Method for determining the range of invalid repeated heating area and heat consumption ratio after high round throughput

Abstract

The present invention provides a method for determining the scope and heat consumption ratio of invalid repeated heating areas after high-cycle throughput, and the method for determining the scope and heat consumption ratio of invalid repeated heating areas after high-cycle throughput includes: step 1, establishing a single-well radial model for numerical simulation of steam throughput reservoir; step 2, drawing the oil layer temperature and oil saturation at the end of periodic steam injection; step 3, drawing the temperature and saturation change curve along the wellbore direction; step 4, determining the invalid repeated heating area near the wellbore and the throughput heating area; step 5, calculating the periodic heat consumption along the wellbore direction at the end of periodic steam injection; step 6, determining the periodic heat consumption and percentage of the invalid repeated heating area near the wellbore. The method for determining the scope and heat consumption ratio of invalid repeated heating areas after high-cycle throughput has a clear idea, is simple and practical, and provides a solid foundation for further improving steam thermal efficiency and steam throughput development effects after high-cycle throughput.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a method for determining the range of an invalid repeated heating area and a heat consumption ratio after high-cycle throughput. Background Art

[0002] As the number of production cycles increases, the effect of steam huff and puff gradually deteriorates. At the end of 2017, there were 1,225 steam huff and puff wells with 6 cycles or more in Shengli East Oilfield, accounting for 34.0% of the total number of wells. After entering the high-cycle huff and puff, the cycle oil production of a single well dropped to less than 1,200 tons, the cycle oil-gas ratio dropped to about 0.6, the cycle water content gradually increased to more than 90%, and the cycle effect gradually deteriorated. The heavy oil reservoir as a whole is in the stage of "high cycle, high water content, low production, low oil-gas ratio, medium-high recovery degree". Analyzing the reasons for the poor effect of high-cycle throughput, in addition to the objective law that the throughput effect deteriorates from cycle to cycle, an important aspect is that after each cycle of steam injection, the steam will repeatedly heat the low oil saturation area within 20-30m near the wellbore, and a considerable amount of heat in the periodic steam injection volume is dissipated near the wellbore and the top and bottom caprocks, resulting in repeated inefficient and ineffective heating near the wellbore, low heat utilization, and difficulty in expanding the steam throughput heating radius, affecting the development effect after high-cycle throughput.

[0003] However, how much heat is ineffectively repeated in the near-wellbore area, how to define the ineffective repeated heating area, how big the range is, and what is the proportion of ineffective heat? How to determine this is a problem worth studying. For this reason, we have invented a new method for determining the range and heat consumption ratio of the ineffective repeated heating area after high-round throughput, which solves the above technical problems. Summary of the invention

[0004] The purpose of the present invention is to provide a simple determination method, which can be used to determine the range of the invalid repeated heating area near the wellbore after high-cycle throughput, as well as the heat and proportion within the range.

[0005] The purpose of the present invention can be achieved by the following technical measures: a method for determining the scope of the invalid repeated heating area and the heat consumption ratio after high-cycle throughput, and the method for determining the scope of the invalid repeated heating area and the heat consumption ratio after high-cycle throughput comprises: step 1, establishing a single-well radial model for numerical simulation of steam throughput oil reservoir; step 2, drawing the oil layer temperature and oil saturation at the end of periodic steam injection; step 3, drawing the temperature and saturation change curve along the wellbore direction; step 4, determining the invalid repeated heating area near the wellbore and the throughput heating area; step 5, calculating the periodic heat consumption along the wellbore direction at the end of periodic steam injection; step 6, determining the periodic heat consumption and percentage of the invalid repeated heating area near the wellbore.

[0006] The purpose of the present invention can also be achieved by the following technical measures:

[0007] In step 1, the basic parameters of the model and steam throughput are taken from the mine, the average value is taken, and the high-cycle steam throughput development effect is simulated and calculated; at the same time, the size of each grid along the radial direction of the throughput well is obtained to facilitate the determination of the relationship between the radial distance from the throughput well and the reservoir parameters, including temperature, saturation and heat.

[0008] In step 2, after the simulation calculation is completed, the oil layer temperature and oil saturation field diagrams at the end of the nth cycle of steam injection and well soaking are checked respectively.

[0009] In step 3, in the temperature field map and the residual oil saturation field map, the temperature value and the oil saturation value of each grid along the radial direction of the huff and puff well are counted respectively, and are plotted on a map with the horizontal axis being the radial distance from the huff and puff well and the vertical axis being the temperature and the oil saturation.

[0010] In step 4, the radial distance from the wellbore and the oil saturation curve are plotted as follows: or The radial distance d1 is marked as the invalid repeated heating area near the wellbore. In this area, after the remaining oil saturation reaches the high-temperature residual oil saturation, the water saturation is relatively high. The steam temperature in this area near the wellbore is high, and a large amount of heat is consumed in the near-wellbore area. The heat heats the oil layer rock and the highly saturated formation water, and each cycle repeatedly heats this area, resulting in a large amount of steam heat being ineffectively utilized in the near-wellbore area, and it is difficult for steam to continue to penetrate the formation to expand the heating range.

[0011] In step 4, on the curve of radial distance from the wellbore and reservoir temperature, the temperature greater than the original reservoir temperature T i The radial distance d2 is marked as the steam throughput heating zone.

[0012] In step 5, the total heat value Q of the oil layer in each grid is calculated at the end of the nth cycle of steam injection and well soaking and at the end of the n-1th cycle of production. k , which is equal to the sum of the heat of oil, water and rock skeleton. At the same time, the radial distance from the wellbore and the total heat curve of the oil layer are plotted; it is calculated according to the following formula:

[0013] Q k =Q ok +Q wk +Q rk (1)

[0014] Q ok =c o ·m ok ·(T k -T i ) (2)

[0015] Q wk =c w ·m wk ·(T k -T i ) (3)

[0016] Q rk =M r ·V rk ·(T k -T i ) (4)

[0017] In the formula, c o 、c w are the specific heats of oil and water, respectively. The specific heat of oil is 2.0 kJ / (kg·℃) and the specific heat of water is 4.2 kJ / (kg·℃); M r is the heat capacity of saturated fluid rock, ranging from 2.3 to 2.8×10 3 kJ / (m 3 ℃); Q ok , Q wk , Q rk are the calorific values ​​of oil, water and rock in the kth grid, KJ; T k represents the temperature of the kth grid, °C; T i Indicates the original oil layer temperature, °C. m ok and m wk Respectively represent the mass of oil and water in the kth grid, kg; V rk represents the rock skeleton volume of the kth grid, m 3 .

[0018] In step 5, the heat consumption ΔQ of each grid in the throughput heating area in the nth cycle is calculated. k , which is equal to the oil layer heat value of each grid at the end of the nth cycle of steam injection and well soaking minus the oil layer heat of each grid at the end of the n-1th cycle of production.

[0019] In step 6, the cumulative value ΔCQ of the heat consumption in the nth cycle within the range of the throughput heating zone along the radial direction of the throughput well is calculated. k and ratio η k , the formula is as follows:

[0020]

[0021]

[0022] In the formula, J represents the total number of radial grids.

[0023] In step 6, the periodic heat consumption and the percentage η of the ineffective repeated heating zone near the wellbore are determined.

[0024] The method for determining the scope of the invalid repeated heating zone and the heat consumption ratio after high-cycle throughput in the present invention aims at the problems of unclear thermal energy action mechanism, unclear thermal energy utilization degree and scope, low actual thermal utilization rate of oil layer, and increased difficulty in expanding the heating and utilization radius after high-cycle throughput development of heavy oil reservoirs. First, a single well radial model is established to draw the temperature and oil saturation curve at the end of high-cycle steam injection and well shutoff, determine the invalid repeated heating zone near the well and the throughput heating zone, and calculate the heat absorbed by the oil layer along the radial direction of the throughput well at the end of high-cycle steam injection and well shutoff and the heat absorbed by the oil layer at the end of the previous round of production, respectively, and calculate the periodic heat consumption and percentage of the invalid repeated heating zone near the well by difference calculation. The method has clear ideas, is simple and practical, has a deep understanding of the scope of the invalid repeated heating zone near the well after high-cycle throughput, and has a reasonable determination method. It solves the previously unclear problems such as the scope of invalid repeated heating near the wellbore, invalid heating amount, and reasons for increased difficulty in expanding the utilization radius after high-cycle huff and puff, and realizes the transformation of understanding from qualitative to quantitative. At the same time, it clarifies the degree of heat loss in the invalid heating area near the wellbore and the proportion of invalid heat, and has a further understanding of the actual thermal utilization rate of reservoir steam after high-cycle huff and puff. This has a further in-depth understanding of the profound and clear mechanism of thermal energy action after high-cycle huff and puff, the increased difficulty in expanding the utilization radius, and provides a solid theoretical basis for optimizing and expanding the periodic steam injection amount and timing after high-cycle huff and puff, improving the steam thermal utilization rate, expanding the heating radius, and improving the steam huff and puff development effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a specific embodiment of the method for determining the range and heat consumption ratio of the invalid repeated heating area after high round throughput of the present invention;

[0026] Figure 2 It is a schematic diagram of a single well radial model for numerical simulation of steam-huffling oil reservoir established in a specific embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of a method for determining an invalid repeated heating area near a wellbore in a specific embodiment of the present invention;

[0028] Figure 4 It is a schematic diagram of a method for determining a throughput heating zone in a specific embodiment of the present invention;

[0029] Figure 5 It is a schematic diagram of a method for determining the periodic heat consumption and percentage of the ineffective repeated heating zone near the wellbore in a model in a specific embodiment of the present invention.

[0030] Figure 6 A radial conceptual model diagram of single-well steam stimulation according to a specific embodiment of the present invention;

[0031] Figure 7 A graph showing the relationship between the grid and the grid size along the wellbore direction according to a specific embodiment of the present invention;

[0032] Figure 8 A temperature and oil saturation curve diagram along the radial direction of the huff-and-puff well at the end of the seventh cycle of steam injection and well soaking in a specific embodiment of the present invention;

[0033] Fig. 9 Schematic diagram of the invalid repeated heating area near the wellbore and the steam injection heating area after the seventh cycle of steam injection and well soaking in a specific embodiment of the present invention

[0034] Fig.10 A temperature and oil saturation curve diagram along the radial direction of the huff-and-puff well at the end of the sixth cycle of production in a specific embodiment of the present invention;

[0035] Fig.11 A heat consumption curve diagram of each grid in the radial direction of the throughput well in the seventh cycle according to a specific embodiment of the present invention;

[0036] Fig.12 The graph is a cumulative value curve of the heat consumption in the radial direction of the throughput well in the 7th cycle of a specific embodiment of a method for determining the range of the invalid repeated heating area and the heat consumption ratio after high-round throughput of the present invention. DETAILED DESCRIPTION

[0037] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings.

[0038] like Figure 1 As shown, Figure 1 The present invention is a flow chart of a method for determining the range of an invalid repeated heating zone and a heat consumption ratio after high-round throughput.

[0039] Step 101, establishing a single well radial model for numerical simulation of steam-huffing and -puffing oil reservoirs; establishing a single well radial model for numerical simulation of steam-huffing and -puffing oil reservoirs, such as Figure 2 As shown in the figure, the basic parameters of the model and steam stimulation are taken from the mine, and the average value is taken to simulate and calculate the effect of high-cycle (more than 7 cycles) steam stimulation development. At the same time, the size of each grid along the radial direction of the stimulation well is obtained to facilitate the determination of the relationship between the radial distance from the stimulation well and the reservoir parameters, including temperature, saturation and heat.

[0040] Step 102, calculating the oil layer temperature and oil saturation field diagram at the end of the nth cycle (n≥7) of steam injection and well soaking at the end of the nth cycle.

[0041] Step 103, in the temperature field map and the remaining oil saturation field map, the temperature value and the oil saturation value of each grid along the radial direction of the huff and puff well are respectively counted, and are plotted on a map with the abscissa being the radial distance from the huff and puff well and the ordinate being the temperature and the oil saturation.

[0042] Step 104, determine the ineffective repeated heating area near the well and the huff and puff heating area; on the radial distance from the huff and puff well and oil saturation curve, the area less than or equal to the residual oil saturation S or The radial distance d1 is marked as the ineffective repeated heating area near the wellbore. Figure 3 As shown in the figure. In this area, after the remaining oil saturation reaches the high-temperature residual oil saturation, the water saturation is relatively high, the steam temperature in this area near the well is high, and a large amount of heat is consumed in the area near the well. The heat mainly heats the oil layer rock and the highly saturated formation water, and each cycle repeatedly heats this area, resulting in a large amount of steam heat being ineffectively utilized in the area near the well, and it is difficult for steam to continue to penetrate the formation to expand the heating range.

[0043] On the curve of radial distance from the wellbore and reservoir temperature, the temperature greater than the original reservoir temperature T i The radial distance d2 is marked as the steam heating area. Figure 4 shown.

[0044] Step 105, calculate the total heat value Q of the oil layer in each grid at the end of the nth round of steam injection and well soaking k , which is equal to the sum of the heat of oil, water and rock skeleton, and the radial distance from the wellbore and the total heat of the oil layer are plotted. Calculate according to the following formula;

[0045] Q k =Q ok +Q wk +Q rk (1)

[0046] Q ok =c o ·m ok ·(T k -T i ) (2)

[0047] Q wk =c w ·m wk ·(T k -T i ) (3)

[0048] Q rk =M r ·V rk ·(T k -T i ) (4)

[0049] In the formula, c o 、c w are the specific heats of oil and water, respectively. The specific heat of oil is generally 2.0 kJ / (kg·℃), and the specific heat of water is 4.2 kJ / (kg·℃); M r is the heat capacity of saturated fluid rock, generally ranging from 2.3 to 2.8×10 3 kJ / (m 3 ℃); Q ok , Q wk , Q rk are the calorific values ​​of oil, water and rock in the kth grid, KJ; T k represents the temperature of the kth grid, °C; T i Indicates the original oil layer temperature, °C. m ok and m wk Respectively represent the mass of oil and water in the kth grid, kg; V rk represents the rock skeleton volume of the kth grid, m 3 .

[0050] The oil layer temperature and oil saturation of each grid along the radial direction of the wellbore are calculated and counted at the end of the production of the n-1th cycle, using the same method as step 102.

[0051] The oil layer temperature and oil saturation along the radial direction of the huff-and-puff well at the end of the production of the n-1th cycle are calculated in the same manner as step 103 .

[0052] The total absorbed heat of each grid oil layer at the end of the n-1th cycle production and the total absorbed heat of each grid oil layer along the radial direction of the huff-and-puff well at the end of the n-1th cycle production are calculated respectively, and the method is the same as step 105.

[0053] Calculate the heat consumption ΔQ of each grid in the nth cycle within the throughput heating area k This value is equal to the oil layer heat value of each grid at the end of the nth cycle of steam injection and well soaking minus the oil layer heat value of each grid at the end of the n-1th cycle of production.

[0054] Step 106, calculating the cumulative value of the heat consumption of the nth cycle within the range of the throughput heating zone along the radial direction of the throughput well; calculating the cumulative value ΔCQ of the heat consumption of the nth cycle within the range of the throughput heating zone along the radial direction of the throughput well k and the ratio η k The formula is as follows:

[0055]

[0056]

[0057] In the formula, J represents the total number of radial grids.

[0058] Determine the cycle heat consumption and percentage η of the ineffective repeated heating area near the wellbore, such as Figure 5 shown.

[0059] The present invention is applicable to the development of heavy oil reservoirs after high-cycle steam injection. The method has clear ideas, is simple and practical, and has a deep understanding of the scope of the invalid repeated heating zone near the wellbore after high-cycle injection, and has a reasonable determination method. It solves the problem that the scope of invalid repeated heating near the wellbore after high-cycle injection, the invalid heating amount, and the reasons for the increased difficulty in expanding the utilization radius are not completely clear in the past, and realizes the transformation from qualitative to quantitative understanding. At the same time, it clarifies the degree of heat loss and the proportion of invalid heat in the invalid heating zone near the wellbore, and has a further understanding and understanding of the actual thermal utilization rate of oil layer steam after high-cycle injection. This has a further in-depth understanding of the reasons for the deep and clear mechanism of thermal energy after high-cycle injection, the increased difficulty in expanding the utilization radius, etc., and provides a solid theoretical basis for optimizing and expanding the periodic steam injection amount and injection timing after high-cycle injection, improving the steam thermal utilization rate, expanding the heating radius, and improving the steam injection development effect.

[0060] In a specific embodiment of the present invention, the following steps are included:

[0061] In step 1, a radial conceptual model of steam stimulation of a single well is established (e.g. Figure 6 As shown in the figure, the model top depth is 1150m, the oil layer thickness is 15m, the permeability is 1500mD, the porosity is 0.31, the original oil layer temperature is 65℃, and the surface crude oil density is 0.92g / cm 3 , water density is 1.0g / cm 3 The specific heat of rock is 2.5×10 3 kJ / (m 3 ·℃), oil specific heat is 2.0kJ / (kg·℃), water specific heat is 4.2kJ / (kg·℃). The model sets the radial grid number J=70, and the grid size along the radial direction of the well is as follows: Figure 7 The simulation calculates steam throughput for 7 cycles until the end of production.

[0062] In step 2, the reservoir temperature and oil saturation field diagram at the end of the seventh cycle of steam injection and well soaking are calculated.

[0063] In step 3, the temperature value and oil saturation value of each grid along the radial direction of the well are counted and a curve is drawn, such as Figure 8 shown.

[0064] In step 4, in the model, the high temperature residual oil saturation S oris 0.126. Based on this value, the invalid repeated heating area near the well is determined to be d1 = 12.4 m. The original oil layer temperature of this block is T i =65℃, based on this value, the steam throughput heating range is determined to be d2=47m. The results are as follows Fig. 9 shown.

[0065] In step 5, the total heat absorbed by the oil layer of each grid along the radial direction of the wellbore is calculated. First, according to formulas (1), (2), (3), and (4), the total heat absorbed by the oil layer of each grid at the end of the 7th cycle of steam injection and well shut-in and at the end of the 6th cycle of production is calculated, and then the heat consumption of each grid in the wellbore heating area in the 7th cycle is calculated. The results are expressed as Fig.10 shown.

[0066] In step 6, the cumulative value of the heat consumption in the 7th cycle in the heating zone along the radial direction of the wellbore is calculated using formula (5). From the calculation results, the total heat consumption in the heating zone in the 7th cycle is 2812.2 GJ. Fig.11 As shown. According to formula (6), the cumulative value percentage curve of the heat consumption in the seventh cycle along the radial direction of the wellbore is calculated and plotted. According to the range value of the invalid repeated heating area near the wellbore, the cycle heat consumption of the invalid repeated heating area near the wellbore is determined to be 1356.8GJ, accounting for a percentage of η = 48.2%. The results are shown in Fig.12 From the calculation results, it can be seen that after entering the high-cycle throughput, nearly half of the steam heat injected into the oil layer is consumed in the high-temperature and low-oil saturation area near the wellbore, resulting in low heat utilization and difficulty in expanding the heating radius, which in turn affects the development effect after high-cycle throughput.

Claims

1. A method for determining the range of invalid repeated heating areas and heat consumption ratio after high round throughput, characterized in that: The method for determining the range of the invalid repeated heating area and the heat consumption ratio after the high round throughput includes: Step 1, establishing a single well radial model for numerical simulation of steam stimulation reservoir; Step 2, plotting the oil layer temperature and oil saturation at the end of the periodic steam injection; Step 3, drawing a curve of temperature and saturation variation along the wellbore direction; Step 4, determining the ineffective repeated heating area near the wellbore and the huff-and-puff heating area; Step 5, calculating the periodic heat consumption along the wellbore direction at the end of the periodic steam injection; Step 6, determining the cycle heat consumption and percentage of the ineffective repeated heating area near the wellbore; In step 4, the radial distance from the wellbore and the oil saturation curve are plotted as follows: or The radial distance d1 is marked as the invalid repeated heating area near the wellbore. In the invalid repeated heating area near the wellbore, after the residual oil saturation reaches the high-temperature residual oil saturation, the water saturation is relatively high. The steam temperature in the invalid repeated heating area near the wellbore is high, and a large amount of heat is consumed in the near-wellbore area. The heat heats the oil layer rock and the highly saturated formation water, and each cycle round repeatedly heats the invalid repeated heating area near the wellbore, resulting in a large amount of steam heat being ineffectively utilized in the near-wellbore area, and it is difficult for the steam to continue to penetrate the formation to expand the heating range.

2. The method for determining the range of the invalid repeated heating area and the heat consumption ratio after high round throughput according to claim 1 is characterized in that: In step 1, the basic parameters of the model and steam throughput are taken from the mine, the average value is taken, and the high-cycle steam throughput development effect is simulated and calculated; at the same time, the size of each grid along the radial direction of the throughput well is obtained to facilitate the determination of the relationship between the radial distance from the throughput well and the reservoir parameters, including temperature, saturation and heat.

3. The method for determining the range of invalid repeated heating area and heat consumption ratio after high round throughput according to claim 1 is characterized in that: In step 2, after the simulation calculation is completed, the oil layer temperature and oil saturation field diagrams at the end of the nth cycle of steam injection and well soaking are plotted respectively.

4. The method for determining the range of the invalid repeated heating area and the heat consumption ratio after high round throughput according to claim 3 is characterized in that: In step 3, in the temperature field map and the residual oil saturation field map, the temperature value and the oil saturation value of each grid along the radial direction of the huff and puff well are counted respectively, and are plotted on a map with the horizontal axis being the radial distance from the huff and puff well and the vertical axis being the temperature and the oil saturation.

5. The method for determining the range and heat consumption ratio of the invalid repeated heating area after high round throughput according to claim 1 is characterized in that: In step 4, on the curve of radial distance from the wellbore and reservoir temperature, the temperature greater than the original reservoir temperature T i The radial distance d2 is marked as the steam throughput heating zone.

6. The method for determining the range and heat consumption ratio of the invalid repeated heating area after high round throughput according to claim 1 is characterized in that: In step 5, the total heat Q of each grid at the end of the nth cycle of steam injection and well soaking and at the end of the n-1th cycle of production is calculated. k , which is equal to the sum of the heat of oil, water and rock skeleton. At the same time, the radial distance from the wellbore and the total heat curve of the oil layer are plotted; it is calculated according to the following formula: Q k =Q ok +Q wk +Q rk (1) Q ok =c o ·m ok ·(T k -T i ) (2) Q wk =c w ·m wk ·(T k -T i ) (3) Q rk =M r ·V rk ·(T k -T i ) (4) In the formula, c o 、c w are the specific heats of oil and water, respectively. The specific heat of oil is 2.0 kJ / (kg·℃) and the specific heat of water is 4.2 kJ / (kg·℃); M r is the heat capacity of saturated fluid rock, ranging from 2.3 to 2.8×10 3 kJ / (m 3 ℃); Q ok , Q wk , Q rk are the calorific values ​​of oil, water and rock in the kth grid, KJ; T k represents the temperature of the kth grid, °C; T i Indicates the original oil layer temperature, ℃; m ok and m wk Respectively represent the mass of oil and water in the kth grid, kg; V rk represents the rock skeleton volume of the kth grid, m 3 .

7. The method for determining the range and heat consumption ratio of the invalid repeated heating area after high round throughput according to claim 6, characterized in that: In step 5, the heat consumption ΔQ of each grid in the steam throughput heating area in the nth cycle is calculated. k , which is equal to the oil layer heat value of each grid at the end of the nth cycle of steam injection and well soaking minus the oil layer heat value of each grid at the end of the n-11th cycle of production.

8. The method for determining the range and heat consumption ratio of the invalid repeated heating area after high round throughput according to claim 1, characterized in that: In step 6, the heat consumption ΔQ of the nth cycle within the throughput heating zone is calculated. j Cumulative value ΔCQ along the radial direction of the well k and ratio η k , the formula is as follows: In the formula, J represents the total number of radial grids.

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