A method for adjusting the well pattern structure of a thick-layered bottom water common heavy oil reservoir

Abstract

This invention provides a method for adjusting the well network structure of thick-layered bottom-water ordinary heavy oil reservoirs. The steps include: determining the cause of water cut rise in the reservoir and the enrichment of remaining oil between wells based on the oil saturation of remaining oil and the logging interpretation results of the wells; calculating the theoretical water cone radius at different depths in the vertical direction of each vertical well and the theoretical water ridge radius at different depths in the vertical direction of each horizontal well based on the oil saturation of remaining oil; creating a vertical waterflood dynamic profile of the wells in the reservoir using reservoir dynamic analysis methods, applying numerical simulation to determine the oil-water distribution in the remaining oil enrichment area, and thus determining the type of remaining oil; determining the well network parameters based on the type of remaining oil using numerical simulation, and adjusting the well network structure based on the well network parameters; and adjusting the production parameters of the horizontal wells based on the determined well network parameters. This invention can more accurately and precisely describe the distribution of remaining oil, effectively slow down the rate of water cut rise in the block, and improve the overall reserve utilization rate.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology and relates to well network structure adjustment technology, specifically a method for adjusting the well network structure of thick-layered bottom water ordinary heavy oil reservoirs. Background Technology

[0002] The Xinhai 27 block was put into development in 1993. In February 1994, the highest daily oil production reached 366 tons, with an oil production rate of 2.68%. However, due to various factors such as the high oil-water viscosity ratio, active bottom and edge water energy, and external channeling of the well casing, the bottom water coning and edge water fingering and tongueing were serious problems. The oil reservoir reserves were unevenly utilized, the water cut increased rapidly, and the oil reservoir was in a low-speed development state and was on the verge of being abandoned. The original strata, well network, and extraction methods are no longer suitable for the needs of reservoir development. Since 2003, the effectiveness of primary reservoir development has been systematically evaluated. Based on a series of studies, including detailed reservoir description, remaining oil distribution characteristics, reservoir formation mechanism of low oil saturation reservoirs, seepage mechanism of thermally recovered heavy oil reservoirs, seepage mechanism of horizontal wells, and secondary development technology strategies, secondary development using horizontal wells has transformed water cones into water ridges, effectively slowing down the water flooding rate. The development indicators of fault blocks have been significantly improved, with daily oil production increasing from 32t to a peak of 358t, reaching the peak level of primary development. The oil production rate increased from 0.26% to 2.8%, and the overall water cut decreased from 93.6% to 81.4%. The secondary development of horizontal wells has achieved significant results.

[0003] However, although secondary development of horizontal wells has achieved many results in laboratory research and field tests, after 14 years of secondary development, 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 properties and fluid viscosity, bottom water rapidly advances from the oil-water interface to the horizontal section, resulting in a rapid increase in water cut in oil wells. The water drive sweep coefficient of the reservoir is low, and there is still a relatively rich residual oil between wells in the structural high part, which is difficult to effectively utilize. The distribution of residual oil is more complicated, and a detailed description of the residual oil is the key factor in determining whether well network 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 development of horizontal wells, which affects the development effect of horizontal wells and further increases the complexity of the distribution of remaining oil. The reason for the uneven utilization is the uneven development of oil layers, drilling mud pollution and differences in production system. Therefore, how to improve the utilization of the horizontal section is extremely important for well pattern adjustment. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a method for adjusting the well network structure of thick-layered bottom water ordinary heavy oil reservoirs, which can more accurately and precisely describe the distribution of remaining oil, effectively slow down the rate of water cut increase in the block, and improve the overall reserve utilization rate.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows:

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

[0009] Based on the calculated oil saturation of the remaining oil in the reservoir and the logging interpretation results of the oil wells, determine the reasons for the increase in water cut in the reservoir in this well area and the enrichment of remaining oil between each oil well;

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

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

[0012] Using theoretical water cone radius and theoretical water ridge radius, a longitudinal water flood dynamic profile of the oil wells in this well area was generated using reservoir dynamic analysis methods. Based on the water flood dynamic profile, numerical simulation was applied to determine the oil-water distribution in the remaining oil enrichment area, and then the type of remaining oil was determined.

[0013] Based on the remaining oil type, the well network parameters are determined by numerical simulation, including the well network deployment boundary, the horizontal section length of horizontal wells, the plane distance between adjacent wells, and the vertical water avoidance distance. The well network structure is then adjusted based on the well network parameters.

[0014] Adjust the production parameters of the horizontal wells according to the determined well network parameters.

[0015] Furthermore, the formula for calculating the oil saturation of the remaining oil is as follows:

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

[0017] In formula (1): S o This indicates the current oil saturation level, in decimal form; S oi Indicates the original oil saturation, in decimal form; S os The value represents the decrease in oil saturation due to the production of oil, in decimal form; R represents the current production level, in decimal form.

[0018] Furthermore, the theoretical water cone radius at different depths along the vertical shaft is calculated using the following formula:

[0019]

[0020] In equation (2): N p This indicates cumulative oil production, in units of 10. 4 t; r represents the water cone radius, in meters; h represents the reservoir thickness, in meters; φ represents porosity, in percent; S o Indicates the current oil saturation; E D ρ represents displacement efficiency, expressed as a percentage (%). o This indicates the density of crude oil, in kg / m³. 3 B o This represents the volume coefficient of crude oil.

[0021] Furthermore, the theoretical water ridge radius at different depths along the longitudinal direction of the horizontal well is calculated using the following formula:

[0022]

[0023] In equation (3): N p This indicates cumulative oil production, in units of 10. 4 t; r' represents the water ridge radius, in meters; H represents the height from the horizontal section to the oil-water interface, in meters; φ represents porosity, in percent; L represents the length of the horizontal section, in meters; S o Indicates the current oil saturation; E D ρ represents displacement efficiency, expressed as a percentage (%). o This indicates the density of crude oil, in kg / m³. 3 B oi This represents the volume coefficient of crude oil.

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

[0025] a. The production of each layer of the oil well is divided. The production of the oil well with a production profile is calculated based on the production percentage. The production of the oil well without a production profile is divided based on the permeability of the perforated thickness of the oil well, i.e., the kh value.

[0026] b. For oil wells located at the oil-water boundary that have water ingress, the water flooding status is determined based on the well's pressure and production rate. If the production rate or pressure is stable, it indicates that there is sufficient energy supply, mainly due to the intrusion of edge water. For oil wells located in structural high positions and far from the oil-water boundary that have water ingress, the water ingress status between oil wells is determined based on the analysis of the well's pressure and production rate, as well as the logging interpretation data of newly drilled adjustment wells or the logging interpretation and production data of sidetracking wells.

[0027] c. Combine detailed reservoir geology studies, including reservoir sedimentary patterns, sand body distribution patterns, and oil-water distribution patterns, analyze the water inflow direction of oil wells, and recalibrate the actual water cone radius of oil wells based on the calculated theoretical water cone radius and theoretical water ridge radius;

[0028] d. For oil wells that have localized water ingress, first determine whether the water ingress is genuine or false: water ingress caused by packer failure during well workover operations or poor cementing is considered false water ingress. Conversely, if the oil well has water ingress, trace the distribution range of the layer by comparing the sub-layers, determine the edge water location of the layer based on the water ingress time of the oil wells in that range, and determine the water flooding range by the absolute production rate.

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

[0030] f. Based on the above steps, create a longitudinal water-flooded 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) Interconical zone type

[0033] This type of distribution is located between vertical and horizontal wells, or between horizontal wells, at the top of the oil layer, with bottom water coning, and the wells between them are not utilized;

[0034] (2) Edge movement difference type

[0035] This type of distribution is located at the edge of the reservoir, in areas where the oil layer is thin and no development wells have been deployed, resulting in an incomplete well network, large well spacing, and low well network control.

[0036] (3) Fault-blocking type

[0037] This type of oil is relatively enriched only near local faults and is due to the residual oil formed mainly 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 interlayer shielding type

[0039] This type exists only 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 activated, it is laterally flooded by the interlayers, and the lower oil layer remains unactivated, forming residual oil.

[0040] Furthermore, the well network structure adjustment is carried out in the remaining oil-rich areas between wells and the untouched peripheral areas.

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

[0042] The beneficial effects of this invention include:

[0043] By calculating the theoretical water cone radius and theoretical water ridge radius based on the remaining oil saturation, and then using reservoir dynamic analysis methods to create a longitudinal waterflood dynamic profile of the oil well, numerical simulation methods, such as numerical simulation software or models, can be used to further determine the oil-water distribution in the remaining oil-rich area. This allows for a more accurate and detailed description of the remaining oil distribution, identification of the remaining oil type, and determination of well network parameters based on the numerical simulation results, further optimization of the well network structure, and improvement of the recovery rate.

[0044] Specifically, by calculating the remaining oil saturation in the reservoir and interpreting well logging results, we can determine the reasons for the increase in water cut in the reservoir area and the enrichment of remaining oil between wells, thus identifying whether water flooding exists and enabling more precise analysis of the reservoir state. By calculating the theoretical water cone radius and theoretical water ridge radius at different depths in vertical and horizontal wells, and judging the dynamic movement of water based on the calculation results, we can understand the distribution of water between wells, thereby better understanding the water migration patterns in the reservoir. By using the theoretical water cone radius and theoretical water ridge radius, and employing reservoir dynamic analysis methods to create a vertical water flooding dynamic profile of the wells, we can visually display the vertical water flooding situation of the wells, which helps in analyzing and understanding the water flooding problem and provides a basis for subsequent well network structure adjustments. Through the water flooding dynamic profile and numerical simulation, we can determine the oil-water distribution in the remaining oil enrichment area and further identify the type of remaining oil, which is of great significance for optimizing development strategies and formulating measures to improve recovery rates.

[0045] Based on the remaining oil type and numerical simulation results, well network parameters are determined, including well network deployment boundaries, horizontal well section lengths, horizontal well spacing, and vertical water avoidance distance. Then, the well network structure is adjusted in the remaining oil-rich areas and undisturbed peripheral areas. The adjusted well network structure can better adapt to dynamic changes in groundwater, improving recovery rates. Based on the determined well network parameters, the steam injection and fluid production intensities of the oil wells are adjusted. By rationally controlling the intensity of steam injection and fluid production, oil well production and water flooding can be better controlled, further optimizing recovery performance.

[0046] In summary, this method of adjusting the well network structure in thick-layered bottom-water ordinary heavy oil reservoirs can help understand the reservoir status, identify water flooding issues, optimize development strategies, and improve recovery rates. It can effectively slow down the rate of water cut increase in the block and improve the overall reserve utilization rate, which has important guiding significance for the development of oilfields in the research block. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the dynamic water flooding of the reservoir in wells C11-15 to C11-33 of this invention, as shown in Embodiment 1 of the present invention.

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

[0049] Figure 3 This is the relationship between the length of the horizontal well in the intercone zone and the production and yield of Embodiment 1 of the present invention;

[0050] Figure 4 This describes the relationship between the length of the horizontal well at the edge of the edge and the production and yield rate in Embodiment 1 of the present invention.

[0051] Figure 5 This is the curve showing the relationship between the water-avoiding distance of the intercone zone and cumulative oil production in Embodiment 1 of the present invention;

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

[0053] Figure 7 This is the cumulative oil production relationship curve of different well spacings in the intercone zone of Embodiment 1 of the present invention;

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

[0055] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] This invention provides a method for adjusting the well network structure of thick-layered bottom water ordinary heavy oil reservoirs, aiming to maximize development effects, effectively improve reservoir development effects during the "high-yield and high-volume" development stage, and further enhance recovery rate.

[0057] To address the development challenges faced by the Xinhai 27 bottom-water reservoirs in the later stages of development, and based on the principles of refined reservoir potential evaluation, quantitative determination of remaining oil distribution, and optimization of technical policy parameters, an innovative approach was adopted: small-spacing, short-radius horizontal wells were implemented to achieve a vertically interlocking, layered, three-dimensional development model, effectively expanding the deployment space. Specific steps included:

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

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

[0060] Oilfield development practice has shown that in water-driven sandstone reservoirs, once fully operational and entering a stable production phase, the relationship between oil saturation and recovery rate is as follows:

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

[0062] In formula (1): S o This indicates the current oil saturation level, in decimal form; S oi Indicates the original oil saturation, in decimal form; S os The value represents the decrease in oil saturation due to the production of oil, in decimal form; R represents the current production level, in decimal form.

[0063] S2: Well logging interpretation for oil wells

[0064] Since the fault block is located in the d1Ⅰ section, and the underlying layer is the Hai 26 block, more than 200 through wells have encountered the Xin 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 in the Xin Hai 27 block well network. At the same time, 4 pilot wells were drilled in different locations in the fault block in 2022. Therefore, the oil saturation between oil wells in the Xin 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 chart of Block 27 in Xinhai, it can be determined that the wells passing through the oil wells in the d1I1 section are all interpreted as oil layers according to the standard chart of oil-water layers.

[0066] S3: Calculate the theoretical water cone radius at different depths along the vertical direction of vertical wells and the theoretical water ridge radius at different depths along the vertical direction of horizontal wells using reservoir engineering methods.

[0067] Since bottom water convections upwards from the oil-water interface into the oil layer, theoretically, the shape of the water cone in a vertical well is basically a cone. At different heights from the oil-water interface, the water cone radius varies. As the height increases, the water cone radius decreases, and as the oil production increases, the water cone radius increases. The water cone radius at different depths in a vertical well can be calculated using the following material balance formula (2):

[0068]

[0069] In equation (2): N p This indicates cumulative oil production, in units of 10. 4 t; r represents the water cone radius, in meters; h represents the reservoir thickness, in meters; φ represents porosity, in percent; S o Indicates the current oil saturation; E D ρ represents displacement efficiency, expressed as a percentage (%). o This indicates the density of crude oil, in kg / m³. 3 B oThis represents the volume coefficient of crude oil.

[0070] Similarly, the bottom water flooding cone of a horizontal well becomes a ridge. At different heights from the oil-water interface, the water cone radius is different. As the height increases, the water cone radius decreases, and as the oil production increases, the water cone radius increases. The water cone radius at different depths of the horizontal well can be calculated according to the following material balance formula (3).

[0071]

[0072] In equation (3): N p This indicates cumulative oil production, in units of 10. 4 t; r' represents the water ridge radius, in meters; H represents the height from the horizontal section to the oil-water interface, in meters; φ represents porosity, in percent; L represents the length of the horizontal section, in meters; S o Indicates the current oil saturation; E D ρ represents displacement efficiency, expressed as a percentage (%). o This indicates the density of crude oil, in kg / m³. 3 B oi This represents the volume coefficient of crude oil.

[0073] S4: A longitudinal waterflood dynamic profile of the oil wells in this well area was generated using reservoir dynamic analysis methods.

[0074] This method mainly relies on various production data collected during the drilling, testing, and production processes of oil and water wells, including production profiles, water shut-off data, C / O ratio logging, electrical logging interpretation of adjustment wells, and production history. Combined with geological research results such as reservoir structure, reservoir, and sedimentary facies, the method comprehensively analyzes the above data to identify the oil and water distribution in the horizontal and vertical directions of the oil layer, thereby determining the remaining oil-rich areas.

[0075] The collection and organization of the above-mentioned production materials include:

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

[0077] 2. Based on the production history data of oil wells, the theoretical water cone radius at different depths of the oil well is calculated using the material balance formula;

[0078] 3. Combine geological maps of reservoir geological layers, reservoir sedimentary patterns, sand body distribution patterns, and oil-water distribution patterns 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 Block 26 of Hai from 2007 to 2022. All of these adjustment wells encountered Block 27 of Xinhai and were passing wells of Block 27. Therefore, the water flooding status of the small layer of Block 27 of Xinhai can be directly determined by the electrical logging interpretation data of the adjustment wells in the d1I1 section.

[0080] The cementing quality diagrams for wells 5.28 are primarily intended to rule out water production caused by cross-flow due to poor cementing quality.

[0081] Specific steps:

[0082] a. The production of each layer of the oil well is divided. The production of the oil well with a production profile is calculated based on the production percentage. The production of the oil well without a production profile is divided based on the permeability of the perforated thickness of the oil well, i.e., the kh value.

[0083] b. For oil wells located at the oil-water boundary that have water ingress, the water flooding status is determined based on the well's pressure and production rate. If the production rate or pressure is stable, it indicates that there is sufficient energy supply, mainly due to the intrusion of edge water. For oil wells located in structural high positions and far from the oil-water boundary that have water ingress, the water ingress status between oil wells is determined based on the analysis of the well's pressure and production rate, as well as the logging interpretation data of newly drilled adjustment wells or sidetracking wells and production data in Block 26 in recent years.

[0084] c. Combine detailed reservoir geology studies, including reservoir sedimentary patterns, sand body distribution patterns, and oil-water distribution patterns, analyze the water inflow direction of oil wells, and recalibrate the actual water cone radius of oil wells based on the calculated theoretical water cone radius and theoretical water ridge radius;

[0085] d. For oil wells that have localized water ingress, first determine whether the water ingress is genuine or false: water ingress caused by packer failure during well workover operations or poor cementing is considered false water ingress. Conversely, if the oil well has water ingress, trace the distribution range of the layer by comparing the sub-layers, determine the edge water location of the layer based on the water ingress time of the oil wells in that range, and determine the water flooding range by the absolute production rate.

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

[0087] f. Based on the above steps, create a longitudinal water-flooded dynamic profile of the oil wells in the well area.

[0088] S5: Determine the boundaries for horizontal well deployment

[0089] Determine the type of remaining oil, and based on the distribution characteristics of the remaining oil, take advantage of the technology of horizontal wells to carry out well network adjustments in the areas where the remaining oil is concentrated between wells and the unused areas at the edges. Use numerical simulation to determine the optimal horizontal section length, well spacing, and vertical water avoidance distance for different locations.

[0090] Numerical simulation and dynamic analysis revealed that the optimal horizontal section length for horizontal wells in the interconical zone is approximately 150-200m, while the optimal length for the horizontal section in the undeveloped edge area is 250-300m. The lower limits for water avoidance distances in the interconical zone and the thin edge area are 10m and 6m, respectively. The lower limit for horizontal well spacing in the interconical zone is 40m, and the lower limit for horizontal well spacing in the thin edge area is 10m.

[0091] S6: Determine reasonable horizontal well production parameters based on the established well network.

[0092] To ensure the best results from horizontal well development and maximize its utilization, numerical simulations are used to predict the production of horizontal wells under different production regimes in order to obtain optimal production parameters.

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

[0094] Example 1

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

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

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

[0098] Statistical analysis was conducted based on well logging data, and the logging interpretation results were plotted on the oil-water interpretation chart of Block 27 in Xinhai. According to the standard chart for oil-water formations, all wells passing through the oil wells in the d1I1 section were interpreted as oil-bearing layers. For example, the Xinhai 27-H40CH pilot well was located between Haiping 1 and HaiC9-15CH wells, with a recoverable reserve recovery rate of 74.1%. This well was 20m and 40m away from Haiping 1 and HaiC9-15CH wells, respectively, and was completed in December 2022. The well section corresponding to the d1I1 section of the Xinhai 27 block was interpreted as an oil-bearing layer, with an oil saturation of 57%, which is only 1.6% lower than the original. Therefore, this fully demonstrates that the increase in water cut in adjacent wells is due to the upward conical effect of bottom water, and there is still enriched residual oil between the wells.

[0099] The water cone radii at different depths along the vertical well in the structural high region of this block were calculated using the water cone calculation formula from the reservoir engineering method (see Table 1). The calculation results show that the water cone radius decreases with decreasing depth and increasing oil-bearing height. According to the calculation results of six wells, from a depth of 1415m to 1395m, the water cone radius decreased from 43.5m to 12.3m, an average decrease of 1.56m for every 1m increase in depth. The sweep efficiency is low, only 0.33, indicating that relatively rich residual oil still exists between vertical wells.

[0100] Table 1. Calculation of water cone radius at different depths in vertical wells in the HaiC9-17~HaiC11-27 well area.

[0101]

[0102] Similarly, the water ridge radius at different depths along the longitudinal direction of the horizontal well was calculated (see Table 2). The calculation results show that as the depth decreases, the water cone radius decreases with the increase of the oil-bearing height. According to the calculation results of the water cone radius of 6 wells, from a depth of 1420m to 1405m, the water cone radius decreased from 30m to 13m, an average decrease of 1.51m for every 1m increase in depth. The sweep efficiency is low, only 0.33, indicating that relatively rich residual oil still exists between horizontal wells.

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

[0104]

[0105] A longitudinal water-flood dynamic profile of the oil well was generated based on the reservoir dynamic analysis method.

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

[0107] Numerical simulations can more realistically reflect the current distribution of oil saturation.

[0108] d1Ⅰ1 3 This is the main oil-producing layer, with oil layers well-developed in the structurally high parts of the reservoir and covering a large area. Therefore, except for some water-flooded areas around wells in lower structural regions, the oil saturation value in most areas remains above 0.50; this is an area with relatively rich remaining oil. d1Ⅰ3 1 The oil layer is developed in the high part of the structure and is relatively small in area. Apart from the high part of the structure, due to the influence of edge water and its proximity to the oil-water interface, the water-flooded area is relatively large, and only the middle part has an oil saturation of more than 0.5.

[0109] Numerical modeling studies indicate that the oil saturation of Block 27 in Xinhai is above 40%, with remaining geological reserves of 260 × 10⁻⁶. 4 t, remaining recoverable reserves 102.2×10 4 There are four main types of residual oil:

[0110] (1) Interconical zone type

[0111] This type of distribution is located between vertical and horizontal wells, or between horizontal wells, at the top of the oil layer, with bottom water coning, and the wells remaining undeveloped. This type accounts for the largest proportion of remaining oil, with remaining geological reserves of 135 × 10⁻⁶. 4 t.

[0112] (2) Edge movement difference type

[0113] This type mainly occurs at the edges of oil reservoirs, in areas where the oil layer is thin and no development wells have been deployed. The well network is incomplete, well spacing is large, and the degree of well network control is low. The remaining geological reserves are 97 × 10⁻⁶. 4 t.

[0114] (3) Fault-blocking type

[0115] This type of oil is relatively enriched only near local faults, primarily due to residual oil formed by faulting. Exploiting this residual oil involves new well drilling and adjusting production well locations; the remaining reserves are 18 × 10⁻⁶. 4 t.

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

[0117] This type exists only where interlayers are developed. Because the thickness of the interlayers within the oil reservoir is greater than 1.5m, although the upper oil layer has been activated, it is laterally flooded due to the interlayers, resulting in unactivated lower oil layers and remaining oil reserves of 10×10⁻⁶. 4 t.

[0118] For example, Xinhai 27-H120 is a horizontal well implemented in 2010, with a cumulative oil production of 1.5 × 10⁻⁶. 4 The well has vertical depths of 1400m and 1400m at points A and B, respectively. Due to the large thickness of the interlayer in the well area, the well is analyzed to be a boundary water intrusion. The reserves below the interlayer have not been utilized. The horizontal well spacing is staggered by 50m. The offshore C13-17CH well is deployed below the interlayer, with designed vertical depths of 1412m and 1415m at points A and B, respectively. It was put into production in March 2023, and currently produces 11.6t of oil per day with a water cut of 63%.

[0119] 2. Well Network Parameter Adjustment Design

[0120] 2.1 Determination of Reasonable Well Pattern and Well Spacing

[0121] Based on the distribution pattern of remaining oil in the reservoir, the results show that due to the influence of bottom water coning in the high structural part of the block, the well points are severely flooded and the oil saturation of the oil layer is low. The remaining oil between wells is relatively rich. Due to the different degrees of production, the water coning radius of the oil wells is different in the vertical direction. Meanwhile, the reserves at the edge of the reservoir have not been utilized and the oil saturation is relatively high.

[0122] Therefore, the 27 horizontal wells in Xinhai are deployed using an irregular well pattern, with the horizontal wells located in the inter-well remaining oil-rich areas and the marginal untapped reserves areas where the oil saturation is currently high.

[0123] 2.2 Length of horizontal segment

[0124] Through numerical simulation and mechanistic research, the development indicators of different horizontal well section lengths (500m, 400m, 300m, 200m) were studied in the upper and lower layers. Combined with economic evaluation, the economic indicators of different horizontal section lengths were compared. The calculation results show that the optimal horizontal section length for horizontal wells in the intercone zone is about 150-200m, and the optimal horizontal section length for the undeveloped edge 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, and the greater the cumulative oil production. Based on comparative analysis of numerical simulation results, for horizontal wells in the intercone zone, the economically limited production rate can be reached when the water-avoidance thickness is greater than 10m, while for thin-layer horizontal wells at the edge, the economically limited production rate can be reached when the water-avoidance distance is greater than 6m. Therefore, the lower limits of the water-avoidance distance in the intercone zone and thin-layer edge areas are 10m and 6m, respectively.

[0127] 2.4 Planar adjacent well spacing

[0128] Since horizontal wells are deployed between wells, their distance from adjacent wells inevitably affects the intrusion rate of the water cone. Comparative analysis of numerical simulation results shows that a well spacing greater than 40m in the inter-cone zone achieves economic targets, while the cumulative oil production increase is relatively small with increasing well spacing. In the thinner edge layer, a larger well spacing results in higher production; a well spacing greater than 60m achieves economic targets. Therefore, the lower limit for horizontal well spacing in the inter-cone zone is 40m, and the lower limit for horizontal well spacing in the thinner edge layer is 10m.

[0129] 3. Horizontal Well Production Parameter Design

[0130] 3.1 Optimization of Steam Injection Intensity

[0131] Numerical simulations were used to predict the development indicators of horizontal wells under different steam injection intensities. The cyclic production indicators of horizontal wells with steam injection intensities of 3-15 t / m in the interconical zone were compared. The results show that at a steam injection intensity of 3 t / m, the initial oil well production is low due to the small steam heating radius, the water cut rises slowly, and the cumulative oil production over the cycle is low. When the steam injection intensity is 15 t / m, the steam heating radius is too large, leading to cross-contamination with bottom water. The initial oil well production is high, but the water cut rises rapidly, resulting in a rapid decline in production and relatively low cumulative oil production over the cycle. When the steam injection intensity is 7-10 t / m, the steam heating radius is moderate, resulting in high initial oil well production, a slow rise in water cut, and high cumulative oil production over the cycle. Therefore, the optimal steam injection intensity for interconical zone steam injection is determined to be 7-10 t / m. Similarly, the optimal steam injection intensity for thin-layer steam injection at the edge is determined to be 4-7 t / m. To prevent excessive steam injection rate from causing steam surge and bottom water cross-contamination, the steam injection rate should be controlled below 200 t / d.

[0132] 3.2 Optimization of fluid collection intensity

[0133] Based on the optimization of steam intensity and injection rate, to ensure that the bottom water does not rapidly advance during production, numerical simulation was used to optimize the reasonable production rate of horizontal wells. The production indicators of horizontal wells with daily production rates of 15-75 m³ were compared. The results show that for horizontal wells in the conical zone, when the daily production rate is 20 m³ (i.e., the production intensity is 0.1 t / (m·d)), the initial daily oil production is low, the water cut rises slowly, and the cumulative oil production over the cycle is low. When the daily production rate reaches 50 m³ (i.e., the production intensity is 0.3 t / (m·d)), the initial daily oil production is high, but the water cut rises rapidly, and the cumulative oil production over the cycle is low. When the daily production rate is 30 m³, the initial daily oil production is high, but the water cut rises rapidly, and the cumulative oil production over the cycle is low. 3 When the fluid production intensity is 0.2 t / (m·d), the daily oil production of the well is relatively high in the initial stage, and the water cut rises at a relatively slow rate, resulting in a relatively high cumulative oil production over the period. Therefore, the optimal fluid production intensity for thermal recovery of horizontal wells in the intercone zone is 0.2 t / (m·d), and similarly, the optimal fluid production intensity for thin layers at the edge is determined to be 0.1-0.15 t / (m·d).

[0134] Based on the above well network adjustment principles, 50 sidetracked horizontal wells will be deployed, with an average controlled reserve of 4×10⁴ t per well. All of these wells will utilize existing wells, and the estimated annual crude oil production capacity is 5.6×10⁴ t. The block is expected to ultimately increase its recovery rate by 6.3%.

[0135] Using the technical solution of this invention, the well network structure adjustment of thick-layered bottom water ordinary heavy oil reservoirs can effectively slow down the rate of water cut increase in the block and improve the overall reserve utilization rate, which has strong guiding significance for the development of oilfields in the research block.

[0136] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for adjusting the well network structure of a thick-layered bottom water ordinary heavy oil reservoir, characterized by the following steps: include: Based on the calculated oil saturation of the remaining oil in the reservoir and the logging interpretation results of the oil wells, determine the reasons for the increase in water cut in the reservoir in this well area and the enrichment of remaining oil between each oil well; Calculate the theoretical water cone radius at different depths along the longitudinal direction of each vertical well in the well area based on the remaining oil saturation, and judge the dynamic movement of water between vertical wells based on the calculation results; Calculate the theoretical water ridge radius at different depths in the longitudinal direction of each horizontal well in the well area based on the remaining oil saturation, and judge the dynamic movement of water between horizontal wells based on the calculation results; Using theoretical water cone radius and theoretical water ridge radius, a longitudinal water flood dynamic profile of the oil wells in this well area was generated using reservoir dynamic analysis methods. Based on the water flood dynamic profile, numerical simulation was applied to determine the oil-water distribution in the remaining oil enrichment area, and then the type of remaining oil was determined. Based on the remaining oil type, the well network parameters are determined by numerical simulation, including the well network deployment boundary, the horizontal section length of horizontal wells, the plane distance between adjacent wells, and the vertical water avoidance distance. The well network structure is then adjusted based on the well network parameters. Adjust the production parameters of the horizontal wells according to the determined well pattern parameters; The reservoir dynamic analysis method specifically includes the following steps: a. The production of each layer of the oil well is divided. The production of the oil well with a production profile is calculated based on the production percentage. For the oil well without a production profile, the production of each layer is divided according to the permeability of the perforated thickness of the oil well. b. For oil wells located at the oil-water boundary that have water ingress, the water flooding status is determined based on the well's pressure and production rate. If the production rate or pressure is stable, it indicates that there is sufficient energy supply, mainly due to the intrusion of edge water. For oil wells located in structural high positions and far from the oil-water boundary that have water ingress, the water ingress status between oil wells is determined based on the analysis of the well's pressure and production rate, as well as the logging interpretation data of newly drilled adjustment wells or the logging interpretation and production data of sidetracking wells. c. Combine detailed reservoir geology studies, including reservoir sedimentary patterns, sand body distribution patterns, and oil-water distribution patterns, analyze the water inflow direction of oil wells, and recalibrate the actual water cone radius of oil wells based on the calculated theoretical water cone radius and theoretical water ridge radius; d. For oil wells that have localized water ingress, first determine whether the water ingress is genuine or false: water ingress caused by packer failure during well workover operations or poor cementing is considered false water ingress. Conversely, if the oil well has water ingress, trace the distribution range of the layer by comparing the sub-layers, determine the edge water location of the layer based on the water ingress time of the oil wells in that range, and determine the water flooding range by the absolute production rate. e. For oil wells that have never contained water during normal production, when treated with dissolved gas drive, their oil saturation is a function of pressure; f. Based on the above steps, create a longitudinal water-flooded dynamic profile of the oil wells in the well area.

2. The method for adjusting the well network structure of a thick-layered bottom-water ordinary heavy oil reservoir according to claim 1, characterized in that, The formula for calculating the oil saturation of the remaining oil is: S o =S oi -S os =S oi -RS oi =S oi (1-R) (1) In formula (1): S o This indicates the current oil saturation level, in decimal form; S oi Indicates the original oil saturation, in decimal form; S os The value represents the decrease in oil saturation due to the production of oil, in decimal form; R represents the current production level, in decimal form.

3. The method for adjusting the well network structure of a thick-layered bottom water ordinary heavy oil reservoir according to claim 2, characterized in that, The theoretical water cone radius at different depths along the vertical shaft is calculated using the following formula: In equation (2): N p This indicates cumulative oil production, in units of 10. 4 t; r represents the radius of the water cone, in meters; h represents reservoir thickness in meters (m); φ represents porosity in percent (%); S o Indicates the current oil saturation; E D ρ represents displacement efficiency, expressed as a percentage (%). o This indicates the density of crude oil, in kg / m³. 3 B o This represents the volume coefficient of crude oil.

4. The method for adjusting the well network structure of a thick-layered bottom-water ordinary heavy oil reservoir according to claim 2, characterized in that, The theoretical water ridge radius at different depths along the longitudinal direction of the horizontal well is calculated using the following formula: In equation (3): N p This indicates cumulative oil production, in units of 10. 4 t; r represents the water ridge radius, in meters; H represents the height from the horizontal section to the oil-water interface, in meters; φ represents porosity, in percent; L represents the length of the horizontal section, in meters; S o Indicates the current oil saturation; E D ρ represents displacement efficiency, expressed as a percentage (%). o This indicates the density of crude oil, in kg / m³. 3 B oi This represents the volume coefficient of crude oil.

5. The method for adjusting the well network structure of a thick-layered bottom-water ordinary heavy oil reservoir according to claim 1, characterized in that, The types of residual oil include, but are not limited to: (1) Interconical zone type This type of distribution is located between vertical and horizontal wells, or between horizontal wells, at the top of the oil layer, with bottom water coning, and the wells between them are not utilized; (2) Edge movement difference type This type of distribution is located at the edge of the reservoir, in areas where the oil layer is thin and no development wells have been deployed, resulting in an incomplete well network, large well spacing, and low well network control. (3) Fault-blocking type This type of oil is relatively enriched only near local faults and is due to the residual oil formed mainly 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 interlayer shielding type This type exists only 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 activated, it is laterally flooded by the interlayers, and the lower oil layer remains unactivated, forming residual oil.

6. The method for adjusting the well network structure of a thick-layered bottom-water ordinary heavy oil reservoir according to claim 1, characterized in that, The well network structure adjustment was carried out in the remaining oil-rich areas between wells and the untouched peripheral areas.

7. The method for adjusting the well network structure of a thick-layered bottom-water ordinary heavy oil reservoir according to claim 1, characterized in that, The horizontal well production parameters include horizontal well steam injection intensity, steam injection rate, and fluid production intensity.

Images