Method and device for determining the productivity of tight gas reservoir

Abstract

The present disclosure is about a method and device for determining the productivity of a tight gas reservoir, and belongs to the field of tight gas. The method includes: determining the permeability of each tight gas reservoir based on the well logging data of the gas well; determining the neutron-density envelope area of ​​each tight gas reservoir based on the well logging data of the gas well, wherein the neutron-density envelope area is the integral of the difference between the density of the tight gas reservoir and the neutron of the tight gas reservoir over the depth of the tight gas reservoir; determining the productivity index of each tight gas reservoir based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir; obtaining the unimpeded flow of each tight gas reservoir; determining the relationship between the unimpeded flow and the productivity index based on the productivity index and the unimpeded flow of each tight gas reservoir; determining the productivity of the tight gas reservoir to be tested based on the productivity index and the relationship of the tight gas reservoir to be tested.

Description

Technical Field

[0001] The present disclosure relates to the field of tight gas, and in particular to a method and device for determining the production capacity of a tight gas reservoir. Background Art

[0002] Tight sandstone gas, referred to as tight gas, is a natural gas distributed in tight sandstone. The tight sandstone layer that stores tight gas can be called a tight gas reservoir.

[0003] A gas well includes multiple tight gas reservoirs, and the production capacity of each tight gas reservoir is different. In the exploration and development of oil and gas fields, the production plan can be optimized according to the production capacity of the tight gas reservoir to improve economic benefits. Therefore, it is particularly important to determine the production capacity of the tight gas reservoir.

[0004] In the related art, the method for determining the production capacity of a tight gas reservoir includes: collecting multiple experimental samples from the tight gas reservoir to be tested; conducting experiments on the multiple experimental samples, respectively calculating multiple production capacities corresponding to the multiple experimental samples; calculating the average of the multiple production capacities; and using the average to characterize the production capacity of the tight gas reservoir to be tested. However, the production capacity of the experimental samples cannot represent the production capacity of the tight gas reservoir to be tested, so that the production capacity of the tight gas reservoir to be tested obtained by this method has a large error, and the production capacity of the tight gas reservoir to be tested is not accurate enough. Summary of the invention

[0005] The embodiment of the present disclosure provides a method and device for determining the productivity of a tight gas reservoir, so that the productivity of the tight gas reservoir to be measured can be determined more accurately. The technical solution is as follows:

[0006] On the one hand, the present disclosure provides a method for determining the productivity of a tight gas reservoir, which is applied to a gas well, wherein the gas well includes a plurality of tight gas reservoirs, and the method for determining the productivity of the tight gas reservoir includes: determining the permeability of each of the plurality of tight gas reservoirs based on the well logging data of the gas well; determining the neutron-density envelope area of ​​each of the plurality of tight gas reservoirs based on the well logging data of the gas well, wherein the neutron-density envelope area is the integral of the difference between the density of the tight gas reservoir and the neutron of the tight gas reservoir with respect to the depth of the tight gas reservoir, and the tight gas reservoir is the permeability of each of the plurality of tight gas reservoirs; and determining the neutron-density envelope area of ​​each of the plurality of tight gas reservoirs based on the well logging data of the gas well. The density of the reservoir and the neutron of the tight gas reservoir refer to the part of the density curve and the neutron curve in the same coordinate system where the density value is greater than the neutron value; based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir, determine the production capacity index of each tight gas reservoir; obtain the open-flow rate of each tight gas reservoir; based on the production capacity index and open-flow rate of each tight gas reservoir, determine the relationship between the open-flow rate and the production capacity index; based on the production capacity index of the tight gas reservoir to be tested and the relationship, determine the production capacity of the tight gas reservoir to be tested.

[0007] In one implementation of the embodiment of the present disclosure, the permeability of each of the multiple tight gas reservoirs is determined based on the logging data of the gas well, including: determining the mud content of each of the tight gas reservoirs based on the logging data; determining the effective porosity of each of the tight gas reservoirs based on the mud content of each of the tight gas reservoirs; and determining the permeability of each of the multiple tight gas reservoirs based on the effective porosity of each of the tight gas reservoirs.

[0008] In an implementation of the embodiment of the present disclosure, the logging data includes a natural gamma curve, a P-wave time difference curve, and an irreducible water saturation curve;

[0009] Determining the shale content of each of the tight gas reservoirs based on the well logging data includes:

[0010] The following formula is used to calculate the shale content of each tight gas reservoir:

[0011]

[0012]

[0013] in:

[0014] V sh ——The mud content of the tight gas reservoir, unit: %;

[0015] I GR ——relative value of natural gamma of the tight gas reservoir, dimensionless;

[0016] GR log ——Natural gamma reading of the tight gas reservoir, unit: API;

[0017] GR matrix ——the average natural gamma response of the pure sandstone formation in the tight gas reservoir, unit: API;

[0018] GR shale ——the average natural gamma response of the pure mudstone formation in the tight gas reservoir, unit: API;

[0019] Determining the effective porosity of each of the tight gas reservoirs based on the shale content of each of the tight gas reservoirs comprises:

[0020] The effective porosity of each tight gas reservoir is calculated using the following formula:

[0021]

[0022] Δt cc =Δt-Vsh ×(Δt sh -Δt ma );

[0023]

[0024] in:

[0025] ——The effective porosity of the tight gas reservoir, unit: %;

[0026] C——intermediate value, dimensionless;

[0027] Δt ma ——the longitudinal wave time difference of the sandstone skeleton in the tight gas reservoir, in μs / ft;

[0028] Δt f ——the longitudinal wave time difference of the pore fluid in the tight gas reservoir, in μs / ft;

[0029] Δt——the longitudinal wave time difference of the tight gas reservoir, in μs / ft;

[0030] Δt cc ——Correction value of the longitudinal wave time difference of the tight gas reservoir, in μs / ft;

[0031] Δt sh ——the longitudinal wave time difference of the mudstone in the tight gas reservoir, in μs / ft;

[0032] Determining the permeability of each of the plurality of tight gas reservoirs based on the effective porosity of each of the tight gas reservoirs comprises:

[0033] The permeability of each tight gas reservoir is calculated using the following formula:

[0034]

[0035] in:

[0036] K——permeability of the tight gas reservoir, unit: mD;

[0037] ——Total porosity of the tight gas reservoir, unit: %;

[0038] S wirr ——the irreducible water saturation of the tight gas reservoir, dimensionless;

[0039] kc——empirical coefficient.

[0040] In one implementation of the embodiment of the present disclosure, the logging data includes a neutron curve and a density curve, and the neutron-density envelope area of ​​each of the multiple tight gas reservoirs is determined based on the logging data of the gas well, including: representing the neutron curve and the density curve in the same coordinate system, the horizontal axis of the coordinate system is the depth, and the vertical axis of the coordinate system is the value corresponding to the neutron and the value corresponding to the density; obtaining the area of ​​the figure formed by the first part of the density curve corresponding to each tight gas reservoir in the coordinate system and the neutron curve, the first part being the curve composed of the part in the coordinate system where, at the same depth, the density value is greater than or equal to the neutron value.

[0041] In one implementation of the embodiment of the present disclosure, the following formula is used to calculate the area wrapped by the first part of the density curve and the neutron curve:

[0042]

[0043] in:

[0044] S N-D ——The neutron-density package area, unit: m 2 ;

[0045] Z(x)——the function corresponding to the density curve;

[0046] N(x)——the function corresponding to the neutron curve;

[0047] x——depth, unit: m;

[0048] Z(x)≥N(x).

[0049] In an implementation of the embodiment of the present disclosure, the gas wells include interconnected vertical wells and horizontal wells, and based on the permeability of each of the tight gas reservoirs and the neutron-density envelope area of ​​each of the tight gas reservoirs, the productivity index of each of the tight gas reservoirs is determined, including:

[0050] When the tight gas reservoir belongs to the vertical well, the productivity index of the vertical well in the tight gas reservoir is determined by the following formula:

[0051] M=S N-D ×K;

[0052] When the tight gas reservoir belongs to the horizontal well, the productivity index of the tight gas reservoir is determined by the following formula:

[0053] M=S N-D ;

[0054] in,

[0055] K——permeability of the tight gas reservoir, unit: mD;

[0056] M——the productivity index of the tight gas reservoir;

[0057] S N-D ——Neutron-density envelope area, unit: m 2 .

[0058] In one implementation of the embodiment of the present disclosure, obtaining the unobstructed flow rate of each of the tight gas reservoirs includes: sampling each of the tight gas reservoirs to obtain a plurality of experimental samples; determining the unobstructed flow rate of each of the plurality of experimental samples, the unobstructed flow rate of the experimental sample being the unobstructed flow rate of the tight gas reservoir to which it belongs.

[0059] In an implementation of the embodiment of the present disclosure, the method further includes: determining the gas production efficiency of the tight gas reservoir to be tested based on the unobstructed flow rate of the tight gas reservoir to be tested and the depth of the tight gas reservoir to be tested, and the gas production efficiency indicates the production capacity of the tight gas reservoir to be tested.

[0060] On the other hand, an embodiment of the present disclosure provides a device for determining the production capacity of a tight gas reservoir, which is applied to a gas well, wherein the gas well includes a plurality of tight gas reservoirs. The device includes: a first determination module, configured to determine the permeability of each of the plurality of tight gas reservoirs based on the well logging data of the gas well; a second determination module, configured to determine the neutron-density envelope area of ​​each of the plurality of tight gas reservoirs based on the well logging data of the gas well, wherein the neutron-density envelope area is an integral of a difference between the density of the tight gas reservoir and the neutrons of the tight gas reservoir and the depth of the tight gas reservoir, and the density of the tight gas reservoir and the neutron density of the tight gas reservoir are respectively The neutron refers to the part of the density curve and the neutron curve in the same coordinate system where the density value is greater than the neutron value; the third determination module is configured to determine the production capacity index of each tight gas reservoir based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir; the acquisition module is configured to acquire the open-flow rate of each tight gas reservoir; the fourth determination module is configured to determine the relationship between the open-flow rate and the production capacity index based on the production capacity index and the open-flow rate of each tight gas reservoir; the fifth determination module is configured to determine the production capacity of the tight gas reservoir to be tested based on the production capacity index of the tight gas reservoir to be tested and the relationship.

[0061] In one implementation of the embodiment of the present disclosure, the first determination module is configured to: determine the mud content of each tight gas reservoir based on the logging data; determine the effective porosity of each tight gas reservoir based on the mud content of each tight gas reservoir; determine the permeability of each of the multiple tight gas reservoirs based on the effective porosity of each tight gas reservoir.

[0062] The beneficial effects brought by the technical solution provided by the embodiments of the present disclosure include at least:

[0063] In the disclosed embodiment, the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir are first determined based on the well logging data of the gas well; then the productivity index of each tight gas reservoir is determined based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir; then the unimpeded flow of each tight gas reservoir is obtained; then the relationship between the unimpeded flow and the productivity index is determined based on the productivity index of each tight gas reservoir and the unimpeded flow of each tight gas reservoir; then the productivity of the tight gas reservoir to be tested is determined based on the productivity index and the relationship of the tight gas reservoir to be tested. Since the data used in the disclosed embodiment are all obtained from well logging data, so that the data can characterize the characteristics of the tight gas reservoir to which it belongs, then the productivity obtained by these data can characterize the productivity of the tight gas reservoir to which it belongs, and the productivity of the tight gas reservoir to be tested is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0065] Figure 1 is a flow chart of a method for determining the productivity of a tight gas reservoir provided by an embodiment of the present disclosure;

[0066] Figure 2 is a flow chart of a method for determining the productivity of a tight gas reservoir provided by an embodiment of the present disclosure;

[0067] Figure 3 is a neutron-density curve graph provided by an embodiment of the present disclosure;

[0068] Figure 4 It is an unobstructed flow-depth intersection chart provided by the embodiment of the present disclosure;

[0069] Figure 5 A neutron-density porosity difference and longitudinal-transverse wave velocity ratio establishment chart provided by an embodiment of the present disclosure;

[0070] Figure 6 is a relationship diagram between a productivity index and an open flow rate of a vertical well provided by an embodiment of the present disclosure;

[0071] Figure 7 is a relationship diagram between a productivity index and an open flow rate of a horizontal well provided by an embodiment of the present disclosure;

[0072] Figure 8 It is a block diagram of a device for determining the productivity of a tight gas reservoir provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0073] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0074] Figure 1 is a flow chart of a method for determining the productivity of a tight gas reservoir provided by an embodiment of the present disclosure. The method is applied to a gas well, which includes multiple tight gas reservoirs. Figure 1 , the method comprising:

[0075] In step S101, the permeability of each of a plurality of tight gas reservoirs is determined based on well logging data of the gas well.

[0076] Before gas well exploitation, in order to better understand the characteristics of underground tight gas reservoirs, well logging will be carried out to obtain logging data, and then the permeability of each tight gas reservoir will be determined from the logging data.

[0077] Exemplarily, the logging data include density curves, neutron curves, natural gamma curves, P-wave time difference curves, irreducible water saturation curves, and the like.

[0078] In step S102, based on the well logging data of the gas well, the neutron-density envelope area of ​​each of the plurality of tight gas reservoirs is determined.

[0079] In the embodiment of the present disclosure, the neutron-density envelope area is the integral of the difference between the density of the tight gas reservoir and the neutrons of the tight gas reservoir and the depth of the tight gas reservoir. The density of the tight gas reservoir and the neutrons of the tight gas reservoir refer to the parts of the density curve and the neutron curve in the same coordinate system where the density value is greater than the neutron value.

[0080] Among them, the horizontal axis of the density curve is depth, and the vertical axis is density; the horizontal axis of the neutron curve is depth, and the vertical axis is the number of neutrons.

[0081] Exemplarily, the density curve and the neutron curve are displayed in the same coordinate system. There is a portion of the density curve and the neutron curve where the density is greater than the number of neutrons. The portion where the density is greater than the number of neutrons is integrated to obtain the neutron-density envelope area. The neutron-density envelope area is the area of ​​the graph formed by the first portion of the density curve and the neutron curve. The first portion is the curve composed of the portion where the density value is greater than or equal to the neutron value at the same depth in the coordinate system.

[0082] In step S103, the productivity index of each tight gas reservoir is determined based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir.

[0083] In the embodiment of the present disclosure, the productivity index is used to indicate the gas content in the tight gas reservoir.

[0084] In step S104, the unimpeded flow rate of each tight gas reservoir is obtained.

[0085] In step S105, based on the productivity index and open flow rate of each tight gas reservoir, a relationship between the open flow rate and the productivity index is determined.

[0086] In step S106, the productivity of the tight gas reservoir to be tested is determined based on the productivity index of the tight gas reservoir to be tested and the relationship.

[0087] In the disclosed embodiment, the maximum theoretical production of a gas well or oil well is also called open flow rate, which is an important indicator to characterize the potential production capacity of a well. The relationship between open flow rate and production capacity index is determined by the production capacity index and open flow rate of each tight gas reservoir. Then, the production capacity of the tight gas reservoir to be tested is determined according to the production capacity index of the tight gas reservoir to be tested.

[0088] In the disclosed embodiment, the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir are first determined based on the well logging data of the gas well; then the productivity index of each tight gas reservoir is determined based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir; then the unimpeded flow of each tight gas reservoir is obtained; then the relationship between the unimpeded flow and the productivity index is determined based on the productivity index of each tight gas reservoir and the unimpeded flow of each tight gas reservoir; then the productivity of the tight gas reservoir to be tested is determined based on the productivity index and the relationship of the tight gas reservoir to be tested. Since the data used in the disclosed embodiment are all obtained from well logging data, so that the data can characterize the characteristics of the tight gas reservoir to which it belongs, then the productivity obtained by these data can characterize the productivity of the tight gas reservoir to which it belongs, and the productivity of the tight gas reservoir to be tested is more accurate.

[0089] Figure 2is a flow chart of a method for determining the productivity of a tight gas reservoir provided by an embodiment of the present disclosure. Figure 2 , the method comprising:

[0090] In step 201, the shale content of each tight gas reservoir is determined based on well logging data.

[0091] In the embodiment of the present disclosure, the logging data includes a natural gamma curve, and the shale content of each tight gas reservoir can be calculated using the following formula (1) and formula (2):

[0092]

[0093]

[0094] in:

[0095] V sh ——Sha content of tight gas reservoir, unit: %;

[0096] I GR ——Relative value of natural gamma of tight gas reservoir, dimensionless;

[0097] GR log ——Natural gamma reading of tight gas reservoir, unit: API;

[0098] GR matrix ——The average natural gamma response of pure sandstone formations in tight gas reservoirs, unit: API;

[0099] GRshale - the average natural gamma response of pure mudstone formations in tight gas reservoirs, unit: API.

[0100] In the embodiment of the present disclosure, the natural gamma curve will display the natural gamma value of the tight gas reservoir, and the average value of the natural gamma value in the tight gas reservoir can be selected as the natural gamma reading GR of the tight gas reservoir. log .

[0101] In the embodiment of the present disclosure, the pure sandstone formation and the pure mudstone formation in the tight gas reservoir can be judged according to the trend of the natural gamma curve. In the natural gamma curve of the tight gas reservoir, the part with obviously lower natural gamma value is the pure sandstone formation, and the part with obviously higher natural gamma value is the pure mudstone formation. The position of the pure sandstone formation is determined according to the natural gamma curve, and then the average value of the natural gamma value of the pure sandstone formation in the tight gas reservoir is used as the average response GR of the natural gamma of the pure sandstone formation in the tight gas reservoir. matrix ; The location of the pure mudstone formation is determined according to the natural gamma curve, and the average value of the natural gamma of the pure mudstone formation in the tight gas reservoir is taken as the average response GR of the natural gamma of the pure mudstone formation in the tight gas reservoir shale.

[0102] In the embodiment of the present disclosure, the relative value of natural gamma of the tight gas reservoir is used as an intermediate quantity.

[0103] In the embodiment of the present disclosure, the above formula (1) and formula (2) are collectively referred to as the Larionov formula.

[0104] In step 202, the effective porosity of each tight gas reservoir is determined based on the shale content of each tight gas reservoir.

[0105] In the embodiment of the present disclosure, the logging data includes a P-wave time difference curve, and the effective porosity of each tight gas reservoir can be obtained by using the following formula (3), formula (4) and formula (5):

[0106]

[0107] Δt cc =Δt-V sh ×(Δt sh -Δt ma ) (4)

[0108]

[0109] in:

[0110] ——Effective porosity of tight gas reservoir, unit: %;

[0111] C——intermediate value, dimensionless;

[0112] Δt ma ——P-wave time difference of sandstone skeleton in tight gas reservoir, unit: μs / ft;

[0113] Δt f ——P-wave time difference of pore fluid in tight gas reservoir, unit: μs / ft;

[0114] Δt——P-wave time difference of tight gas reservoir, unit: μs / ft;

[0115] Δt cc ——Correction value of the P-wave time difference of tight gas reservoir, unit: μs / ft;

[0116] Δt sh ——P-wave time difference of mudstone in tight gas reservoirs, unit: μs / ft.

[0117] In the disclosed embodiment, the P-wave time difference value of the tight gas reservoir can be obtained from the P-wave time difference curve, and the average value of the P-wave time difference values ​​in the tight gas reservoir can be selected as the P-wave time difference Δt of the tight gas reservoir.

[0118] In the embodiment of the present disclosure, the longitudinal wave time difference Δt of the sandstone skeleton in the tight gas reservoir can be directly obtained from the longitudinal wave time difference curve. ma , the P-wave time difference Δt of pore fluid in tight gas reservoir f The P-wave time difference Δt between the mudstone and the tight gas reservoir sh .

[0119] In the embodiment of the present disclosure, the correction value Δt of the P-wave time difference of the tight gas reservoir cc As an intermediate amount.

[0120] In the embodiments of the present disclosure, the above formula (3), formula (4) and formula (5) are collectively referred to as the Raymer Hunt formula.

[0121] In step 203, the permeability of each of the plurality of tight gas reservoirs is determined based on the effective porosity of each tight gas reservoir.

[0122] In the embodiment of the present disclosure, the well logging data includes irreducible water saturation curves, and the permeability of each tight gas reservoir can be calculated using the following formula (6):

[0123]

[0124] in:

[0125] K——permeability of tight gas reservoir, unit: mD;

[0126] ——Total porosity of tight gas reservoir, unit: %;

[0127] ——Effective porosity of tight gas reservoir, unit: %;

[0128] S wirr ——Immobile water saturation of tight gas reservoir, dimensionless;

[0129] kc——empirical coefficient.

[0130] In the embodiment of the present disclosure, the irreducible water saturation S of the tight gas reservoir can be directly obtained from the irreducible water saturation curve. wirr .

[0131] In the embodiment of the present disclosure, the logging data also includes the total porosity of the tight gas reservoir. During the logging process, the total porosity of the tight gas reservoir is also measured to obtain the total porosity of the tight gas reservoir. It can be directly obtained from the logging data. The value of the empirical coefficient kc is between 0.7 and 0.9.

[0132] In step 204, the neutron curve and the density curve are represented in the same coordinate system, where the abscissa of the coordinate system is the depth, and the ordinate of the coordinate system is the value corresponding to the neutron and the value corresponding to the density.

[0133] In the disclosed embodiment, the depth of a point in a gas well represents the path from the horizontal plane to the point along the trajectory of the gas well.

[0134] In step 205, the area of ​​the figure formed by the first part of the density curve corresponding to each tight gas reservoir in the coordinate system and the neutron curve is calculated, and the first part is the curve composed of the part where the density value is greater than or equal to the neutron value at the same depth in the coordinate system.

[0135] The area of ​​the first part of the density curve and the neutron curve is obtained by using the following formula (7):

[0136]

[0137] in:

[0138] S N-D ——Neutron-density package area, unit: m 2 ;

[0139] Z(x)——the function corresponding to the density curve;

[0140] N(x)——Function corresponding to the neutron curve;

[0141] x——depth, unit: m;

[0142] Z(x)≥N(x).

[0143] In the disclosed embodiment, the logging data includes a neutron curve and a density curve. The gas content of the tight gas reservoir is related to the neutrons of the tight gas reservoir and the density of the tight gas reservoir. The greater the density of the tight gas reservoir, the smaller the neutrons, and the greater the gas content of the tight gas reservoir. In other words, the greater the neutron-density envelope area of ​​the tight gas reservoir, the greater the gas content of the tight gas reservoir. The gas content of the tight gas reservoir is related to the production capacity of the tight gas reservoir, so the neutron-density envelope area can be used to characterize the production capacity of the tight gas reservoir.

[0144] Figure 3 is a neutron-density curve provided by an embodiment of the present disclosure. Figure 3 The horizontal axis x represents the depth in meters; the vertical axis represents the value, where the density is expressed in g / cm 3The corresponding value when , the neutron represents the corresponding value when the unit is v / v. Z(x) is the function corresponding to the density curve, N(x) is the function corresponding to the neutron curve, x1, x2, x3 and x4 are the intersection points of the two curves, between x1 and x2 and between x3 and x4, Z(x) ≥ N(x). Corresponding Figure 3 The neutron-density curve shown in Figure 1 shows that the neutron-density enveloping area is equal to the area of ​​A plus the area of ​​B. Figure 3 It is explained only as an example and only parts are shown.

[0145] In step 206, when the tight gas reservoir belongs to a vertical well, the productivity index of the tight gas reservoir is determined using the following formula (8):

[0146] M=S N-D ×K (8)

[0147] in,

[0148] K——permeability of tight gas reservoir, unit: mD;

[0149] M – productivity index of tight gas reservoir;

[0150] S N-D ——Neutron-density envelope area, unit: m 2 .

[0151] In the disclosed embodiment, the gas wells include interconnected vertical wells and horizontal wells. The calculation method of the production capacity coefficient of the tight gas reservoir is different depending on the wells to which the tight gas reservoir belongs. The permeability of the vertical well has a great influence on the unimpeded flow of a single tight gas reservoir. Therefore, when the tight gas reservoir belongs to a vertical well, the neutron-density envelope area needs to be multiplied by the permeability.

[0152] In step 207, when the tight gas reservoir belongs to a horizontal well, the productivity index of the tight gas reservoir is determined using the following formula (9):

[0153] M=S N-D (9)

[0154] In the disclosed embodiment, after the horizontal wells have undergone large-scale volume fracturing transformation to roughly the same degree, the permeability difference between them is not large, so the open flow rate of the tight gas reservoir is not sensitive to the permeability, and the neutron-density envelope area is directly used to represent the production capacity index.

[0155] In step 208, sampling is performed on each tight gas reservoir to obtain a plurality of experimental samples.

[0156] In step 209, the open-flow rate of each experimental sample among the multiple experimental samples is determined, and the open-flow rate of the experimental sample is the open-flow rate of the tight gas reservoir to which it belongs.

[0157] In the disclosed embodiment, each tight gas reservoir is sampled, and the open-flow rate of each experimental sample is obtained through a gas test, and the open-flow rate of the experimental sample is used to represent the open-flow rate of the tight gas reservoir to which it belongs.

[0158] Exemplarily, multiple experimental samples are taken for each tight gas reservoir, and the multiple experimental samples are evenly distributed in the tight gas reservoir. Then, multiple open-flow rates corresponding to the multiple experimental samples are calculated, and then the average value of the multiple open-flow rates is calculated as the open-flow rate of the tight gas reservoir.

[0159] In step 210, based on the productivity index and the open flow rate of each tight gas reservoir, a relationship between the open flow rate and the productivity index is determined.

[0160] In the above process of obtaining the open-flow rate of the tight gas reservoir, there may be errors, so that the open-flow rate of the experimental sample cannot represent the open-flow rate of the tight gas reservoir to which it belongs. In the embodiment of the present disclosure, for multiple production capacity indices and multiple open-flow rates, a relationship between the open-flow rate and the production capacity index is obtained, and the influence of the errors can be eliminated in the process of obtaining the relationship, so that the subsequent production capacity of the tight gas reservoir to be measured is more accurate.

[0161] For example, a plurality of capacity indexes and a plurality of corresponding unimpeded flows may be input into software such as Excel or Mathtype to fit a relationship between the unimpeded flow and the capacity index.

[0162] In step 211, the productivity of the tight gas reservoir to be tested is determined based on the productivity index and the relationship of the tight gas reservoir to be tested.

[0163] In the embodiment of the present disclosure, after the production capacity index of the tight gas reservoir to be measured is calculated, the production capacity index of the tight gas reservoir to be measured is substituted into the relationship between the unobstructed flow rate and the production capacity index to determine the unobstructed flow rate of the tight gas reservoir to be measured, and the unobstructed flow rate can be calculated. The unobstructed flow rate is the production capacity of the tight gas reservoir to be measured.

[0164] In the embodiment of the present disclosure, the method may further include: roughly classifying the gas production efficiency of the tight gas reservoir based on the unimpeded flow rate of the tight gas reservoir and the thickness of the tight gas reservoir.

[0165] In the disclosed embodiment, the classification method includes: determining the gas production efficiency of the tight gas reservoir to be tested based on the unimpeded flow rate and the depth of the tight gas reservoir to be tested, and the gas production efficiency indicates the production capacity of the tight gas reservoir to be tested.

[0166] For example, a double logarithmic coordinate open flow-depth intersection chart is drawn. In the open flow-depth intersection chart, the horizontal axis represents the depth, unit: m, and the vertical axis represents the open flow, unit: 1000m 3 / d. According to the distribution of the midpoints of the unobstructed flow-depth intersection chart, a trend line is drawn in the unobstructed flow-depth intersection chart. The gas layers above the trend line are of Class I with higher gas production efficiency, and the gas layers below the trend line are of Class II with lower gas production efficiency.

[0167] The gas production efficiency classification method provided in the embodiment of the present disclosure can be used for vertical wells and can also be used for the classification of horizontal wells. The following is an explanation in conjunction with experiments.

[0168] For an experimental well, after determining the open flow rate of the tight gas reservoir, a double logarithmic coordinate open flow rate-depth intersection chart was drawn. Figure 4 This is an unobstructed flow-depth intersection diagram provided by the embodiment of the present disclosure. Figure 4 , the open flow rates of tight gas reservoirs are marked with dots and triangles in the figure. It can be seen that although the open flow rates of the horizontal well (upper right) and the vertical well (lower left) test gas sections are not in the same order of magnitude, the two are comparable in terms of gas production efficiency, that is, the open flow rate per meter. Using the parameter of open flow rate per meter, the reservoirs of the horizontal well section and the vertical well section can be uniformly graded and evaluated. According to the overall fitting trend, the reservoir types are simply divided into two levels: relatively high-yield (Class I gas layer) and relatively low-yield (Class II gas layer). The gas layers above the trend line in the figure are Class I gas layers with higher gas production efficiency, and the gas layers below the trend line are Class II gas layers with lower gas production efficiency. In this example, the open flow rate per meter corresponding to this classification standard is about 450m 3 / d, converted into the usual unobstructed flow unit, it is: the daily production of a vertical well per 10 meters is 0.45×10 4 m 3 The above are high-yield wells, with a daily production of 45×10 4 m 3 The above are high-yield wells. For different blocks, this value will be different. In this way, vertical wells and horizontal well sections have a unified evaluation standard.

[0169] In order to verify this inference, a chart was established by using the neutron-density porosity difference and the longitudinal-transverse wave velocity ratio to determine the gas production efficiency of the tight gas reservoir. Figure 5 This is a neutron-density porosity difference and longitudinal-transverse wave velocity ratio established in an embodiment of the present disclosure. Figure 5 , it is possible to clearly distinguish between type I and type II gas layers. In this example, the gas layers that simultaneously meet the requirements of neutron-density porosity difference ≥ 10.7% and longitudinal-transverse wave velocity ratio ≤ 1.74 are all type I, and the other gas layers are almost all type II. Figure 4 and Figure 5 , Figure 4 The CCP has 17 locations. Figure 5 There are 16 points in total. Figure 4 There is only one point that is consistent with Figure 4 There is no inconsistency, so the agreement rate between the two plates is 94.4%.

[0170] The gas production efficiency classification method provided in the embodiment of the present disclosure has a high accuracy rate, takes into account the differences between vertical wells and horizontal wells in petroleum geology and engineering construction, and combines the gas test results to select conventional logging parameters with strong popularity and high sensitivity to identify the production capacity level of the gas layer, and establish a unified distinction standard for vertical wells and horizontal wells.

[0171] The method for determining the production capacity of a tight gas reservoir disclosed in the present invention is explained below with reference to an embodiment.

[0172] The natural gamma value of the horizontal section of a well is 56.5API. The shale content calculated by Larionov formula is 11%, and the acoustic time difference logging value is 73.3us / ft. The effective porosity is further calculated by Raymer Hunt formula to be 13.3%, and the permeability is further calculated to be 17.039mD. According to neutron density logging, the neutron-density porosity difference is 19%, and according to array acoustic logging, the longitudinal / short wave velocity ratio is 1.682, which is located in the Class II gas layer area in the plate.

[0173] Then the formula for the productivity index and unimpeded flow rate of the vertical well is obtained as formula (10):

[0174] log(GFR)=0.699lgM+0.301 (10)

[0175] in,

[0176] GFR——unimpeded flow rate of tight gas reservoir, unit: 1000m 3 / d;

[0177] M – productivity index of tight gas reservoir.

[0178] Figure 6 is a relationship diagram between the productivity index and the open flow rate of a vertical well provided by an embodiment of the present disclosure. Figure 6 The corrected coefficient of determination for the fit is R 2 =0.971, indicating that formula (10) matches the original data well.

[0179] The formula for the productivity index and open flow rate of a horizontal well is formula (11):

[0180] GFR=0.203M-107.355 (11)

[0181] Figure 7 is a relationship diagram between the productivity index and the open flow rate of a horizontal well provided by an embodiment of the present disclosure. Figure 7 The corrected coefficient of determination for the fit is R 2=0.903, indicating that formula (11) matches the original data well.

[0182] After integrating the neutron-density, the neutron density envelope area is obtained to be 1354.593. This tight gas reservoir belongs to a horizontal well. Substituting the neutron density envelope area into formula (11), the predicted unimpeded flow is obtained to be 81,900 cubic meters per day, and the predicted flow per meter is 177.31 cubic meters per day, which is interpreted as a Class II gas layer.

[0183] At the same time, after testing, the horizontal section of the well obtained an open flow rate of 89,700 cubic meters per day. After conversion, the open flow rate per meter is 194.16 cubic meters per day, which belongs to Class II gas formation and is consistent with the predicted production capacity level. The absolute error of the predicted total open flow rate is 7,800 cubic meters per day, and the relative error is 8.68%, which is small, indicating that this method is reliable.

[0184] The embodiment of the present disclosure provides a device for determining the productivity of a tight gas reservoir, which is applied to a gas well. The gas well includes a plurality of tight gas reservoirs. Figure 8 is a block diagram of a device for determining the productivity of a tight gas reservoir provided by an embodiment of the present disclosure. Figure 8 The device for determining the productivity of a tight gas reservoir includes: a first determination module 301 , a second determination module 302 , a third determination module 303 , an acquisition module 304 , a fourth determination module 305 and a fifth determination module 306 .

[0185] The first determination module 301 is configured to determine the permeability of each of the plurality of tight gas reservoirs based on the well logging data of the gas well.

[0186] The second determination module 302 is configured to determine the neutron-density envelope area of ​​each of the multiple tight gas reservoirs based on the logging data of the gas well, where the neutron-density envelope area is the integral of the difference between the density of the tight gas reservoir and the neutron of the tight gas reservoir and the depth of the tight gas reservoir, and the density of the tight gas reservoir and the neutron of the tight gas reservoir refer to the part of the density curve and the neutron curve in the same coordinate system where the density value is greater than the neutron value.

[0187] The third determination module 303 determines the productivity index of each tight gas reservoir based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir.

[0188] The acquisition module 304 is configured to acquire the unimpeded flow of each tight gas reservoir.

[0189] The fourth determination module 305 is configured to determine a relationship between the open flow rate and the productivity index based on the productivity index and the open flow rate of each tight gas reservoir.

[0190] The fifth determination module 306 is configured to determine the productivity of the tight gas reservoir to be tested based on the productivity index of the tight gas reservoir to be tested and the relationship.

[0191] In the embodiment of the present disclosure, the first determination module 301 is configured to: determine the mud content of each tight gas reservoir based on well logging data; determine the effective porosity of each tight gas reservoir based on the mud content of each tight gas reservoir; determine the permeability of each tight gas reservoir in multiple tight gas reservoirs based on the effective porosity of each tight gas reservoir.

[0192] In the embodiment of the present disclosure, the logging data includes a natural gamma curve, a P-wave time difference curve, and an irreducible water saturation curve.

[0193] The first determination module 301 is configured to calculate the shale content of each tight gas reservoir using the following formula:

[0194]

[0195]

[0196] in:

[0197] V sh ——Sha content of tight gas reservoir, unit: %;

[0198] I GR ——Relative value of natural gamma of tight gas reservoir, dimensionless;

[0199] GR log ——Natural gamma reading of tight gas reservoir, unit: API;

[0200] GR matrix ——The average natural gamma response of pure sandstone formations in tight gas reservoirs, unit: API;

[0201] GR shale ——The average natural gamma response of pure mudstone formations in tight gas reservoirs, unit: API;

[0202] The first determination module 301 is configured to: use the following formula to calculate the effective porosity of each tight gas reservoir:

[0203]

[0204] Δt cc =Δt-V sh ×(Δt sh -Δt ma );

[0205]

[0206] in:

[0207] ——Effective porosity of tight gas reservoir, unit: %;

[0208] C - intermediate value, dimensionless;

[0209] Δt ma ——P-wave time difference of sandstone skeleton in tight gas reservoir, unit: μs / ft;

[0210] Δt f ——P-wave time difference of pore fluid in tight gas reservoir, unit: μs / ft;

[0211] Δt——P-wave time difference of tight gas reservoir, unit: μs / ft;

[0212] Δt cc ——Correction value of the P-wave time difference of tight gas reservoir, unit: μs / ft;

[0213] Δt sh ——P-wave time difference of mudstone in tight gas reservoir, unit: μs / ft;

[0214] The first determination module 301 is configured to: calculate the permeability of each tight gas reservoir using the following formula:

[0215]

[0216] in:

[0217] K——permeability of tight gas reservoir, unit: mD;

[0218] ——Total porosity of tight gas reservoir, unit: %;

[0219] S wirr ——Immobile water saturation of tight gas reservoir, dimensionless;

[0220] kc——empirical coefficient.

[0221] In the disclosed embodiment, the logging data includes a neutron curve and a density curve, and the second determination module 302 is configured to: represent the neutron curve and the density curve in the same coordinate system, where the horizontal axis of the coordinate system is the depth, and the vertical axis of the coordinate system is the value corresponding to the neutron and the value corresponding to the density; calculate the area of ​​the figure formed by the first part of the density curve corresponding to each tight gas reservoir in the coordinate system and the neutron curve, the first part being the curve composed of the part where the density value is greater than or equal to the neutron value at the same depth in the coordinate system.

[0222] The second determination module 302 is configured to use the following formula to obtain the enveloping area of ​​the first part of the density curve and the neutron curve:

[0223]

[0224] in:

[0225] S N-D ——Neutron-density parcel area, unit: m2;

[0226] Z(x)——the function corresponding to the density curve;

[0227] N(x)——Function corresponding to the neutron curve;

[0228] x——depth, unit: m;

[0229] Z(x)≥N(x).

[0230] In the embodiment of the present disclosure, the gas well includes a vertical well and a horizontal well that are interconnected. The third determination module 303 is configured to determine the productivity index of the vertical well of the tight gas reservoir using the following formula when the tight gas reservoir belongs to the vertical well:

[0231] M=S N-D ×K;

[0232] When the tight gas reservoir belongs to a horizontal well, the following formula is used to determine the productivity index of the tight gas reservoir:

[0233] M=S N-D ;

[0234] in,

[0235] K——permeability of tight gas reservoir, unit: mD;

[0236] M – productivity index of tight gas reservoir;

[0237] S N-D ——Neutron-density envelope area, unit: m 2 .

[0238] The acquisition module 304 is configured to: sample each tight gas reservoir to obtain multiple experimental samples; determine the open flow rate of each experimental sample in the multiple experimental samples, the open flow rate of the experimental sample being the open flow rate of the tight gas reservoir to which it belongs.

[0239] In the embodiment of the present disclosure, the device for determining the production capacity of the tight gas reservoir also includes: a sixth determination module 307, which is configured to determine the gas production efficiency of the tight gas reservoir to be measured based on the unobstructed flow rate of the tight gas reservoir to be measured and the depth of the tight gas reservoir to be measured, and the gas production efficiency indicates the production capacity of the tight gas reservoir to be measured.

[0240] The above description is only an optional embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for determining the productivity of a tight gas reservoir, characterized in that: Applied to a gas well, the gas well includes a plurality of tight gas reservoirs, and the method for determining the production capacity of the tight gas reservoirs includes: Determining the permeability of each of the plurality of tight gas reservoirs based on the well logging data of the gas well; Based on the well logging data of the gas well, determine the neutron-density envelope area of ​​each of the multiple tight gas reservoirs, wherein the neutron-density envelope area is the integral of the difference between the density of the tight gas reservoir and the neutron of the tight gas reservoir with respect to the depth of the tight gas reservoir, and the density of the tight gas reservoir and the neutron of the tight gas reservoir refer to the portion of the density curve and the neutron curve in the same coordinate system where the value of the density is greater than the value of the neutron; Determining a productivity index of each tight gas reservoir based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir; Obtaining an unimpeded flow rate of each of the tight gas reservoirs; Based on the productivity index and open flow rate of each tight gas reservoir, determining a relationship between the open flow rate and the productivity index; Based on the productivity index of the tight gas reservoir to be measured and the relationship, the open flow rate of the tight gas reservoir to be measured is obtained, and the open flow rate of the tight gas reservoir to be measured is determined as the productivity of the tight gas reservoir to be measured; The logging data includes a neutron curve and a density curve. Based on the logging data of the gas well, the neutron-density envelope area of ​​each of the multiple tight gas reservoirs is determined, including: representing the neutron curve and the density curve in the same coordinate system, the abscissa of the coordinate system is the depth, and the ordinate of the coordinate system is the value corresponding to the neutron and the value corresponding to the density; obtaining the area of ​​the figure formed by the first part of the density curve corresponding to each tight gas reservoir in the coordinate system and the neutron curve, the first part being the curve composed of the part of the density value greater than or equal to the neutron value at the same depth in the coordinate system; The gas wells include interconnected vertical wells and horizontal wells. Based on the permeability of each tight gas reservoir and the neutron-density envelope area of ​​each tight gas reservoir, the productivity index of each tight gas reservoir is determined, including: When the tight gas reservoir belongs to the vertical well, the productivity index of the vertical well in the tight gas reservoir is determined by the following formula: ； When the tight gas reservoir belongs to the horizontal well, the productivity index of the tight gas reservoir is determined by the following formula: ； in, ——The permeability of the tight gas reservoir, unit: mD; ——the productivity index of the tight gas reservoir; ——Neutron-density envelope area, unit: m 2 .

2. The method for determining the productivity of a tight gas reservoir according to claim 1, characterized in that: The step of determining the permeability of each of the plurality of tight gas reservoirs based on the well logging data of the gas well comprises: Determine the shale content of each of the tight gas reservoirs based on the well logging data; Determining the effective porosity of each of the tight gas reservoirs based on the shale content of each of the tight gas reservoirs; The permeability of each of the plurality of tight gas reservoirs is determined based on the effective porosity of each of the tight gas reservoirs.

3. The method for determining the productivity of a tight gas reservoir according to claim 2, characterized in that: The logging data include natural gamma curve, P-wave time difference curve and irreducible water saturation curve; Determining the shale content of each of the tight gas reservoirs based on the well logging data includes: The following formula is used to calculate the shale content of each tight gas reservoir: ； ； in: ——The mud content of the tight gas reservoir, unit: %; ——relative value of natural gamma of the tight gas reservoir, dimensionless; ——Natural gamma reading of the tight gas reservoir, unit: API; ——the average natural gamma response of the pure sandstone formation in the tight gas reservoir, unit: API; ——the average natural gamma response of the pure mudstone formation in the tight gas reservoir, unit: API; Determining the effective porosity of each of the tight gas reservoirs based on the shale content of each of the tight gas reservoirs comprises: The effective porosity of each tight gas reservoir is calculated using the following formula: ； ； ； in: ——The effective porosity of the tight gas reservoir, unit: %; C——intermediate value, dimensionless; ——the longitudinal wave time difference of the sandstone skeleton in the tight gas reservoir, in μs / ft; ——the longitudinal wave time difference of the pore fluid in the tight gas reservoir, in μs / ft; ——the longitudinal wave time difference of the tight gas reservoir, in μs / ft; ——Correction value of the longitudinal wave time difference of the tight gas reservoir, in μs / ft; ——the longitudinal wave time difference of the mudstone in the tight gas reservoir, in μs / ft; Determining the permeability of each of the plurality of tight gas reservoirs based on the effective porosity of each of the tight gas reservoirs comprises: The permeability of each tight gas reservoir is calculated using the following formula: ； in: ——The permeability of the tight gas reservoir, unit: mD; ——Total porosity of the tight gas reservoir, unit: %; ——the irreducible water saturation of the tight gas reservoir, dimensionless; ——Experience coefficient.

4. The method for determining the productivity of a tight gas reservoir according to claim 1, characterized in that: The enveloping area of ​​the first part of the density curve and the neutron curve is calculated using the following formula: ； in: ——The neutron-density package area, unit: m 2 ; ——the function corresponding to the density curve; ——the function corresponding to the neutron curve; ——Depth, unit: m; ≥ 。 5. The method for determining the productivity of a tight gas reservoir according to any one of claims 1 to 3, characterized in that: Obtaining the unimpeded flow rate of each of the tight gas reservoirs, including: Sampling each of the tight gas reservoirs to obtain a plurality of experimental samples; The open-flow rate of each experimental sample among the multiple experimental samples is determined, and the open-flow rate of the experimental sample is the open-flow rate of the tight gas reservoir to which it belongs.

6. The method for determining the productivity of a tight gas reservoir according to any one of claims 1 to 3, characterized in that: The method further comprises: Based on the unimpeded flow of the tight gas reservoir to be measured and the depth of the tight gas reservoir to be measured, the gas production efficiency of the tight gas reservoir to be measured is determined, and the gas production efficiency indicates the production capacity of the tight gas reservoir to be measured.

7. A device for determining the productivity of a tight gas reservoir, characterized in that: Applied to a gas well, the gas well includes a plurality of tight gas reservoirs, the determination device is applicable to the determination method according to claim 1, and the determination device includes: A first determination module is configured to determine the permeability of each of the plurality of tight gas reservoirs based on the well logging data of the gas well; A second determination module is configured to determine the neutron-density envelope area of ​​each of the plurality of tight gas reservoirs based on the well logging data of the gas well, wherein the neutron-density envelope area is the integral of the difference between the density of the tight gas reservoir and the neutron of the tight gas reservoir with respect to the depth of the tight gas reservoir, and the density of the tight gas reservoir and the neutron of the tight gas reservoir refer to the portion of the density curve and the neutron curve in the same coordinate system where the value of the density is greater than the value of the neutron; A third determination module is configured to determine a productivity index of each of the tight gas reservoirs based on the permeability of each of the tight gas reservoirs and the neutron-density envelope area of ​​each of the tight gas reservoirs; An acquisition module is configured to acquire the unimpeded flow of each of the tight gas reservoirs; A fourth determination module is configured to determine a relationship between the open flow rate and the productivity index based on the productivity index and the open flow rate of each tight gas reservoir; The fifth determination module is configured to determine the productivity of the tight gas reservoir to be tested based on the productivity index of the tight gas reservoir to be tested and the relationship.

8. The device for determining the productivity of a tight gas reservoir according to claim 7, characterized in that: The first determination module is configured to: Determine the shale content of each of the tight gas reservoirs based on the well logging data; Determining the effective porosity of each of the tight gas reservoirs based on the shale content of each of the tight gas reservoirs; The permeability of each of the plurality of tight gas reservoirs is determined based on the effective porosity of each of the tight gas reservoirs.

Images