Combination parameter optimization design method for fracturing and filling double-particle-size proppant for loose sandstone reservoir

Abstract

The invention belongs to the petroleum and natural gas exploitation industry, and particularly relates to a loose sandstone reservoir fracturing filling double-particle-size proppant combination parameter optimization design method, which performs optimization design on specific parameters of the proppant such as filling particle size, filling seam length proportion, filling sequence and the like according to reservoir and oil well conditions and a corresponding double-particle-size combination mode. And finally, effective sand blocking is achieved, meanwhile, invasion blocking and permeability damage of stratum sand to a crack filling layer are reduced, the crack flow resistance is reduced, the comprehensive flow conductivity is improved, and the comprehensive effects of releasing the oil and gas well productivity are achieved.

Description

Technical Field

[0001] The invention belongs to the oil and gas mining industry, and in particular relates to a method for optimizing the design of combined parameters of double-size proppants for fracturing and filling of loose sandstone reservoirs. Background Art

[0002] Fracturing filling is a commonly used sand prevention and production enhancement technology for medium-to-high permeability loose sandstone oil and gas reservoirs prone to sand production. It uses hydraulic fracturing to form cracks in loose sandstone reservoirs, and fills the cracks with solid granular materials such as conventional quartz sand or artificial ceramsite as proppants to form high-conductivity cracks supported by proppants (such as Figure 1 As shown in Figure 2). High conductivity fractures become the main channels for reservoir fluid to flow into the wellbore, which increases production. At the same time, the solid particles filled in the fractures have a sand retaining effect and play a sand prevention role.

[0003] Among the traditional medium- and high-permeability reservoir fracturing proppants, offshore oil fields mostly use artificial ceramsite, while onshore oil fields mostly use conventional quartz sand, and artificial ceramsite is rarely used. Generally, the fracturing filling design and design of the same well adopts a single particle size. The proppant particle sizes currently used on site are mainly 0.3-0.6mm, 0.4-0.8mm and 0.6-1.2mm.

[0004] Since loose sandstones with medium and high permeability are prone to sand production, the design and implementation of reservoir fracturing and filling require that the proppant in the fracture has a sand retaining function that can effectively block the formation sand that invades the fracture; at the same time, the formation sand that invades the fracture will cause blockage and loss of fracture conductivity, affecting production capacity. Therefore, for the fracturing and filling of loose sandstones with medium and high permeability, it is required to ensure both the sand retaining capacity and the fracture conductivity (this is quite different from the requirement to maintain the conductivity only when the low permeability reservoir does not produce sand). Since the current single particle size proppant is difficult to meet the above requirements under some reservoir conditions, a dual particle size proppant combination filling mode has emerged, mainly including three modes: fine outside and coarse inside, coarse outside and fine inside, and coarse and fine mixed (such as Figure 2 as shown).

[0005] At present, when fracturing and filling the medium- and high-permeability loose sandstone reservoir with dual-size proppant combination filling, although the above three combination modes can be adopted, there are the following key problems in its specific design and implementation: (1) Currently, there is a lack of methods to design the specific sizes of coarse and fine particle proppants for the three coarse and fine particle size combination modes. It is difficult to fully consider the reservoir geological conditions and production conditions based on the design based on experience to ensure the sand control and production increase effects. Therefore, there is an urgent need for a fast and simple method that can design and select the specific particle sizes of coarse and fine proppants according to the formation sand particle size and characteristic parameters to improve the sand control and production increase effects of the dual-size proppant combination fracturing and filling process.

[0006] (2) Currently, there is a lack of design methods for the filling length (ratio) and specific filling amount of coarse and fine particle proppants in fractures. The permeability gradient of medium and high permeability reservoirs is wide. According to the different reservoir permeabilities and fluidity as well as the length of fractures, the reservoir fluid will invade and block fractures in various flow modes, mainly at the toe of the fracture, mainly at the root of the fracture, or mainly at uniform invasion. Under different flow modes, the invasion and blocking forms of formation sand on the fracture filling layer are different. It is urgent to design the filling positions of coarse and fine particle sizes in the fractures and the corresponding filling section lengths and filling amounts according to the key invasion positions and forms, so as to give full play to the respective functions of coarse and fine particle proppants and give full play to the sand control and production increase effects of the dual particle size combination fracturing filling process technology.

[0007] (3) At present, the commonly used fracturing proppant for medium and high permeability reservoirs are 0.3-0.6mm, 0.4-0.8mm and 0.6-1.2mm, so the optimization design result of fracturing filling particle size can only choose one of the three. However, the interval between these three particle sizes is large, and it is difficult to accurately match the formation sand particle size according to the optimization matching criterion, resulting in excessive invasion blockage or loss of fluidity, which restricts the effect of fracturing production increase and sand control. Summary of the invention

[0008] The present invention proposes a method for optimizing the design of the combined parameters of double-particle proppants for fracturing and filling of loose sandstone reservoirs, which aims to optimize the specific parameters of proppants such as filling particle size, filling seam length ratio, filling order, etc. according to the reservoir, oil well conditions and the corresponding double-particle size combination mode, so as to finally achieve the comprehensive effect of effectively blocking sand, reducing the invasion and blockage of formation sand on the fracture filling layer and the damage to the permeability, reducing the flow resistance of the fracture, improving the comprehensive flow conductivity, and releasing the production capacity of oil and gas wells. Among them, the purpose of optimizing the filling length ratio and filling amount of double-particle proppants is to design corresponding coarse and fine proppants to fill the fracture positions according to the key invasion and blockage positions of formation sand on the fracture, so as to achieve the balance of overall sand blocking and flow diversion of the fracture, and ensure that the combined filling technology of coarse and fine particle proppants can play its potential and role, and improve the effect of sand control and production increase. The purpose of the dual-size proppant particle size optimization design for fracturing and filling wells is to design the particle size according to the characteristics of the formation sand particle size, to ensure that the ratio of the fracturing and filling proppant particle size to the formation sand particle size is always in the optimal range, which can not only ensure the sand retaining effect, but also avoid the damage to the fracture conductivity and production capacity caused by excessive intrusion of formation sand.

[0009] The present invention provides a method for optimizing the design of combined parameters of double-size proppants for fracturing and filling of loose sandstone reservoirs, comprising: S1. Calculate the invasion site discrimination characteristic index: First, the severity of sand production is evaluated according to formation parameters and production conditions; then the characteristic coefficient of fracture filling formation sand for distinguishing fracture invasion position (Fracture Sand Invasion, F SIindex).

[0010] S2. Optimize the filling sequence and seam length ratio of dual-size proppant in fracturing filling wells: According to the F calculated in step S1 SI The index divides the blockage area of ​​formation sand invasion into fractures into slightly invaded areas and severely invaded areas, thereby distinguishing the flow patterns of reservoir fluids and formation sand into fractures; According to the F calculated in step S1 SI The filling order of coarse-grained proppant and fine-grained proppant and the ratio of fracture length are obtained by using the index.

[0011] Preferably, the volume usage of coarse and fine proppants can be calculated based on the ratio of the filling seam lengths of the coarse-grained proppants and the fine-grained proppants and the fracture geometric parameters.

[0012] S3. Optimize the coarse and fine particle size of the dual-size proppant combination for fracturing and filling wells: According to the severity of formation sand production, the median size of formation sand and the uniformity coefficient, the design value of the median size of fine-grained proppant is calculated to optimize the design of proppant size.

[0013] In step S1, the formation parameters include reservoir thickness, original permeability, and fracture scale geometry.

[0014] In step S2, the severely invaded area refers to the area where the reservoir fluid and formation sand flow into the fracture unevenly, the inflow velocity is relatively high, the formation sand invades quickly, and the filling proppant blocks the fracture seriously. The length of the area in the fracture is recorded as L. fa .

[0015] The slightly invaded area refers to the area where the reservoir fluid and formation sand flow into the fracture unevenly, the inflow velocity is relatively low, the formation sand invades slowly, and the degree of blockage of the filling proppant is relatively weak. The length of the area in the fracture is recorded as L. fb .

[0016] According to the reservoir geological conditions, fracture geometry parameters and conductivity, production conditions and other characteristics, there are two modes for the relative positions of the slightly invaded area and the severely invaded area: Mode A: As attached Figure 3 As shown, the area close to the crack toe is a serious invasion area, and the area close to the crack root is a slight invasion area; Mode B: As attached Figure 4 As shown, the area close to the crack root is a severe invasion area, and the area close to the crack toe is a slight invasion area.

[0017] The scientific principle and basis for the above-mentioned invasion area division are: the fracturing filling has a high permeability and conductivity (the product of the fracture width and the filling permeability), which makes it easier for the fluid in the reservoir to flow in the fracture. Unlike the low permeability reservoir in which the reservoir permeability is extremely low and the reservoir flow mainly enters the fracture in a bilinear flow and inflow mode, the medium- and high-permeability loose sandstone reservoir itself has a high permeability, and the fluid has a certain flow capacity in the reservoir itself. Therefore, in the medium- and high-permeability loose sandstone fracture-reservoir flow system, the reservoir fluid closer to the fracture flows into the fracture, while some fluids farther away from the fracture flow in the reservoir toward the well, forming a more complex flow pattern, resulting in the flow of the reservoir carrying formation sand to the fracture is generally not a uniform inflow, but a non-uniform inflow; according to the specific flow conditions and characteristics, it can be divided into a slight invasion area and a severe invasion area.

[0018] Furthermore, if the fracture length is shorter than the reservoir control radius, the fracture conductivity is excellent, and its fluidity is much higher than that of the reservoir, and it is easier to flow into the fracture from the fracture toe position, forming mode A (such as Figure 3 On the contrary, it is easier to form mode B (such as Figure 4 as shown).

[0019] For the flow of mode A and mode B, if the length L of the slightly intruded region can be obtained fb and the length of the severe intrusion area L fa The size of the proppant can be used to design the filling length and amount of coarse and fine proppants.

[0020] Specifically, a method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs includes: S1. Calculate the invasion site discrimination characteristic index.

[0021] S101. Evaluate the severity of sand production and obtain the sand production and inflow intrusion index of the reservoir into the fracture of the fracturing filling well.

[0022] The Sanding Inflow Index (S I ) characterizes the severity of sand production when the reservoir of the fracturing filling well flows into the fracture. Its calculation formula is: (1); In the above formula, △P is the average production pressure difference of the oil well, MPa; △P c is the critical production pressure difference of oil well sand production, obtained by sand production prediction calculation, MPa; B s is the reservoir sand production index, MP 2 ; B scThe sand index limit corresponding to the severity of sand production in the empirical qualitative sand production prediction is 1.5×10 4 MPa 2 ; S I It is the sand inflow intrusion index, dimensionless.

[0023] S I is an exponent with a value around 1, S I The larger the value above 1, the more serious the sand inflow invasion of the reservoir into the fracture. S I When it is lower than 1 and the array is smaller, it means that the sand inflow invasion of the reservoir into the fracture is weaker.

[0024] The above S I The scientificity and rationality of index calculation lies in: the sand production index represents the sand production risk based on reservoir geological conditions and rock strength properties. B sc / B s The larger the ratio, the higher the risk of sand production from the perspective of reservoir geology; its weight is relatively weak, with a value of 0.25. On the other hand, the severity of sand production depends more on the comparison between the actual production pressure difference and the critical pressure difference of sand production. The greater the former exceeds the latter, the more serious the actual sand production is, and the ratio is △P / △P c The larger it is, the more serious the sand inflow invasion of the reservoir into the fracture is; its weight is relatively large, with a value of 0.75.

[0025] S102. Calculate the Fracture Sand Invasion (Fracture Sand Invasion, F SI The index is used to evaluate the relative positions of the slightly invaded and severely invaded areas of fluid and formation sand flowing into the fractures and their boundary positions.

[0026] F SI The index is: (5); In the formula, F SI is the discriminant characteristic index of the invasion site, dimensionless; X Lf , X hf、 X kwf They are the single influencing factor of the length of the hydraulic fracturing filling seam, the single influencing factor of the height of the hydraulic fracturing filling seam, and the single influencing factor of the conductivity of the hydraulic fracturing filling fracture, which are dimensionless; W Lf , Whf and W kwf They are the weight coefficients of the single influencing factor of seam length, the single influencing factor of seam height, and the influencing factor of conductivity.

[0027] Preferably, W Lf , W hf and W kwf The values ​​are 0.45±0.02, 0.25±0.02 and 0.3±0.02 respectively.

[0028] Among them, the single influencing factor of the fracturing filling seam length is X Lf for: (2); In the formula, X Lf is the single factor affecting the length of the fracturing filling seam, dimensionless; R e is the reservoir radius controlled by the oil well, m; L f is the length of the single wing of the crack, m; α It is the correction factor of fracturing filling seam length.

[0029] The fracturing filling seam length correction factor α This is to achieve a weighted average of the same order of magnitude as other individual influencing factors.

[0030] Preferably, the fracturing filling seam length correction factor α The value is 1.5385.

[0031] Single factor affecting the length of fracture filling X Lf The smaller it is, the shorter the radius of the fracture is compared to the reservoir controlled by the oil well, and the more the flow of reservoir fluid into the fracture tends to mode B; otherwise, it tends to mode A.

[0032] The single factor influencing the high fracturing filling crack X hf for: (3); In the formula, X hf is the single factor affecting the height of the fracture filling crack, dimensionless; H e is the reservoir thickness, m; h f is the crack height, m; β It is the correction factor for the fracture filling seam height.

[0033] The high correction factor of the fracturing filling seam β This is to achieve a weighted average of the same order of magnitude as other individual influencing factors.

[0034] Preferably, the fracturing filling seam height correction coefficient β The value is 1.058.

[0035] Single factor influencing the height of fracture filling X Lf The smaller it is, the shorter the fracture height is compared to the reservoir thickness, and the more the flow of reservoir fluid into the fracture tends to mode B; otherwise, it tends to mode A.

[0036] The single factor affecting the conductivity of the fracture filling X kwf for: (4); In the formula, X kwf is the single factor affecting the conductivity of the fracturing filling, dimensionless; K e is the reservoir permeability, D; k f is the fracture filling permeability, D; w f is the crack width, mm; γ It is the correction factor of conductivity of fracture filling.

[0037] The fracturing filling fracture conductivity correction factor γ This is to achieve a weighted average of the same order of magnitude as other individual influencing factors.

[0038] Preferably, the γ The value is 2.15.

[0039] Single influencing factor of conductivity of fracture filling X kwf The smaller it is, the closer the fracture conductivity is to the reservoir fluidity, and the reservoir fluid is less inclined to flow into the fracture, but more inclined to flow to the fracture root, that is, it is more inclined to mode B; conversely, it is more inclined to mode A.

[0040] S2. Optimize the filling sequence and seam length ratio of dual-size proppant in fracturing filling wells: S201, according to F SI Index determines the flow pattern of reservoir fluid and formation sand toward fractures: If F SI >1.15, the flow pattern of reservoir fluid and formation sand toward fractures is mode A; If F SI<0.85, the flow pattern of reservoir fluid and formation sand toward fractures is mode B; If 0.85≤F SI ≤1.15, the flow pattern of reservoir fluid and formation sand toward the fracture tends to be uniform flow, not mode A and mode B.

[0041] According to F SI The definition and characteristics of the index, when F SI When the index is greater than 1.15, the flow pattern is A; F SI The higher the index, the more obvious the flow invasion pattern tends to pattern A, and the boundary between the internal slightly invaded area near the wellbore direction and the external severely invaded area near the reservoir direction moves outward. In order to achieve the balance and best effect of sand blocking, coarse-grained proppant is used to fill the internal slightly invaded area, and fine-grained proppant is used to fill the external severely invaded area. SI As the index increases, the filling length of the inner coarse-grained proppant becomes longer and the filling length of the outer fine-grained proppant becomes shorter.

[0042] Similarly, when F SI When the index is less than 0.85, the flow pattern is mode B; F SI The lower the index, the more obvious the flow invasion pattern tends to pattern B, and the boundary between the internal severe invasion area close to the wellbore direction and the external slight invasion area close to the reservoir direction moves inward (toward the wellbore). The filling section of the internal fine-grained proppant is shorter, and the filling length of the external coarse-grained proppant is longer.

[0043] S202, according to the flow pattern and F SI Index design of the ratio of the filling length and filling sequence of coarse and fine particle proppants: Based on the above principles, a design method for the ratio of coarse and fine particle proppant filling seam length is proposed, as shown in Table 1; The packing sequence is carried out according to the rule that the severely invaded area is filled with fine-grained proppant, and the slightly invaded area is filled with coarse-grained proppant.

[0044] Table 1 Design method for the ratio of coarse-grained and fine-grained proppant filling seam length

[0045] S3. Optimize the coarse and fine particle size of the dual-size proppant combination for fracturing and filling wells: The specific particle size of coarse and fine particle proppants is designed according to the severity of formation sand production, the median particle size of the formation sand and the uniformity coefficient. In the combination filling mode of coarse and fine particle proppants for fracturing filling, the fine particle proppant mainly plays a role of sand blocking, and the method for designing the median particle size is as follows: (6); In the formulaS I is the sand inflow invasion index of the reservoir into the fracture, dimensionless; J s is the formation sand uniformity coefficient, dimensionless; d s50 is the median size of formation sand, mm; D g50a is the design value of the median particle size of fine-particle proppant, mm.

[0046] when D g50a <0.3, the particle size of the fine-grained proppant is selected to be 0.3-0.6 mm, and the particle size of the coarse-grained proppant is selected to be 0.3-0.6 mm; When 0.3≤ D g50a <0.6, the particle size of the fine-grained proppant is selected to be 0.3-0.6 mm, and the particle size of the coarse-grained proppant is selected to be 0.4-0.8 mm; When 0.6≤ D g50a <0.8, the particle size of the fine-grained proppant is 0.4-0.8 mm, and the particle size of the coarse-grained proppant is 0.6-1.2 mm; When 0.8≤ D g50a When selecting fine-grained proppant, the particle size of the fine-grained proppant is 0.6-1.2 mm, and the particle size of the coarse-grained proppant is 0.6-1.2 mm.

[0047] For example, the traditional Saucier method designs the proppant particle size according to the median particle size of the sand retaining proppant being equal to 5-6 times the median particle size of the formation sand, without considering the production and sand production conditions, and only considering the median particle size of the formation sand, which makes it difficult to balance the production capacity and sand control effect. However, the present invention not only considers the median particle size of the formation sand, but also considers the severity of sand production and the uniformity coefficient of the formation sand, which can ensure the sand retaining effect and avoid the damage to the fracture conductivity and production capacity caused by excessive intrusion of formation sand.

[0048] The optimization principle of the dual-size proppant particle size of the fracturing filling well is: the more serious the sand production is, the more difficult it is to block it, and the easier it is for formation sand to invade the fracture filling zone to cause blockage and production capacity loss; the worse the uniformity of the formation sand (the higher the uniformity coefficient), the more difficult it is to block it; under the above two trends, a finer proppant particle size should be used; otherwise, a coarser proppant particle size should be selected.

[0049] Beneficial effects: (1) The method for optimizing the design of the combination parameters of dual-particle-size proppants for fracturing and filling of loose sandstone reservoirs proposed in the present invention can optimize the design of specific parameters such as proppant filling particle size, filling seam length ratio, and filling sequence according to the selected reservoir and oil well conditions and the corresponding dual-particle-size combination mode, thereby ultimately achieving the comprehensive effect of effectively blocking sand while reducing the invasion and permeability damage of formation sand to the fracture filling layer, reducing the flow resistance of the fracture, improving the comprehensive conductivity, and releasing the production capacity of the oil and gas well.

[0050] (2) The present invention designs and selects the particle size of coarse and fine proppants according to the particle size of the formation sand and its characteristic indexes, and can design the blending ratio of coarse and fine proppants according to the particle size characteristics of the formation sand, solving the problem that the particle sizes of the three commonly used proppants in oil and gas fields are relatively large, and it is difficult to cover part of the formation sand particle size with the optimal particle size ratio. Overall, it ensures that the ratio of the particle size of the fracturing filling proppant to the particle size of the formation sand is always in the optimal range, which can not only ensure the sand blocking effect, but also avoid the damage to the fracture conductivity and production capacity caused by excessive intrusion of formation sand.

[0051] (3) The present invention proposes a method for the filling length ratio of coarse and fine proppants in fractures and the corresponding filling amount for two combination modes of coarse proppants (coarse outside and fine inside, and fine outside and coarse inside). The method fully considers the influence of reservoir geological conditions, fracture geometric parameters, and production fluid conditions on the key invasion and blockage locations of formation sand. According to the key invasion and blockage locations, the corresponding coarse and fine proppants are designed to fill the fracture locations, which can achieve "fine-grained sand blocking and coarse-grained diversion", give full play to the respective functions of coarse and fine-grained proppants, achieve a balance between overall sand blocking and diversion in fractures, and ensure that the combined filling technology of coarse and fine-grained proppants can exert its potential and function, and improve the effect of sand prevention and production increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic diagram of single-size proppant fracturing filling; Figure 2 Schematic diagram of three dual-size proppant combination modes; Figure 3 Schematic diagram of reservoir fluid and formation sand filling mode A into fractures; Figure 4 Schematic diagram of reservoir fluid and formation sand filling into fracture flow mode B; Figure 5 Schematic diagram of the filling ratio of reservoir fluid and formation sand into fracture flow pattern A; Figure 6 Schematic diagram of the filling ratio of reservoir fluid and formation sand into fracture flow pattern B.

[0053] Among them, 1-1 is the wellbore, 1-2 is the reservoir, 1-3 is the proppant filling the fracture, 2-1 is the wellbore, 2-2 is the coarse-grained proppant, and 2-3 is the fine-grained proppant. DETAILED DESCRIPTION

[0054] Embodiment 1: There is an oil well with loose geological bonding, belonging to loose sandstone oil and gas reservoir. The reservoir radius controlled by the oil well is R e The average production pressure difference of the oil well is 200m. △P is 4.2MPa. According to the sand production prediction, the critical production pressure difference of sand production in this oil well is △P c 4MPa, reservoir sand index B s 1.6×10 4 MPa 2 The oil well is in a sand state as a whole. Double-size filling fracturing construction is now adopted.

[0055] The critical production pressure difference of sand production in oil well △P c The prediction method refers to Dong Changyin. Theory and Technology of Sand Control in Oil and Gas Wells[M]. China University of Petroleum Press, 2012:45.

[0056] The boundaries of severe sanding, slight sanding and no sanding in the empirical qualitative sanding prediction are based on the combined modulus method. For details, please refer to Dong Changyin. Theory and Technology of Sand Control in Oil and Gas Wells [M]. China University of Petroleum Press, 2012: 32.

[0057] S101, calculate the sand inflow intrusion index (Sanding Inflow, S I ) According to the given data and formula (1), S I It is 1.054, and it is preliminarily judged that the sand inflow intrusion of the reservoir into the fracture is serious.

[0058] S102, calculate F SI According to formulas (2), (3), and (4), calculate the single factor influencing the length of the fracturing filling seam X Lf , Single factor influencing the height of fracturing filling cracks X hf , Single influencing factors of fracture conductivity of hydraulic fracturing filling X kwf The calculation conditions and results are shown in Table 2.

[0059] Table 2 Calculation conditions and results

[0060] In this embodiment, the weight coefficients W of the single influencing factor of the length of the fracturing filling seam, the single influencing factor of the height of the fracturing filling seam, and the influencing factor of the conductivity of the fracturing filling are Lf , W hf and W kwf , with values ​​of 0.45, 0.25 and 0.3 respectively. The FSI index value calculated according to formula (5) is 1.32.

[0061] S201. Since the FSI index is greater than 1.15, it is determined that the flow mode of the reservoir fluid and formation sand toward the fracture is mode A.

[0062] S202, judging the filling order of coarse proppant and fine proppant as inner coarse and outer fine according to the flow pattern; According to F SI The index shows that the ratio of coarse-grained proppant to fine-grained proppant filling seam length is 4:6.

[0063] S3. Optimization of coarse and fine particle size of dual-size proppant combination The reservoir sand uniformity coefficient J s is 2.25, the median size of the formation sand d s50 The median design value of the fine-grained proppant particle size is 0.1 mm. According to formula (6), is 0.65.

[0064] Since 0.6≤ D g50a <0.8, the particle size of the fine-grained proppant is 0.4-0.8mm, and the particle size of the coarse-grained proppant is 0.6-1.2mm.

[0065] According to the total length of the fracturing filling seam of 35m, it is calculated that the filling length of the coarse-grained proppant is 14m and the fine-grained proppant is 21m.

[0066] In summary, the design result is: according to the design scheme of coarse inside and fine outside, coarse-grained proppant with a filling length of 14m is filled near the wellbore end, and fine-grained proppant with a filling length of 0.4-0.8mm is continued to be filled, and the filling length is 21m.

[0067] Comparative Example 1: In this comparative example, the proppant particle size is designed according to the traditional Saucier method, and the median particle size of the sand-retaining proppant is equal to 5-6 times the median particle size of the formation sand. The proppant particle size used is 0.4-0.8 mm. In addition, this comparative example does not distinguish between severe invasion areas and slight invasion areas, and uses single-size proppant filling.

[0068] Table 3 Comparison of the effects of Example 1 and Comparative Example 1

[0069] The initial relative permeability is measured by a gas permeability instrument. For double-size filling, a weighted average method is required, that is, (permeability of section A × length of section A + permeability of section B × length of section B) / total length of the fracture.

[0070] The time of first sand production, the stable sand content after sand production, and the production increase effect before and after construction can be obtained from the field data. The samples were taken from Shengli Oilfield in Dongying.

[0071] Although the initial relative permeability of the proppant is slightly lower in the case of dual-particle filling, it can be seen from the field practice results that dual-particle filling can significantly increase the time for the first sand production in the oil well and the stable sand content after sand production, which has a sufficient sand control effect while maintaining the effect of stable and increased production of the oil well.

Claims

1. A method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs, characterized in that: include: S1. Calculate the invasion site discrimination characteristic index: First, the severity of sand production is evaluated according to formation parameters and production conditions; then the characteristic coefficient F of the fracture invasion position of the fracturing filling formation sand is calculated. SI index; S2. Optimize the filling sequence and seam length ratio of dual-size proppants in fracturing filling wells: According to the F calculated in step S1 SI Index, distinguish the flow patterns of reservoir fluid and formation sand to fractures; obtain the filling order of coarse-grained proppant and fine-grained proppant, and the ratio of fracture length; S3. Optimize the coarse and fine particle size of the dual-size proppant combination for fracturing and filling wells: According to the severity of formation sand production, the median size of formation sand and the uniformity coefficient, the design value of the median size of fine-grained proppant is calculated to optimize the design of proppant size.

2. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs according to claim 1, characterized in that: The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs specifically includes: S1. Calculate the invasion site discrimination characteristic index: S101. Obtain the sand inflow intrusion index of the reservoir into the fracture of the fracturing filling well: The calculation formula of the sand inflow intrusion index of the reservoir into the fracture of the fracturing filling well is: (1)； In the above formula, △P is the average production pressure difference of the oil well, MPa; △P c is the critical production pressure difference of oil well sand production, MPa; B s is the reservoir sand production index, MPa 2 ; B sc The sand index limit corresponding to the severity of sand production in the empirical qualitative sand production prediction is 1.5×10 4 MPa 2 ; S I is the sand inflow intrusion index, dimensionless; S102, calculating the invasion site discrimination characteristic index: The characteristic index for discriminating the invasion site is: (5)； In the formula, F SI is the discriminant characteristic index of the invasion site, dimensionless; X Lf , X hf , X kwf They are the single influencing factor of the length of the hydraulic fracturing filling seam, the single influencing factor of the height of the hydraulic fracturing filling seam, and the single influencing factor of the conductivity of the hydraulic fracturing filling fracture, which are dimensionless; W Lf , W hf and W kwf They are the weight coefficients of the single influencing factor of the length of the fracture filling seam, the single influencing factor of the height of the fracture filling seam, and the influencing factor of the conductivity of the fracture filling; S2. Optimize the filling sequence and seam length ratio of dual-size proppants in fracturing filling wells: S201, according to F SI Index determines the flow pattern of reservoir fluid and formation sand toward fractures: If F SI >1.15, the flow pattern of reservoir fluid and formation sand toward fractures is mode A; If F SI <0.85, the flow pattern of reservoir fluid and formation sand toward fractures is mode B; If 0.85≤F SI ≤1.15, the flow modes of reservoir fluid and formation sand toward fractures are non-mode A and non-mode B; Among them, mode A is: the area near the crack toe is the severe invasion area, and the area near the crack root is the slight invasion area; Mode B: The area near the crack root is a severe invasion area, and the area near the crack toe is a slight invasion area; S202, according to the flow pattern and F SI Index design of the ratio of the filling length and filling sequence of coarse and fine particle proppants: When 2.0 <F SI When the filling seam length ratio of coarse-grained proppant to fine-grained proppant is 7:3; When 1.75 <F SI When ≤2.0, the ratio of the filling seam length of coarse-grained proppant to that of fine-grained proppant is 6:4; When 1.55 <F SI When ≤1.75, the ratio of the filling seam length of coarse-grained proppant to that of fine-grained proppant is 5:5; When 1.25 <F SI When ≤1.55, the ratio of the filling seam length of coarse-grained proppant to that of fine-grained proppant is 4:6; When 1.15 <F SI When ≤1.25, the ratio of the filling seam length of coarse-grained proppant to that of fine-grained proppant is 3:7; When 0.7≤F SI When I<0.85, the ratio of the filling seam length of fine-grained proppant to that of coarse-grained proppant is 7:3; When 0.55≤F SI When <0.7, the ratio of the filling seam length of fine-grained proppant to that of coarse-grained proppant is 6:4; When 0.4≤F SI When <0.55, the ratio of the filling seam length of fine-grained proppant to that of coarse-grained proppant is 5:5; When 0.25≤F SI When <0.4, the ratio of the filling seam length of fine-grained proppant to that of coarse-grained proppant is 4:6; When FSI < 0.25, the ratio of the filling seam length of fine-grained proppant to that of coarse-grained proppant is 3:7; The packing sequence is carried out according to the rule that the severely invaded area is filled with fine-grained proppant and the slightly invaded area is filled with coarse-grained proppant; S3. Optimize the coarse and fine particle size of the dual-size proppant combination for fracturing and filling wells: The method for designing the median particle size of the fine particle size proppant is as follows: (6)； In the formula, S I is the sand inflow intrusion index, dimensionless; J s is the formation sand uniformity coefficient, dimensionless; d s50 is the median size of formation sand, mm; D g50a is the design value of the median particle size of fine-particle proppant, mm; when D g50a <0.3, the particle size of the fine-grained proppant is selected to be 0.3-0.6 mm, and the particle size of the coarse-grained proppant is selected to be 0.3-0.6 mm; When 0.3≤ D g50a <0.6, the particle size of the fine-grained proppant is 0.3-0.6 mm, and the particle size of the coarse-grained proppant is 0.4-0.8 mm; When 0.6≤ D g50a <0.8, the particle size of the fine-grained proppant is 0.4-0.8mm, and the particle size of the coarse-grained proppant is 0.6-1.2mm; When 0.8≤ D g50a When selecting fine-grained proppant, the particle size of the fine-grained proppant is 0.6-1.2 mm, and the particle size of the coarse-grained proppant is 0.6-1.2 mm.

3. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs according to claim 2, characterized in that: W Lf , W hf and W kwf The values ​​are 0.45±0.02, 0.25±0.02 and 0.3±0.02 respectively.

4. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs according to claim 2, characterized in that: The single factor affecting the length of the fracturing filling seam X Lf for: (2)； In the formula, X Lf is the single factor affecting the length of the fracturing filling seam, dimensionless; R e is the reservoir radius controlled by the oil well, m; L f is the length of the single wing of the crack, m; α It is the correction factor of fracturing filling seam length.

5. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs according to claim 4, characterized in that: The fracturing filling seam length correction factor α The value is 1.5385.

6. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling loose sandstone reservoirs according to claim 2, characterized in that: The single factor influencing the high fracturing filling crack X hf for: (3)； In the formula, X hf is the single factor affecting the height of the fracture filling crack, dimensionless; H e is the reservoir thickness, m; h f is the crack height, m; β It is the correction factor for the fracture filling seam height.

7. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling loose sandstone reservoirs according to claim 6, characterized in that: The high correction factor of the fracturing filling seam β The value is 1.

058.

8. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs according to claim 2, characterized in that: The single factor affecting the conductivity of the fracture filling X kwf for: (4)； In the formula, X kwf is the single factor affecting the conductivity of the fracturing filling, dimensionless; K e is the reservoir permeability, D; k f is the fracture filling permeability, D; w f is the crack width, mm; γ It is the correction factor of conductivity of fracture filling.

9. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs according to claim 8, characterized in that: The fracturing filling fracture conductivity correction factor γ The value is 2.

15.

10. The method for optimizing the design of combined parameters of dual-size proppants for fracturing and filling of loose sandstone reservoirs according to claim 2, characterized in that: The volume usage of coarse and fine proppants is calculated based on the filling seam length ratio of coarse-grained proppants and fine-grained proppants and the fracture geometric parameters.

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