Method and system for determining bound water saturation of a tight reservoir

Abstract

This invention provides a method and system for determining the bound water saturation of tight reservoirs, belonging to the field of well logging technology. The method includes: constructing a bound water saturation model under the same centrifugal force based on multiple characteristic parameters of multiple first core samples taken from the target oil and gas reservoir under the same centrifugal force; constructing a bound water saturation model under multiple centrifugal forces based on multiple characteristic parameters of each second core sample taken from the target oil and gas reservoir under each of multiple centrifugal forces; obtaining multiple fitting coefficients for the bound water saturation model under each of the multiple centrifugal forces; determining a bound water saturation correction coefficient based on the multiple fitting coefficients and the multiple centrifugal forces; and determining the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient. This invention can improve the accuracy of determining bound water saturation.

Description

Technical Field

[0001] This invention relates to the field of well logging technology, and more specifically to a method and system for determining the saturation of bound water in tight reservoirs. Background Technology

[0002] Bound water saturation is a crucial parameter in oil and gas reservoir evaluation, and the most widely used method in the industry is well logging. The common practice is to obtain bound water saturation data through core testing, establish a model relating bound water saturation to the permeability-to-porosity ratio (the ratio of permeability to porosity), and then calculate the bound water saturation using well logging. This method is based on medium-to-high porosity reservoirs and emphasizes the relationship between reservoir porosity / permeability and bound water saturation. However, increasing production practice has demonstrated the limitations of this traditional method, making it unsuitable for the current requirements of precise bound water saturation evaluation in tight sandstone reservoirs (which are typically characterized by low porosity and low permeability). Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for determining the bound water saturation of tight reservoirs. This method and system can partially or completely solve the problem of low accuracy in determining bound water saturation using existing methods.

[0004] To achieve the above objectives, embodiments of the present invention provide a method for determining the bound water saturation of a tight reservoir. The method includes: constructing a bound water saturation model under the same centrifugal force based on multiple characteristic parameters of multiple first core samples taken from a target oil and gas reservoir under the same centrifugal force; wherein the multiple characteristic parameters include porosity, permeability, and bound water saturation; and the bound water saturation model under the same centrifugal force is a segmented bound water saturation model, and the permeability of the multiple first core samples belongs to different permeability ranges; and determining the bound water saturation of each of the multiple second core samples taken from the target oil and gas reservoir under multiple centrifugal forces. Multiple characteristic parameters under each centrifugal force are used to construct bound water saturation models for the multiple second core samples under each centrifugal force. Multiple fitting coefficients of the bound water saturation models under each centrifugal force are obtained, wherein the permeability of the multiple second core samples belongs to different permeability ranges. Based on the multiple fitting coefficients and the multiple centrifugal forces, bound water saturation correction coefficients are determined, wherein the bound water saturation correction coefficients are parameters corresponding to the centrifugal forces. Finally, the bound water saturation of the target oil and gas reservoir is determined based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficients.

[0005] Optionally, constructing the bound water saturation model under the same centrifugal force includes: constructing the bound water saturation model under the same centrifugal force according to the following formula: Swi 静态 = f(perm / por), where Swi 静态 Perm represents the degree of bound water saturation under the same centrifugal force, and por represents the porosity.

[0006] Optionally, constructing the segmented bound water saturation model includes: constructing the segmented bound water saturation model based on the ratio of permeability to porosity and the change points of the bound water saturation fitting relationship under the same centrifugal force.

[0007] Optionally, constructing the bound water saturation model for each of the plurality of second core samples under each centrifugal force includes: constructing a bound water saturation model for each of the plurality of centrifugal forces according to the following formula: Swi j =A j (perm / por) B Among them, Swi j A represents the degree of bound water saturation under centrifugal force j. j represents the fitting coefficient of the bound water saturation model under centrifugal force j, and B represents a constant.

[0008] Optionally, determining the bound water saturation correction coefficient based on multiple fitting coefficients and the multiple centrifugal forces includes: adjusting the multiple fitting coefficients A... j The system is fitted with the plurality of centrifugal forces j to obtain the fitting coefficient A between any centrifugal force x and any centrifugal force, as shown in the following formula. x Functional relationship: A x =a*(x) b Where a and b are constants; and according to the fitting coefficient A under any centrifugal force and the fitting coefficient A under the same centrifugal force y. y The correction coefficient J for the bound water saturation is determined by the following formula: J = A x / A y Wherein, the same centrifugal force y is one of any centrifugal forces x.

[0009] Optionally, determining the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient includes: based on the bound water saturation model Swir corresponding to the same centrifugal force... 静态 The bound water saturation Swi of the target oil and gas reservoir is determined using the bound water saturation correction coefficient J and the following formula. 动态 Swi 动态 =J*Swi 静态 .

[0010] On the other hand, this invention also provides a system for determining the bound water saturation of tight reservoirs. The system includes: a first construction device for constructing a bound water saturation model under the same centrifugal force based on multiple characteristic parameters of multiple first core samples taken from a target oil and gas reservoir under the same centrifugal force, wherein the multiple characteristic parameters include porosity, permeability, and bound water saturation, and the bound water saturation model under the same centrifugal force is a segmented bound water saturation model, and the permeability of the multiple first core samples belongs to different permeability ranges; and a second construction device for determining the bound water saturation of each of the multiple second core samples taken from the target oil and gas reservoir under multiple centrifugal forces. Multiple characteristic parameters under centrifugal force are used to construct bound water saturation models for the multiple second core samples under each centrifugal force, and multiple fitting coefficients of the bound water saturation models under each centrifugal force are obtained, wherein the permeability of the multiple second core samples belongs to different permeability ranges; a first determining device is used to determine bound water saturation correction coefficients based on the multiple fitting coefficients and the multiple centrifugal forces, wherein the bound water saturation correction coefficients are parameters corresponding to the centrifugal forces; and a second determining device is used to determine the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficients.

[0011] Optionally, the first constructing device for constructing a bound water saturation model under the same centrifugal force includes: constructing the bound water saturation model under the same centrifugal force according to the following formula: Swi 静态 = f(perm / por), where Swi 静态 Perm represents the degree of bound water saturation under the same centrifugal force, and por represents the porosity.

[0012] Optionally, the second construction apparatus for constructing the bound water saturation model of the plurality of second core samples under each centrifugal force includes: constructing the bound water saturation model under each of the plurality of centrifugal forces according to the following formula: Swi j =A j (perm / por) B Among them, Swi j A represents the degree of bound water saturation under centrifugal force j. j represents the fitting coefficient of the bound water saturation model under centrifugal force j, and B represents a constant.

[0013] Optionally, the first determining module is used to determine the bound water saturation correction coefficient based on multiple fitting coefficients and the multiple centrifugal forces, including: for the multiple fitting coefficients A jThe system is fitted with the plurality of centrifugal forces j to obtain the fitting coefficient A between any centrifugal force x and any centrifugal force, as shown in the following formula. x Functional relationship: A x =a*(x) b Where a and b are constants; and according to the fitting coefficient A under any centrifugal force x The fitting coefficient A under the same centrifugal force y y The correction coefficient J for the bound water saturation is determined by the following formula: J = A x / A y Wherein, the same centrifugal force y is one of any centrifugal forces x.

[0014] Optionally, the second determining module is used to determine the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient, including: based on the bound water saturation model Swir corresponding to the same centrifugal force. 静态 The bound water saturation Swi of the target oil and gas reservoir is determined using the bound water saturation correction coefficient J and the following formula. 动态 Swi 动态 =J*Swi 静态 .

[0015] Using the above technical solution, a bound water saturation model under the same centrifugal force is constructed based on multiple characteristic parameters of multiple first core samples taken from the target oil and gas reservoir under the same centrifugal force. These multiple characteristic parameters include porosity, permeability, and bound water saturation. The bound water saturation model under the same centrifugal force is a segmented bound water saturation model, where the permeability of the multiple first core samples belongs to different permeability ranges. Based on multiple characteristic parameters of each second core sample taken from the target oil and gas reservoir under each of the multiple centrifugal forces, a bound water saturation model for each of the multiple second core samples is constructed under each centrifugal force. Multiple fitting coefficients of the bound water saturation model under each of the multiple centrifugal forces are obtained, where the permeability of the multiple second core samples belongs to different permeability ranges. A bound water saturation correction coefficient is determined based on the multiple fitting coefficients and the multiple centrifugal forces. Wherein, the bound water saturation correction coefficient is a parameter corresponding to centrifugal force; and the bound water saturation of the target oil and gas reservoir is determined according to the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient.

[0016] In constructing a bound water saturation model under the same centrifugal force, this invention obtains core samples from different permeability ranges to determine the points of change in the permeability-to-porosity ratio (the ratio of permeability to porosity). A relationship model between the permeability-to-porosity ratio and bound water saturation is then established for each range. Compared to previous methods of establishing a single bound water saturation model, this invention reflects the actual changes in the reservoir, thus improving the fitting and calculation accuracy of the bound water saturation model. Considering the high pressure sensitivity of tight reservoirs and the impact of pressure changes on bound water saturation, a correction coefficient is determined under different centrifugal forces (i.e., using centrifugal force to represent the actual well's production pressure differential in experimental conditions). This method determines the bound water saturation of the actual target layer under different production pressure differentials. Compared to the previous fixed bound water saturation, this method provides bound water saturation that varies with production pressure differentials, providing more scientific data support for the analysis of the actual dynamic oil, gas, and water production of oil and gas reservoirs.

[0017] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 This is a flowchart of a method for determining the bound water saturation of a tight reservoir according to an embodiment of the present invention;

[0020] Figure 2 These are experimental data from 42 core samples provided in this embodiment of the invention;

[0021] Figure 3 It is based on the cross-plot of the permeability ratio and bound water saturation of 42 sets of core samples;

[0022] Figure 4 This is a piecewise model of bound water saturation under the same centrifugal force fitted by an embodiment of the present invention;

[0023] Figure 5 These are the porosity and permeability experimental data of four core samples provided in this embodiment of the invention;

[0024] Figure 6 These are experimental data from four core samples under multiple centrifugal forces provided in this embodiment of the invention.

[0025] Figure 7 This is a model of bound water saturation under four centrifugal forces constructed in an embodiment of the present invention;

[0026] Figure 8 The arbitrary centrifugal force x and fitting coefficient A fitted by the embodiments of the present invention are... x Relationship diagram;

[0027] Figure 9 The results were obtained through existing methods;

[0028] Figure 10 This is the result obtained through the present invention;

[0029] Figure 11 This is a system for determining the saturation of bound water provided in an embodiment of the present invention. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0031] Figure 1 This is a flowchart of a method for determining the bound water saturation of a tight reservoir according to an embodiment of the present invention. The method for determining the bound water saturation includes the following steps S10-S13.

[0032] S10. Based on multiple characteristic parameters of multiple first core samples taken from the target oil and gas reservoir under the same centrifugal force, construct a bound water saturation model under the same centrifugal force.

[0033] The multiple characteristic parameters include porosity, permeability, and bound water saturation. The bound water saturation model for the same centrifugal force is a segmented bound water saturation model, and the permeability of the multiple first core samples belongs to different permeability ranges.

[0034] For example, the target oil and gas reservoir can be an actual well in a region under study, specifically a tight reservoir. Multiple core samples are drilled from the location of the target oil and gas reservoir, and these samples undergo physical property tests (according to SY / T 5336-2006 "Core Analysis Methods") to obtain the porosity and permeability of these core samples. From these samples, some cores with different porosities and permeabilities (the porosity and permeability of these cores should be as uniformly distributed as possible to represent the characteristics of the target oil and gas reservoir) are selected for nuclear magnetic resonance (NMR) experiments (the NMR experiments are conducted according to the procedures specified in SY / T 6490-2014 "Laboratory Measurement Specifications for Nuclear Magnetic Resonance Parameters of Rock Samples"). For example... Figure 2The present invention uses 42 core samples with different porosity and permeability. All 42 core samples are placed under the same centrifugal force y (for example, the centrifugal force y can be selected as 300 PSI or any other centrifugal force) for nuclear magnetic resonance experiments to obtain the bound water saturation of these core samples.

[0035] Based on 42 sets of porosity, permeability and bound water saturation data of the obtained core samples, a bound water saturation model under the same centrifugal force y was constructed.

[0036] Furthermore, constructing the segmented bound water saturation model includes: constructing the segmented bound water saturation model based on the ratio of permeability to porosity of multiple first core samples under the same centrifugal force and the change points of the bound water saturation fitting relationship under the same centrifugal force.

[0037] Specifically, in terms of model construction methodology, data analysis was conducted based on cross-plots of 42 sets of core permeability ratios and bound water saturation under the same centrifugal force. Figure 3 The porosity ratios of 0.1, 0.2, and 0.7 represent several turning points in the relationship between bound water saturation and porosity ratio, reflecting the complex relationship between the reservoir and bound water saturation under different porosity and permeability conditions. These turning points (…) Figure 3 A classification model for bound water saturation under the same centrifugal force is established by identifying the inflection point where the slope of the fitted line changes. Specifically, a segmented model is established according to the porosity ratios: 0-0.1 (corresponding to a permeability range of 0-1 mD), 0.1-0.2 (corresponding to a permeability range of 1-3 mD), 0.7 (corresponding to a permeability range of 3-10 mD), and greater than 0.7 (corresponding to a permeability range greater than 10 mD). Figure 4 Table 1 shows the segmental model of bound water saturation under the same centrifugal force fitted by embodiments of the present invention.

[0038] Furthermore, the construction of the bound water saturation classification model under the same centrifugal force includes: constructing the bound water saturation model under the same centrifugal force according to the following formula: Swi 静态 =f(perm / por).

[0039] Among them, Swi 静态 Perm represents the degree of bound water saturation under the same centrifugal force, and por represents the porosity.

[0040] For example, based on 42 sets of porosity, permeability, and bound water saturation data obtained from core samples, functional relationships between porosity, permeability, and bound water saturation were fitted. Table 1 shows the relationship models between bound water saturation, permeability, and porosity established for permeability distribution ranges of 0-1 mD, 1-3 mD, 3-10 mD, and above 10 mD, respectively.

[0041] Classification conditions Model 0 mD < Permeability ≤ 1 mD <![CDATA[Swi 静态 =30.602*(perm / por) -0.098 ]]> 1 mD < Permeability ≤ 3 mD <![CDATA[Swi 静态 =19.352*(perm / por) -0.31 ]]> 3 mD < Permeability ≤ 10 mD <![CDATA[Swi 静态 =26.201*(perm / por) -0.094 ]]> Permeability > 10mD <![CDATA[Swi 静态 =25.587*(perm / por) -0.128 ]]>

[0042] Table 1

[0043] This invention uses multiple physical property parameters obtained from first core samples with different permeability ranges (different permeability-to-porosity ranges) to establish relationship models between bound water saturation, permeability, and porosity. Compared with traditional methods, by characterizing the change points in the relationship between bound water saturation and permeability-to-porosity, it more realistically reflects the characteristics of the actual reservoir and improves the fitting and calculation accuracy of bound water saturation.

[0044] S11. Based on the multiple characteristic parameters of each second core sample taken from the target oil and gas reservoir under each centrifugal force, construct the bound water saturation model of the multiple second core samples under each centrifugal force, and obtain multiple fitting coefficients of the bound water saturation model under each centrifugal force.

[0045] The permeability of the multiple second core samples falls within different permeability ranges.

[0046] For example, multiple second core samples are selected from the target oil and gas reservoir. These second core samples can be selected from the first core samples or re-selected from the target oil and gas reservoir. However, the selection principle is that the samples should ideally be distributed within different permeability ranges, such as 0-1 mD, 1-3 mD, 3 mD-10 mD, and greater than 10 mD. Figure 5 The embodiments of this invention provide porosity and permeability experimental data for a sample selected from each permeability range, with these samples distributed across the aforementioned different permeability ranges. The number of multiple second core samples can be either one core sample selected from each permeability range or multiple core samples selected from each permeability range; neither embodiment of this invention imposes a specific limitation.

[0047] For example, based on the four obtained second core samples, nuclear magnetic resonance (NMR) experiments can be performed on them. Four centrifugal forces can be set: 100 PSI, 300 PSI, 500 PSI, and 700 PSI. The four second core samples are subjected to a centrifugal force of 100 PSI, yielding four sets of characteristic parameters at this condition: porosity, permeability, and bound water saturation. Then, the four second core samples are subjected to a centrifugal force of 300 PSI, yielding the same four sets of porosity, permeability, and bound water saturation parameters. Next, the four second core samples are subjected to a centrifugal force of 500 PSI, again yielding the same four sets of porosity, permeability, and bound water saturation parameters. Finally, the four second core samples are subjected to a centrifugal force of 700 PSI, yielding the same four sets of porosity, permeability, and bound water saturation parameters. For details, please refer to [reference needed]. Figure 6 , Figure 6 These are experimental data from four core samples under multiple centrifugal forces provided in this embodiment of the invention. Similarly, more characteristic parameters under various centrifugal forces can be obtained. This embodiment of the invention is provided for illustrative purposes only; the invention does not impose specific limitations on the number of centrifugal forces selected or the order of experiments under different centrifugal force conditions.

[0048] Furthermore, based on the following formula, a model for the bound water saturation under each of the plurality of centrifugal forces is constructed: Swi j =A j (perm / por) B .

[0049] Among them, Swi j A represents the degree of bound water saturation under centrifugal force j. j represents the fitting coefficient of the bound water saturation model under centrifugal force j, and B represents a constant.

[0050] For example, based on the data obtained in step S11, the bound water saturation models of the multiple second core samples under each centrifugal force are constructed according to the multiple characteristic parameters obtained under each centrifugal force. For details, please refer to the table below. Table 2 shows the bound water saturation models of the multiple second core samples under each centrifugal force.

[0051] Centrifugal force j <![CDATA[Model Swi j = A j (perm / por) B > 100PSI <![CDATA[Swi 100 =34*(perm / por) -0.46 ]]> 300PSI <![CDATA[Swi 300 =26*(perm / por) -0.46 ]]> 500PSI <![CDATA[Swi 500 =21*(perm / por) -0.46 ]]> 700PSI <![CDATA[Swi 700 =19*(perm / por) -0.46 ]]>

[0052] Table 2

[0053] Among them, A 100 =34, A 300 =26, A 500 =21, A 700 =19, B=-0.46.

[0054] Based on step S11, bound water saturation models were fitted for four second core samples under different centrifugal forces j (j = 100 PSI, 300 PSI, 500 PSI, 700 PSI). For details, please refer to [reference needed]. Figure 7 . Figure 7 The bound water saturation model constructed in the embodiments of the invention under four centrifugal forces can be expressed in a general way as: Swi j =A j (perm / por) B .

[0055] S12. Determine the bound water saturation correction coefficient based on the plurality of fitting coefficients and the plurality of centrifugal forces.

[0056] The bound water saturation correction coefficient is a parameter corresponding to the centrifugal force.

[0057] Furthermore, for multiple fitting coefficients A j The system is fitted with the plurality of centrifugal forces j to obtain the fitting coefficient A between any centrifugal force x and any centrifugal force, as shown in the following formula. x Functional relationship: A x =a*(x) b Where a and b are constants; and according to the fitting coefficient A under any centrifugal force and the fitting coefficient A under the same centrifugal force y. y The correction coefficient J for the bound water saturation is determined by the following formula: J = A * / A y Wherein, the same centrifugal force y is one of any centrifugal forces x.

[0058] For example, based on the four fitting coefficients A obtained in step S11 j (A 100 =34, A 300 =26, A 500 =21, A 700 =19) and multiple centrifugal forces j (j = 100 PSI, 300 PSI, 500 PSI, 700 PSI). From Table 2, it can be easily concluded that the only difference between different centrifugal force j conditions is the coefficient A. j By establishing coefficient A j The fitting coefficient A under any centrifugal force x can be determined by the relationship between the centrifugal force j and the centrifugal force j. x A x =a*(x) b ,refer to Figure 8 It is the fitted arbitrary centrifugal force x and the fitting coefficient A x The relationship diagram shows that the fitted value of a is 138.31 and b is -0.301, i.e., A x=138.31×p -0.301 .

[0059] Based on the fitting coefficient A under arbitrary centrifugal force x The correction coefficient J for the bound water saturation is determined by the following formula: J = A x / A y The same centrifugal force y refers to any centrifugal force x. Taking the same centrifugal force y = 100 PSI in the embodiment of the present invention as an example, the correction coefficient J = A is further obtained. x / A 100 =138.31×p -0.301 / A 100 =138.31×p -0.301 / 34.

[0060] S13. Determine the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient.

[0061] Further, determining the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient includes: based on the bound water saturation model Swir corresponding to the same centrifugal force... 静态 The bound water saturation Swi of the target oil and gas reservoir is determined using the bound water saturation correction coefficient J and the following formula. 动态 Swi 动态 =J*Swi 静态 .

[0062] Specifically, the experiments on core samples under different centrifugal force conditions can be approximated to the pressure of actual production wells, with the unit conversion relationship being: 1 MPa ≈ 145 PSI. Therefore, by conducting experiments on core samples under different centrifugal force conditions and further obtaining the correction coefficients through the above steps, the bound water saturation (Swi) of the target oil and gas reservoir under arbitrary pressure conditions can be predicted. 动态 .

[0063] To illustrate the direct technical effects of this invention, an embodiment of the invention is based on a well, specifically referring to [reference needed]. Figure 9 This is the result obtained using existing methods. Figure 10 This is the result obtained through the method of the present invention. The embodiments of the present invention are as follows: Figure 9 Taking the No. 15 layer of the medium-production well as an example ( Figure 9 (Channel 8 in the middle) In the early stages of production, the pressure differential of this layer remained stable at 1 MPa, producing only gas and no water. Later, the pressure differential was adjusted to 2 MPa, at which point gas production increased and water production began. It is believed that Layer 15 should be a gas-water co-existing layer, and this layer should be sealed off to extract other gas layers.

[0064] Therefore, a detailed analysis was conducted using the method provided by this invention. By calculating the bound water saturation under different production pressure differentials of 1 MPa (J = 31 / 34), 2 MPa (J = 25 / 34), 3.5 MPa (J = 21 / 34), and 5 MPa (J = 19 / 34), and comparing the curves with the water saturation (SW), it can be seen that… Figure 10 In the middle sections (6th to 9th), when the 15th layer of this well is producing under a production pressure differential of approximately 1 MPa, the SWI (1 MPa) in this section basically overlaps with the SW. Figure 10 The sixth point indicates the absence of movable water, thus only gas is produced, not water. When the production pressure is adjusted to 2 MPa, the SWI (2 MPa) and SW in this section do not overlap and show a significant difference. Figure 10 The 7th reading indicates the presence of movable water in this layer, consistent with the water outflow phenomenon. Similarly, at 3.5 MPa and 5 MPa, the increase in movable water is significantly greater.

[0065] The method for determining bound water saturation provided by this invention, specifically applied to this actual well, determined that layer 15 is a pure gas layer. However, this gas layer is relatively sensitive to pressure. Water production is caused by an unreasonable production pressure differential, which causes some bound water in the reservoir to transform into mobile water. Controlling the production pressure differential to within 1 MPa would achieve the goal of controlling water production and gas generation. After the production operations department adopted the suggestion and adjusted to a reasonable production pressure differential, the well returned to a state of producing only gas and no water, eliminating the operational costs of adjusting the gas-producing layer and saving tens of millions of yuan in expenses.

[0066] This invention takes into account the high pressure sensitivity of tight reservoirs and the significant impact of pressure changes on bound water saturation. Therefore, it uses pressure changes to determine the bound water saturation in oil and gas production, thereby improving the accuracy of the method for determining bound water saturation and providing support for dynamic analysis such as perforation selection of oil and gas reservoirs and water production in producing formations.

[0067] On the other hand, the present invention also provides a system for determining the saturation of bound water. Figure 11This invention provides a system for determining bound water saturation. The system includes a first construction device 1, used to construct a bound water saturation model under the same centrifugal force based on multiple characteristic parameters of multiple first core samples taken from a target oil and gas reservoir under the same centrifugal force. The multiple characteristic parameters include porosity, permeability, and bound water saturation. The bound water saturation model for the same centrifugal force is a segmented bound water saturation model, and the permeability of the multiple first core samples belongs to different permeability ranges. The second construction device 2 is used to construct the bound water saturation model of the multiple second core samples under each centrifugal force based on multiple characteristic parameters of each second core sample taken from the target oil and gas reservoir under each centrifugal force, and to obtain multiple fitting coefficients of the bound water saturation model under each centrifugal force, wherein the permeability of the multiple second core samples belongs to different permeability ranges. The first determining device 3 is used to determine the bound water saturation correction coefficient based on the multiple fitting coefficients and the multiple centrifugal forces, wherein the bound water saturation correction coefficient is a parameter corresponding to the centrifugal force. The second determining device 4 is used to determine the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient.

[0068] The method and effects of the system for determining the bound water saturation in this embodiment of the invention are similar to the method for determining the bound water saturation described above, and will not be repeated here.

[0069] Preferably, the first constructing device 1, for constructing a bound water saturation model under the same centrifugal force, includes: constructing the bound water saturation model under the same centrifugal force according to the following formula: Swi 静态 =f(perm / por).

[0070] Among them, Swi 静态 Perm represents the degree of bound water saturation under the same centrifugal force, and por represents the porosity.

[0071] Preferably, the second construction device 2, used to construct the bound water saturation model of the plurality of second core samples under each centrifugal force, comprises: constructing the bound water saturation model under each of the plurality of centrifugal forces according to the following formula: Swi j =A j (perm / por) B .

[0072] Among them, Swi j A represents the degree of bound water saturation under centrifugal force j. jrepresents the fitting coefficient of the bound water saturation model under centrifugal force j, and B represents a constant.

[0073] Preferably, the first determining module 3 is used to determine the bound water saturation correction coefficient based on multiple fitting coefficients and the multiple centrifugal forces, including: for the multiple fitting coefficients A j The system is fitted with the plurality of centrifugal forces j to obtain the fitting coefficient A between any centrifugal force x and any centrifugal force, as shown in the following formula. x Functional relationship: A x =a*(x) b Where a and b are constants; and according to the fitting coefficient A under any centrifugal force x The fitting coefficient A under the same centrifugal force y y The correction coefficient J for the bound water saturation is determined by the following formula: J = A x / A y .

[0074] Wherein, the same centrifugal force y is one of any centrifugal forces x.

[0075] Preferably, the second determining module 4 is used to determine the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient, including: based on the bound water saturation model Swir corresponding to the same centrifugal force. 静态 The bound water saturation Swi of the target oil and gas reservoir is determined using the bound water saturation correction coefficient J and the following formula. 动态 Swi 动态 =J*Swi 静态 .

[0076] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0077] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for determining the bound water saturation of a tight reservoir, characterized in that, The determination method includes: Based on multiple characteristic parameters of multiple first core samples taken from the target oil and gas reservoir under the same centrifugal force, a bound water saturation model under the same centrifugal force is constructed. The multiple characteristic parameters include porosity, permeability and bound water saturation. The bound water saturation model under the same centrifugal force is a segmented bound water saturation model, and the permeability of the multiple first core samples belongs to different permeability ranges. Based on multiple characteristic parameters of each second core sample taken from multiple second core samples in the target oil and gas reservoir under each centrifugal force, a bound water saturation model of the multiple second core samples under each centrifugal force is constructed, and multiple fitting coefficients of the bound water saturation model under each centrifugal force are obtained, wherein the permeability of the multiple second core samples belongs to different permeability ranges. Based on the plurality of fitting coefficients and the plurality of centrifugal forces, a bound water saturation correction coefficient is determined, wherein the bound water saturation correction coefficient is a parameter corresponding to the centrifugal force; and The bound water saturation of the target oil and gas reservoir is determined based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient.

2. The determination method according to claim 1, characterized in that, The construction of the bound water saturation model under the same centrifugal force includes: Construct a model for the bound water saturation under the same centrifugal force based on the following formula: = ( )， in, This indicates the degree of bound water saturation under the same centrifugal force. Indicates penetration rate. Indicates porosity.

3. The determination method according to claim 2, characterized in that, The segmented bound water saturation model is constructed by: based on the ratio of permeability to porosity of multiple first core samples under the same centrifugal force and the change points of the bound water saturation fitting relationship under the same centrifugal force, the segmented bound water saturation model is constructed.

4. The determination method according to claim 1, characterized in that, The construction of the bound water saturation model for the plurality of second core samples under each centrifugal force includes: Construct a bound water saturation model for each of the plurality of centrifugal forces according to the following formula: = ， in, Centrifugal force is The bound water saturation below Centrifugal force is The fitting coefficients of the bound water saturation model under the given conditions. represents a constant, perm represents permeability, and por represents porosity.

5. The determination method according to claim 4, characterized in that, The determination of the bound water saturation correction coefficient based on multiple fitting coefficients and multiple centrifugal forces includes: For multiple fitting coefficients and the multiple centrifugal forces Perform a fitting to obtain the arbitrary centrifugal force shown in the following formula. Fit coefficients under arbitrary centrifugal force Functional relationship: Where a and b are both constants; and Based on the fitting coefficient under any centrifugal force and the same centrifugal force Fit coefficients under The correction coefficient for the bound water saturation is determined by the following formula. for: The same centrifugal force For any centrifugal force One of the centrifugal forces.

6. The determination method according to claim 5, characterized in that, The step of determining the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient includes: According to the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient And the following formula is used to determine the bound water saturation of the target oil and gas reservoir. : 。 7. A system for determining the bound water saturation of a tight reservoir, characterized in that, The determining system includes: a first construction device, used to construct a bound water saturation model under the same centrifugal force based on multiple characteristic parameters of multiple first core samples taken from the target oil and gas reservoir under the same centrifugal force, wherein the multiple characteristic parameters include porosity, permeability and bound water saturation, the bound water saturation model under the same centrifugal force is a segmented bound water saturation model, and the permeability of the multiple first core samples belongs to different permeability ranges; The second construction device is used to construct a bound water saturation model of the multiple second core samples under each centrifugal force based on multiple characteristic parameters of each second core sample taken from the target oil and gas reservoir under each centrifugal force, and to obtain multiple fitting coefficients of the bound water saturation model under each centrifugal force, wherein the permeability of the multiple second core samples belongs to different permeability ranges. A first determining device is configured to determine a bound water saturation correction coefficient based on the plurality of fitting coefficients and the plurality of centrifugal forces, wherein the bound water saturation correction coefficient is a parameter corresponding to the centrifugal force; and The second determining device is used to determine the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient.

8. The determining system according to claim 7, characterized in that, The first construction device, used to construct a bound water saturation model under the same centrifugal force, includes: Construct a model for the bound water saturation under the same centrifugal force based on the following formula: = ( )， in, This indicates the degree of bound water saturation under the same centrifugal force. Indicates penetration rate. Indicates porosity.

9. The determining system according to claim 8, characterized in that, The second construction device, used to construct a bound water saturation model for the plurality of second core samples under each centrifugal force, includes: Construct a bound water saturation model for each of the plurality of centrifugal forces according to the following formula: = ， in, Centrifugal force is The bound water saturation below Centrifugal force is The fitting coefficients of the bound water saturation model under the given conditions. represents a constant, perm represents permeability, and por represents porosity.

10. The determining system according to claim 9, characterized in that, The first determining module is used to determine the bound water saturation correction coefficient based on multiple fitting coefficients and the multiple centrifugal forces, including: For multiple fitting coefficients and the multiple centrifugal forces Perform a fitting to obtain the arbitrary centrifugal force shown in the following formula. Fit coefficients under arbitrary centrifugal force Functional relationship: Where a and b are both constants; as well as Based on the fitting coefficient under any centrifugal force and the same centrifugal force Fit coefficients under The correction coefficient for the bound water saturation is determined by the following formula. for: The same centrifugal force For any centrifugal force One of the centrifugal forces.

11. The determining system according to claim 10, characterized in that, The second determining module is used to determine the bound water saturation of the target oil and gas reservoir based on the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient, including: According to the bound water saturation model corresponding to the same centrifugal force and the bound water saturation correction coefficient And the following formula is used to determine the bound water saturation of the target oil and gas reservoir. : 。

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