A method for horizontal fracture fracture initiation diagnosis and identification

Abstract

A horizontal fracture fracturing crack diagnosis and identification method. Mainly solve the existing horizontal fracture fracturing crack judgment method operation cost is high, the construction cycle is long problem. Its characterized in that it includes the following steps: S1, after the stratum is pressed, test fracturing is carried out, and the pressure drop curve is measured; S2, calculate the friction along the fracturing string; according to the test fracturing pressure after pressing, the ground construction pressure under the highest construction displacement, calculate the hole friction of the fracturing layer; S3, determine the single hole displacement; and determine the effective liquid absorbing gun hole number, calculate the opening rate; S4, preliminarily determine the horizontal fracture fracturing crack initiation characteristics; S5, carry out the pressure drop curve G function interpretation analysis, determine the equivalent number of artificial cracks, combined with the result of step S4, determine the horizontal fracture fracturing crack initiation characteristics. The method has low cost, short construction period, can accurately identify the horizontal fracture fracturing crack initiation characteristics in real time, so as to optimize the suitable fracturing process, realize the effective reconstruction of all small layers.

Description

Technical Field

[0001] This invention relates to the field of oilfield production engineering technology, specifically a method for diagnosing and identifying horizontal fracture initiation. Background Technology

[0002] The Sa Ling Formation reservoir in the Changyuan old reservoir area features thin interbedded layers, with some sub-layers containing 1-2 argillaceous or calcareous interlayers, exhibiting strong vertical heterogeneity. Fracturing in the Sa Ling Formation primarily involves horizontal fractures. For target formations with fracture spacing less than 2m, mechanical stratification is not feasible; multi-layer or intra-layer multi-cluster perforation fracturing is mainly employed to generate multiple horizontal fractures. Due to fracture stress interference and heterogeneous physical properties, some sub-layers struggle to initiate fracturing during the fracturing process, resulting in uneven fracturing across sub-layers and impacting the effectiveness of fracturing techniques. Therefore, it is necessary to diagnose and analyze the fracture initiation characteristics of each sub-layer to improve the targeting of reservoir stimulation.

[0003] Currently, the determination of whether a horizontal fracture has been opened by hydraulic fracturing mainly relies on post-fracturing tracer fracture profile testing or production fluid (oil) profile testing during the production process. However, these testing methods are costly to operate, have long construction cycles, and often cannot accurately identify the initiation characteristics of horizontal fractures in real time. Summary of the Invention

[0004] To overcome the problems of high operating costs and long construction cycles in existing horizontal fracture fracturing crack identification methods, this invention provides a horizontal fracture fracturing crack initiation diagnosis and identification method. This method is low in cost and has a short construction cycle. It can accurately identify the initiation characteristics of fracturing cracks in real time, thereby selecting a suitable fracturing process, effectively transforming all sub-layers, and improving the vertical utilization of the reservoir.

[0005] The technical solution of the present invention is: a method for diagnosing and identifying the initiation of horizontal pressure fracturing cracks, comprising the following steps:

[0006] S1. After fracturing the formation, test fracturing is performed, and the pressure drop curve is measured.

[0007] S2. Calculate the friction resistance of the fracturing tubing based on the relationship between the construction flow rate and friction resistance; calculate the pore friction resistance of the fracturing layer based on the instantaneous pump stop pressure after fracturing and the ground construction pressure at the highest construction flow rate.

[0008] S3. Based on the orifice friction calculated in step S2, refer to the chart showing the relationship between orifice friction and single-hole discharge rate for different perforation depths to determine the single-hole discharge rate; and determine the effective number of suction holes and calculate the opening rate.

[0009] S4. Based on the relationship charts between the spacing of the fracturing layers and the porosity, and the relationship charts between the permeability ratio and the porosity, the characteristics of the horizontal fracturing fractures are preliminarily determined.

[0010] S5. Perform G-function interpretation analysis of the pressure drop curve to determine the equivalent number of artificial fractures. Combined with the results of step S4, determine the initiation characteristics of horizontal fracture fracturing.

[0011] Furthermore, in step S1, the pressure drop curve is measured until the crack closes.

[0012] Furthermore, in step S2, P pf =P i -P is -P fr ,

[0013] In the formula: P pf P represents the pore friction of the fracturing layer, in MPa. i The ground construction pressure at the highest construction displacement, in MPa; P is To test the instantaneous pump shutdown pressure after fracturing, MPa; P fr The frictional resistance along the friction line is expressed in MPa.

[0014] Furthermore, the diagram showing the relationship between the fracturing fluid displacement and frictional resistance along the pipeline is selected based on the type of fracturing fluid and the model of the fracturing tubing.

[0015] Furthermore, in step S3, n 有效 =Q / Q 单 ,

[0016] Where: n 有效 The effective number of suction holes; Q is the total construction discharge volume, in meters. 3 / min; Q 单 For single-hole discharge, m 3 / min.

[0017] Furthermore, in step S3, Φ = n 有效 / n×100%,

[0018] In the formula: Φ is the porosity; n 有效 The effective number of suction holes; n is the total number of perforations.

[0019] Furthermore, in step S5, when it is determined that a small layer has not been modified, a multi-fracture fracturing process is adopted. By inserting temporary plugging balls to seal the already fractured small layers, the un-fractured small layers are opened up, so that all small layers are modified.

[0020] Furthermore, the process for establishing the relationship charts between fracturing layer spacing and porosity, and between permeability ratio and porosity, as described in step S4, is as follows:

[0021] 1.1 Select several test wells, and based on the pressure drop curves of the test wells, perform G-function interpretation analysis to determine the equivalent number of artificial fractures;

[0022] 1.2 Calculate the frictional resistance along the fracturing tubing string for each well; calculate the pore frictional resistance of the fracturing layer based on the instantaneous pump stop pressure after fracturing and the surface construction pressure at the highest construction flow rate.

[0023] 1.3. By referring to the chart showing the relationship between perforation penetration depth, hole friction and single-hole discharge rate, determine the single-hole discharge rate for each well; and determine the effective number of suction holes and calculate the opening rate.

[0024] 1.4. Collect data on the fracture spacing and permeability of each sublayer of the above wells, calculate the permeability ratio, and establish a graph showing the relationship between fracture spacing and porosity, and between permeability ratio and porosity based on the data.

[0025] This invention offers the following advantages: Due to the aforementioned approach, this method is suitable for wells with poorly developed natural fractures and horizontal fractures. It can determine the initiation characteristics of horizontal fractures in real time, solving the problem of insufficient reservoir stimulation in previous horizontal fracture fracturing methods. Through G-function interpretation and porosity calculation, the initiation status of multiple horizontal fractures is determined, allowing for the selection of suitable fracturing techniques, improving the vertical utilization of the reservoir, and enhancing the effectiveness of fracturing measures. This method fills the gap in horizontal fracture fracturing construction diagnosis and control technology. Attached Figure Description

[0026] Figure 1 This is a flowchart of the present invention;

[0027] Figure 2 This is the G function interpretation curve of well B1 in Example 1;

[0028] Figure 3 This is the G function interpretation curve of well B2 in Example 2;

[0029] Figure 4 It is a graph showing the relationship between construction displacement and frictional resistance along the road;

[0030] Figure 5 A graph showing the relationship between perforation depth, hole friction, and single-hole displacement;

[0031] Figure 6 It is a graph showing the relationship between slit spacing and open area ratio;

[0032] Figure 7 It is a graph showing the relationship between the permeability ratio and the porosity. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings:

[0034] Depend on Figure 1 As shown, a method for diagnosing and identifying the initiation of horizontal pressure fracturing includes the following steps:

[0035] S1. After fracturing the formation, a small-scale test fracturing is first carried out to measure the pressure drop curve until the fracture is closed.

[0036] S2. Select the appropriate fracturing fluid displacement and friction-relationship chart based on the type of fracturing fluid and the model of the fracturing tubing. Since the fracturing fluid used in this invention is guar gum fracturing fluid, and the 2... 7 / 8 In the fracturing tubing, therefore, the corresponding guar gum fracturing fluid should be selected, 2 7 / 8 Based on the empirical chart of friction resistance under fracturing tubing conditions, calculate the friction resistance along the fracturing string according to the chart. Calculate the orifice friction resistance of the fracturing layer based on the instantaneous pump stop pressure after fracturing and the surface operating pressure at the highest operating displacement.

[0037] P pf =P i -P is -P fr (1)

[0038] In the formula: P pf P represents the pore friction of the fracturing layer, in MPa. i The ground construction pressure at the highest construction displacement, in MPa; P is To test the instantaneous pump shutdown pressure after fracturing, MPa; P fr The frictional resistance along the friction line is expressed in MPa.

[0039] S3. Based on the orifice friction calculated in step S2, refer to the chart showing the relationship between orifice friction and single-orifice discharge rate for different perforation depths to determine the single-orifice discharge rate. This chart is based on existing experience. Determine the effective number of suction holes based on the single-orifice discharge rate and the total construction discharge rate.

[0040] n 有效 =Q / Q 单 (2)

[0041] Where: n 有效 The effective number of suction holes; Q is the total construction discharge volume, in meters. 3 / min; Q 单 For single-hole discharge, m 3 / min.

[0042] And calculate the open area ratio.

[0043] Φ=n 有效 / n×100% (3)

[0044] In the formula: Φ is the porosity; n 有效 The effective number of suction holes; n is the total number of perforations.

[0045] S4. Based on the relationship charts between the spacing of the fracture layers and the porosity, and the relationship charts between the permeability ratio and the porosity, the initiation characteristics of horizontal fractures are preliminarily determined, and it is determined whether the fracture layer is initiated by a single fracture or multiple fractures.

[0046] S5. Perform G-function interpretation analysis of the pressure drop curve to determine the equivalent number of artificial fractures; combine the results of step S4 to determine the fracture initiation characteristics of horizontal fractures. Based on the fracture initiation characteristics of horizontal fractures, select a suitable fracturing process to ensure that each sub-layer is fully modified. When it is determined that all sub-layers have been fractured, a conventional fracturing process (e.g., flow-limited fracturing process) is adopted; when it is determined that some sub-layers have not been fully modified, a multi-fracture fracturing process is adopted (if the number of sub-layers is relatively small, one temporary plugging is performed; if the number of sub-layers is relatively large, multiple temporary pluggings can be performed). By deploying a certain number of temporary plugging balls, the fractured sub-layers are sealed, and then the un-fractured sub-layers are fractured to ensure that all sub-layers are effectively modified.

[0047] The graphs showing the relationship between fracture spacing and porosity, and the graphs showing the relationship between permeability ratio and porosity, mentioned in step S4, are established based on test fracturing data from several wells and the G-function interpretation analysis of the pressure drop curves. The specific process is as follows:

[0048] 1.1 Select several test wells with poorly developed natural fractures and horizontal fractures. Based on the pressure drop curves of the test wells, perform G-function interpretation analysis to determine the equivalent number of artificial fractures.

[0049] 1.2. Based on the relationship between fracturing fluid displacement and friction resistance, calculate the friction resistance of the fracturing tubing string for each well. The relationship between fracturing fluid displacement and friction resistance is based on experience; selection is only required according to the fracturing fluid and tubing type. Calculate the pore friction of the fracturing layer based on the instantaneous pump stop pressure after fracturing and the surface operating pressure at the highest fracturing fluid displacement.

[0050] 1.3. By referring to the charts showing the relationship between perforation penetration depth, hole friction and single-hole discharge rate, determine the single-hole discharge rate for each well. The charts showing the relationship between perforation penetration depth, hole friction and single-hole discharge rate are also empirical charts. Determine the effective number of suction holes and calculate the opening rate.

[0051] 1.4. Collect data on the fracture spacing and permeability of each sublayer of the above wells, calculate the permeability ratio, and establish a graph showing the relationship between fracture spacing and porosity, and between permeability ratio and porosity based on these data.

[0052] When implementing this method, this chart can be used to make a preliminary judgment on the characteristics of horizontal fracture cracks.

[0053] Example 1:

[0054] Well B1 is a horizontal fracture fracturing test well in the Sa Ling Formation of the Daqing Changyuan old area. The No. 3 sandstone layer of the Sa Ling Formation has a thickness of 1.1m, an effective thickness of 0.6m, and an air permeability of 7.6mD. The perforated section is 892.35-891.85m, with a perforation thickness of 0.5m and 8 perforations. The No. 2 sandstone layer of the Sa Ling Formation has a thickness of 1.23m, an effective thickness of 0.9m, and an air permeability of 9.9mD. The perforated section is 890.75-890.25m, with a perforation thickness of 0.5m and 8 perforations. The perforation spacing between the No. 3 and No. 2 layers is 1.1m, making mechanical layered fracturing impossible.

[0055] S1. After fracturing the formation, a small-scale test fracturing is first carried out, and the pressure drop curve is measured until the fracture closes.

[0056] S2, Measure the instantaneous pump stop pressure P after pressure is measured is The pressure is 8.9 MPa, and the maximum construction discharge is 4.0 m³. 3 / min, stable construction pressure P i It is 35.2 MPa; referring to the frictional resistance chart, as shown... Figure 4 As shown, the frictional resistance P along the path can be obtained. fr If the pressure is 8.02 MPa, then according to formula (1)

[0057] P pf =P i -P is -P fr

[0058] The calculated pore friction P of the target fracturing layer pf It is 18.28 MPa.

[0059] S3. This well uses the YD-89 perforating gun and DP41RDX-1 projectile, with a perforation depth of 8.8mm. Refer to the chart showing the relationship between orifice friction and single-hole displacement for different perforation depths, as follows: Figure 5 As shown, determine the single-orifice displacement Q. 单 It is 0.43m 3 / min; because the total construction discharge Q is 4.0m 3 / min, calculate the effective number of suction holes according to formula (2),

[0060] n 有效 =Q / Q 单

[0061] Therefore, the effective number of suction holes n is obtained. 有效 It has 9.3 holes;

[0062] Since the total number of perforations is 16, the opening ratio is calculated according to formula (3).

[0063] Φ=n 有效 / n×100%

[0064] Therefore, the aperture ratio is Φ58.1%.

[0065] S4. The fracture spacing between layer 3 and layer 2 of the Sa Zero Group in this well is 1.1m. Refer to the chart showing the relationship between fracture spacing and porosity, as follows: Figure 6 As shown, this is determined to be a single crack initiation characteristic; the permeability ratio of layer 2 to layer 3 in the Sa0 group is 1.30. Referring to the permeability ratio versus porosity relationship chart, as shown... Figure 7 As shown, the characteristics of multiple crack initiation are determined.

[0066] S5. Use FracproPT fracturing software to interpret the pressure drop curve using the G function, such as... Figure 2 As shown, the G-function curve indicates two distinct crack closures, suggesting that two horizontal cracks were forced open. Combined with the results of step S4, it was determined that the horizontal fracture fracturing opened two small layers.

[0067] Based on the identified fracture initiation characteristics, conventional flow-limited fracturing techniques can ensure sufficient modification of each sub-layer. The B1 well had a displacement of 4.0 m³ / s. 3 / min, sand ratio program 10-20-25-28-32-35%, total proppant added 36m 3 Fracturing fluid usage: 240.0 m³ 3 The initial oil production after compression is 2.4 t / d, and the effective oil production intensity reaches 1.60 t / dm.

[0068] Example 2:

[0069] Well B2 is a horizontal fracture testing well in the Sa Ling Formation of the Changyuan Old Area in Daqing. The No. 3 sandstone layer of the Sa Ling Formation has a thickness of 1.8m, an effective thickness of 1.7m, and an air permeability of 19.0mD. The perforated section is 938.5-938.0m, with a perforation thickness of 0.5m and 8 perforations. The No. 2 sandstone layer of the Sa Ling Formation has a thickness of 2.1m (containing a 0.3m mudstone interlayer), an effective thickness of 0.6m, and an air permeability of 14.9mD. The perforated sections are 936.7-936.5m and 936.2-935.8m, with a perforation thickness of 0.6m and 10 perforations. The No. 1 sandstone layer of the Sa Ling Formation has a thickness of 2.4m, an effective thickness of 1.2m, and an air permeability of 13.6mD. The perforated section is 930.0-929.5m, with a perforation thickness of 0.5m and 8 perforations. The perforation spacing between layers 3 and 2 in the Sa0 group is 1.2m, and the perforation spacing within layer 2 of the Sa0 group is 0.3m. Mechanical stratification is not possible, so the flow-limited method is used for combined fracturing. The perforation spacing between layer 1 and layer 2 below in the Sa0 group is 5.8m, so mechanical stratification is used for separate fracturing.

[0070] S1. First, perform hydraulic fracturing on layers 3 and 2 of the Sa0 group. After fracturing the formation, perform small-scale test fracturing and measure the pressure drop curve until the fracture closes.

[0071] S2. The instantaneous pump stop pressure after pressure testing was measured to be 10.0 MPa, and the maximum construction discharge was 4.0 m³ / h. 3 / min, stable construction pressure P i The pressure is 40.6 MPa. Referring to the frictional resistance chart, as shown... Figure 4 As shown, the frictional resistance P along the path can be obtained. fr The pressure is 8.4 MPa. The pore friction P of the target layer fracture can be calculated using formula (1). pf It is 22.2 MPa.

[0072] S3. This well uses the YD-89 perforating gun and DP41RDX-1 projectile, with a perforation depth of 8.8mm. Refer to the chart showing the relationship between orifice friction and single-hole displacement for different perforation depths, as follows: Figure 5 As shown, determine the single-orifice displacement Q. 单 It is 0.48m 3 / min, since the total construction discharge Q is 4.0m 3 / min, calculate the effective number of suction holes n according to formula (2). 有效 The number of holes is 8.3; since the total number of perforations is 18, the opening ratio Φ is calculated to be 46.1% according to formula (3).

[0073] S4. The fracture spacing between layers 3 and 2 in the Sa Zero Group of this well is 1.2m, and the fracture spacing within layer 2 is 0.3m. Refer to the chart showing the relationship between fracture spacing and porosity. Figure 6 As shown, this is determined to be a single crack initiation characteristic; the permeability ratio of layer 3 to layer 2 in the Sa0 group is 1.27. Referring to the permeability ratio versus porosity chart, as shown... Figure 7 As shown, the characteristics of multiple crack initiation are determined.

[0074] S5. Use FracproPT fracturing software to interpret the pressure drop curve using the G function, such as... Figure 3 As shown, the G-function curve indicates a clear crack closure, suggesting that a horizontal crack was opened. Combined with the results of step S4, it is concluded that the horizontal crack was fracturing and opened a small layer.

[0075] Based on the characteristics of fracture initiation, the multi-fracture flow-limiting fracturing process can ensure that each sub-layer is fully modified.

[0076] Construction displacement for layers 3 and 2 of the B2 well (Sa Zero Group) is 4.0 m³. 3 / min, sand ratio program 10-20-25-28-32-35%, total proppant added 32m 3 Fracturing fluid usage: 210.0 m³ 31.0 kg of temporary blocking ball was thrown, and the construction displacement was 4.0 m³. 3 / min, the ground construction pressure increased from 26.9MPa to 30.8MPa, an increase of 3.9MPa, the sand ratio program was 10-20-25-28-32-35%, and 29m of proppant was added. 3 The fracturing fluid usage was 190.0 m³. 3 The construction displacement for the No. 1 floor of the Sa Zero Group is 4.0 m³. 3 / min, sand ratio program 10-20-25-28-32-35%, total proppant added 28m 3 Fracturing fluid usage: 180.0 m³ 3 The initial oil production after compression was 5.78 t / d, with an effective oil production intensity of 1.65 t / dm.

Claims

1. A method for diagnosing and identifying the initiation of horizontal pressure fracturing cracks, characterized in that... Includes the following steps: S1. After fracturing the formation, test fracturing is performed, and the pressure drop curve is measured. S2. Calculate the friction resistance of the fracturing tubing based on the relationship between the construction flow rate and friction resistance; calculate the pore friction resistance of the fracturing layer based on the instantaneous pump stop pressure after fracturing and the ground construction pressure at the highest construction flow rate. S3. Based on the orifice friction calculated in step S2, refer to the chart showing the relationship between orifice friction and single-hole discharge rate for different perforation depths to determine the single-hole discharge rate; and determine the effective number of suction holes and calculate the opening rate. S4. Based on the relationship charts of fracture spacing and porosity in the fracturing layer and the relationship charts of permeability ratio and porosity in the fracturing layer, the characteristics of single or multiple fracture initiation in horizontal fracture fracturing can be preliminarily determined. S5. Perform G-function interpretation analysis of the pressure drop curve to determine the equivalent number of artificial cracks. Combined with the results of step S4, determine the single or multiple crack initiation characteristics of horizontal crack fracturing.

2. The method for diagnosing and identifying horizontal fracture initiation according to claim 1, characterized in that: In step S1, the pressure drop curve is measured until the crack closes.

3. The method for diagnosing and identifying horizontal fracture initiation according to claim 1, characterized in that: In step S2, P pf =P i -P is -P fr , In the formula: P pf P represents the pore friction of the fracturing layer, in MPa. i The ground construction pressure at the highest construction displacement, in MPa; P is To test the instantaneous pump shutdown pressure after fracturing, MPa; P fr The frictional resistance along the friction line is expressed in MPa.

4. The method for diagnosing and identifying horizontal fracture initiation according to claim 3, characterized in that: The diagram showing the relationship between fracturing fluid displacement and friction along the tubing is selected based on the type of fracturing fluid and the model of the fracturing tubing.

5. The method for diagnosing and identifying horizontal fracture initiation according to claim 1, characterized in that: In step S3, n 有效 =Q / Q 单 , Where: n 有效 The effective number of suction holes; Q is the total construction discharge volume, in meters. 3 / min; Q 单 For single-hole discharge, m 3 / min.

6. The method for diagnosing and identifying horizontal fracture initiation according to claim 5, characterized in that: In step S3, Φ = n 有效 / n×100%, In the formula: Φ is the porosity; n 有效 The effective number of suction holes; n is the total number of perforations.

7. The method for diagnosing and identifying horizontal fracture initiation according to claim 1, characterized in that: In step S5, when it is determined that a small layer has not been modified, a multi-fracture fracturing process is adopted. By inserting temporary plugging balls to seal the fractured small layer and pressing open the small layer that has not yet cracked, all small layers are modified.

8. The method for diagnosing and identifying horizontal fracture initiation according to claim 1, characterized in that: The process of establishing the relationship charts between fracturing layer spacing and porosity, and between permeability ratio and porosity, as described in step S4, is as follows: 1.1 Select several test wells, and based on the pressure drop curves of the test wells, perform G-function interpretation analysis to determine the equivalent number of artificial fractures; 1.2 Calculate the frictional resistance along the fracturing tubing string for each well; calculate the pore frictional resistance of the fracturing layer based on the instantaneous pump stop pressure after fracturing and the surface construction pressure at the highest construction flow rate. 1.

3. By referring to the chart showing the relationship between perforation penetration depth, hole friction and single-hole discharge rate, determine the single-hole discharge rate for each well; and determine the effective number of suction holes and calculate the opening rate. 1.

4. Collect data on the fracture spacing and permeability of each sublayer of the above wells, calculate the permeability ratio, and establish a graph showing the relationship between fracture spacing and porosity, and between permeability ratio and porosity based on the data.

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