Well pattern structure adjusting method for thick-layer-shaped bottom water common heavy oil reservoir

Abstract

The invention provides a thick layered bottom water common heavy oil reservoir well pattern structure adjusting method, which comprises the following steps of: according to the oil saturation of remaining oil in a reservoir and a well logging interpretation result of an oil well, judging a water content rising reason of the reservoir in a well area and the enrichment condition of the remaining oil among the oil wells; theoretical water cone radiuses of different depths in the longitudinal direction of each vertical well and theoretical water ridge radiuses of different depths in the longitudinal direction of each horizontal well in the well area are calculated according to the oil saturation of the remaining oil; making a longitudinal water logging dynamic profile map of the oil well in the well area by adopting an oil reservoir dynamic analysis method, and determining oil-water distribution in a remaining oil enrichment area by applying numerical simulation so as to determine the type of remaining oil; according to the type of the remaining oil, well pattern parameters are determined through numerical simulation, and well pattern structure adjustment is carried out according to the well pattern parameters; and horizontal well production parameters are adjusted according to the determined well pattern parameters. According to the method, the remaining oil distribution can be described more accurately and finely, the water content rising speed of the block is effectively slowed down, and the overall reserve utilization degree is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum exploitation, relates to a well pattern structure adjustment technology, and specifically is a well pattern structure adjustment method for a thick-layer bottom water common heavy oil reservoir. Background Art

[0002] Block 27 of Xinhai was put into development in 1993. In February 1994, the daily oil production reached a maximum of 366 tons, with an oil production rate of 2.68%. However, due to the influence of various factors such as the large oil-water viscosity ratio, active energy of edge and bottom water, and external grooves in the oil well casing, the bottom water coning and edge water pointing and tongueing are serious, the oil reservoir reserves are unevenly utilized, the water content increases rapidly, and the oil reservoir is in a state of low-speed development and is on the verge of abandonment. The original formations, well patterns and mining methods are no longer suitable for the needs of reservoir development. Since 2003, the effect of primary reservoir development has been systematically evaluated. Based on a series of studies such as detailed reservoir description, residual oil distribution characteristics, reservoir formation mechanism of low oil saturation reservoirs, seepage mechanism of thermal recovery heavy oil reservoirs, seepage mechanism of horizontal wells, and technical countermeasures for secondary development, horizontal wells have been used for secondary development, changing water cones into water ridges, effectively slowing down the flooding rate, and significantly improving block development indicators. Daily oil production has increased from 32 tons to a maximum of 358 tons, reaching the peak level of primary development. The oil production rate has increased from 0.26% to 2.8%, and the comprehensive water content has decreased from 93.6% to 81.4%. The secondary development of horizontal wells has achieved significant results.

[0003] However, although the secondary development of horizontal wells has achieved many results in indoor research and field tests, after 14 years of secondary development of horizontal wells, the existing well pattern design can no longer meet the needs of reservoir development and still faces the following challenges:

[0004] (1) Due to the influence of reservoir physical properties and fluid viscosity, bottom water rapidly advances from the oil-water interface to the horizontal section, causing the water cut in the oil well to rise rapidly, resulting in a low water flooding sweep coefficient in the reservoir. There is still relatively rich residual oil between wells in the high structural parts, which is difficult to effectively mobilize, and the distribution of residual oil is more complicated. The detailed description of residual oil is the key factor in determining whether the well pattern adjustment is effective.

[0005] (2) The results of the production profile test show that there is an uneven utilization of the horizontal section during the horizontal well development process, which affects the development effect of the horizontal well and further increases the complexity of the remaining oil distribution. The reasons for the uneven utilization are uneven development of the oil layer, drilling mud pollution and differences in production systems. Therefore, how to improve the utilization of the horizontal section is extremely important for well network adjustment. Summary of the invention

[0006] In order to overcome the deficiencies in the prior art, the present invention provides a method for adjusting the well pattern structure of a thick-layered bottom water ordinary heavy oil reservoir, which can more accurately and finely describe the distribution of remaining oil, effectively slow down the rate of water content increase in the block, and improve the overall reserve utilization.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] A method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir, comprising the following steps:

[0009] According to the calculated oil saturation of the remaining oil in the reservoir and the logging interpretation results of the oil wells, the reasons for the increase of water content in the reservoir in the well area and the enrichment of the remaining oil between the oil wells are determined;

[0010] Calculate the theoretical water cone radius at different depths of each vertical well in the well area according to the remaining oil saturation, and judge the dynamic movement of water between vertical wells according to the calculation results;

[0011] Calculate the theoretical water ridge radius at different depths of each horizontal well in the well area according to the remaining oil saturation, and judge the dynamic movement of water between horizontal wells according to the calculation results;

[0012] Using the theoretical water cone radius and theoretical water ridge radius, the reservoir dynamic analysis method is used to make the vertical water flooding dynamic profile of the oil wells in the well area. Based on the water flooding dynamic profile, numerical simulation is used to determine the oil and water distribution in the remaining oil-rich area, and then the type of remaining oil is determined;

[0013] According to the type of remaining oil, numerical simulation is used to determine the well network parameters, including the well network deployment boundary, the horizontal section length of the horizontal well, the plane adjacent well spacing, and the vertical water avoidance distance, and the well network structure is adjusted according to the well network parameters;

[0014] Adjust the horizontal well production parameters according to the determined well pattern parameters.

[0015] Furthermore, the calculation formula of the residual oil saturation is:

[0016] S o =S oi -S os =S oi -RS oi =S oi (1-R) (1)

[0017] In formula (1): S o Indicates the current oil saturation, in decimals; S oi Indicates the original oil saturation, in decimals; S os It indicates the reduction of oil saturation due to produced oil, in decimals; R indicates the current degree of production, in decimals.

[0018] Furthermore, the theoretical water cone radius at different depths in the vertical direction of the vertical well is calculated according to the following formula:

[0019]

[0020] In formula (2): N p Indicates the cumulative oil production, unit 10 4 t; r is the water cone radius, unit is m; h is the reservoir thickness, unit is m; φ is the porosity, unit is %; S o Indicates the current oil saturation; E D Indicates displacement efficiency, unit: %; ρ o Indicates crude oil density, unit: kg / m 3 ; B o Represents the volume coefficient of crude oil.

[0021] Furthermore, the theoretical water ridge radius at different depths in the horizontal well is calculated according to the following formula:

[0022]

[0023] In formula (3): N p Indicates the cumulative oil production, unit 10 4 t; r' represents the water ridge radius, unit is m; H represents the height from the horizontal section to the oil-water interface, unit is m; φ represents the porosity, unit is %; L represents the length of the horizontal section, unit is m; S o Indicates the current oil saturation; E D Indicates displacement efficiency, unit: %; ρ o Indicates crude oil density, unit: kg / m 3 ; B oi Represents the volume coefficient of crude oil.

[0024] Furthermore, the reservoir dynamic analysis method specifically comprises the following steps:

[0025] a. Split the liquid production of each sub-layer of the oil well. The liquid production of the oil well with a liquid production profile is calculated based on the percentage of liquid production. The liquid production of the oil well without a liquid production profile is split based on the permeability of the well perforation thickness, that is, the kh value;

[0026] b. For oil wells located at the oil-water boundary that have water, the water flooding status is judged based on the oil well pressure and liquid production. If the liquid production or pressure is stable, it means that there is sufficient energy replenishment, which is mainly due to the invasion of edge water. For oil wells located at high structural parts and far away from the oil-water boundary, the water content between oil wells is judged based on the analysis of oil well pressure and liquid production, and the logging interpretation data of newly drilled adjustment wells or the logging interpretation and production data of side-drilled wells;

[0027] c. Combined with detailed research on reservoir geology, including reservoir sedimentation pattern, sand body distribution law, oil-water distribution law, analyze the water inflow direction of the oil well, and recalibrate the actual water cone radius of the oil well based on the calculated theoretical water cone radius and theoretical water ridge radius;

[0028] d. For oil wells with partial water, first determine whether the water is real or fake: the water in the channel caused by the failure of the packer to seal during the workover operation and poor cementing is regarded as false water. On the contrary, if the oil well contains water, track the distribution range of the layer based on the comparison of small layers, determine the edge water position of the layer based on the time when the oil wells in this range see water, and determine the flooding range based on the absolute liquid production;

[0029] e. For oil wells that have never contained water during normal production, they are treated as dissolved gas drive, and their oil saturation is a function of pressure;

[0030] f. According to the above steps, make a vertical water flooding dynamic profile of the oil wells in the well area.

[0031] Furthermore, the types of residual oil include but are not limited to:

[0032] (1) Intercone type

[0033] This type of distribution is located between vertical wells and horizontal wells, or between horizontal wells, at the top of the oil layer, with bottom water coning, and the wells are unused;

[0034] (2) Edge mobilization difference

[0035] This type of distribution is located at the edge of the reservoir. Due to the thin oil layer, the development wells are not deployed in the area, the well network is imperfect, the well spacing is large, and the well network control is low;

[0036] (3) Fault-blocking type

[0037] This type of oil is relatively enriched only near local faults. It is residual oil mainly formed by fault action. The potential of this type of residual oil is to drill new wells and adjust production well points.

[0038] (4) Thick oil layer internal barrier shielding type

[0039] This type only exists in places where interlayers are developed. Since the thickness of the interlayers in the oil layer is greater than 1.5m, although the upper oil layer has been produced, it is laterally flooded due to the effect of the interlayers, resulting in residual oil in the lower oil layer that has not been produced.

[0040] Furthermore, the well network structure adjustment is carried out in the residual oil-rich area between wells and the edge unmoved area.

[0041] Furthermore, the horizontal well production parameters include horizontal well steam injection intensity, steam injection rate and liquid production intensity.

[0042] The beneficial effects of the present invention include:

[0043] By calculating the theoretical water cone radius and theoretical water ridge radius according to the oil saturation of the remaining oil, and then using the reservoir dynamic analysis method to make a vertical water flooding dynamic profile of the oil well, based on the results of the profile, numerical simulation methods, such as numerical simulation software or models, can be used to further determine the oil and water distribution in the remaining oil-rich area. This can more accurately and finely describe the remaining oil distribution, determine the remaining oil type, and determine the well network parameters based on the numerical simulation results, further optimize the well network structure, and improve the recovery rate.

[0044] Specifically, through the calculated oil saturation of the remaining oil in the reservoir and the logging interpretation results of the oil wells, it is possible to determine the reasons for the increase in water content in the reservoir in the well area and the enrichment of remaining oil between the wells, determine whether there is a water flooding problem, and analyze the reservoir status more accurately; by calculating the theoretical water cone radius and theoretical water ridge radius of vertical wells and horizontal wells at different depths in the vertical direction, and judging the dynamic movement of water based on the calculation results, it is possible to understand the distribution of water between wells, so as to better understand the migration law of water in the reservoir; by using the theoretical water cone radius and theoretical water ridge radius, and adopting the reservoir dynamic analysis method to produce the vertical water flooding dynamic profile of the oil well, it is possible to intuitively display the vertical water flooding of the oil well, which is helpful to analyze and understand the water flooding problem of the oil well and provide a basis for the subsequent adjustment of the well network structure; through the water flooding dynamic profile and numerical simulation, the oil and water distribution in the remaining oil enrichment area can be determined, and the type of remaining oil can be further determined, which is of great significance for optimizing development strategies and formulating measures to improve recovery.

[0045] According to the type of remaining oil and the results of numerical simulation, the well network parameters are determined, including the well network deployment boundary, the length of the horizontal section of the horizontal well, the plane adjacent well spacing, and the vertical water avoidance distance. Then, the well network structure is adjusted in the remaining oil-rich area between the wells and the edge unmoved area. The adjusted well network structure can better adapt to the dynamic changes of the groundwater body and improve the recovery rate. According to the determined well network parameters, the steam injection intensity and liquid production intensity of the oil well are adjusted. By reasonably controlling the intensity of steam injection and liquid production, the output and water flooding of the oil well can be better controlled, and the recovery effect can be further optimized.

[0046] In summary, this method of adjusting the well pattern structure of ordinary heavy oil reservoirs with thick bottom water can help understand the reservoir status, determine the water flooding problem, optimize the development strategy and improve the recovery rate, effectively slow down the water content increase rate of the block, and improve the overall reserve utilization, which has important guiding significance for the development of oil fields in the study block. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of dynamic flooding of the oil reservoirs of Haic11-15 to Haic11-33 wells according to Example 1 of the present invention;

[0048] Figure 2 This is the oil saturation distribution map of Xinhai Block 27 in Example 1 of the present invention;

[0049] Figure 3 The relationship between the length of the horizontal well in the inter-conical zone and the production and yield rate of Example 1 of the present invention;

[0050] Figure 4 The relationship between the length of the side horizontal well and the production and yield rate of Example 1 of the present invention;

[0051] Figure 5 is a curve showing the relationship between the water avoidance distance between the cones and the cumulative oil production in Example 1 of the present invention;

[0052] Figure 6 : is the relationship curve between the water avoidance distance of the edge thin layer and the cumulative oil production in Example 1 of the present invention;

[0053] Figure 7 is a relationship curve of cumulative oil production at different well spacings in the inter-cone zone of Example 1 of the present invention;

[0054] Figure 8 This is the relationship curve of cumulative oil production at different well spacings in the edge thin layer of Example 1 of the present invention. DETAILED DESCRIPTION

[0055] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] The invention discloses a method for adjusting the well pattern structure of a thick-layered bottom water common heavy oil reservoir, which aims to maximize the development effect, effectively improve the reservoir development effect in the "double-high" development stage, and further improve the recovery rate.

[0057] In order to improve the development contradictions faced by the bottom water oil reservoirs in Block 27 of Xinhai in the later stage of development, we innovatively implement small well spacing and short radius horizontal wells based on the principles of fine reservoir potential evaluation, quantitative implementation of remaining oil distribution, and optimization of technical policy parameters, realize the vertical cross-stacked "layered" three-dimensional development mode, and effectively expand the deployment space. The specific steps include:

[0058] (1) Study the distribution type of residual oil and accurately estimate the residual oil:

[0059] S1: Calculation of oil saturation using material balance method

[0060] Oilfield development practice has proved that, for water-driven sandstone reservoirs, when fully put into operation and enter the stable production stage, the oil saturation and recovery degree have the following relationship:

[0061] S o =Soi -S os =S oi -RS oi =S oi (1-R) (1)

[0062] In formula (1): S o Indicates the current oil saturation, in decimals; S oi Indicates the original oil saturation, in decimals; S os It indicates the reduction of oil saturation due to produced oil, in decimals; R indicates the current degree of production, in decimals.

[0063] S2: Well logging interpretation

[0064] Since the mining layer of the fault block is the d1Ⅰ section, and the layer below this block is the Hai 26 block, a total of more than 200 passing wells have been drilled in the new Hai 27 block. In particular, 28 new adjustment wells of various types were deployed in the Hai 26 block from 2007 to 2022, all of which are located between the wells of the new Hai 27 block well network. At the same time, a total of 4 pilot wells were implemented in different parts of the fault block in 2022. Therefore, the oil saturation between the oil wells in the new Hai 27 block can be monitored based on the logging interpretation of these wells in the d1Ⅰ section.

[0065] By statistically analyzing the logging data of these wells and applying the logging interpretation results to the oil-water interpretation plates of Block 27 in Xinhai, it can be determined based on the standard oil-water layer plates that the passing wells between oil wells are all interpreted as oil layers in the d1I1 section.

[0066] S3: Calculate the theoretical water cone radius at different depths in the vertical direction of a vertical well and the theoretical water ridge radius at different depths in the vertical direction of a horizontal well according to reservoir engineering methods

[0067] Since the bottom water cones upward from the oil-water interface to the oil layer, theoretically the shape of the water cone of a vertical well is basically a cone. At different heights from the oil-water interface, there are different water cone radii. With the increase of height, the water cone radius decreases, and with the increase of oil production, the water cone radius increases. The water cone radius at different depths of a vertical well can be calculated according to the following material balance formula (2):

[0068]

[0069] In formula (2): N p Indicates the cumulative oil production, unit 10 4 t; r is the water cone radius, unit is m; h is the reservoir thickness, unit is m; φ is the porosity, unit is %; S o Indicates the current oil saturation; E D Indicates displacement efficiency, unit: %; ρ o Indicates crude oil density, unit: kg / m 3 ; B oRepresents the volume coefficient of crude oil.

[0070] Similarly, the bottom water of a horizontal well turns the cone into a ridge. At different heights from the oil-water interface, there are different water cone radii. The water cone radius decreases with increasing height and increases with increasing oil production. The water cone radius at different depths of a horizontal well is calculated using the following material balance formula (3).

[0071]

[0072] In formula (3): N p Indicates the cumulative oil production, unit 10 4 t; r' represents the water ridge radius, unit is m; H represents the height from the horizontal section to the oil-water interface, unit is m; φ represents the porosity, unit is %; L represents the length of the horizontal section, unit is m; S o Indicates the current oil saturation; E D Indicates displacement efficiency, unit: %; ρ o Indicates crude oil density, unit: kg / m 3 ; B oi Represents the volume coefficient of crude oil.

[0073] S4: Use reservoir dynamic analysis method to make a vertical water flooding dynamic profile of the oil wells in the well area

[0074] This method is mainly based on various production data recorded during the drilling, oil testing and production process of oil and water wells, including liquid production profiles, water plugging data, C / O ratio logging, electrical logging interpretation of adjustment wells and production history, etc., combined with the results of geological research on reservoir structure, reservoir, sedimentary phase, etc., through comprehensive analysis of the above data, the oil and water distribution in the plane and vertical direction of the oil layer is found, thereby determining the remaining oil-rich area.

[0075] The collection and collation of the above-mentioned means of production include:

[0076] 1. Based on the results of sub-layer comparison, the electrical measurement interpretation data of 28 oil wells and the production process of the past 10 years are counted by sub-layer, mainly to verify the geological reserves of crude oil in the reservoir, the utilization status of stratified reserves, and the changes in oil well production, so as to reasonably determine the water flooding status of each sub-layer.

[0077] 2. Based on the historical data of oil well production, use the material balance formula to calculate the theoretical water cone radius at different depths of the oil well;

[0078] 3. Combine the geological layer structure of the reservoir, the reservoir sedimentary pattern, the sand body distribution law, and the geological map of oil and water distribution law to comprehensively analyze the actual water cone radius of the oil well;

[0079] 4. A total of 28 adjustment wells of various types were drilled in the Hai 26 block from 2007 to 2022. All of these adjustment wells encountered the Xinhai 27 block and were passing wells of the Xinhai 27 block. Therefore, the electrical logging interpretation data of the adjustment wells in the d1I1 section can be used to directly determine the flooding status of the small layers in the Xinhai 27 block.

[0080] 5. The cementing quality map of 28 wells is mainly used to eliminate water leakage caused by cross-groove due to poor cementing quality.

[0081] Specific steps:

[0082] a. Split the liquid production of each sub-layer of the oil well. The liquid production of the oil well with a liquid production profile is calculated based on the percentage of liquid production. The liquid production of the oil well without a liquid production profile is split based on the permeability of the well perforation thickness, that is, the kh value;

[0083] b. For oil wells located at the oil-water boundary that have water, their waterlogging status is judged based on the oil well pressure and liquid production. If the liquid production or pressure is stable, it means that there is sufficient energy replenishment, which is mainly affected by the invasion of edge water. For oil wells located at structural highs and far away from the oil-water boundary, the water content between oil wells is judged based on the analysis of oil well pressure and liquid production, and based on the logging interpretation data of newly drilled adjustment wells in Block 26 in recent years or the logging interpretation and production data of side-drilling wells;

[0084] c. Combined with detailed research on reservoir geology, including reservoir sedimentation pattern, sand body distribution law, oil-water distribution law, analyze the water inflow direction of the oil well, and recalibrate the actual water cone radius of the oil well based on the calculated theoretical water cone radius and theoretical water ridge radius;

[0085] d. For oil wells with partial water, first determine whether the water is real or fake: the water in the channel caused by the failure of the packer to seal during the workover operation and poor cementing is regarded as false water. On the contrary, if the oil well contains water, track the distribution range of the layer based on the comparison of small layers, determine the edge water position of the layer based on the time when the oil wells in this range see water, and determine the flooding range based on the absolute liquid production;

[0086] e. For oil wells that have never contained water during normal production, they are treated as dissolved gas drive, and their oil saturation is a function of pressure;

[0087] f. According to the above steps, make a vertical water flooding dynamic profile of the oil wells in the well area.

[0088] S5: Determine the horizontal well deployment boundaries

[0089] Determine the type of remaining oil, based on the distribution characteristics of the remaining oil, use the technical advantages of horizontal wells, try to adjust the well network in the remaining oil-rich areas between wells and the unused areas on the edges, and use numerical simulation to determine the optimal horizontal section length, well spacing, and vertical water avoidance distance in different locations.

[0090] Through numerical simulation, dynamic analysis and research, it is found that the optimal horizontal section length of the inter-cone zone horizontal well is about 150-200m, and the optimal horizontal section length of the unused edge area is 250-300m. The lower limits of the water avoidance distance between the inter-cone zone and the edge thin layer area are 10m and 6m respectively. The lower limit of the well spacing of the inter-cone zone horizontal well is 40m, and the lower limit of the horizontal well in the edge thin layer area is 10m.

[0091] S6: Determine reasonable horizontal well production parameters based on the set well pattern

[0092] In order to ensure that horizontal well development can achieve the best results and maximize the utilization of horizontal wells, numerical simulation is used to predict the production of horizontal wells under different production systems to obtain the optimal production parameters.

[0093] Through numerical simulation, dynamic analysis and calculation, the optimal steam injection intensity for steam throughput in the inter-conical zone is 7-10t / m, and the optimal steam injection intensity for steam throughput in the thin layer at the edge is 4-7t / m. The steam injection rate should be controlled below 200t / d, and the optimal liquid production intensity for thermal recovery of horizontal wells in the inter-conical zone is 0.2t / (m·d). Similarly, the optimal liquid production intensity for the thin layer at the edge is 0.1-0.15t / (m·d).

[0094] Example 1

[0095] This embodiment provides a specific application method of the technical solution of the present invention to the Xinhai 27 block of the Haiwaihe Oilfield:

[0096] 1. Determine the distribution pattern of residual oil

[0097] According to the material balance method, the current average remaining oil saturation of Xinhai 27 block is 42.4%, of which d1Ⅰ1 3 The remaining oil saturation of the sandstone group is 41.7%, d1Ⅰ3 1 The sandstone group is 44.2%.

[0098] According to the well logging data, statistical analysis is carried out, and the logging interpretation results are placed on the oil-water interpretation chart of Xinhai Block 27. According to the standard chart of oil and water layers, it can be determined that the passing wells between oil wells are interpreted as oil layers in the d1I1 section. For example, the Xinhai 27-H40CH pilot is deployed between the Haiping 1 and Hai C9-15CH wells, and the recovery rate of the recoverable reserves in the well area reaches 74.1%. The distance between the well and the Haiping 1 and Hai C9-15CH wells is 20 and 40m respectively. The drilling was completed in December 2022. The well logging of the well section corresponding to the d1I1 oil layer of Xinhai Block 27 is interpreted as an oil layer with an oil saturation of 57%, which is only 1.6% lower than the original. Therefore, this fully shows that the reason for the increase in water content in the adjacent wells is due to the upward cone effect of the bottom water, and there is still enriched residual oil between the wells.

[0099] According to the water cone calculation formula of the reservoir engineering method, the water cone radius of different depths in the vertical direction of the vertical wells in the high structural area of ​​the block is calculated (see Table 1). From the calculation results, it can be seen that with the decrease of depth, the water cone radius decreases with the increase of oil-bearing height. According to the calculation results of the water cone radius of 6 wells, from the depth of 1415m to 1395m, the water cone radius decreases from 43.5m to 12.3m, and the average water cone radius decreases by 1.56m for every 1m rise. The sweep coefficient is small, only 0.33, and there is still relatively rich residual oil between vertical wells.

[0100] Table 1. Calculation table of water cone radius at different depths of vertical wells in Hai C9-17 to Hai C11-27 well area

[0101]

[0102] Similarly, the water ridge radius at different depths in the vertical direction of the horizontal well is calculated (see Table 2). From the calculation results, it can be seen that as the depth decreases, the water cone radius decreases with the increase of oil-bearing height. According to the calculation results of the water cone radius of 6 wells, from the depth of 1420m to 1405m, the water cone radius decreases from 30m to 13m, and the average water cone radius decreases by 1.51m for every 1m rise. The sweep coefficient is small, only 0.33, and there is still relatively rich residual oil between horizontal wells.

[0103] Table 2 Calculation of water ridge radius at different depths of horizontal wells

[0104]

[0105] Based on the reservoir dynamic analysis method, a vertical water flooding dynamic profile of the oil well was made.

[0106] From the above research on the water cone characteristics and water cone radius of oil wells, it can be seen that the water content of the 27 oil wells in Xinhai Block is mainly caused by bottom water coning. The water cone shape is basically a cone, and there are still residual oil-rich areas between oil wells in high structural parts.

[0107] The application of numerical simulation can more realistically reflect the current distribution of oil saturation.

[0108] d1Ⅰ1 3 :It is the main oil-producing layer. The oil layer is more developed in the high part of the reservoir structure and the oil layer development range is large. Therefore, except for the water flooding around the oil wells in some lower parts of the structure, the oil saturation value in most areas remains above 0.50; it is an area with relatively rich remaining oil. d1Ⅰ3 1 :The oil layer is developed in the high part of the structure and has a small range. Except for the high part of the structure, due to the influence of edge water and the close distance to the oil-water interface, the flooded area is large, and only the middle part has an oil saturation above 0.5.

[0109] Numerical modeling studies have shown that the oil saturation of Xinhai Block 27 is above 40%, and the remaining geological reserves are 260×10 4 t, the remaining recoverable reserves are 102.2×10 4 t, there are 4 main types of residual oil:

[0110] (1) Intercone type

[0111] This type of oil is distributed between vertical wells and horizontal wells, or between horizontal wells, at the top of the oil layer, with bottom water coning, and the wells are unused. This type of oil is the largest type of remaining oil, with a remaining geological reserve of 135×10 4 t.

[0112] (2) Edge mobilization difference

[0113] This type is mainly due to the edge of the reservoir, where the oil layer is thin and no development wells are deployed, the well network is imperfect, the well spacing is large, and the well network control is low. The remaining geological reserves are 97×10 4 t.

[0114] (3) Fault-blocking type

[0115] This type of oil is relatively rich only near local faults, which is mainly due to the residual oil formed by fault action. The potential of this residual oil is to drill new wells and adjust production well points. The remaining reserves are 18×10 4 t.

[0116] (4) Thick oil layer internal barrier shielding type

[0117] This type of oil layer only exists in places where interlayers are developed. Since the thickness of interlayers in the oil layer is greater than 1.5 m, although the upper oil layer has been produced, it is laterally flooded due to the effect of the interlayer, and the remaining oil formed by the unproduced lower oil layer has a remaining reserve of 10×10 4 t.

[0118] For example, Xinhai 27-H120 is a horizontal well implemented in 2010, with a cumulative oil production of 1.5×10 4 t, the vertical depths of points A and B are 1400m and 1400m, respectively. Due to the thick interlayer in the well area, the well is analyzed to be edge water intrusion, and the reserves under the interlayer are not used. The horizontal well spacing is staggered by 50m, and the Hai C13-17CH well is deployed under the interlayer. The vertical depths of points A and B are designed to be 1412m and 1415m. It will be put into production in March 2023, and currently produces 11.6t of oil per day with a water cut of 63%.

[0119] 2. Well pattern parameter adjustment design

[0120] 2.1 Determination of reasonable well pattern and well spacing

[0121] The results were determined based on the distribution law of the remaining oil in the reservoir. Due to the influence of bottom water cone advance, the high part of the structure is severely flooded near the oil wells, the oil saturation of the oil layer is low, and the remaining oil between the wells is relatively enriched. Due to the different degree of production, the water cone radius of the oil wells is different in the vertical direction; while the reserves at the edge of the reservoir are not used and the oil saturation is relatively high.

[0122] Therefore, the horizontal well deployment of Block 27 in Xinhai adopts an irregular well pattern, and the horizontal wells are deployed in the inter-well residual oil-rich areas and the unused reserves areas at the margins where the oil saturation is currently high.

[0123] 2.2 Horizontal segment length

[0124] Through numerical simulation mechanism research, the development indicators of different horizontal well section lengths (500m, 400m, 300m, 200m) were divided into upper and lower layers, and the economic indicators of different horizontal section lengths were compared in combination with economic evaluation. From the calculation results, it can be seen that the optimal horizontal section length of the inter-conical zone horizontal well is about 150-200m, and the optimal horizontal section length of the edge unused area is 250-300m.

[0125] 2.3 Vertical water avoidance distance

[0126] For bottom water reservoirs, the greater the water avoidance distance, the later the water breakthrough time and the greater the cumulative oil production. According to the comparative analysis of numerical simulation results, for horizontal wells in the inter-cone zone, when the water avoidance thickness is greater than 10m, the economic limit production can be reached, while for horizontal wells in the edge thin layer, when the water avoidance distance is greater than 6m, the economic limit production can be reached. Therefore, the lower limits of the water avoidance distances in the inter-cone zone and the edge thin layer area are 10m and 6m.

[0127] 2.4 Spacing between adjacent wells in the plane

[0128] Since horizontal wells are deployed between wells, the distance from the adjacent wells will inevitably affect the invasion speed of the water cone of the adjacent wells. According to the comparative analysis of the numerical simulation results, the well spacing between the cones is greater than 40m, which can achieve economic indicators. At the same time, the cumulative oil production increase is small with the increase of the well spacing; the larger the well spacing of the thin layer horizontal wells in the edge, the higher the production, and the well spacing greater than 60m can achieve economic indicators. Therefore, the lower limit of the well spacing of horizontal wells deployed in the cone zone is 40m, and the lower limit of the horizontal wells in the thin layer area is 10m.

[0129] 3. Horizontal well production parameter design

[0130] 3.1 Optimization of steam injection intensity

[0131] The development indicators of horizontal wells under different steam injection intensities were numerically simulated and predicted, and the periodic production indicators of horizontal wells in the inter-cone zone were compared when the steam injection intensities were 3-15t / m. The results showed that when the steam injection intensity was 3t / m, the initial production of the oil well was low, the water content rose slowly, and the cumulative oil production in the period was small due to the small steam heating radius. When the steam injection intensity was 15t / m, the initial production of the oil well was high due to the excessive steam heating radius, which was connected with the bottom water. However, the water content rose quickly, the production decreased rapidly, and the cumulative oil production in the period was relatively small. When the steam injection intensity was 7-10t / m, the steam heating radius was moderate, the initial production of the oil well was high, the water content rose slowly, and the cumulative oil production in the period was high. Therefore, the best steam injection intensity for steam throughput in the inter-cone zone was determined to be 7-10t / m, and the best steam injection intensity for steam throughput in the thin layer of the edge was determined to be 4-7t / m. At the same time, in order to prevent the steam injection speed from being too high, causing steam to rush and cause bottom water to flow, the steam injection speed should be controlled below 200t / d.

[0132] 3.2 Optimization of liquid extraction intensity

[0133] On the basis of steam intensity and steam injection speed optimization, in order to ensure that the edge and bottom water does not advance rapidly during the production process, numerical simulation is used to optimize the reasonable liquid production of horizontal wells, and the production indicators of horizontal wells with daily liquid production of 15-75m3 are compared. The results show that for inter-cone zone horizontal wells, when the daily liquid production is 20m3, that is, the liquid production intensity is 0.1t / (m·d), the initial daily oil production of the oil well is small, the water content rises slowly, and the cumulative oil production of the cycle is low. When the daily liquid production reaches 50m3, that is, the liquid production intensity is 0.3t / (m·d), the initial daily oil production of the oil well is high, but the water content rises quickly, and the cumulative oil production of the cycle is low. When the daily liquid production is 30m 3 That is, when the liquid production intensity is 0.2t / (m·d), the oil well has a higher initial daily oil production, and the water content rises slowly, resulting in a higher cumulative oil production in the cycle. Therefore, the optimal liquid production intensity for thermal recovery of horizontal wells in the inter-conical zone is 0.2t / (m·d), and the optimal liquid production intensity for the thin layer at the edge is determined to be 0.1-0.15t / (m·d).

[0134] According to the above well network adjustment principles, 50 side-drilling horizontal wells were deployed, with an average controlled reserve of 4×104t per well. All of them were old wells. The annual production capacity of new crude oil was expected to be 5.6×104t, and the ultimate recovery rate of the block was expected to increase by 6.3%.

[0135] By using the technical solution of the present invention, the well pattern structure of thick-layered bottom water common heavy oil reservoirs is adjusted, which can effectively slow down the water content increase rate of the block and improve the overall reserve utilization, which has a strong guiding significance for the development of oil fields in the research block.

[0136] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir, wherein the characteristic steps are include: According to the calculated oil saturation of the remaining oil in the reservoir and the logging interpretation results of the oil wells, the reasons for the increase of water content in the reservoir in the well area and the enrichment of the remaining oil between the oil wells are determined; Calculate the theoretical water cone radius at different depths of each vertical well in the well area according to the remaining oil saturation, and judge the dynamic movement of water between vertical wells according to the calculation results; Calculate the theoretical water ridge radius at different depths of each horizontal well in the well area according to the remaining oil saturation, and judge the dynamic movement of water between horizontal wells according to the calculation results; Using the theoretical water cone radius and theoretical water ridge radius, the reservoir dynamic analysis method is used to make the vertical water flooding dynamic profile of the oil wells in the well area. Based on the water flooding dynamic profile, numerical simulation is used to determine the oil and water distribution in the remaining oil-rich area, and then the type of remaining oil is determined; According to the type of remaining oil, numerical simulation is used to determine the well network parameters, including the well network deployment boundary, the horizontal section length of the horizontal well, the plane adjacent well spacing, and the vertical water avoidance distance, and the well network structure is adjusted according to the well network parameters; Adjust the horizontal well production parameters according to the determined well pattern parameters.

2. The method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir according to claim 1, characterized in that: The calculation formula of the residual oil saturation is: S o =S oi -S os =S oi -RS oi =S oi (1-R) (1) In formula (1): S o Indicates the current oil saturation, in decimals; S oi Indicates the original oil saturation, in decimals; S os It indicates the reduction of oil saturation due to produced oil, in decimals; R indicates the current degree of production, in decimals.

3. The method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir according to claim 2, characterized in that: The theoretical water cone radius at different depths in the vertical direction of the vertical well is calculated according to the following formula: In formula (2): N p Indicates the cumulative oil production, unit 10 4 t; r represents the radius of the water cone, in m; h is the reservoir thickness, in m; φ is the porosity, in %; S o Indicates the current oil saturation; E D Indicates displacement efficiency, unit: %; ρ o Indicates crude oil density, unit: kg / m 3 ; B o Represents the volume coefficient of crude oil.

4. The method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir according to claim 2, characterized in that: The theoretical water ridge radius at different depths in the horizontal well is calculated according to the following formula: In formula (3): N p Indicates the cumulative oil production, unit 10 4 t; r' represents the radius of the water ridge, in m; H represents the height from the horizontal section to the oil-water interface, in m; φ represents the porosity, in %; L represents the length of the horizontal section, in m; S o Indicates the current oil saturation; E D Indicates displacement efficiency, unit: %; ρ o Indicates crude oil density, unit: kg / m 3 ; B oi Represents the volume coefficient of crude oil.

5. The method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir according to claim 1, characterized in that: The reservoir dynamic analysis method specifically comprises the following steps: a. Split the liquid production of each sub-layer of the oil well. The liquid production of the oil well with a liquid production profile is calculated based on the percentage of liquid production. The liquid production of the oil well without a liquid production profile is split based on the permeability of the well perforation thickness, that is, the kh value; b. For oil wells located at the oil-water boundary that have water, the water flooding status is judged based on the oil well pressure and liquid production. If the liquid production or pressure is stable, it means that there is sufficient energy replenishment, which is mainly due to the invasion of edge water. For oil wells located at high structural parts and far away from the oil-water boundary, the water content between oil wells is judged based on the analysis of oil well pressure and liquid production, and the logging interpretation data of newly drilled adjustment wells or the logging interpretation and production data of side-drilled wells; c. Combined with detailed research on reservoir geology, including reservoir sedimentation pattern, sand body distribution law, oil-water distribution law, analyze the water inflow direction of the oil well, and recalibrate the actual water cone radius of the oil well based on the calculated theoretical water cone radius and theoretical water ridge radius; d. For oil wells with partial water, first determine whether the water is real or fake: the water in the channel caused by the failure of the packer to seal during the workover operation and poor cementing is regarded as false water. On the contrary, if the oil well contains water, track the distribution range of the layer based on the comparison of small layers, determine the edge water position of the layer based on the time when the oil wells in this range see water, and determine the flooding range based on the absolute liquid production; e. For oil wells that have never contained water during normal production, they are treated as dissolved gas drive, and their oil saturation is a function of pressure; f. According to the above steps, make a vertical water flooding dynamic profile of the oil wells in the well area.

6. The method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir according to claim 1, characterized in that: The types of residual oil include but are not limited to: (1) Intercone type This type of distribution is located between vertical wells and horizontal wells, or between horizontal wells, at the top of the oil layer, with bottom water coning, and the wells are unused; (2) Edge mobilization difference This type of distribution is located at the edge of the reservoir. Due to the thin oil layer, the development wells are not deployed in the area, the well network is imperfect, the well spacing is large, and the well network control is low; (3) Fault-blocking type This type of oil is relatively enriched only near local faults. It is residual oil mainly formed by fault action. The potential of this type of residual oil is to drill new wells and adjust production well points. (4) Thick oil layer internal barrier shielding type This type only exists in places where interlayers are developed. Since the thickness of the interlayers in the oil layer is greater than 1.5m, although the upper oil layer has been produced, it is laterally flooded due to the effect of the interlayers, resulting in residual oil in the lower oil layer that has not been produced.

7. The method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir according to claim 1, characterized in that: The well network structure adjustment is carried out in the residual oil-rich area between wells and the edge unmoved area.

8. The method for adjusting the well pattern structure of a thick layered bottom water common heavy oil reservoir according to claim 1, characterized in that: The horizontal well production parameters include horizontal well steam injection intensity, steam injection speed and liquid production intensity.

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