Stratigraphic dip angle quantification method and system based on gamma curve

Abstract

The invention discloses a stratigraphic dip angle quantification method and system based on a gamma curve, belongs to the technical field of petroleum engineering hydrocarbon reservoir structure evaluation, and is suitable for structure evaluation of a complex fault block low-porosity low-permeability thin interbed. Two natural gamma curves with similar natural gamma curve shapes are selected, and the stratigraphic dip angle is obtained according to the drill bit size and the hole drift angle. The method for calculating the stratigraphic dip angle by adopting the gamma curve has the advantages of rapidness, quantification and accuracy, and can accurately calculate the stratigraphic dip angle in time, identify the structural form and reservoir distribution and guide optimization and adjustment while drilling.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas layer structure evaluation in petroleum engineering, and in particular to a formation dip quantitative method and system based on a gamma curve. Background Art

[0002] With the deepening of oil and gas field exploration and development, it is becoming increasingly difficult to find high-quality oil and gas reservoirs. The field of exploration and development has gradually expanded to complex oil and gas reservoirs and unconventional oil and gas reservoirs. The evaluation of complex reservoirs such as "complex fault blocks, low porosity and low permeability, thin interlayers" is particularly important. Since the production capacity of such oil and gas reservoirs is generally low, it is extremely demanding to ensure the improvement of reservoir drilling rate during the implementation of drilling. Especially in the process of drilling tracking research, the accuracy and speed of evaluation are crucial. It is necessary to evaluate complex structural reservoirs in real time, quickly and accurately, calculate the formation dip in a timely and accurate manner, identify the structural morphology and reservoir distribution, and guide drilling optimization and adjustment.

[0003] Considering that the geophysical methods mainly used in structural reservoir identification and evaluation during drilling can only qualitatively identify structural depth and structural morphology, and are slow and have large errors, it is difficult to quickly and accurately identify the depth of the formation structure and the size of the structural dip, and it is even more impossible to quickly and accurately calculate the size of the formation dip in real time during drilling. It cannot meet the speed and accuracy requirements of drilling, and cannot guide the implementation of drilling. This not only increases the difficulty of real-time decision-making while drilling oil and gas wells, but also affects the implementation effect of drilling oil and gas wells, affects the reservoir drilling rate and drilling success rate of oil and gas wells, and thus affects the success rate of exploration and development. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a logging method for quickly calculating the formation dip, which can quickly, real-time and accurately obtain the size of the structural dip and realize the evaluation of the oil and gas layer structure.

[0005] In order to achieve the above technical purpose, the present application provides a quantitative method for formation dip angle based on gamma curve, which is suitable for structural evaluation of thin interlayers with low porosity and low permeability in complex fault blocks, including the following steps:

[0006] Based on the upper and lower natural gamma data, drill bit data and well deviation data, the formation dip is obtained by selecting two natural gamma curves with similar natural gamma curve shapes and according to the drill bit size and well deviation angle.

[0007] Preferably, in the process of obtaining the formation dip, two natural gamma curves with similar natural gamma curve shapes are selected according to the depth difference when the upper and lower natural gamma curves pass through the same layer interface.

[0008] Preferably, in the process of obtaining the formation inclination, based on the depth measurement difference, according to the drill bit size and the well inclination angle, the vertical right-angled side lengths and horizontal right-angled side lengths of the upper and lower cut formations are respectively obtained to obtain the formation inclinations of the upper and lower cut formations respectively.

[0009] Preferably, in the process of respectively obtaining the vertical right-angled side length and the horizontal right-angled side length of the upper-cut stratum and the lower-cut stratum, the vertical right-angled side length of the upper-cut stratum is expressed as FH=MD*cosα+d*sinα:

[0010] The length of the horizontal right angle side of the upper cut stratum is expressed as: HG = MD*sinα-d*cosα;

[0011] The length of the vertical right angle side of the downcut stratum is expressed as: FH = MD*cosα-d*sinα;

[0012] The length of the horizontal right angle side of the downcut stratum is expressed as: HE = MD*sinα+d*cosα;

[0013] Among them, d is the drill bit size; α is the well inclination angle, and MD is the depth difference.

[0014] Preferably, in the process of respectively obtaining the formation dip angles of the upper cut formation and the lower cut formation, the formation dip angle of the upper cut formation is expressed as:

[0015] tanθ=(MD*cosα+d*sinα) / (MD*sinα-d*cosα);

[0016] The dip angle of the downcut stratum is expressed as:

[0017] tanθ=(MD*cosα-d*sinα) / (MD*sinα+d*cosα);

[0018] Where θ is the formation inclination.

[0019] The present invention discloses a formation dip quantitative system based on a gamma curve, which is applicable to the structural evaluation of thin interlayers with low porosity and low permeability in complex fault blocks, and includes:

[0020] Data acquisition module, used to obtain upper and lower natural gamma data, drill bit data and well deviation data;

[0021] The formation dip quantitative module is used to obtain the formation dip based on the upper and lower natural gamma data, drill bit data and well deviation data by selecting two natural gamma curves with similar natural gamma curve shapes, according to the drill bit size and well deviation angle.

[0022] Preferably, the formation dip quantitative module is further used to select two natural gamma curves with similar natural gamma curve shapes according to the depth difference when the upper and lower natural gamma curves pass through the same layer interface.

[0023] Preferably, the formation dip quantification module is also used to obtain the vertical right-angle side lengths and horizontal right-angle side lengths of the upper and lower formations respectively based on the depth measurement difference, according to the drill bit size and the well inclination, so as to obtain the formation dips of the upper and lower formations respectively.

[0024] Preferably, the vertical right-angle side length of the upper cut stratum is expressed as FH=MD*cosα+d*sinα:

[0025] The length of the horizontal right angle side of the upper cut stratum is expressed as: HG = MD*sinα-d*cosα;

[0026] The length of the vertical right angle side of the downcut stratum is expressed as: FH = MD*cosα-d*sinα;

[0027] The length of the horizontal right angle side of the downcut stratum is expressed as: HE = MD*sinα+d*cosα;

[0028] Among them, d is the drill bit size; α is the well inclination angle, and MD is the depth difference.

[0029] Preferably, the formation dip angle of the upper cut formation is expressed as:

[0030] tanθ=(MD*cosα+d*sinα) / (MD*sinα-d*cosα);

[0031] The dip angle of the downcut stratum is expressed as:

[0032] tanθ=(MD*cosα-d*sinα) / (MD*sinα+d*cosα);

[0033] Where θ is the formation inclination.

[0034] The present invention discloses the following technical effects:

[0035] Since the present invention adopts the method of calculating the formation dip using the gamma curve, it has the advantages of being fast, quantitative and accurate, and can timely and accurately calculate the formation dip, identify the structural morphology and reservoir distribution, and guide while-drilling optimization and adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1This is the calculation model of the cut stratum in Example 1, wherein the green line is the layer interface and the black line is the position of the drill bit (the arrow indicates the center line of the drill bit).

[0038] Figure 2 This is the natural gamma logging curve of the formation cut in Example 1, wherein the upper red curve is the natural gamma curve below the drill bit, the upper dark blue curve is the natural gamma curve above the drill bit, and the lower green curve is the average natural gamma curve.

[0039] Figure 3 This is the calculation model of the upper stratum in Example 2, where the green line is the layer interface and the black line is the position of the drill bit (the arrow indicates the center line of the drill bit);

[0040] Figure 4 The natural gamma logging curve of the upper formation in Example 2, wherein the upper red curve is the natural gamma curve below the drill bit, the upper dark blue curve is the natural gamma curve above the drill bit, and the lower green curve is the average natural gamma curve;

[0041] Figure 5 A schematic diagram of the method flow of the present invention;

[0042] In the figure, E and F are the intersection points of the upper and lower natural gamma rays and the layer interface, respectively; d is the drill bit size; α is the well inclination angle; θ is the formation dip angle, and MD is the depth difference when the upper and lower natural gamma rays pass through the same layer interface. DETAILED DESCRIPTION

[0043] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0044] like Figure 1-5 As shown, the present invention provides a quantitative method for formation dip angle based on a gamma curve, which is applicable to the structural evaluation of thin interlayers with low porosity and low permeability in complex fault blocks, and includes the following steps:

[0045] Based on the upper and lower natural gamma data, drill bit data and well deviation data, the formation dip is obtained by selecting two natural gamma curves with similar natural gamma curve shapes and according to the drill bit size and well deviation angle.

[0046] Further preferably, in a formation dip quantification method based on gamma curves disclosed in the present invention, in the process of obtaining the formation dip, two natural gamma curves with similar natural gamma curve shapes are selected according to the depth difference when the upper and lower natural gammas pass through the same layer interface.

[0047] Further preferably, the present invention discloses a formation inclination quantification method based on a gamma curve, in the process of obtaining the formation inclination, based on the depth measurement difference, according to the drill bit size and the well inclination, respectively obtains the vertical right-angle side lengths and horizontal right-angle side lengths of the upper and lower cut formations, so as to respectively obtain the formation inclinations of the upper and lower cut formations.

[0048] Further preferably, in a formation dip quantification method based on a gamma curve disclosed by the present invention, in the process of respectively obtaining the vertical right-angle side length and the horizontal right-angle side length of the upper-cut formation and the lower-cut formation, the vertical right-angle side length of the upper-cut formation is expressed as FH=MD*cosα+d*sinα:

[0049] The length of the horizontal right angle side of the upper cut stratum is expressed as: HG = MD*sinα-d*cosα;

[0050] The length of the vertical right angle side of the downcut stratum is expressed as: FH = MD*cosα-d*sinα;

[0051] The length of the horizontal right angle side of the downcut stratum is expressed as: HE = MD*sinα+d*cosα;

[0052] Among them, d is the drill bit size; α is the well inclination angle, and MD is the depth difference.

[0053] Further preferably, in a formation dip quantification method based on a gamma curve disclosed in the present invention, in the process of respectively obtaining the formation dips of the upper and lower formations, the formation dip of the upper formation is expressed as:

[0054] tanθ=(MD*cosα+d*sinα) / (MD*sinα-d*cosα);

[0055] The dip angle of the downcut stratum is expressed as:

[0056] tanθ=(MD*cosα-d*sinα) / (MD*sinα+d*cosα);

[0057] Where θ is the formation inclination.

[0058] The present invention discloses a formation dip quantitative system based on a gamma curve, which is applicable to the structural evaluation of thin interlayers with low porosity and low permeability in complex fault blocks, and includes:

[0059] Data acquisition module, used to obtain upper and lower natural gamma data, drill bit data and well deviation data;

[0060] The formation dip quantitative module is used to obtain the formation dip based on the upper and lower natural gamma data, drill bit data and well deviation data by selecting two natural gamma curves with similar natural gamma curve shapes, according to the drill bit size and well deviation angle.

[0061] Further preferably, the formation dip quantification module of the formation dip quantification system based on gamma curves disclosed in the present invention is also used to select two natural gamma curves with similar natural gamma curve shapes according to the depth difference when the upper and lower natural gammas pass through the same layer interface.

[0062] Further preferably, the formation dip angle quantification module of the formation dip angle quantification system based on the gamma curve disclosed in the present invention is also used to obtain the vertical right-angle side length and the horizontal right-angle side length of the upper cut formation and the lower cut formation respectively based on the depth difference, according to the drill bit size and the well inclination angle, so as to obtain the formation dip angles of the upper cut formation and the lower cut formation respectively;

[0063] The length of the vertical right angle side of the upper stratum is expressed as FH = MD*cosα+d*sinα:

[0064] The length of the horizontal right angle side of the upper cut stratum is expressed as: HG = MD*sinα-d*cosα;

[0065] The length of the vertical right angle side of the downcut stratum is expressed as: FH = MD*cosα-d*sinα;

[0066] The length of the horizontal right angle side of the downcut stratum is expressed as: HE = MD*sinα+d*cosα;

[0067] Where, d is the drill bit size; α is the well inclination angle, and MD is the depth difference;

[0068] The dip angle of the upper stratum is expressed as:

[0069] tanθ=(MD*cosα+d*sinα) / (MD*sinα-d*cosα);

[0070] The dip angle of the downcut stratum is expressed as:

[0071] tanθ=(MD*cosα-d*sinα) / (MD*sinα+d*cosα);

[0072] Where θ is the formation inclination.

[0073] Embodiment 1, the present invention provides a quantitative method for quickly calculating formation dip using a gamma curve, comprising the following steps:

[0074] Step 1, collect real-time upper and lower natural gamma data, drill bit data and well deviation data that meet the standards;

[0075] Step 2: Establish a stratigraphic amplitude structure calculation model, where the downcut stratigraphic calculation model is shown in Figure 1 ;

[0076] Step 3, calculate the depth difference MD when the upper and lower natural gamma rays pass through the same layer interface, and select points where the shapes of the two natural gamma curves are as similar as possible;

[0077] Step 4, calculate the length of the vertical right angle side, the formula for cutting the stratum is FH = MD*cosα-d*sinα;

[0078] Step 5, calculate the length of the horizontal right angle side, and the formula for cutting the stratum is HE = MD*sinα+d*cosα;

[0079] Step 6, calculate the formation dip angle, the formation cutting formula is tanθ=(MD*cosα-d*sinα) / (MD*sinα+d*cosα); where d is the drill bit size; α is the well inclination angle; θ is the formation dip angle.

[0080] From △ABC, we can get: AB = MD*cosα, from △AFG and △CED, we can get: AG = DC = 1 / 2*d*sinα, therefore: FH = AB-AG-DC = MD*cosα-d*sinα; from △ABC, we can get: BC = MD*sinα, from △AFG and △CED, we can get: FG = DE = 1 / 2*d*cosα, therefore: HE = BC+FG+DE = MD*sinα+d*cosα, tanθ = (MD*cosα-d*sinα) / (MD*sinα+d*cosα).

[0081] In this example, the natural gamma logging curve of a well in a domestic oil field is shown in Figure 3 As shown in the figure, during the drilling process of this well, the formation amplitude slowed down and the formation dip became smaller. Relying on the upper and lower natural gamma curves, the formation dip was calculated to be 4.5°. The post-drilling research results confirmed that the formation dip was around 4°.

[0082] Embodiment 2, the present invention provides a quantitative method for quickly calculating the formation dip using a gamma curve, comprising the following steps:

[0083] Step 1, collect real-time upper and lower natural gamma data, drill bit data and well deviation data that meet the standards;

[0084] Step 2: Establish the stratigraphic amplitude structure calculation model. The upper stratigraphic calculation model is shown in Figure 3 ;

[0085] Step 3, calculate the depth difference MD when the upper and lower natural gamma rays pass through the same layer interface, and select points where the shapes of the two natural gamma curves are as similar as possible;

[0086] Step 4, calculate the length of the vertical right angle side, the formula for cutting the stratum is FH = MD*cosα+d*sinα;

[0087] Step 5, calculate the length of the horizontal right angle side, the formula for cutting the stratum is HG = MD*sinα-d*cosα;

[0088] Step 6, calculate the formation dip angle, the formula for cutting the formation is tanθ=(MD*cosα+d*sinα) / (MD*sinα-d*cosα); where d is the drill bit size; α is the well inclination angle; θ is the formation dip angle.

[0089] From △ABC, we can get: BC = MD*cosα, from △FBD and △GAE, we can get: FD = EG = 1 / 2*d*sinα, therefore: FH = BC+FD+EG = MD*cosα+d*sinα; from △ABC, we can get: AC = MD*sinα, from △FBD and △GAE, we can get: BD = EA = 1 / 2*d*cosα, therefore: HG = AC-BD-EA- = MD*sinα-d*cosα, tanθ = (MD*cosα+d*sinα) / (MD*sinα-d*cosα).

[0090] In this example, the natural gamma logging curve of a well in a domestic oil field is shown in Figure 4 As shown in the figure, during the drilling process of this well, the formation amplitude dropped suddenly and the formation dip increased, which was much larger than the 1° formation dip predicted by geophysics; relying on the upper and lower natural gamma curves, the formation dip was calculated to be 7°, and the post-drilling research results confirmed that the formation dip was around 7°.

[0091] The present invention can quickly and in real time obtain the size of the structural dip angle and realize the evaluation of the oil and gas layer structure.

[0092] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0093] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0094] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A formation dip quantitative method based on a gamma curve, characterized in that: Applicable to the structural evaluation of low porosity and low permeability thin interlayers in complex fault blocks, including the following steps: Based on the upper and lower natural gamma data, drill bit data and well deviation data, the formation dip is obtained by selecting two natural gamma curves with similar natural gamma curve shapes and according to the drill bit size and well deviation angle.

2. A formation dip quantitative method based on a gamma curve according to claim 1, characterized in that: In the process of obtaining the formation dip, two natural gamma curves with similar shapes are selected according to the depth difference when the upper and lower natural gamma curves pass through the same layer interface.

3. A formation dip quantitative method based on a gamma curve according to claim 2, characterized in that: In the process of obtaining the formation inclination, based on the depth measurement difference, according to the drill bit size and the well inclination angle, the vertical right-angled side lengths and horizontal right-angled side lengths of the upper cut formation and the lower cut formation are respectively obtained to obtain the formation inclination of the upper cut formation and the lower cut formation respectively.

4. A formation dip quantitative method based on a gamma curve according to claim 3, characterized in that: In the process of respectively obtaining the vertical right-angle length and the horizontal right-angle length of the upper and lower strata, the vertical right-angle length of the upper strata is expressed as FH=MD*cosα+d*sinα: The horizontal right-angle side length of the upper cut stratum is expressed as: HG = MD*sinα-d*cosα; The vertical right-angle side length of the undercut stratum is expressed as: FH = MD*cosα-d*sinα; The horizontal right-angle side length of the undercut stratum is expressed as: HE=MD*sinα+d*cosα; Among them, d is the drill bit size; α is the well inclination angle, and MD is the depth difference.

5. A formation dip quantitative method based on a gamma curve according to claim 4, characterized in that: In the process of respectively obtaining the formation dip angles of the upper cut formation and the lower cut formation, the formation dip angle of the upper cut formation is expressed as: tanθ=(MD*cosα+d*sinα) / (MD*sinα-d*cosα); The formation dip angle of the undercut formation is expressed as: tanθ=(MD*cosα-d*sinα) / (MD*sinα+d*cosα); Where θ is the formation inclination.

6. A formation dip quantification system based on a gamma curve, characterized in that: Applicable to structural evaluation of thin interbedded layers of low porosity and low permeability in complex fault blocks, including: Data acquisition module, used to obtain upper and lower natural gamma data, drill bit data and well deviation data; The formation dip quantitative module is used to obtain the formation dip based on the upper and lower natural gamma data, drill bit data and well deviation data by selecting two natural gamma curves with similar natural gamma curve shapes, according to the drill bit size and well deviation angle.

7. A formation dip quantitative system based on a gamma curve according to claim 6, characterized in that: The formation dip quantitative module is also used to select two natural gamma curves with similar natural gamma curve shapes according to the depth difference when the upper and lower natural gamma curves pass through the same layer interface.

8. A formation dip quantification system based on a gamma curve according to claim 7, characterized in that: The formation dip quantification module is also used to obtain the vertical right-angle side lengths and horizontal right-angle side lengths of the upper and lower cut formations respectively based on the depth measurement difference, according to the drill bit size and the well inclination angle, so as to obtain the formation dips of the upper and lower cut formations respectively.

9. A formation dip quantitative system based on a gamma curve according to claim 8, characterized in that: The vertical right-angle length of the upper-cut stratum is expressed as FH=MD*cosα+d*sinα: The horizontal right-angle side length of the upper cut stratum is expressed as: HG = MD*sinα-d*cosα; The vertical right-angle side length of the undercut stratum is expressed as: FH = MD*cosα-d*sinα; The horizontal right-angle side length of the undercut stratum is expressed as: HE=MD*sinα+d*cosα; Among them, d is the drill bit size; α is the well inclination angle, and MD is the depth difference.

10. A formation dip quantitative system based on a gamma curve according to claim 9, characterized in that: The formation dip angle of the upper cut formation is expressed as: tanθ=(MD*cosα+d*sinα) / (MD*sinα-d*cosα); The formation dip angle of the undercut formation is expressed as: tanθ=(MD*cosα-d*sinα) / (MD*sinα+d*cosα); Where θ is the formation inclination.

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