Ultra-low permeability carbonate reservoir saturation modeling method and device

Abstract

The invention discloses an ultra-low permeability carbonate reservoir saturation modeling method and device, and the method comprises the steps: obtaining an Archie saturation curve; based on the rock core data, a rock type saturation height function is constructed; on the basis of the single-well rock type of the target well, the porosity and permeability interpretation curve and the rock type saturation height function, a saturation height change curve is constructed; constructing a saturation trend body model based on the Archie saturation curve and the saturation change curve along with the height; and constructing a saturation model based on an Archie saturation curve and the saturation trend body model. According to the method, the advantages of two saturation modeling methods of stochastic simulation and saturation height function are fused, the reliability of the surface saturation is guaranteed, and the inter-well saturation reflects the trend of changing along with the height and the physical property. According to the method, the apparent saturation body established by the saturation height function method serves as a trend body to participate in modeling, and the problem that the saturation height function method cannot be applied is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development geology and geological modeling, and in particular to a method and device for saturation modeling of ultra-low permeability carbonate reservoirs. Background Art

[0002] Saturation models are crucial for reservoir reserve calculation, well pattern deployment, perforation plan development, water avoidance, reservoir development economics, risk reduction, and improving the economic benefits of oilfield development. Saturation modeling methods vary, and their accuracy and compatibility with dynamic models vary. Furthermore, geological conditions also influence the applicability of modeling methods. For example, for ultra-low permeability reservoirs, due to their extremely low permeability and limited data testing accuracy, conventional saturation modeling methods struggle to achieve reasonable accuracy, making saturation modeling a major challenge.

[0003] Currently, the most commonly used saturation modeling method in China is to calculate wellbore saturation using well logging curves (resistivity curves, porosity interpretation curves) and formulas (primarily Archie's formula), and then establish a saturation model through interwell random simulation. This saturation modeling method has the following disadvantages: ① Interwell saturation simulation lacks constraints and cannot reflect the trend of saturation changes with physical properties and altitude, resulting in a lack of reliability in interwell prediction results; ② It cannot reflect the fluid equilibrium state. Model initialization is generally performed through enumeration, which poorly matches the dynamic model.

[0004] The saturation height function method, which is more closely integrated with dynamic models, can better reflect the variation of saturation between wells with physical properties and height, and can also reflect the saturation under original reservoir conditions. However, the difficulties of using this method include: ① The saturation height function is primarily derived from core data (mercury intrusion capillary force curves), but for ultra-low permeability reservoirs, the mercury intrusion curve values ​​often deviate from the actual values; ② The saturation derived from the uphole saturation height function is difficult to reconcile with the Archie interpretation of saturation, which means that it is difficult to ensure the accuracy of the uphole saturation; ③ A clear free water surface (FWL) is required, but currently, the inclined oil-water contact and free water surface cannot be obtained. For ultra-low permeability carbonate reservoirs, the permeability is extremely low. Experiments based on core flooding to obtain capillary force (such as mercury intrusion experiments) often have systematic errors, making the subsequently derived saturation height function inappropriate for direct modeling. Moreover, ultra-low permeability reservoirs often have sharply inclined oil-water contacts or free water surfaces, and even these cannot be detected in the contract area. Currently, there is no effective solution. Summary of the Invention

[0005] The present invention aims to provide a method and apparatus for saturation modeling of ultra-low permeability carbonate reservoirs. To improve the accuracy of saturation modeling for ultra-low permeability reservoirs, a more reliable saturation model for ultra-low permeability reservoirs is established by establishing an apparent saturation model using a saturation height function method and using this model as a trend body. To achieve this objective, the present invention provides the following technical solutions:

[0006] A method for modeling saturation of ultra-low permeability carbonate reservoirs, comprising:

[0007] Get the Archie saturation curve;

[0008] Based on core data, a saturation height function for each rock type is constructed;

[0009] Based on the single well rock type of the target well, the porosity and permeability interpretation curve and the rock type saturation height function, a saturation height variation curve is constructed;

[0010] Based on the Archie saturation curve and the saturation change with height curve, a saturation trend body model is constructed;

[0011] A saturation model is constructed based on the Archie saturation curve and the saturation trend body model.

[0012] Furthermore, the core data includes core rock classification and capillary force curve.

[0013] Furthermore, based on the Archie saturation curve and the saturation-altitude variation curve, a visual saturation volume model is constructed, including:

[0014] By adjusting the FWL depth, the similarity between the saturation variation curve with height and the Archie saturation curve reaches a threshold value, and the apparent FWL of all single wells is determined;

[0015] Performing well point interpolation on the single well apparent FWL to obtain an apparent inclined FWL surface;

[0016] Based on the apparent tilt FWL surface, establishing a height model above the FWL;

[0017] Obtain rock type model and property model of target well;

[0018] An apparent saturation volume model is constructed based on the height above FWL model and the rock type model and property model of the target well.

[0019] Furthermore, the single well visual FWL is the FWL depth point on the well.

[0020] Furthermore, the property model includes a porosity and permeability model.

[0021] Furthermore, based on the Archie saturation curve and the saturation trend body model, a saturation model is constructed, including:

[0022] The Archie saturation curve is discretized to construct a one-dimensional saturation model;

[0023] performing data analysis on the one-dimensional saturation model and the apparent saturation trend model;

[0024] A saturation model is established based on the results of the data analysis and the one-dimensional saturation model.

[0025] The present invention also provides a saturation modeling device for ultra-low permeability carbonate reservoirs, the device comprising:

[0026] An acquisition module for acquiring Archie saturation curve;

[0027] The first construction module is used to construct a rock type saturation height function based on core data;

[0028] The second construction module is used to construct a saturation-height variation curve based on the single well rock type of the target well, the porosity-permeability interpretation curve and the rock type-specific saturation height function;

[0029] A third construction module is configured to construct a saturation trend model based on the Archie saturation curve and the saturation-altitude variation curve;

[0030] The fourth building module is used to build a saturation model based on the Archie saturation curve and the apparent saturation trend model.

[0031] Furthermore, the steps performed by the third building block include:

[0032] By adjusting the FWL depth, the similarity between the saturation variation curve with height and the Archie saturation curve reaches a threshold value, and the apparent FWL of all single wells is determined;

[0033] Performing well point interpolation on the single well apparent FWL to obtain an apparent inclined FWL surface;

[0034] Based on the apparent tilt FWL surface, establishing a height model above the FWL;

[0035] Obtain rock type model and property model of target well;

[0036] An apparent saturation volume model is constructed based on the height above FWL model and the rock type model and property model of the target well.

[0037] Furthermore, the steps performed by the fourth building block include:

[0038] The Archie saturation curve is discretized to construct a one-dimensional saturation model;

[0039] performing data analysis on the one-dimensional saturation model and the visual saturation volume model;

[0040] A saturation model is established based on the results of the data analysis and the one-dimensional saturation model.

[0041] The present invention further provides an electronic device, comprising at least one processor and at least one memory, wherein the memory is data-connected to the processor,

[0042] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 6.

[0043] Technical effects and advantages of the present invention:

[0044] 1. The present invention integrates the advantages of two saturation modeling methods: random simulation and saturation height function, which ensures the reliability of well saturation and enables the inter-well saturation to reflect the trend of changes with height and physical properties.

[0045] 2. The present invention uses the apparent saturation body established by the saturation height function method as a trend body to participate in modeling, overcoming the problem that the saturation height function method cannot be applied.

[0046] This method was first applied to an ultra-low-permeability carbonate reservoir in a Middle Eastern oilfield to establish a saturation model. Compared to the saturation model established using the original stochastic simulation method, the proposed model not only ensures the reliability of saturation at the wellbore, but also reflects the trend of saturation changes with elevation and properties between wells. This improves the accuracy of interwell oil saturation calculations, confirms the reservoir's 4.6 billion barrels of geological reserves, and achieves better historical fit results than the dynamic model, laying a solid foundation for forecasting and planning. The method will continue to be applied to other similar reservoirs in the Middle East.

[0047] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A schematic flow chart of a method for saturation modeling of ultra-low permeability carbonate reservoirs according to an embodiment of the present invention is shown;

[0049] Figure 2 A schematic diagram of a saturation modeling device for ultra-low permeability carbonate reservoirs according to an embodiment of the present invention is shown;

[0050] Figure 3 An implementation diagram of a method for modeling saturation of ultra-low permeability carbonate reservoirs according to an embodiment of the present invention is shown;

[0051] Figure 4a A schematic diagram illustrating adjusting the FWL depth so that the saturation curve calculated by the saturation height function coincides as closely as possible with the saturation curve calculated by Archie is shown in an embodiment of the present invention;

[0052] Figure 4b A comparison diagram of SW_LAM and SW when the FWL depth is -3180m according to an embodiment of the present invention is shown;

[0053] Figure 5 Shows a three-dimensional display diagram of FWL at all well points in an embodiment of the present invention;

[0054] Figure 6 A schematic diagram of an inclined FWL surface according to an embodiment of the present invention is shown;

[0055] Figure 7a A curve showing the relationship between Archie saturation and saturation trend body saturation fitting for all wells of rock type 1 in the B1 layer of the oil reservoir according to an embodiment of the present invention is shown;

[0056] Figure 7b The figure shows the relationship between Archie saturation and saturation trend body saturation fitting for all wells of rock type 2 in the B1 layer of the oil reservoir according to the embodiment of the present invention;

[0057] Figure 7c The figure shows the relationship between Archie saturation and saturation trend body saturation fitting for all wells of rock type 1 in the B2 layer of the oil reservoir according to the embodiment of the present invention;

[0058] Figure 7d The figure shows the relationship between Archie saturation and saturation trend body saturation fitting for all wells of rock type 2 in the B2 layer of the oil reservoir according to the embodiment of the present invention;

[0059] Figure 8 A structural block diagram of an electronic device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0060] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0061] In order to solve the shortcomings of the existing technology, the present invention discloses a saturation modeling method for ultra-low permeability carbonate reservoirs, such as Figure 1 As shown, the method includes,

[0062] Get the Archie saturation curve;

[0063] Based on core data, a saturation height function for each rock type is constructed;

[0064] Based on the single well rock type of the target well, the porosity and permeability interpretation curve and the rock type saturation height function, a saturation height variation curve is constructed;

[0065] Based on the Archie saturation curve and the saturation change with height curve, a saturation trend body model is constructed;

[0066] A saturation model is constructed based on the Archie saturation curve and the saturation trend body model.

[0067] In a specific embodiment of the present invention, a saturation-versus-height curve is constructed based on the rock type of the target well, the porosity-permeability interpretation curve of the target well, and the rock type-specific saturation height function. The specific steps are as follows:

[0068] Wells that can reflect the original reservoir conditions (non-flooded wells) are screened to obtain the rock type and porosity / permeability interpretation curves of the single wells. Combined with the rock type saturation height function established in step 1), a saturation change curve with a given FWL depth is established.

[0069] In a specific embodiment of the present invention, a visual saturation volume model is constructed based on the Archie saturation curve, the saturation variation curve with altitude, and the saturation altitude function, including:

[0070] Obtain Archie saturation curve;

[0071] Adjust the FWL depth so that the saturation-versus-height curve is as consistent as possible with the Archie saturation curve, and then determine the apparent FWL at that well point. This method is used to determine the apparent FWL of all wells that meet the criteria. Well point interpolation is performed to form a surface, ultimately forming the final apparent tilt FWL surface, where the apparent FWL of a well is the FWL depth point on the well.

[0072] Using the apparent tilt FWL surface, a height model above the FWL is established;

[0073] Obtain a rock type model and an attribute model (pore permeability model); for the above models, establish an apparent saturation body model, wherein the rock type model and the attribute model (pore permeability model) are obtained based on conventional methods, such as constructing a rock type model through a sequential indicator random simulation method and constructing a porosity permeability model through a sequential Gaussian random simulation method, which will not be elaborated in detail in the present invention.

[0074] The height model above the FWL and the rock type model and property model of the target well are calculated using the saturation height function to construct an apparent saturation body model (ie, a saturation trend body model).

[0075] In a specific embodiment of the present invention, a saturation model of an ultra-low permeability carbonate reservoir is constructed based on the Archie saturation curve and the apparent saturation volume model, specifically:

[0076] The Archie saturation curve of the well is discretized to construct a one-dimensional saturation model;

[0077] Data analysis is performed on the one-dimensional saturation model and the apparent saturation body model, and correlation curves between the well Archie saturation and the saturation trend body saturation are fitted layer by layer and rock type by rock type. A random simulation is performed, and a discretized Archie saturation curve (i.e., a one-dimensional saturation model) is applied on the well. The data analysis results are applied between wells to establish a saturation model, which is a saturation model for ultra-low permeability carbonate reservoirs.

[0078] The method of the present invention combines the advantages of two saturation modeling methods, random simulation and saturation height function, which ensures the reliability of well saturation and enables the inter-well saturation to reflect the trend of changes with height and physical properties.

[0079] The method of the present invention uses the apparent saturation body established by the saturation height function method as a trend body to participate in modeling, thereby overcoming the difficulty that the saturation height function method cannot be applied.

[0080] The present invention also provides a saturation modeling device for ultra-low permeability carbonate reservoirs, such as Figure 2 As shown, the device includes,

[0081] An acquisition module for acquiring Archie saturation curve;

[0082] The first construction module is used to construct a rock type saturation height function based on core data;

[0083] The second construction module is used to construct a saturation-height variation curve based on the single well rock type of the target well, the porosity-permeability interpretation curve and the rock type-specific saturation height function;

[0084] A third construction module is configured to construct a saturation trend model based on the Archie saturation curve and the saturation-altitude variation curve;

[0085] The fourth construction module is used to construct a saturation model of an ultra-low permeability carbonate reservoir based on the Archie saturation curve and the saturation trend body model.

[0086] In a specific embodiment of the present invention, the steps performed by the third construction module include: adjusting the FWL depth so that the saturation variation with height curve is as consistent as possible with the Archie saturation curve and the similarity of the two curves reaches a threshold value, thereby determining the apparent FWL of all single wells; performing well point interpolation on the apparent FWL of the single well to obtain an apparent inclined FWL surface; establishing a height above FWL model based on the apparent inclined FWL surface; obtaining a rock type model and an attribute model of the target well; and constructing an apparent saturation volume model based on the height above FWL model and the rock type model, attribute model, and saturation height function of the target well.

[0087] In a specific embodiment of the present invention, the steps performed by the fourth construction module include: discretizing the Archie saturation curve to construct a one-dimensional saturation model; performing data analysis on the one-dimensional saturation model and the apparent saturation volume model to construct a saturation model for an ultra-low permeability carbonate reservoir.

[0088] Regarding the apparatus in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0089] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0090] Based on this method, saturation modeling was carried out for the Sad i ultra-low permeability reservoir in Halfaya Oilfield, as shown in the following example: Figure 3 As shown, the specific steps include:

[0091] 1. Establish saturation height function for different rock types

[0092] By classifying the core rock types, combining the capillary force curves for each type with other necessary data (fluid data, etc.), a saturation height function for each rock type was established. By classifying the core data into two rock types, combining the capillary force curves for each type with other necessary data (fluid data, etc.), two saturation height functions were established (Table 1).

[0093] Table 1 Saturation height function by rock type

[0094]

[0095] According to Table 1, there are two core rock types in this area, namely RT1 and RT2. The corresponding saturation height function formulas are shown in Table 1, where RT1 represents rock type 1, RT2 represents rock type 2, SW represents water saturation, Por represents porosity, Perm represents permeability, and HAFWL represents the height above the free water surface.

[0096] The saturation height function is a mathematical model that describes how saturation distribution changes with depth and physical properties. The saturation height function in this example is an established equation that relates saturation SW to saturation height HAFWL and porosity Por. This equation is derived from the core capillary force curve and is a well-known general method.

[0097] 2. Establish tilted FWL

[0098] 60 wells that can reflect the original reservoir conditions were screened, and the rock types and porosity and permeability curves of non-cored wells were obtained. Combined with the rock type saturation height function established in step 1), a saturation variation with height curve was established for a given FWL depth. The Archie saturation curve of the non-cored well was obtained. Taking Well N021 as an example, the FWL depth was adjusted to -2994m TVDSS, and the saturation variation with height curve was basically consistent with the Archie saturation curve ( Figure 4a and 4b ), then the apparent FWL at the well point is determined to be -2994mTVDSS. This method is used to determine the apparent FWL of all single wells that meet the conditions ( Figure 5 ), perform well point interpolation to form a surface, and form the final apparent tilt FWL ( Figure 6 ).

[0099] Among them, the FWL depth is adjusted so that the saturation curve calculated by the saturation height function coincides with the saturation curve calculated by Archie as much as possible ( Figure 4a ), at this time, the FWL is the final FWL of the well point.

[0100] Figure 4b The comparison chart of SW_LAM and SW when the FWL depth is -3180m shows that the fitting relationship between the two is not good. The right chart is obtained by continuing to adjust the FWL depth. At this time, the FWL depth is -3120m, and the fitting effect of SW_LAM and SW reaches the best (maximum overlap), so this depth is determined as the FWL depth point of the well. Figure 4a and Figure 4b RT1 indicates rock type 1, SW indicates water saturation calculated by Archie, SW_LAM indicates water saturation calculated by saturation height function, Por indicates porosity curve, Perm_CD_RIPED indicates permeability curve, B1 and B2 indicate formation names

[0101] Well point FWL interpolation to establish inclined FWL surface Figure 5 and Figure 6 As shown, according to Figure 4a and Figure 4b By using this method, a FWL depth point (a point on the well trajectory) can be determined for each well. Figure 2 That is, the three-dimensional display of all well FWL depth points. Figure 2By interpolating all the FWL depth points of the wells in the , a surface can be formed. This surface is a curved surface, that is, an inclined FWL surface.

[0102] 3. Calculation saturation model

[0103] Apply the FWL apparent inclination surface established in step 2) to establish a height model above the FWL; obtain a rock type model and a property model; apply the saturation height function to the above models to establish an apparent saturation model (saturation trend body).

[0104] 4. Random simulation modeling of well saturation

[0105] The well Archie saturation curve was discretized to establish a one-dimensional saturation model; data analysis was performed, and the correlation curve between the well Archie saturation and saturation trend body saturation was fitted layer by layer and rock type. Figures 7a-7d ); perform random simulation, apply discretized Archie saturation curve on the well, apply data analysis results between wells, and establish a saturation model. Figures 7a-7d The vertical axis of each graph is the Archie saturation (Sw_Archie), and the horizontal axis is the saturation trend (Sw_Trend). This saturation trend is the apparent saturation model mentioned above. Figures 7a-7d This paper describes the relationship between the two saturations at the wellbore for each layer and each RT, along with the corresponding fitting curve. This describes the relationship between the two at the wellbore level. By further applying this fitting curve relationship to interwell saturations, we can simulate interwell saturations. This simulation is performed using the Petrel software and is not covered by this patent and will not be elaborated in detail.

[0106] Based on the above disclosed content, the present invention also provides an electronic device. Figure 8 As shown, the electronic device of an embodiment of the present invention includes at least one electrically connected processor and at least one memory, wherein the memory is electrically connected to the processor, wherein the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method steps executed by the controller as above.

[0107] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A saturation modeling method for ultra-low permeability carbonate reservoirs, characterized in that: The method comprises, Get the Archie saturation curve; Based on core data, a saturation height function for each rock type is constructed; Based on the single well rock type of the target well, the porosity and permeability interpretation curve and the rock type saturation height function, a saturation height variation curve is constructed; Based on the Archie saturation curve and the saturation change with height curve, a saturation trend body model is constructed; A saturation model is constructed based on the Archie saturation curve and the saturation trend body model.

2. The method for saturation modeling of ultra-low permeability carbonate reservoirs according to claim 1, characterized in that: The core data includes core rock classification and capillary force curve.

3. The method for saturation modeling of ultra-low permeability carbonate reservoirs according to claim 1, characterized in that: Based on the Archie saturation curve and the saturation-altitude variation curve, a visual saturation body model is constructed, including: By adjusting the FWL depth, the similarity between the saturation variation curve with height and the Archie saturation curve reaches a threshold value, and the apparent FWL of all single wells is determined; Performing well point interpolation on the single well apparent FWL to obtain an apparent inclined FWL surface; Based on the apparent tilt FWL surface, establishing a height model above the FWL; Obtain rock type model and property model of target well; An apparent saturation volume model is constructed based on the height above FWL model and the rock type model and property model of the target well.

4. The method for saturation modeling of ultra-low permeability carbonate reservoirs according to claim 3, characterized in that: The single well visual FWL is the FWL depth point on the well.

5. The method for saturation modeling of ultra-low permeability carbonate reservoirs according to claim 3, characterized in that: The property model includes a porosity model.

6. The method for saturation modeling of ultra-low permeability carbonate reservoirs according to claim 1, characterized in that: Based on the Archie saturation curve and the saturation trend body model, a saturation model is constructed, including: The Archie saturation curve is discretized to construct a one-dimensional saturation model; performing data analysis on the one-dimensional saturation model and the apparent saturation trend model; A saturation model is established based on the results of the data analysis and the one-dimensional saturation model.

7. A saturation modeling device for ultra-low permeability carbonate reservoirs, characterized in that: The device comprises, An acquisition module for acquiring Archie saturation curve; The first construction module is used to construct a rock type saturation height function based on core data; The second construction module is used to construct a saturation-height variation curve based on the single well rock type of the target well, the porosity-permeability interpretation curve and the rock type-specific saturation height function; A third construction module is configured to construct a saturation trend model based on the Archie saturation curve and the saturation-altitude variation curve; The fourth building module is used to build a saturation model based on the Archie saturation curve and the apparent saturation trend model.

8. The ultra-low permeability carbonate reservoir saturation modeling device according to claim 7, characterized in that: The steps performed by the third building block include: By adjusting the FWL depth, the similarity between the saturation variation curve with height and the Archie saturation curve reaches a threshold value, and the apparent FWL of all single wells is determined; Performing well point interpolation on the single well apparent FWL to obtain an apparent inclined FWL surface; Based on the apparent tilt FWL surface, establishing a height model above the FWL; Obtain rock type model and property model of target well; An apparent saturation volume model is constructed based on the height above FWL model and the rock type model and property model of the target well.

9. The ultra-low permeability carbonate reservoir saturation modeling device according to claim 7, characterized in that: The steps performed by the fourth building block include: The Archie saturation curve is discretized to construct a one-dimensional saturation model; performing data analysis on the one-dimensional saturation model and the visual saturation volume model; A saturation model is established based on the results of the data analysis and the one-dimensional saturation model.

10. An electronic device comprising at least one processor and at least one memory, wherein the memory is data-connected to the processor, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 6.

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