of the target well is drawn based on the energy change data.

[0067] Specifically, in step S101, the energy change data includes cumulative production data and bottom-hole flowing pressure data, and an energy indicator curve is drawn with the cumulative production data as the horizontal axis and the bottom-hole flowing pressure data as the vertical axis.

[0068] Generally speaking, in the early stage of natural flow, the energy indication curve generally has a stage of stable pressure decline. The corresponding curve form is a straight line with a certain slope, and the slopes of all energy indication curves are negative. This reflects that as the formation energy decreases during oilfield development, the wellhead pressure decreases accordingly. Moreover, the slopes of the energy indication curves of each well are different. The slopes of the energy indication curves of some wells are larger and the curves are flatter (the slope is negative), while the slopes of the energy indication curves of some wells are smaller and the curves are steeper.

[0069] In one embodiment, the physical meaning of the slope of the energy indication curve is that for every unit of underground fluid produced, the corresponding formation pressure loss will occur. Reflected in the wellhead dynamic data, it is the decrease of the wellhead pressure. Different slopes represent different formation pressure losses corresponding to the same production volume.

[0070] In one embodiment, the energy indication curve refers to the relationship curve between the cumulative production and the bottom-hole flowing pressure or the liquid level. It can directly reflect the change of formation energy within the exploited range, and can also reflect the situation of the wellbore communicating with the reservoir body, the physical properties of the reservoir, and the change of the well energy during the exploitation process, etc. During on-site application, analyze the relationship curve between pressure and cumulative oil production to guide the reasonable production of oil wells.

[0071] Due to the sufficient natural energy of the formation, after the fluid in the near-well formation is produced, the sufficient formation energy can be quickly replenished. Under the combined action of the energy loss of the produced fluid and the timely replenishment of the formation energy, it is manifested as a relatively slow decrease in the wellhead pressure (such as Figure 4 ), which is reflected as a relatively large slope of the energy indication curve and a relatively small formation pressure loss corresponding to a flatter curve. On the contrary, when the natural energy of the formation is insufficient, after the fluid in the near-well formation is produced, the sufficient formation energy is not enough to be quickly replenished. Under the combined action of the energy loss of the produced fluid and the timely replenishment of the formation energy, it is manifested as a relatively fast decrease in the wellhead pressure, and thus the slope of the energy indication curve is relatively small (such as Figure 5 ).

[0072] As Figure 1 shown, in step S102, calculate the energy coefficient of the target well during the natural flow period, and combine the energy change data to obtain the classification result of the natural energy level of the target well according to the energy strength classification standard.

[0073] In one embodiment, based on the production level and the energy coefficient level, combine the energy strength classification standard to obtain the classification result of the natural energy level.

[0074] Specifically, count the cumulative production data of the target well during the natural flow period, and determine the production level of the target well according to the production level standard in the energy strength classification standard.

[0075] Furthermore, the production level is divided into three levels, including: the first level, the second level, and the third level. The first level represents that the natural energy of the formation near the single well is sufficient, the second level represents that the natural energy of the formation near the single well is average, and the third level represents that the natural energy of the formation near the single well is insufficient.

[0076] Specifically, the target wells with cumulative production data greater than or equal to the first threshold are classified into the first level, the target wells with cumulative production data greater than the second threshold and less than the first threshold are classified into the second level, and the target wells with cumulative production data less than or equal to the second threshold are classified into the third level. In one embodiment, the first threshold is set to 50,000 tons, and the second threshold is set to 10,000 tons.

[0077] Regarding the energy coefficient level, Figure 2 shows a flowchart of a method for determining the energy coefficient level of a target well according to an embodiment of the present invention.

[0078] As Figure 2 shown, in step S201, curve fitting is performed on the energy indication curve of the target well during the flowing well period to obtain the fitting curve during the flowing well period. Specifically, the energy indication curve is generally a scatter plot, and curve fitting needs to be performed on the energy indication curve during the flowing well period to obtain the fitting curve during the flowing well period. Further, the energy indication curve of the target well is plotted, and a trend line is drawn for the stable straight line segment to obtain the slope of the energy indication curve of each well during the flowing well period, and the cumulative production data during the flowing well period is statistically analyzed, specifically the cumulative liquid production.

[0079] As Figure 2 shown, in step S202, the slope of the fitting curve during the flowing well period is used as the energy coefficient during the flowing well period. Specifically, for the obtained fitting curve during the flowing well period, the slope of the fitting curve during the flowing well period is calculated through its mathematical expression, and the obtained slope is used as the energy coefficient during the flowing well period.

[0080] As Figure 2 shown, in step S203, based on the energy coefficient during the flowing well period, the energy coefficient level of the target well is determined according to the coefficient standard in the energy strength classification standard.

[0081] Furthermore, the energy coefficient level is divided into three levels, including: the first level, the second level, and the third level. The first level represents that the natural energy of the formation near the single well is sufficient, the second level represents that the natural energy of the formation near the single well is average, and the third level represents that the natural energy of the formation near the single well is insufficient.

[0082] Specifically, target wells with an energy coefficient greater than or equal to the third threshold are classified into the first level, target wells with an energy coefficient greater than the fourth threshold and less than the third threshold are classified into the second level, and target wells with an energy coefficient less than or equal to the fourth threshold are classified into the third level. In one embodiment, the third threshold is -0.0001 and the fourth threshold is -0.005.

[0083] Further, in step S102, it is determined whether both the production level and the energy coefficient level point to the same natural energy level. If the determination result is yes, the current natural energy level is used as the classification result of the natural energy level of the target well.

[0084] For example, Figure 6 , target wells with a slope greater than or equal to -0.0001 and an accumulated liquid production greater than or equal to 50,000 tons correspond to target wells of the first level, that is, wells with sufficient energy (strong); target wells with a slope between -0.005 and -0.0001 and an accumulated liquid production between 10,000 and 50,000 tons correspond to target wells of the second level, that is, target wells with average energy (medium); target wells with a slope less than or equal to -0.005 and an accumulated liquid production less than or equal to 10,000 tons correspond to target wells of the third level, that is, wells with insufficient energy (weak).

[0085] Such as Figure 6 shown, in Area 3, the formation energy is strong, the formation pressure is well maintained, the stable production time is long, the absolute value of the slope of the energy indication curve of a single well is low, and the cumulative production during the flowing production stage is large; in Area 7, the formation energy is weak, the absolute value of the slope of the energy indication curve of a single well is high, and the cumulative production during the flowing production stage is small; in Area 5, the energy is medium.

[0086] In one embodiment, for regions 1, 2, 4, 6, 8, and 9 in the transition zone, Region 1 indicates small cumulative production and slow decline, and Region 9 indicates high cumulative production and fast decline. The decline in Region 2 is slow, the cumulative production in Region 6 is relatively high, belonging to sub-strong energy; the cumulative production in Region 4 is relatively low, and the decline in Region 8 is fast, belonging to sub-weak energy regions.

[0087] Generally speaking, for wells with a larger slope of the energy indication curve, the curve is flatter, and the cumulative liquid production during the flowing production period is generally higher; while for wells with a smaller slope, the curve is steeper, and the cumulative liquid production during the flowing production period is generally lower. According to the slope of the energy indication curve of each well and the cumulative liquid production during the flowing production period, the natural energy level of the near-well formation of a single well is delimited, and it can be classified as sufficient (first level), average (second level), and insufficient (third level) natural energy in the near-well formation of a single well.

[0088] Such as Figure 1 shown, in step S103, the production stages of the target wells are divided according to the changing trend of the energy indication curve, the energy coefficient corresponding to each production stage is calculated, and the energy replenishment timing is determined in combination with the classification result of the natural energy level.

[0089] Specifically, step S103 includes the following steps: performing curve fitting on the energy indication curve corresponding to each production stage to obtain a fitting curve corresponding to each production stage one by one.

[0090] Specifically, step S103 includes the following steps: calculating the slope of the fitting curve of each production stage as the energy coefficient corresponding to each production stage.

[0091] Figure 3 The flowchart shows a method for determining the energy replenishment timing according to an embodiment of the present invention.

[0092] As Figure 3 , in step S301, calculate the difference between the energy coefficient of the subsequent production stage and the energy coefficient of the previous production stage to obtain a difference result. Specifically, △k = k n+1 -k n , where △k represents the difference result, k n+1 represents the energy coefficient of the subsequent production stage, and k n represents the energy coefficient of the previous production stage, and n takes a positive integer value.

[0093] As Figure 3 , in step S302, based on the difference result and the energy coefficient during the self-jetting period, calculate the replenishment timing coefficient. Specifically, use the difference result as the dividend and the energy coefficient during the self-jetting period as the divisor for a division operation, and take the obtained quotient as the replenishment timing coefficient.

[0094] In one embodiment, the formula for calculating the replenishment timing coefficient is as follows:

[0095] k 0 = △k / k = (k n+1 -k n ) / k (Formula a)

[0096] k 0 = △k / k 1 = (k n+1 -k n ) / k 1 (Formula b)

[0097] Among them, k 0 represents the replenishment timing coefficient, k represents the energy coefficient during the self-jetting period, and k 1 represents the energy coefficient of the first stage. Specifically, when segmenting the energy indication curve, the energy during the self-jetting period can be divided into the first stage. At this time, Formula a and Formula b are equivalent. When segmenting the energy indication curve, the energy during the self-jetting period may not be divided into the first stage. At this time, Formula b is used for calculation.

[0098] As Figure 3, in step S303, based on the supplementary timing coefficient and the classification result of the natural energy level, the energy supplementation timing is determined by combining the supplementary timing standard.

[0099] The characteristics of the energy indication curve and the difference in its slope value during the stable production stage of production wells with different natural energy strengths are quite different. Different identification criteria are used to identify the energy supplementation timing for production wells with sufficient, general, and insufficient natural energy respectively. When the energy of the oil well changes, the energy indication curve shows a decrease in slope. However, due to the difference in the natural energy of the near-well formation of a single well, the present invention uses the rate of change of the slope of the energy indication curve as the identification standard for the energy supplementation timing.

[0100] For wells with sufficient natural energy, since the absolute value of the slope of the energy indication curve is small, the rate of change of the slope of the energy indication curve obtained during the identification of the energy supplementation timing is large, and the identified rate of change of the slope of the energy indication curve is greater than or equal to the fifth threshold; for wells with insufficient natural energy, since the absolute value of the slope of the energy indication curve is large, the rate of change of the slope of the energy indication curve obtained during the identification of the energy supplementation timing is small, and the identified rate of change of the slope of the energy indication curve is less than or equal to the sixth threshold. The identification standard for production wells with general natural energy is between that of sufficient wells and insufficient wells, which is greater than the sixth threshold and less than the fifth threshold.

[0101] Table 3 shows the identification boundaries of the energy supplementation timing based on the energy indication curve. The supplementary timing standard for the first level is that the rate of change of the slope is greater than or equal to the fifth threshold, the supplementary timing standard for the second level is greater than the sixth threshold and less than the fifth threshold, and the supplementary timing standard for the third level is less than or equal to the sixth threshold. In one embodiment, the fifth threshold is taken as 4 and the sixth threshold is taken as 0.5.

[0102] Table 3 Identification Boundaries of Energy Supplementation Timing Based on Energy Indication Curve

[0103]

[0104] Furthermore, according to the determined energy supplementation timing, a reasonable energy supplementation method is further selected to achieve the purpose of stable production or increased production.

[0105] The present invention avoids the defect of ignoring the difference in the natural energy of the near-well formation of a single well in the conventional analysis of energy strength, and considers the difference in different natural energy levels in the carbonate reservoir and the change in energy strength during production. The energy strength is judged according to the slope of the energy indication curve. The larger the slope, the stronger the energy; for production wells with stronger energy, the elastic energy is strong, and the energy retention degree during production is relatively high, and the slope of the energy indication curve is large; for production wells with weaker energy, the overall elastic energy is weak, and the energy retention degree during production is relatively low, and the slope of the energy indication curve is small. Furthermore, the energy supplementation timing is identified from the change of the energy indication curve.

[0106] In one embodiment, taking Well TH10346 as an example, the energy replenishment timing is determined by the method for identifying the energy replenishment timing for carbonate reservoirs proposed by the present invention.

[0107] First, draw the energy indicator curve of the target well (Well No.: TH10346) (as Figure 7 ). The cumulative production data during the flowing well stage of this well is greater than 5×10 4 t. Quantified according to the energy indicator curve during the initial stable production stage, the fitted mathematical expression is y = -1E-05x + 7.3882, and the slope of the curve is -1×10 -5 . Therefore, it is determined that this well is a production well with sufficient natural energy.

[0108] Next, segment the energy indicator curve and analyze and calculate the energy indicator curve and its curve change rate for each production stage in stages, as Figure 8 shown. In the order from left to right, they are stage 1, stage 2, stage 3, stage 4, stage 5, and stage 6:

[0109] The production time of stage 1 is from October 25, 2008 to June 17, 2009, and the mathematical expression is y = -1E-05x + 7.2959, and the slope of the energy indicator curve is -1×10 -5 .

[0110] The production time of stage 2 is from June 18, 2009 to April 21, 2010, and the mathematical expression is y = -2E-05x + 7.8298, and the slope of the energy indicator curve is -2×10 -5 .

[0111] The production time of stage 3 is from April 22, 2010 to August 26, 2010, and the mathematical expression is y = -9E-06x + 6.8267, and the slope of the energy indicator curve is -9×10 -6 .

[0112] The production time of stage 4 is from October 12, 2010 to February 22, 2012, and the mathematical expression is y = -4E-06x + 6.4714, and the slope of the energy indicator curve is -4×10 -6 .

[0113] The production time of stage 5 is from April 9, 2012 to August 12, 2013, and the mathematical expression is y = -1E-06x + 6.3312, and the slope of the energy indicator curve is -1×10 -6 .

[0114] The production time of stage 6 is from August 13, 2013 to June 3, 2014, and the mathematical expression is y = -6E-05x + 21.533, and the slope of the energy indicator curve is -6×10-5 。

[0115] Finally, calculate the rate of change of the slope of the energy indication curve. Compared with the initial production stage (Stage 1), the rate of change of the slope of the energy indication curve in Stage 2 is 1; the rate of change of the slope of the energy indication curve in Stage 3 is -1.1; the rate of change of the slope of the energy indication curve in Stage 4 is -0.5; the rate of change of the slope of the energy indication curve in Stage 5 is -0.3; the rate of change of the slope of the energy indication curve in Stage 6 is 5.9. Since the rate of change of the slope of the energy indication curve in Stage 6 is greater than the threshold value of 4, the energy replenishment timing for Well TH10346 is identified around June 2014.

[0116] Based on the production characteristics of oil wells in fractured-vuggy carbonate reservoirs, the present invention analyzes the characteristics of the energy indication curve of production wells by plotting the energy indication curve, evaluates the energy level through the slope of the energy indication curve, and on this basis, identifies the energy replenishment timing during the development of production wells according to the identification criteria for the energy replenishment timing at different energy levels.

[0117] Figure 9 shows a structural block diagram of an energy replenishment timing identification device for a carbonate reservoir according to an embodiment of the present invention. As Figure 9 shown, the energy replenishment timing identification device 900 includes a first module 901, a second module 902, and a third module 903.

[0118] The first module 901 is used to collect the energy change data of the target well during the flowing well period and the stable production stage, and draw the energy indication curve of the target well based on the energy change data.

[0119] The second module 902 is used to calculate the energy coefficient of the target well during the flowing well period, and combine the energy change data to obtain the classification result of the natural energy level of the target well according to the energy strength classification standard.

[0120] The third module 903 is used to divide the production stage of the target well according to the change trend of the energy indication curve, calculate the energy coefficient corresponding to each production stage, and determine the energy replenishment timing in combination with the classification result of the natural energy level.

[0121] In summary, the present invention includes drawing the energy indication curve of a single well, classifying the energy strength of a single well, and identifying the energy replenishment timing, gradually realizing the classification analysis of energy strength, and further identifying the energy replenishment timing.

[0122] In the stage of drawing the energy indication curve, clarify the curve relationship between the cumulative production and pressure of the production well.

[0123] In the stage of classifying the strength of energy, determine the strength of the natural energy of the reservoir and the energy change during development. During the production process of wells with strong energy, the degree of energy retention is relatively high, and the slope of the energy indicator curve is large; during the production process of wells with weak energy, the degree of energy retention is relatively low, and the slope of the energy indicator curve is small. Judge the strength of energy based on the slope of the energy indicator curve. The larger the slope, the stronger the energy; furthermore, identify the timing of energy replenishment from the change of the energy indicator curve.

[0124] In the stage of identifying the timing of energy replenishment, through the change rate of the slope of the energy indicator curve, and on the premise that production wells with different natural energy levels have different identification boundaries, identify the timing of energy replenishment.

[0125] In summary, the method and device for identifying the timing of energy replenishment for carbonate reservoirs provided by the present invention are based on a full evaluation of the mutual relationship between the bottom-hole flowing pressure and the cumulative production during the production process of wells. Through the analysis of the energy indicator curves of a large number of production wells in the field, combined with the characteristics of the production performance curves, the boundaries of the energy indicator curves of different wells under different natural energy conditions are divided to indicate that the energy of the well weakens and effective energy replenishment measures need to be taken. The change rate of the energy indicator curve indicates the law of energy decay of the well, the cumulative production in the evaluation stage indicates the production characteristics of different energy strength stages of the well, and the method for identifying the timing of energy replenishment determined by the comprehensive constraint of the cumulative production and the slope of the energy indicator curve can effectively evaluate the change of the energy strength of the well, and then determine the timing of energy replenishment in combination with the production performance analysis.

[0126] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and do not mean to limit.

[0127] The phrase "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" that appear throughout the specification do not necessarily all refer to the same embodiment.

[0128] Although the disclosed embodiments of the present invention are as above, the content described is only an embodiment for facilitating the understanding of the present invention and is not intended to limit the present invention. Any person skilled in the technical field to which the present invention pertains, without departing from the spirit and scope disclosed by the present invention, can make any modifications and changes in the form of implementation and details, but the scope of patent protection of the present invention must still be subject to the scope defined by the appended claims.

Claims

1. A method for identifying the energy replenishment timing for carbonate rock reservoirs, characterized in that, the method comprises the following steps: Step 1: Collect the energy change data of the target well during the flowing well period and the stable production stage, and draw an energy indication curve of the target well based on the energy change data; Step 2: Calculate the energy coefficient of the target well during the flowing well period, and combine the energy change data to obtain the classification result of the natural energy level of the target well according to the energy strength classification standard; Step 3: Divide the production stage of the target well according to the change trend of the energy indication curve, calculate the energy coefficient corresponding to each production stage, and determine the energy replenishment timing in combination with the classification result of the natural energy level; The specific steps in Step 2 include: Statistically collect the cumulative production data of the target well during the flowing well period, and determine the production level of the target well according to the production level standard in the energy strength classification standard; The specific steps in Step 2 include: Curve fit the energy indication curve of the target well during the flowing well period to obtain a fitting curve during the flowing well period; Use the slope of the fitting curve during the flowing well period as the energy coefficient during the flowing well period; Based on the energy coefficient during the flowing well period, determine the energy coefficient level of the target well according to the coefficient standard in the energy strength classification standard; The specific steps in Step 2 include: Based on the production level and the energy coefficient level, combine the energy strength classification standard to obtain the classification result of the natural energy level.

2. The method for identifying the energy replenishment timing for carbonate rock reservoirs according to claim 1, characterized in that, the energy change data includes cumulative production data and bottom hole flowing pressure data, and the energy indication curve is drawn with the cumulative production data as the horizontal axis and the bottom hole flowing pressure data as the vertical axis.

3. The method for identifying the energy replenishment timing for carbonate rock reservoirs according to claim 1, characterized in that, the specific steps in Step 2 include: Judge whether both the production level and the energy coefficient level point to the same natural energy level; If the judgment result is yes, use the current natural energy level as the classification result of the natural energy level of the target well.

4. The method for identifying the energy replenishment timing for carbonate rock reservoirs according to claim 1, characterized in that, the specific steps in Step 3 include: Curve fit the energy indication curve corresponding to each production stage to obtain a fitting curve corresponding to each production stage; Calculate the slope of the fitting curve of each production stage as the energy coefficient corresponding to each production stage.

5. The method for identifying the energy replenishment timing for carbonate rock reservoirs according to claim 4, characterized in that, the specific steps in Step 3 include: Calculate the difference between the energy coefficient of the latter production stage and the energy coefficient of the former production stage to obtain a difference result; Based on the difference result and the energy coefficient during the flowing well period, calculate a replenishment timing coefficient; Based on the replenishment timing coefficient and the classification result of the natural energy level, combine the replenishment timing standard to determine the energy replenishment timing.

6. The method for identifying the energy supplement timing for carbonate reservoirs as described in claim 5, characterized in that, the specific steps in step three include the following steps: Using the difference result as the dividend and the energy coefficient during the natural flow period as the divisor, perform a division operation, and use the obtained quotient as the supplement timing coefficient.

7. An apparatus for identifying the energy supplement timing for carbonate reservoirs, characterized in that, executing the method as described in any one of claims 1-6, the apparatus includes: A first module, which is used to collect the energy change data of the target well during the natural flow period and the stable production stage, and draw an energy indicator curve of the target well based on the energy change data; A second module, which is used to calculate the energy coefficient of the target well during the natural flow period, and combine the energy change data to obtain the classification result of the natural energy level of the target well according to the energy strength classification standard; A third module, which is used to divide the production stage of the target well according to the change trend of the energy indicator curve, calculate the energy coefficient corresponding to each production stage, and determine the energy supplement timing in combination with the natural energy level classification result.

Images