Method and system for improving the recovery of a straight SAGD process in a compartmentalized reservoir

Abstract

The application discloses a mining method and system for improving direct SAGD development of interlayer development oil reservoirs, and the mining method comprises the following steps: determining geological main control influence factors affecting steam cavity rising; constructing a well pattern based on the geological main control influence factors; fracturing the interlayer based on the well pattern; breaking through the interlayer based on the well pattern; and switching to SAGD steam injection after steam stimulation of fishbone wells according to the thickness of the upper oil layer of the broken interlayer. The application determines the geological main control influence factors of the interlayer affecting SAGD steam cavity rising, establishes a well pattern form of direct well steam injection, fishbone well auxiliary steam injection and horizontal well production, adopts high-pressure steam injection, and the interlayer may be broken due to the change of rock mechanics characteristics under the condition of high-pressure steam injection, thereby improving the vertical permeability of the oil layer, adopting high-pressure gas auxiliary injection into the formation, using the fast seepage speed of the gas to form a seepage channel by penetrating a low physical property section, and realizing the development of the upper oil layer of the interlayer.

Description

Technical Field

[0001] This invention belongs to the field of oilfield production technology, and specifically relates to a method and system for improving the exploitation of vertical-level SAGD reservoirs with interlayer development. Background Technology

[0002] SAGD (Super Aquatic Gas Diffusion) technology is a cutting-edge technology for developing extra-heavy oil. Its extraction mechanism involves injecting high-dryness steam into a steam injection well. The steam rises and overlaps the formation, forming a steam chamber. This steam chamber expands upwards and laterally, exchanging heat with the crude oil in the oil reservoir. The heated and viscosity-reduced crude oil and steam condensate drain under gravity into the horizontal production wells below. The steam chamber continues to expand, gradually occupying more of the crude oil volume. Invented by Dr. Butler in 1978, this technology has been widely applied in some oilfields both domestically and internationally. In China, the Xinjiang Oilfield and Liaohe Oilfield have successfully introduced SAGD technology and implemented it in extra-heavy oil reservoirs, achieving good development results. It has significantly reversed the trend of continuously declining annual oil production from steam injection, offering high oil recovery rates and low extraction costs. Its technological advantages have been recognized by the petroleum industry and it is considered one of the most efficient thermal recovery technologies.

[0003] Chinese patent CN201911319507.2 discloses a method for fracturing interlayers in SAGD (Super Aquaculture Distillation) production, used to promote the development rate of steam chambers and reservoir sweep volume in SAGD well groups with interlayers, thereby improving SAGD oil production efficiency. The fracturing steps include: analyzing the development status of SAGD steam chambers; determining the distribution of interlayers above the SAGD injection well; determining the vertical well and fracturing interval for interlayer fracturing; and performing interlayer fracturing operations using reservoir fracturing technology. This invention effectively solves the problems in existing technologies where interlayers obstruct the expansion and ascent of SAGD steam chambers and the downward flow of crude oil, leading to low oil production rates, low oil-steam ratios, and low recovery rates.

[0004] Chinese patent CN201510044914.2 discloses a method for breaking through interlayers in oil-bearing formations during dual-horizontal-well SAGD production. This method involves drilling multiple branch lateral wells into the oil-bearing formation using high-pressure jet drilling in the radial direction of a horizontal steam injection well. During drilling, the branch lateral wells extend radially outward from the horizontal steam injection well, allowing them to penetrate the interlayer from below. Alternatively, during drilling, the branch lateral wells extend radially outward from the horizontal steam injection well, extending into the wedge-shaped unexploited area between adjacent steam chambers, thereby further improving recovery. This invention effectively delivers steam above the interlayer, ensuring balanced development of steam chambers in both horizontal and vertical directions, and has low construction costs.

[0005] Chinese patent CN201510171035.6 discloses a method for breaking through interlayers in oil reservoirs during dual-horizontal-well SAGD production. This method involves excavating a tunnel within the production area of ​​the steam injection well and the production well. The tunnel extends laterally towards the horizontal section of the steam injection well and longitudinally penetrates the interlayer, connecting the oil layers on both sides of the interlayer. A guiding medium is filled within the tunnel to create a flow channel for steam and crude oil. Steam is injected into the steam injection well and transported through the flow channel to the oil layer above the interlayer, heating and reducing the viscosity of the heavy oil above the interlayer. The reduced-viscosity crude oil then enters the production well through the flow channel for oil extraction. This invention enables communication between the oil layers on both sides of the interlayer, effectively transporting steam and crude oil from one side of the interlayer to the other, ensuring balanced development of the steam chamber in both horizontal and vertical directions, fully utilizing the advantages of horizontal wells, and achieving low cost.

[0006] Chinese patent CN201911066562.5 discloses a method for fracturing interlayers in a dual horizontal well for SAGD heavy oil. The method includes: excavating a horizontal well; after excavating 20m, drilling a branch to detect interlayers at an angle upwards; identifying the interlayers using identification criteria; identifying whether it is an interlayer and its thickness; for formations with interlayers and a thickness of less than 30cm, finding a side-drilling point on the wellbore of the branch below the interlayer, drilling a secondary branch from the side-drilling point and extending the secondary branch directly above the gas injection wellbore, and breaking up the interlayers with a drill bit along the production well direction.

[0007] Chinese patent CN201310075101.0 discloses a gravity and steam drive combined exploitation method for thick, interlayered ordinary heavy oil reservoirs, comprising the following steps: 1) determining the geological parameters and fluid characteristics of the reservoir block to meet the exploitation conditions; 2) in the interlayered heavy oil reservoir block, using a combination of vertical and horizontal wells, drilling horizontal production wells near the lower part of the oil layer, placing steam injection vertical wells obliquely above the horizontal production wells, and deploying production vertical wells in the same layer area as the steam injection vertical wells according to the development of the interlayers; 3) the horizontal production wells and steam injection vertical wells simultaneously perform steam injection and steam flow to form thermal communication between the steam injection vertical wells and the horizontal production wells, and the reservoir pressure drops to 3-4 MPa, after which steam injection is switched to the steam injection vertical wells for steam injection, and the horizontal production wells for production exploitation; 4) after the lower oil layer of the interlayers is basically exploited, perforating the steam injection vertical wells and production vertical wells located above the interlayers, and intermittently increasing the number of steam injection wells and increasing the steam injection rate, with the horizontal production wells and production vertical wells simultaneously producing and exploiting.

[0008] Chinese patent CN201510128592.X discloses an acidification modification method for SAGD low-property-value interlayers. The method includes: deploying a layered injection pipe in the modified oil layer, sealing the upper and lower parts of the layered injection pipe, and connecting the middle of the layered injection pipe to a distribution valve; injecting a modification fluid into the layered injection pipe, the modification fluid comprising 4-6 wt% hydrochloric acid, 20-30 wt% hydrofluoric acid, and the remainder water, based on a total volume of 100 wt%, to complete the acidification modification of the SAGD low-property-value interlayer; according to m 岩层 =ρV=ρπR 2 h / 5 gives the mass of the modified oil layer, and ρ is the density of the rock layer, in g / cm³. 3 R is the treatment radius in meters; h is the thickness of the modified oil layer in meters; the amount of substance in the modified oil layer is calculated; the amount of HF used is calculated; finally, based on the amount of HF used, the amounts of HCl and water are determined. The acidification modification method for SAGD low-property interlayers provided by this invention is reasonable and effective, with low construction risk and a high success rate.

[0009] The core of SAGD development is the effective formation and expansion of the steam chamber. The height of the steam chamber directly determines the oil production of SAGD. The presence of interlayers in the reservoir directly affects the vertical expansion of the steam chamber. (1) Due to the decrease in vertical permeability, the rising rate of the steam chamber slows down, the gravity drainage height under the same operating time decreases, and the time for SAGD to reach peak production is prolonged. If there are continuous interlayers in the oil layer, the height of the steam chamber and the peak oil production of gravity drainage will also be reduced. (2) The presence of continuous interlayers in the oil layer will also terminate the further rise of the steam chamber, limit the height of the steam chamber in the vertical direction, reduce the actual drainage thickness of the oil layer, and ultimately reduce the recovery rate of SAGD. (3) The location of the interlayers also affects the SAGD effect to varying degrees. Interlayers near horizontal production wells have a greater impact on the SAGD effect than interlayers at the top of the oil layer. Summary of the Invention

[0010] To address the aforementioned problems, this invention discloses a method for enhancing the exploitation of straight-line SAGD reservoirs with interlayer development, comprising:

[0011] Identify the main geological factors controlling the rise of the steam chamber;

[0012] A well network was constructed based on the aforementioned key geological influencing factors;

[0013] Based on the well network fracturing interlayer;

[0014] Based on the well pattern, the interlayer is broken;

[0015] Based on the thickness of the oil layer above the interlayer after the breakthrough, the fishbone well will switch to SAGD steam injection after steam huff and puff.

[0016] Furthermore, the main geological influencing factors include the thickness of the interlayer, the permeability of the interlayer, and the spatial distribution morphology of the interlayer.

[0017] Furthermore, when the thickness of the interlayer is greater than the first set thickness, the interlayer hinders oil leakage.

[0018] Furthermore, when the permeability of the interlayer is less than a first set permeability, the interlayer hinders oil leakage.

[0019] Furthermore, the spatial distribution of the interlayer includes the interlayer located between the horizontal production well and the horizontal steam injection well, and the interlayer located above the horizontal steam injection well.

[0020] Furthermore, when the interlayer is located between a horizontal production well and a horizontal steam injection well, the interlayer reduces the connectivity between the two wells.

[0021] Furthermore, when the interlayer is located above the horizontal steam injection well, the interlayer will affect the expansion direction of the steam chamber.

[0022] Furthermore, the specific steps for constructing the well network based on the aforementioned key geological influencing factors are as follows:

[0023] Based on the thickness, permeability, and spatial distribution of the interlayer in the upper part of the vertical well combined SAGD well group, horizontal wells are drilled in the interlayer development area. The horizontal wells are then branched into fishbone wells, which pass between the two vertical wells to construct a vertical well steam injection-assisted double horizontal well SAGD well network.

[0024] Furthermore, the specific steps for fracturing interlayers based on the well network are as follows:

[0025] In the well network, steam injection vertical wells are perforated simultaneously on both the upper and lower sides of the interlayer, and the steam injection pressure is increased. The fishbone wells emit high-pressure steam to rapidly fracture the interlayer.

[0026] Furthermore, the specific steps for breaking through the interlayer based on the well pattern are as follows:

[0027] Injecting non-hydrocarbon gases into vertical wells within the well network utilizes the gas's piercing effect to assist in breaking through interlayers.

[0028] Furthermore, the non-hydrocarbon gases include nitrogen and carbon dioxide.

[0029] Furthermore, the injection pressure of the non-hydrocarbon gas is higher than the formation fracturing pressure.

[0030] Production systems for enhancing the utilization of straight-line SAGD in reservoirs with interlayer development include:

[0031] The unit is defined to identify the main geological influencing factors affecting the rise of the steam chamber;

[0032] Construction unit, used to construct well pattern based on the main geological influencing factors;

[0033] Fracturing unit, used for fracturing interlayers based on the well network;

[0034] Breakthrough unit, used to break through interlayers based on the well network;

[0035] The steam injection unit is used to switch to SAGD steam injection after the fishbone well steam injection, based on the thickness of the oil layer above the broken interlayer.

[0036] Furthermore, the main geological influencing factors include the thickness of the interlayer, the permeability of the interlayer, and the spatial distribution morphology of the interlayer.

[0037] Furthermore, when the thickness of the interlayer is greater than the first set thickness, the interlayer hinders oil leakage.

[0038] Furthermore, when the permeability of the interlayer is less than a first set permeability, the interlayer hinders oil leakage.

[0039] Furthermore, the building unit is specifically used for:

[0040] Based on the thickness, permeability, and spatial distribution of the interlayer in the upper part of the vertical well combined SAGD well group, horizontal wells are drilled in the interlayer development area. The horizontal wells are then branched into fishbone wells, which pass between the two vertical wells to construct a vertical well steam injection-assisted double horizontal well SAGD well network.

[0041] Furthermore, the fracturing unit is specifically used for:

[0042] In the well network, steam injection vertical wells are perforated simultaneously on both the upper and lower sides of the interlayer, and the steam injection pressure is increased. The fishbone wells emit high-pressure steam to rapidly fracture the interlayer.

[0043] Furthermore, the breakthrough unit is specifically used for:

[0044] Injecting non-hydrocarbon gases into vertical wells within the well network utilizes the gas's piercing effect to assist in breaking through interlayers.

[0045] Furthermore, the non-hydrocarbon gases include nitrogen and carbon dioxide.

[0046] Furthermore, the injection pressure of the non-hydrocarbon gas is higher than the formation fracturing pressure.

[0047] Compared with the prior art, the beneficial effects of the present invention are:

[0048] 1) During the SAGD mining process, the main geological factors that affect the rise of the SAGD steam cavity by interlayers were identified. The uneven development of the reservoir, mainly the permeability, has a significant impact on the rise of the steam cavity.

[0049] 2) Establish a well network configuration with vertical wells for steam injection, fishbone wells for auxiliary steam injection, and horizontal wells for production;

[0050] 3) High-pressure steam injection is used. Under high-pressure steam injection conditions, the interlayer rock mechanical properties change and may be broken, thus improving the vertical permeability of the oil layer.

[0051] 4) High-pressure gas-assisted injection into the formation is used to utilize the high gas flow rate to penetrate low-property sections and form flow channels, thereby enabling the mobilization of the oil layer above the interlayer.

[0052] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 A schematic diagram of a vapor chamber shielded by a partition layer according to an embodiment of the present invention is shown;

[0055] Figure 2 The influence of interlayers on SAGD in a dual-horizontal well (20m oil layer thickness, 600m horizontal well section length) according to an embodiment of the present invention is shown.

[0056] Figure 3 The curves showing the influence of interlayer thickness and permeability on the SAGD effect according to an embodiment of the present invention are illustrated.

[0057] Figure 4 The relationship between oil recovery rate and oil-gas ratio predicted by the model according to an embodiment of the present invention is shown (homogeneous model);

[0058] Figure 5 The relationship between oil recovery rate and oil-gas ratio predicted by the model according to an embodiment of the present invention is shown (including discontinuous interlayers, k = 0.0 mD);

[0059] Figure 6The relationship between oil recovery rate and oil-gas ratio predicted by the model according to an embodiment of the present invention is shown (including discontinuous interlayers, k = 200mD);

[0060] Figure 7 A comparison of the recovery rate and oil-gas ratio predicted by the model according to an embodiment of the present invention is shown;

[0061] Figure 8 A comparison of oil production predicted by the model according to an embodiment of the present invention is shown;

[0062] Figure 9 The model predicts the oil saturation profile along the main flow direction (interlayer, k = 0.0 mD) after 120 days of gravity-driven oil draining according to an embodiment of the present invention.

[0063] Figure 10 The model predicts an oil saturation profile in the non-mainstream direction (interlayer, k = 0.0 mD) after 120 days of gravity-driven oil draining according to an embodiment of the present invention.

[0064] Figure 11 The model predicts the oil saturation profile along the main flow direction (interlayer, k = 0.0 mD) after 665 days of gravity-induced oil draining according to an embodiment of the present invention.

[0065] Figure 12 The model predicts an oil saturation profile along the non-mainstream line direction (interlayer, k = 0.0 mD) after 665 days of gravity-induced oil draining according to an embodiment of the present invention.

[0066] Figure 13 A schematic diagram of a vertical well steam injection assisted dual horizontal well SAGD well pattern according to an embodiment of the present invention is shown;

[0067] Figure 14 A schematic diagram of the expansion of the steam chamber before and after the modification of the interlayer according to an embodiment of the present invention is shown. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

[0069] The present invention proposes a method for improving the exploitation of straight-line SAGD reservoirs with interlayer development, comprising the following steps:

[0070] Identify the main geological factors controlling the rise of the steam chamber;

[0071] A well network was constructed based on the aforementioned key geological influencing factors;

[0072] Based on the well network fracturing interlayer;

[0073] Based on the well pattern, the interlayer is broken;

[0074] Based on the thickness of the oil layer above the interlayer after the breakthrough, the newly drilled fishbone well will switch to SAGD steam injection after steam huff and puff.

[0075] The invention proposes a method for improving the utilization of vertical horizontal SAGD in reservoirs with interlayer development, which enables the simultaneous development of steam chambers above and below the interlayer, allowing crude oil from the upper part of the interlayer to drain to the lower horizontal production well.

[0076] The mining method of the present invention will be further described in detail below with reference to the accompanying drawings. The specific steps are as follows:

[0077] Step S1: Determine the limits of different permeability interlayers to prevent the vapor from rising from the cavity;

[0078] During the development of SAGD, the development of the steam cavity varies due to the influence of the interlayer. Numerical simulation technology was used to simulate the influence of interlayer properties at different permeabilities on the formation and development morphology of the steam cavity, and to clarify the limits of the steam cavity rise blocked by interlayers with different permeabilities.

[0079] like Figure 1 As shown, when using a dual-horizontal-well combination, the steam chamber volume gradually expands upwards from the horizontal steam injection well. If a thin interlayer exists between the horizontal steam injection well and the horizontal production well, it will reduce the connectivity between them. If a thin interlayer exists above the horizontal steam injection well, the expansion direction of the steam chamber will change. Although the steam chamber will extend around the edge of the interlayer and continue to rise, it will affect the gravity drainage height within a certain time and range, thus affecting the gravity drainage rate.

[0080] like Figure 2 As shown, the impact of thin interlayers on the SAGD effect can be seen from the simulation example below. In the numerical simulation model containing interlayers, the total oil layer thickness is 20m, horizontal production wells are located at the bottom of the model, and horizontal steam injection wells are deployed 5m above the horizontal production wells. It is assumed that a thin interlayer is located 5m below the top of the oil layer, and the size of the thin interlayer distribution is equal to the entire well group control area of ​​the SAGD well pair, which is equivalent to the thin interlayer being continuously distributed in the oil layer. In the simulation, three different physical properties are assumed for the thin interlayer:

[0081] (1) Homogeneous model (without interlayer);

[0082] (2) The permeability of the interlayer is 0 mD;

[0083] (3) The permeability of the interlayer is 200 mD.

[0084] The impact of the presence of the diaphragm on the SAGD effect depends primarily on the permeability of the diaphragm. If the diaphragm is impermeable, its presence will completely block the rise of the steam chamber, reducing the height of gravity-driven oil drainage and thus decreasing the oil production and oil-to-steam ratio of SAGD.

[0085] like Figure 3 As shown, numerical simulation results indicate that under the same interlayer thickness, as the permeability decreases, the steam chamber becomes difficult to rise, the temperature above the interlayer decreases, the utilization rate decreases, and the remaining oil saturation increases. However, as the interlayer thickness increases, the cumulative oil production per stage decreases. Therefore, when the interlayer thickness is greater than 1.0 m and the permeability is less than 40 mD, the interlayer hinders oil drainage, making it difficult to achieve SAGD.

[0086] Step S2: Determine the main geological factors affecting the rise of the steam chamber; among which, the main geological factors include the thickness of the interlayer, the permeability of the interlayer, and the spatial distribution pattern of the interlayer.

[0087] To qualitatively study the impact of thin interlayers in oil reservoirs on gravity drainage, a numerical simulation model containing interlayers was established, adding some thin interlayers to the homogeneous model. The spatial distribution and physical properties of the thin interlayers can be artificially varied according to the research objectives. The numerical simulation model containing interlayers includes some discontinuous thin interlayers. The simulation includes three vertical wells with a well spacing of 70m and two infill horizontal wells, with an oil reservoir thickness of 60m and a grid size of (i,j,k)3m×3m×2m. If the length of the horizontal section of the horizontal well is assumed to be 350m, then this numerical simulation model containing interlayers represents 1 / 10 of the actual well pattern. In the pure oil layer portion of the numerical simulation model containing interlayers, the permeability is 1500mD, the porosity is 30%, and the oil saturation is 68%; other parameters are those determined by historical fitting from the SAGD test area. The vertical wells initially undergo steam injection production, and after a period of production, infill horizontal wells are drilled in the middle position of the two rows of vertical wells. Horizontal and vertical wells are simultaneously put into steam injection production. Once thermal connectivity is established between the horizontal well and the surrounding vertical wells, the vertical wells are converted into continuous steam injection wells, and the horizontal wells become continuous production wells, entering the gravity drainage production stage. The total volume of interlayers accounts for approximately 4% of the total volume of the numerical simulation model containing interlayers. The distribution of these interlayers is discontinuous. The main purpose is to analyze the impact of the existence of these discontinuous interlayers on the distribution and development morphology of steam cavities and on the SAGD effect. The presence of continuous interlayers completely prevents the development of steam cavities; the oil layer above the interlayer cannot be effectively developed. In this case, the existence of continuous interlayers is equivalent to reducing the thickness of the oil layer available for SAGD production, and its production effect is equivalent to SAGD production of a thinner oil layer.

[0088] To compare the effects of discontinuous interlayers on steam injection and gravity drainage, the study predicted the effects of homogeneous models (such as...). Figure 4 The steam injection and gravity drainage effects (as shown) are illustrated in the numerical simulation model of the interlayer, representing the overall production effect of the steam injection and gravity drainage stages. Among them, for example... Figure 5 The results shown are the predictions when the interlayer permeability is 0 mD, while... Figure 6 The effect shown is the predicted result when the interlayer permeability is 200 mD.

[0089] It can be seen that the predicted steam injection and SAGD dynamics are similar in the three models mentioned above. If an economic oil-steam ratio of 0.15 is used as the cutoff production period for SAGD, the predicted final recovery rate under all three models exceeds 70%. It should be noted that in the models, both vertical and horizontal wells are deployed near the bottom of the oil layer, which can make full use of the gravity drainage effect, resulting in a high recovery rate.

[0090] like Figure 7 The figure shows a comparison of the cumulative steam-oil ratio under three simulated conditions for steam injection and gravity drainage. Although the cumulative steam-oil ratio differs slightly in the early stages, the overall difference is relatively small. When the distribution of thin interlayers is discontinuous, it has a smaller impact on the extraction efficiency of steam injection and gravity drainage. Figure 8 The figure shows the predicted daily oil production of horizontal wells during the gravity drainage stage. The initial high daily production is due to steam injection in the horizontal well during the transition from steam injection to gravity drainage. When the interlayer is discontinuous, it has little impact on the production of gravity drainage. Simulation results show that when the permeability of the thin interlayer is assigned 0 and 200 mD, the oil production remains unchanged. This indicates that during the gravity drainage stage, as long as the permeability of the thin interlayer is significantly lower than that of the surrounding oil layer, the permeability of the interlayer has the same effect on SAGD. This is because during gravity drainage, there is no pressure difference in the steam chamber, and the pressure above and below the interlayer is the same, making it difficult for fluid to flow within the interlayer.

[0091] Within the steam chamber, both the interlayer and the pure oil layer will be heated to steam temperature. Therefore, to understand the impact of the interlayer on the development of the steam chamber, the distribution of oil saturation within the steam chamber should be analyzed. For example... Figure 9 The image shows the oil saturation distribution in the oil reservoir after 120 days of gravity drainage. Although the presence of the thin interlayer (white rectangular area) affects the expansion channel of the steam chamber, the discontinuity of the interlayer allows the steam chamber to expand around it, and the heated crude oil can also drain down through this pathway. The irregular shape of the steam chamber, as seen from the oil saturation distribution, indicates that the presence of the interlayer alters the expansion channel of the steam chamber. This can also be seen from... Figure 10 Another non-mainstream line shows the oil saturation distribution profile. Figure 11 and Figure 12 These are two oil saturation distribution profiles predicted on the mainstream and non-mainstream lines after 665 days of gravity-driven oil production. Compared with homogeneous reservoirs, the presence of interlayers reduces the rise rate of the steam chamber in the formation around the vertical well.

[0092] As mentioned earlier, the SAGD effect is exactly the same when the interlayer permeability is 0 and 200 mD. Although the interlayer has some permeability, due to its low permeability, its impact on gravity drainage is basically the same as that of a thin interlayer with no permeability at all. It can be seen that the thin interlayer mainly affects the expansion and development morphology of the steam chamber.

[0093] Step S3: Construct a well network based on the aforementioned key geological influencing factors. The specific steps are as follows:

[0094] Based on the thickness, permeability, and spatial distribution of the interlayers in the upper part of the vertical well combined SAGD well group, horizontal wells are drilled in the interlayer development area. These horizontal wells then branch into fishbone wells, passing between the two vertical wells, thus constructing a vertical well steam injection-assisted dual-horizontal well SAGD well network. For example, such as... Figure 13 As shown, the newly constructed well network is as follows: A1, A2, and A3 are vertical steam injection wells on the same side, located on one side of the fishbone well; C1, C2, and C3 are vertical steam injection wells on the same side, located on the other side of the fishbone well; B2 is the original horizontal production well; B1 is a newly drilled fishbone well in the interlayer, with branches passing between the vertical steam injection wells. The fishbone well increases the contact range with the upper interlayer, which can further increase the fracture creation in the interlayer and improve the oil drainage effect. Modifying the interlayer through vertical well perforation allows for flexible adjustment of the longitudinal perforation position, which is beneficial for the modification of the interlayer.

[0095] Step S4: Based on the well pattern fracturing interlayer, the specific steps are as follows:

[0096] like Figure 14 As shown in (a), this is a schematic diagram of the expansion of the steam chamber before the interlayer was modified. The expansion of the steam chamber was slow, which affected the rate of gravity-driven oil drainage. Figure 14 (b) shows a schematic diagram of the expansion of the steam chamber after the modification of the interlayer. The steam injection vertical wells in the well network perforate on both the upper and lower sides of the interlayer at the same time and increase the steam injection pressure. The newly drilled fishbone wells emit high-pressure steam to quickly fracture the interlayer.

[0097] Due to the high-pressure steam injection in vertical wells, some thin interlayers may break down under high-pressure steam injection conditions due to changes in their rock mechanical properties. This is beneficial for improving the vertical permeability of the reservoir and reducing the impact of the interlayers on gravity drainage. When the steam injection pressure reaches the reservoir's expansion pressure, some continuous thin interlayers (thickness < 2.0 m) will lose their fluid-blocking effect, resulting in a significant increase in the reservoir's porosity and compressibility, as well as a substantial increase in steam injection capacity.

[0098] Step S5: Based on the well pattern, break through the interlayer, the specific steps are as follows:

[0099] In vertical wells within a well network, non-hydrocarbon gases are injected to aid in the breakthrough of interlayers through gas penetration. The gas seepage velocity is rapid, penetrating cold oil zones to form seepage channels and reducing steam flow resistance. Simultaneously with steam injection, non-hydrocarbon gases are injected into vertical wells in areas with well-developed interlayers to improve their permeability. For example, in… Figure 13 Non-hydrocarbon gases are injected into A1, A2, and C1 as auxiliary treatments, with the injection pressure increased to above the formation fracturing pressure. These non-hydrocarbon gases include nitrogen and carbon dioxide, among others.

[0100] Step S6: Based on the thickness of the oil layer above the interlayer after the breakthrough, the newly drilled fishbone well is switched to SAGD steam injection after steam huff and puff.

[0101] The newly drilled fishbone well employs high-pressure steam injection. Some thin interlayers may break under high-pressure steam injection due to changes in their rock mechanical properties, which is beneficial for improving the vertical permeability of the oil reservoir and reducing the impact of the interlayers on gravity drainage. When the steam injection pressure reaches the expansion pressure of the oil reservoir, some continuous thin interlayers (<2.0m) will lose their fluid-blocking effect, resulting in a significant increase in the porosity and compressibility of the oil reservoir, as well as a substantial increase in steam injection capacity.

[0102] Based on the above-mentioned method for enhancing the exploitation of vertical-slope SAGD in reservoirs with interlayer development, this invention proposes an exploitation system for enhancing the exploitation of vertical-slope SAGD in reservoirs with interlayer development, comprising:

[0103] The unit is defined to identify the main geological influencing factors affecting the rise of the steam chamber;

[0104] Construction unit, used to construct well pattern based on the main geological influencing factors;

[0105] Fracturing unit, used for fracturing interlayers based on the well network;

[0106] Breakthrough unit, used to break through interlayers based on the well network;

[0107] The steam injection unit is used to switch to SAGD steam injection after the fishbone well steam injection, based on the thickness of the oil layer above the broken interlayer.

[0108] The main geological influencing factors include the thickness of the interlayer, the permeability of the interlayer, and the spatial distribution pattern of the interlayer.

[0109] When the thickness of the interlayer is greater than the first set thickness, the interlayer hinders oil leakage.

[0110] When the permeability of the interlayer is less than the first set permeability, the interlayer hinders oil leakage.

[0111] Building units, specifically used for:

[0112] Based on the thickness, permeability, and spatial distribution of the interlayer in the upper part of the vertical well combined SAGD well group, horizontal wells are drilled in the interlayer development area. The horizontal wells are then branched into fishbone wells, which pass between the two vertical wells to construct a vertical well steam injection-assisted double horizontal well SAGD well network.

[0113] The fracturing unit is specifically used for:

[0114] In the well network, steam injection vertical wells are perforated simultaneously on both the upper and lower sides of the interlayer, and the steam injection pressure is increased. The fishbone wells emit high-pressure steam to rapidly fracture the interlayer.

[0115] Breakthrough unit, specifically used for:

[0116] Injecting non-hydrocarbon gases into vertical wells within the well network utilizes the gas's piercing effect to assist in breaking through interlayers.

[0117] Non-hydrocarbon gases include nitrogen and carbon dioxide.

[0118] The injection pressure of non-hydrocarbon gases is higher than the formation fracturing pressure.

[0119] This invention proposes a method and system for improving the utilization of vertical horizontal SAGD reservoirs with interlayer development. During SAGD production, the main geological factors influencing the rise of the SAGD steam cavity by interlayers were identified. Uneven reservoir development, particularly permeability, significantly impacts steam cavity rise. A well network configuration was established, consisting of vertical wells for steam injection, fishbone wells for auxiliary steam injection, and horizontal wells for production. High-pressure steam injection was employed, which alters the rock mechanical properties of the interlayers under high-pressure conditions, potentially leading to their fracturing and improving the vertical permeability of the oil layer. High-pressure gas-assisted injection into the formation was used, leveraging the high gas flow velocity to penetrate low-property sections and form seepage channels, thereby enabling the utilization of the oil layer above the interlayers.

[0120] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the exploitation of straight-line SAGD in reservoirs with interlayer development, characterized in that, include: Identify the main geological factors controlling the rise of the steam chamber; A well network was constructed based on the aforementioned key geological influencing factors; Based on the well network fracturing interlayer; Based on the well pattern, the interlayer is broken; Based on the thickness of the oil layer above the interlayer after the breakthrough, the fishbone well will switch to SAGD steam injection after steam huff and puff. The main geological influencing factors include the thickness of the interlayer, the permeability of the interlayer, and the spatial distribution morphology of the interlayer. The specific steps for constructing the well network based on the aforementioned key geological influencing factors are as follows: Based on the thickness, permeability, and spatial distribution of the interlayer in the upper part of the vertical well combined SAGD well group, horizontal wells are drilled in the interlayer development area. The horizontal wells are then branched into fishbone wells, which pass between the two vertical wells to construct a vertical well steam injection-assisted double horizontal well SAGD well network.

2. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 1, characterized in that, When the thickness of the interlayer is greater than the first set thickness, the interlayer hinders oil drainage.

3. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 1 or 2, characterized in that, When the permeability of the interlayer is less than the first set permeability, the interlayer hinders oil leakage.

4. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 1, characterized in that, The spatial distribution of the interlayer includes the interlayer located between the horizontal production well and the horizontal steam injection well, and the interlayer located above the horizontal steam injection well.

5. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 4, characterized in that, When the interlayer is located between a horizontal production well and a horizontal steam injection well, the interlayer will reduce the connectivity between the horizontal production well and the horizontal steam injection well.

6. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 5, characterized in that, When the interlayer is located above the horizontal steam injection well, the interlayer will affect the expansion direction of the steam chamber.

7. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 1, characterized in that, The specific steps for fracturing interlayers based on the well network are as follows: In the well network, steam injection vertical wells are perforated simultaneously on both the upper and lower sides of the interlayer, and the steam injection pressure is increased. The fishbone wells emit high-pressure steam to rapidly fracture the interlayer.

8. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 1, characterized in that, The specific steps for breaking through the interlayer based on the well pattern are as follows: Injecting non-hydrocarbon gases into vertical wells within the well network utilizes the gas's piercing effect to assist in breaking through interlayers.

9. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 8, characterized in that, The non-hydrocarbon gases include nitrogen and carbon dioxide.

10. The method for improving the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 8, characterized in that, The injection pressure of the non-hydrocarbon gas is higher than the formation fracturing pressure.

11. A production system for enhancing the utilization of straight-line SAGD in reservoirs with interlayer development, characterized in that, include: The unit is defined to identify the main geological influencing factors affecting the rise of the steam chamber; Construction unit, used to construct well pattern based on the main geological influencing factors; Fracturing unit, used for fracturing interlayers based on the well network; Breakthrough unit, used to break through interlayers based on the well network; The steam injection unit is used to switch to SAGD steam injection after steam injection from the fishbone well, based on the thickness of the oil layer above the broken interlayer; The main geological influencing factors include the thickness of the interlayer, the permeability of the interlayer, and the spatial distribution morphology of the interlayer. The building unit is specifically used for: Based on the thickness, permeability, and spatial distribution of the interlayer in the upper part of the vertical well combined SAGD well group, horizontal wells are drilled in the interlayer development area. The horizontal wells are then branched into fishbone wells, which pass between the two vertical wells to construct a vertical well steam injection-assisted double horizontal well SAGD well network.

12. The production system for enhancing the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 11, characterized in that, When the thickness of the interlayer is greater than the first set thickness, the interlayer hinders oil drainage.

13. The production system for enhancing the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 11, characterized in that, When the permeability of the interlayer is less than the first set permeability, the interlayer hinders oil leakage.

14. The production system for enhancing the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 11, characterized in that, The fracturing unit is specifically used for: In the well network, steam injection vertical wells are perforated simultaneously on both the upper and lower sides of the interlayer, and the steam injection pressure is increased. The fishbone wells emit high-pressure steam to rapidly fracture the interlayer.

15. The production system for enhancing the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 11, characterized in that, The breakthrough unit is specifically used for: Injecting non-hydrocarbon gases into vertical wells within the well network utilizes the gas's piercing effect to assist in breaking through interlayers.

16. The production system for enhancing the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 15, characterized in that, The non-hydrocarbon gases include nitrogen and carbon dioxide.

17. The production system for enhancing the utilization of straight-line SAGD in reservoirs with interlayer development according to claim 15, characterized in that, The injection pressure of the non-hydrocarbon gas is higher than the formation fracturing pressure.

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