Horizontal well fracturing cluster spacing and sand adding scale optimization design method

Abstract

The invention belongs to the field of oil development, and particularly relates to a horizontal well fracturing cluster spacing and sand adding scale optimization design method. According to the optimization design method, while the cluster spacing and the sand adding scale are matched, the influence of fracturing parameters of different cluster spacing and sand adding scales on the fracturing cost is compared, geological engineering limiting conditions are set, and finally the reasonable cluster spacing and sand adding scale are optimized to guide fracturing design parameters. The method is reliable in result, good in economical efficiency, convenient and fast.

Description

Technical Field

[0001] The invention belongs to the field of petroleum development, and in particular relates to a method for optimizing the design of horizontal well fracturing cluster spacing and sand adding scale. Background Art

[0002] Unconventional oil and gas reservoirs account for an increasing proportion of oil and gas resources. Unconventional oil reservoirs have the characteristics of "no cracks, no oil and gas", and all require horizontal well volume fracturing to build production. Cluster spacing and sand addition scale are key parameters that affect the effect and investment of horizontal well fracturing. If the cluster spacing is set too large, the reservoir will not be fully transformed and the crude oil cannot be fully mobilized; if the cluster spacing is set too small, the reservoir will be over-transformed, resulting in excessively high reservoir transformation costs.

[0003] At present, cluster spacing design methods often only consider stress interference factors, and the designed cluster spacing is generally the minimum limit value, which is easy to cause repeated transformation, excessive transformation and increase fracturing investment costs. Reservoir values ​​show that after increasing the cluster spacing, a single well can achieve the same single-well recoverable reserves (EUR) by increasing the conductivity of the fracture. Increasing the cluster spacing can reduce the number of construction sections and reduce construction costs to a certain extent, but increasing the conductivity requires increasing the amount of sand and liquid in a single fracture, which will increase material costs to a certain extent.

[0004] Chinese invention patent application CN107237616A provides a method for optimizing cluster spacing in horizontal well volume fracturing. It uses a finite element numerical simulation method and is based on ABAQUS finite element software. It establishes a minimum cluster spacing optimization model and a maximum transformation volume cluster spacing optimization model from two aspects: reducing the adverse effects of stress shadow effect and utilizing the favorable effects of stress shadow effect. It also calculates the stress turning angle and transformation volume during fracturing, and finally determines the optimal cluster spacing by combining the optimization results of the minimum cluster spacing and the maximum transformation volume cluster spacing. The minimum cluster spacing determined by this method is prone to repeated transformation, excessive transformation, and increased fracturing investment costs. The determined optimal cluster spacing can only achieve the maximum transformation volume, but cannot guarantee that the construction cost is economical and effective.

[0005] In actual application, the cost of a single well under different segment cluster combinations can be calculated as a basis, and the combinations with too small and too large cluster spacing can be eliminated based on the maximum sand concentration limit allowed for a single seam, the maximum segment length limit for balanced fracturing, the construction cost limit, and other conditions, so as to select the cluster spacing and single seam sand addition amount combination with lower construction cost.

[0006] Therefore, it is necessary to develop an optimization design method for the horizontal well fracturing cluster spacing and sand addition scale, with the goal of achieving the single-well EUR of the geological reservoir. While matching the cluster spacing and sand addition scale, the single-well fracturing construction cost can be reduced to achieve the economical and efficient utilization of the reservoir during horizontal well fracturing. Summary of the invention

[0007] To achieve the above objectives, the present invention provides a method for optimizing the design of cluster spacing and sand addition scale for horizontal well fracturing, with the goal of achieving single-well EUR of geological reservoirs. While matching the cluster spacing and sand addition scale, the influence of fracturing parameters with different cluster spacing and sand addition scale on fracturing costs is compared and geological engineering constraints are set, and finally a reasonable cluster spacing and sand addition scale are selected to guide the fracturing design parameters.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for optimizing the spacing between fracturing clusters and the scale of sand addition in a horizontal well comprises the following steps:

[0010] (1) According to the upper and lower reservoir barriers and well pattern conditions of the formation, the fracture height and length of a single fracture matching under the conditions of fracture network transformation are simulated;

[0011] (2) Establish a reservoir simulation geological model based on reservoir geological parameters to simulate the cumulative oil production under different cluster spacing and different single fracture conductivity;

[0012] (3) Based on the recoverable reserves of a single well predicted by the reservoir geological plan, the cluster spacing and conductivity combinations are screened;

[0013] (4) Determine the single-slit sand concentration required to meet different conductivity according to the conductivity of different proppants under the effective closure stress condition of the formation;

[0014] (5) determining the amount of sand added to a single seam of different types of proppants according to the seam height and seam length determined in step (1) and the sand concentration determined in step (4);

[0015] (6) Calculate the single well fracturing cost according to different segment cluster combinations and single seam sand addition and particle size combinations;

[0016] (7) According to the following conditions: "① As the cluster spacing decreases, stress interference increases. When stress interference exceeds the perforation pressure difference, it affects the balanced fracturing; ② As the cluster spacing decreases, the segment spacing decreases accordingly, the sand addition intensity increases, and the transformation cost increases; ③ After the cluster spacing increases, the diversion demand increases. To meet the diversion capacity, the required sand concentration increases. When the proppant width required to meet the sand concentration is greater than the width of the crack opening, the construction requirements cannot be met; ④ After the cluster spacing increases, the transformation volume does not increase, the fracture network coverage rate decreases, and the software simulated production decreases." Some combinations are eliminated, and the cluster spacing and sand addition scale combinations that meet the economic limit of the single well cost and the on-site construction are selected.

[0017] Preferably, the method for simulating fracture height and fracture length in step (1) comprises: establishing a geological model, importing the geological model into a fracturing simulation software, and using the fracturing simulation software to simulate fracture height and fracture length data under different sand and liquid volumes.

[0018] Preferably, the method for establishing the reservoir simulation geological model in step (2) includes: inputting data such as formation depth, pressure, porosity, permeability, saturation, oil layer and interlayer data, ground stress data, horizontal well trajectory, well network and well spacing into geological model software to establish a geological model.

[0019] Preferably, the method for simulating the cumulative oil production in step (2) comprises: using fracturing software to simulate the cumulative oil production under different cluster spacing conditions and different single fracture conductivity.

[0020] Preferably, the screening criterion in step (3) is that the predicted final cumulative production of a single well under the combination of cluster spacing and conductivity is greater than the final cumulative production required by the geological plan.

[0021] Preferably, the method for determining the single seam sand concentration in step (4) comprises: determining the required conductivity of the single seam, determining the formation closure stress and the effective closure stress acting on the proppant under production conditions, and determining the proppant conductivity chart (such as Figure 3 Determine the single seam sand concentration as shown).

[0022] Preferably, the method for determining the amount of sand added to a single seam in step (5) comprises: calculating the amount of sand added to a single seam using seam height × seam length × sand concentration based on the seam height and seam length data determined in step (1) and the sand concentration determined in step (4).

[0023] Preferably, the calculation method of the single well fracturing cost in step (6) is: according to the pricing standard of each oil field unit, the single well sand volume determined in step 5, the required single well fluid volume, horizontal section length, number of fracturing sections, cluster spacing and other data are determined based on the single well sand volume to calculate the single well fracturing cost.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) On the basis of ensuring that the EUR of a single well remains unchanged, an optimization strategy for matching cluster spacing with conductivity requirements is proposed, which has been verified in the Mahu block of Xinjiang Oilfield and the results are reliable;

[0026] (2) Good economic efficiency. The technical method of the present invention can provide clear guidance for optimizing the design scheme of on-site fracturing parameters while achieving the effect of single well transformation, thereby improving the overall development effect of the oil field;

[0027] (3) Convenient and fast. According to the technical solution of the present invention, the design of cluster spacing and sand addition scale in horizontal well fracturing design can be realized conveniently and quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a simulation diagram of the height and length of a single fracture in the XX block in Example 1;

[0029] Figure 2 is a curve diagram showing the relationship between different cluster spacings, flow conductivity and cumulative oil production in the XX block in Example 1;

[0030] Figure 3 It is a chart showing the conductivity provided by proppants with different sand-laying concentrations. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are further clearly described. The described embodiments are only a part of the present invention and are used to explain the present invention but not to limit the present invention. Therefore, other embodiments obtained by other technicians in the field without creative work all belong to the protection scope of the present invention.

[0032] Example 1

[0033] The reservoir of this embodiment is located in Block XX of Xiazijie Oilfield in Junggar Basin.

[0034] (1) According to the upper and lower reservoir barriers and well pattern conditions of the formation, the fracture height and fracture length of a single fracture matching under the fracture network transformation conditions are simulated, such as Figure 1 shown.

[0035] (2) A reservoir simulation geological model is established based on reservoir geological parameters to simulate the cumulative oil production under different cluster spacings and different single fracture conductivity. Several curves of cumulative oil production changing with single fracture conductivity under different cluster spacings are obtained, such as Figure 2 shown.

[0036] (3) Based on the curve obtained in step (2), a line (EUR target line) is drawn with the single well EUR predicted by the reservoir geological plan as the condition. The intersection of the EUR target line and the cumulative production curves of different cluster spacings is the single fracture conductivity that needs to be achieved under this cluster spacing condition when the EUR target condition is achieved, as shown in Figure 2 As shown in the figure, the conductivity of a single slit needs to reach 19D·cm when the cluster spacing is 20m, and the conductivity of a single slit needs to reach 26D·cm when the cluster spacing is 25m. By analogy, a set of corresponding relationships between cluster spacing and conductivity that meet the conditions are obtained.

[0037] (4) According to the conductivity chart of different proppants (such as Figure 3 According to the effective closure stress of the formation, the proppant particle size and paving concentration required to achieve different conductivity in step 3 are determined. For example, when 20 / 40 mesh quartz sand is used to achieve a conductivity of 26D·cm, the corresponding paving sand concentration is 5.1kg / m 2When 30 / 50 mesh quartz sand is used to achieve a conductivity of 26D·cm, the corresponding sand concentration is 7.8kg / m 2 When quartz sand with 40 / 70 mesh is used to achieve a flow conductivity of 26D·cm, the corresponding sand concentration is 20.1kg / m 2 In the actual construction process, the maximum support seam width of 0.7 cm is used as the limiting condition for the sand concentration of different types of proppants. Under this condition, the concentration of quartz sand should not exceed 10.5 kg / m 2 Therefore, 40 / 70 mesh quartz sand cannot meet the fracture conductivity requirements under the restricted conditions. The 40 / 70 mesh quartz sand combination condition can be eliminated first to reduce the subsequent calculation workload.

[0038] (5) According to the seam height and seam length determined in step (1) and the sand concentration determined in step (4), the amount of sand added to each seam of different types of proppants is determined (as shown in Table 1).

[0039] (6) Under the existing construction conditions, the single well fracturing cost is calculated according to different segment cluster combinations and single seam sand volume and particle size combinations (as shown in Table 2).

[0040] (7) According to the demand for 40 / 70 mesh quartz sand, the concentration of the sand is too high to be met in on-site construction. The cost is high under the condition of 20m cluster spacing. The construction cost of 30 / 50 mesh quartz sand is high under the condition of 25-30m cluster spacing. These conditions eliminate some combinations. Finally, the fracturing parameter combination of single-stage 3 clusters + cluster spacing 25-30m segment combination and 20 / 40 mesh quartz sand is recommended.

[0041] Table 1 Calculation of sand addition amount for single joint under different sand concentration conditions

[0042]

[0043] Table 2 Statistics of single well cost calculation parameters for different segment cluster combinations (taking XX well area as an example)

[0044]

[0045] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A method for optimizing the spacing between clusters and the scale of sand addition in horizontal well fracturing, characterized in that: The following steps are involved: (1) According to the upper and lower reservoir barriers and well pattern conditions of the formation, the fracture height and length of a single fracture matching under the conditions of fracture network transformation are simulated; (2) Establish a reservoir simulation geological model based on reservoir geological parameters to simulate the final cumulative production under different cluster spacing and different single fracture conductivity; (3) Based on the final cumulative production of a single well predicted by the geological reservoir plan, the cluster spacing and conductivity combination are screened; (4) Determine the single-slit sand concentration required to meet different conductivity according to the conductivity of different proppants under the effective closure stress condition of the formation; (5) determining the amount of sand added to a single seam of different types of proppants according to the seam height and seam length determined in step (1) and the sand concentration determined in step (4); (6) Calculate the single well fracturing cost according to different segment cluster combinations and single seam sand addition and particle size combinations; (7) Screen out the combination of single well cost that meets the economic limit and the cluster spacing and sand addition scale that meet the on-site construction requirements.

2. The method for optimizing the distance between clusters and the scale of sand addition for horizontal well fracturing according to claim 1, characterized in that: The method for simulating the fracture height and fracture length in step (1) comprises: establishing a geological model, importing the geological model into a fracturing simulation software, and using the fracturing simulation software to simulate fracture height and fracture length data under different sand and liquid volumes.

3. The method for optimizing the distance between clusters and the scale of sand addition for horizontal well fracturing according to claim 2, characterized in that: The method for establishing the geological model includes: inputting formation depth, pressure, porosity, permeability, saturation, oil layer and interlayer data, ground stress data, horizontal well trajectory and well network spacing data into geological model software to establish the geological model.

4. The method for optimizing the distance between clusters and the scale of sand addition for horizontal well fracturing according to claim 1, characterized in that: The method for simulating the cumulative oil production in step (2) includes: using fracturing software to simulate the cumulative oil production under different cluster spacing conditions and different single fracture conductivity.

5. The method for optimizing the distance between clusters and the scale of sand addition for horizontal well fracturing according to claim 1, characterized in that: The screening criteria in step (3) are: the predicted final cumulative production of a single well under the combination of cluster spacing and conductivity is greater than the final cumulative production required by the geological reservoir plan.

6. The method for optimizing the distance between clusters and the scale of sand addition for horizontal well fracturing according to claim 1, characterized in that: The method for determining the single-slit sand concentration in step (4) includes: determining the required conductivity of the single seam, determining the formation closure stress and the effective closure stress acting on the proppant under production conditions, and determining the single-slit sand concentration based on a proppant conductivity chart at different sand concentrations under different closure stress conditions.

7. The method for optimizing the distance between clusters and the scale of sand addition for horizontal well fracturing according to claim 1, characterized in that: The method for determining the amount of sand added to a single seam in step (5) includes: calculating the amount of sand added to a single seam based on the seam height and seam length data determined in step (1) and the sand concentration determined in step (4).

8. The method for optimizing the distance between clusters and the scale of sand addition for horizontal well fracturing according to claim 1, characterized in that: The calculation method of the single well fracturing cost in step (6) is as follows: the single well fracturing cost is calculated based on the pricing standards of each oil field unit, the single well sand volume and the single well sand volume to determine the required single well fluid volume, horizontal section length, number of fracturing sections and cluster spacing data.

9. The method for optimizing the spacing between clusters and the scale of sand addition for horizontal well fracturing according to any one of claims 1 to 8, characterized in that: The screening method described in step (7) includes: according to the following four conditions: "① As the cluster spacing decreases, the stress interference increases. When the stress interference exceeds the perforation pressure difference, the balanced fracturing is affected; ② As the cluster spacing decreases, the segment spacing decreases accordingly, the sand adding intensity increases, and the transformation cost increases; ③ After the cluster spacing increases, the diversion demand increases. In order to meet the diversion capacity, the required sand concentration increases. When the proppant width required to meet the sand concentration is greater than the width of the crack opening, the construction requirements cannot be met; ④ After the cluster spacing increases, the transformation volume does not increase, the seam network coverage rate decreases, and the software simulated production decreases". Eliminate the corresponding combination.

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