Shale horizontal well fracturing section selecting and dividing method based on logging curve

Abstract

The invention relates to a shale horizontal well fracturing section selecting and dividing method based on a logging curve. The method mainly solves the problem that reservoir lithology cannot be distinguished according to an existing shale reservoir classification standard. The method is characterized by comprising the following steps: acquiring logging curves of a plurality of shale horizontal wells; establishing a shale reservoir horizontal well lithology layering standard according to the shale reservoir corresponding to the logging curve; and S3, obtaining a logging curve of the horizontal well to be measured, and classifying the shale reservoir of the horizontal well to be measured according to the layering standard in the step S2. According to the shale horizontal well fracturing section selecting and dividing method based on the logging curve, the lithology of the reservoir can be effectively evaluated, the horizontal well fracturing section can be accurately divided, and help is provided for logging evaluation of the reservoir and exploration and development of an oil field.

Description

Technical Field

[0001] The invention relates to the field of petroleum exploration and development, in particular to a method for dividing shale horizontal well fracturing sections based on well logging curves. Background Art

[0002] In the current oilfield exploration and development, shale oil and gas has gradually become an important field for oil and gas replacement. In addition to geological conditions, the effect of engineering transformation is the key to shale oil and gas production. However, before the transformation of shale reservoirs, it is necessary to identify the reservoir lithology in order to explore reserves and build production capacity. However, the current shale reservoir classification standards are mainly based on the evaluation of oil and gas content, which cannot effectively distinguish lithology, and thus it is impossible to establish a standard for fracturing segment division. Summary of the invention

[0003] In order to overcome the deficiency of the existing shale reservoir classification standard that cannot distinguish reservoir lithology, the present invention provides a shale horizontal well fracturing section division method based on well logging curves. The shale horizontal well fracturing section division method based on well logging curves can effectively evaluate reservoir lithology and can more accurately divide horizontal well fracturing sections, thereby providing assistance for well logging evaluation of reservoirs and oilfield exploration and development.

[0004] The technical solution of the present invention is: a method for selecting sections for shale horizontal well fracturing based on well logging curves, comprising:

[0005] S1. Obtain logging curves of several shale horizontal wells;

[0006] S2. Establishing lithology stratification standards for horizontal wells in shale reservoirs according to the shale reservoirs corresponding to the well logging curves;

[0007] S3, obtaining the logging curve of the horizontal well to be tested, and classifying the shale reservoir of the horizontal well to be tested according to the stratification standard in step S2.

[0008] Furthermore, the stratification standard is: according to the natural gamma, resistivity, acoustic wave time difference, neutron and density in the logging curve, the shale reservoir is divided into four categories, including pure shale reservoir, transitional reservoir, tight reservoir and fracture reservoir.

[0009] Furthermore, the pure shale reservoir is divided into high organic pure shale and medium organic pure shale, wherein the natural gamma value of high organic pure shale is 113-157gAP1, the resistivity value is 11.1-26.3ohm.m, the acoustic time difference value is 67-78us / ft, the neutron value is 20.2-26.5%, and the density value is 2.44-2.57g / cm 3The natural gamma value of pure organic shale is 97-162gAP1, the resistivity value is 7.2-21.3ohm.m, the acoustic time difference value is 66-77us / ft, the neutron value is 17.4-26.8%, and the density value is 2.41-2.58g / cm 3 .

[0010] Furthermore, the natural gamma value of the transitional reservoir is 81-153gAP1, the resistivity value is 7.8-27.6ohm.m, the acoustic time difference value is 60-75us / ft, the neutron value is 15.3-25.4%, and the density value is 2.46-2.61g / cm 3 .

[0011] Furthermore, the dense reservoir is divided into near-wellbore reservoir and far-wellbore reservoir, wherein the near-wellbore reservoir has a natural gamma value of 98-130gAP1, a resistivity value of 7.6-44.35ohm.m, an acoustic time difference value of 65-70us / ft, a neutron value of 15.4-21.5%, and a density value of 2.52-2.62g / cm 3 The natural gamma value of the reservoir at the far end of the wellbore is 116-149gAP1, the resistivity value is 8.2-75.4ohm.m, the acoustic time difference value is 65-74us / ft, the neutron value is 18.7-24.0%, and the density value is 2.46-2.58g / cm 3 .

[0012] Furthermore, the natural gamma value of the fractured reservoir is 93-113gAP1, the resistivity value is 8.1-19.4ohm.m, the acoustic time difference value is 65-70us / ft, the neutron value is 17.1-24.4%, and the density value is 2.52-2.58g / cm 3 .

[0013] The present invention has the following beneficial effects: By adopting the above scheme, the present invention solves the problem that the existing reservoir classification standard can evaluate the oil and gas content of the reservoir but cannot determine the reservoir lithology. According to the horizontal well curve and its corresponding target layer characteristics, the horizontal well fracturing section can be divided more accurately, which provides assistance for logging evaluation of reservoirs and oilfield exploration and development. The actual application effect is remarkable and has great promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a flow chart of the present invention;

[0015] Figure 2 This is the logging curve response characteristic of the high-organic pure shale reservoir of the present invention.

[0016] Figure 3 This is the logging curve response characteristic of the medium-organic pure shale reservoir of the present invention.

[0017] Figure 4 This is the transitional reservoir logging curve response characteristic of the present invention.

[0018] Figure 5 This is the logging curve response characteristic of the near-wellbore dense reservoir of the present invention.

[0019] Figure 6 This is the logging curve response characteristic of the far wellbore tight reservoir of the present invention.

[0020] Figure 7 It is the logging curve response characteristic of the fractured reservoir of the present invention;

[0021] Figure 8 , Fig. 9 is the logging curve of the well in the embodiment. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings:

[0023] Depend on Figure 1 As shown, a method for selecting sections for shale horizontal well fracturing based on well logging curves includes:

[0024] S1. Obtain logging curves of several shale horizontal wells.

[0025] S2. Analyze the logging curve and its corresponding target layer characteristics, classify the curve characteristics representing the same type of lithology, and then subdivide the horizontal wells according to lithology to establish the lithology stratification standard for shale reservoir horizontal wells. According to the natural gamma, resistivity, acoustic wave time difference, neutron, and density in the logging curve, shale reservoirs are divided into four categories, including pure shale reservoirs, transitional reservoirs, dense reservoirs, and fracture reservoirs.

[0026] The pure shale reservoir type 1 reservoir has a lithology of pure shale, and its logging curve features a high natural gamma value, a high resistivity value, a relatively high acoustic time difference value, a relatively high neutron value, and a relatively low density value. According to the change in resistivity value, the pure shale reservoir is subdivided into 1-1 type and 1-2 type reservoirs, among which the 1-1 type reservoir has a high organic pure shale lithology, and the logging curve diagram is shown in Figure 2 Its natural gamma value is between 113-157gAP1, with an average value of 135gAP1. Its resistivity value is relatively high, between 11.1-26.3ohm.m, with an average value of 17.2ohm.m. Its acoustic time difference value is between 67-78us / ft, with an average value of 75us / ft. Its neutron value is between 20.2-26.5%, with an average value of 23.5%. Its density value is between 2.44-2.57g / cm 3 The average value is 2.51g / cm 3The lithology of the 1-2 reservoir is pure shale with medium organic matter. The well logging curve is shown in Figure 3 Its natural gamma value is between 97-162gAP1, with an average value of 134gAP1, its resistivity value is between 7.2-21.3ohm.m, with an average value of 10.6ohm.m, its acoustic time difference value is between 66-77us / ft, with an average value of 71us / ft, its neutron value is between 17.4-26.8%, with an average value of 22.4%, and its density value is between 2.41-2.58g / cm 3 The average value is 2.52g / cm 3 .

[0027] The transitional reservoir is a type 2 reservoir, the lithology is laminar shale, and the logging curve is shown in Figure 4 The logging curve is characterized by a relatively high natural gamma value, ranging from 81-153gAP1, with an average value of 123gAP1, a high resistivity value, ranging from 7.8-27.6ohm.m, with an average value of 14.5ohm.m, a low acoustic time difference value, ranging from 60-75us / ft, with an average value of 58us / ft, a low neutron value, ranging from 15.3-25.4%, with an average value of 20.7%, and a relatively high density value, ranging from 2.46-2.61g / cm 3 The average value is 2.54g / cm 3 .

[0028] The dense reservoirs are classified into three types, with lithology of siltstone, limestone and dolomite. According to the curve characteristics, the dense reservoirs are subdivided into 3-1 near-wellbore type and 3-2 far-end reservoirs. Among them, the 3-1 type reservoirs are siltstone, limestone and dolomite developed near the wellbore end, and the logging curve is Figure 5 Its natural gamma value is low, between 98-130gAP1, with an average value of 113gAP1, its resistivity value is between 7.6-44.35ohm.m, with an average value of 14.71ohm.m, its acoustic time difference value is low, between 65-70us / ft, with an average value of 66us / ft, its neutron value is low, between 15.4-21.5%, with an average value of 17.3%, and its density value is high, between 2.52-2.62g / cm 3 The average value is 2.56g / cm 3 3-2 type reservoirs are siltstone, limestone and dolomite developed far from the wellbore end. Figure 6Its natural gamma value is high, ranging from 116-149gAP1, with an average value of 133gAP1, its resistivity value is high, ranging from 8.2-75.4ohm.m, with an average value of 28.4ohm.m, its acoustic time difference value is between 65-74us / ft, with an average value of 70us / ft, its neutron value is low, ranging from 18.7-24.0%, with an average value of 21.4%, and its density value is low, ranging from 2.46-2.58g / cm 3 The average value is 2.51g / cm 3 .

[0029] The fractured reservoir is a type 4 reservoir, which is a suspected high-resistance fracture. The logging curve shows Figure 7 The logging curve is characterized by a low natural gamma value, ranging from 93-113gAP1, with an average value of 106gAP1, a resistivity value between 8.1-19.4ohm.m, with an average value of 13.7ohm.m, a low acoustic time difference value, ranging from 65-70us / ft, with an average value of 67us / ft, a neutron value between 17.1-24.4%, with an average value of 20.1%, and a high density value, ranging from 2.52-2.58g / cm 3 The average value is 2.55g / cm 3 .

[0030] The lithology subdivision standards for horizontal wells in shale reservoirs are shown in Table 1.

[0031] Table 1

[0032]

[0033]

[0034] S3, obtaining the logging curve of the horizontal well to be tested, and classifying the shale reservoir of the horizontal well to be tested according to the stratification standard in step S2.

[0035] Example: The above segment division method was applied in an actual well. Figure 8 , Fig. 9 This is the well logging curve of the well. According to the well logging curve, we can know the types of various reservoirs. In the figure, layer 1-1 is a high-organic pure shale layer: the natural gamma value is about 120gAP1, the resistivity value is about 14.2ohm.m, the acoustic time difference value is about 73us / ft, the neutron value is about 24.5%, and the density value is about 2.51g / cm 3 Layers 1-2 in the figure are pure shale layers with medium organic matter: the natural gamma value is about 130gAP1, the resistivity value is about 10.0ohm.m, the acoustic time difference value is about 70us / ft, the neutron value is about 22.3%, and the density value is about 2.52g / cm 3; Layer 2 in the figure is laminar shale: the natural gamma value is about 110gAP1, the resistivity value is about 15.0ohm.m, the acoustic time difference value is about 60us / ft, the neutron value is about 20.3%, and the density value is about 2.53g / cm 3 Figure 3-1 is a near-wellbore type dense layer: the natural gamma value is about 100gAP1, the resistivity value is about 14.0ohm.m, the acoustic time difference value is about 68us / ft, the neutron value is about 18.5%, and the density value is about 2.60g / cm 3 Figure 3-2 is a far-cylinder type dense layer: the natural gamma value is about 120gAP1, the resistivity value is about 18.0ohm.m, the acoustic time difference value is about 71us / ft, the neutron value is about 22.0%, and the density value is about 2.50g / cm 3 ; Figure 4 is a suspected high-resistance fracture layer: the natural gamma value is about 65gAP1, the resistivity value is about 16.0ohm.m, the acoustic time difference value is about 69us / ft, the neutron value is about 20.0%, and the density value is about 2.55g / cm 3 .

Claims

1. A method for selecting sections for shale horizontal well fracturing based on well logging curves, characterized in that: S1. Obtain logging curves of several shale horizontal wells; S2. Establishing lithology stratification standards for horizontal wells in shale reservoirs according to the shale reservoirs corresponding to the well logging curves; S3, obtaining the logging curve of the horizontal well to be tested, and classifying the shale reservoir of the horizontal well to be tested according to the stratification standard in step S2.

2. The method for selecting sections for shale horizontal well fracturing based on well logging curves according to claim 1, characterized in that: The stratification standard is: according to the natural gamma, resistivity, acoustic wave time difference, neutron and density in the logging curve, the shale reservoir is divided into four categories, including pure shale reservoir, transitional reservoir, tight reservoir and fracture reservoir.

3. The method for selecting sections for shale horizontal well fracturing based on well logging curves according to claim 2, characterized in that: The pure shale reservoir is divided into high organic pure shale and medium organic pure shale, wherein the natural gamma value of high organic pure shale is 113-157gAP1, the resistivity value is 11.1-26.3ohm.m, the acoustic time difference value is 67-78us / ft, the neutron value is 20.2-26.5%, and the density value is 2.44-2.57g / cm 3 The natural gamma value of pure organic shale is 97-162gAP1, the resistivity value is 7.2-21.3ohm.m, the acoustic time difference value is 66-77us / ft, the neutron value is 17.4-26.8%, and the density value is 2.41-2.58g / cm 3 .

4. The method for selecting sections for shale horizontal well fracturing based on well logging curves according to claim 2, characterized in that: The transitional reservoir has a natural gamma value of 81-153 gAP1, a resistivity value of 7.8-27.6 ohm.m, an acoustic time difference value of 60-75 us / ft, a neutron value of 15.3-25.4%, and a density value of 2.46-2.61 g / cm 3 .

5. The method for selecting sections for shale horizontal well fracturing based on well logging curves according to claim 2, characterized in that: The dense reservoir is divided into a near-wellbore reservoir and a far-wellbore reservoir. The near-wellbore reservoir has a natural gamma value of 98-130 gAP1, a resistivity value of 7.6-44.35 ohm.m, an acoustic time difference value of 65-70 us / ft, a neutron value of 15.4-21.5%, and a density value of 2.52-2.62 g / cm 3 The natural gamma value of the reservoir at the far end of the wellbore is 116-149gAP1, the resistivity value is 8.2-75.4ohm.m, the acoustic time difference value is 65-74us / ft, the neutron value is 18.7-24.0%, and the density value is 2.46-2.58g / cm 3 .

6. The method for selecting sections for shale horizontal well fracturing based on well logging curves according to claim 2, characterized in that: The natural gamma value of the fractured reservoir is 93-113gAP1, the resistivity value is 8.1-19.4ohm.m, the acoustic time difference value is 65-70us / ft, the neutron value is 17.1-24.4%, and the density value is 2.52-2.58g / cm 3 .

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