A method for normalizing interlayer formation properties

Abstract

The present application belongs to the technical field of basin simulation, and particularly relates to an interlayer stratum physical property normalization method. 1, basic stratum parameters are obtained, the burial depth of a target normalization interface is determined, and whether porosity and other physical property data are complete is determined; 2, if the data are complete, step three is directly performed, and if the physical property parameters are missing, logging data can be used for conversion; 3, natural index fitting is performed on the porosity by a stratum physical property empirical model, and the porosity-depth relationship of each of the upper and lower interfaces is obtained; 4, the density-depth relationship corresponding to the strata of the upper and lower interfaces is respectively calculated; 5, the inversion fitting burial depth is calculated, the physical property parameter data points are inversed and matched, and the corresponding fitting burial depth is obtained; 6, the original fitting stratum pressure of the stratum correction point is obtained by integration, the density-depth parameter of the target standard lithology is substituted, and the depth value corresponding to the pressure is calculated by integration again; 7, the depth value is substituted into the physical property-depth formula of the target standard lithology, and the physical property normalization result is obtained.

Description

Technical Field

[0001] This invention belongs to the field of basin simulation technology, specifically relating to a method for normalizing inter-strata physical properties. Background Technology

[0002] Basin simulation technology is one of the core technologies for characterizing stratigraphic evolution and reconstructing tectonic-sedimentary history in oil and gas resource exploration and development. Formation properties are key fundamental parameters for reconstructing erosion and inverting formation pressure from well logging data in this technology. In actual strata, lithology often exhibits a mixed distribution, with significant differences in compaction characteristics and physical property responses among different lithologies. Therefore, existing basin simulations typically select continuous pure lithological sections to construct normal compaction trend curves, in order to standardize the characterization of physical property parameters.

[0003] However, such methods rely heavily on geological stratification or pure lithological sections, which not only discards a large amount of depth data from non-pure lithological sections, leading to scattered sampling points and difficulty in covering key depth sections, but also causes uneven compaction and inconsistent values ​​of physical parameters such as sonic transit time due to lithological mixing, which can interfere with the regularity of compaction trends and reduce the accuracy of basin simulation work such as well logging data processing and erosion recovery. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for normalizing inter-layer stratigraphic properties. On one hand, it reduces interference from lithological mixing, such as uneven compaction and inconsistent sonic transit time values, while also making the regularity of compaction trends more pronounced. On the other hand, it effectively covers key depths that traditional methods struggle to address, significantly improving data utilization efficiency; moreover, it can effectively identify false tectonic interfaces caused by lithological factors.

[0005] This invention employs the following technical solution: a method for normalizing inter-layer stratigraphic properties, which characterizes different rock types using a preset standard lithology. When different lithologies are at the same burial depth and corresponding pressure conditions are consistent, their compaction properties are replaced with the compaction properties of the preset standard lithology under the same conditions. The method for normalizing inter-layer stratigraphic properties includes the following steps:

[0006] Step 1: Obtain basic stratigraphic parameters, including rock skeleton density. Rock pore fluid density Measured porosity values ​​matched at corresponding stratum depth measuring points Or sonic transit time logging data of corresponding formations Because sonic transit time logging data is obtained by measuring at a point every 0.25m along the well depth, it can be converted into measured porosity values ​​matched to the formation depth measurement points. The depth of the target normalized interface is determined, and the basic lithology and core physical properties of the strata above and below the interface are analyzed to determine whether porosity parameters are missing. Since porosity logging is rarely used in actual production logging, formation porosity and other formation physical properties are difficult to obtain directly. However, sonic transit time logging data is collected in the vast majority of wells; therefore, it can be converted into porosity parameters using the Willy formula to broaden the applicability of the method.

[0007] Step 2: If porosity property parameters are missing, use sonic transit time logging data for conversion. The conversion formula is formula (1). If porosity property parameters are not missing, proceed directly to step 3.

[0008] (1).

[0009] In the formula, These are the measured porosity values ​​matched to the corresponding formation depth measuring points. The data points are the acoustic transit time logging values. This represents the time difference of sound waves in the rock skeleton. This represents the time difference of sound waves in the pore fluid of the rock.

[0010] Step 3: Perform depth projection on the porosity physical property parameters of the upper and lower strata of the interface, and use depth as the independent variable to fit the porosity using the empirical model of strata physical properties to obtain the porosity-depth relationship between the upper and lower strata of the interface. The fitting formula is formula (2).

[0011] (2).

[0012] in, The porosity-depth relationship function for data points. This represents the original sedimentary porosity value of the strata. The porosity compaction coefficient is... The data point embedding depth value.

[0013] Step 4: Based on the porosity-depth relationship fitted in Step 3, and combined with the basic parameters such as rock skeleton density in Step 1 and Step 2, calculate the density-depth relationship of the upper and lower strata of the interface respectively. The calculation formula is Formula (3).

[0014] (3).

[0015] In the formula, This is a density-depth relationship function. The data points represent the porosity-depth relationship function values. Density of the rock skeleton The density of the pore fluid in the rock.

[0016] Step 5: Invert and fit the burial depth. Eliminate the interference generated by the sedimentary discontinuity during the later burial process, and use the physical property parameter data points to invert and match to obtain the corresponding fitted burial depth, as shown in formula (4).

[0017] (4).

[0018] In the formula, These are the measured porosity values ​​matched to the corresponding formation depth measuring points. This represents the original sedimentary porosity value of the strata. is the porosity compaction coefficient.

[0019] Step 6: Obtain the original fitted formation pressure of the formation correction point through integration. According to the principle of constant pressure conditions, substitute the density-depth parameters of the target standard lithology and integrate again to calculate the depth value x corresponding to the pressure. The overall integration formula is formula (5).

[0020] (5).

[0021] In the formula, These are the measured porosity values ​​matched to the corresponding formation depth measuring points. This represents the original sedimentary porosity value of the strata. The porosity compaction coefficient is... To correct the density-depth relationship function of the target lithology, To correct the density-depth relationship function of the target lithology, This represents the conditional pressure depth value.

[0022] Step 7: Substitute the depth value obtained in Step 6 into the physical property-depth formula of the target standard lithology to obtain the physical property normalization result. The calculation formula is formula (6).

[0023] (6).

[0024] In the formula, This is the result of normalizing formation porosity. To correct the initial sedimentary porosity value of the target lithology, To correct the porosity compaction coefficient of the target lithology, This represents the conditional pressure depth value.

[0025] Furthermore, in step two, if the measured porosity values ​​of the corresponding stratum depth measuring points match... If all conditions are met, proceed directly to step three, the natural exponent fitting operation.

[0026] Furthermore, in step three, since the goal of the property normalization method is to eliminate the interference of inter-layer lithological differences on property, its working unit does not need to be strictly bounded by geological strata, and can be flexibly adjusted to a stratigraphic section with basically uniform lithology.

[0027] Furthermore, in formula (3), the relationship between density and depth is required to calculate the subsequent isobaric conditions, so the density-depth relationship must be obtained. The core factors affecting formation density are rock skeleton density and pore fluid density. Based on the pore-depth relationship, the pore volume ratio and rock skeleton volume ratio can be separated at different depths, and then multiplied by the pore fluid density and rock skeleton density respectively to calculate the formation density.

[0028] Furthermore, in step six, the depth value used to calculate the conditional pressure corresponding to the target stratum cannot be the current burial depth. This is because strata are easily affected by reburial after sedimentary discontinuities, and the lithology of the newly deposited overlying strata is diverse. Simply using the current burial depth cannot directly calculate its true stress state. Therefore, the fitted burial depth obtained by inversion matching of physical property parameter data points in step five is used. Based solely on the original porosity data of the target lithology, the compaction depth at which it reaches that original porosity under a single lithological depositional scenario is inverted; then, the conditional pressure is calculated using this fitted burial depth. Under ideal strata compaction conditions without considering other complex factors, the calculated conditional pressure has a high consistency with the actual strata pressure and can effectively eliminate the interference of the diverse lithologies of the current overlying strata, simplifying the calculation process. The parameters involved should use the parameters of the target lithology. and rather than correcting the target lithology and .

[0029] Further, in step six, the left side of formula (5) uses the inverse fitting burial depth as the upper limit of integration, which is the density-depth relationship function of the lithology to be corrected; the right side uses the depth value x corresponding to the conditional pressure as the upper limit of integration, which is the density-depth relationship function of the target lithology to be corrected. For example: to correct lithology type 1 to type 2, firstly, the conditional pressure is derived based on the compaction characteristics of type 1 lithology, and then the conditional pressure is assigned to type 2 lithology; the depth corresponding to the conditional pressure is obtained by integral calculation using the density-depth relationship of type 2 lithology. The physical meaning of depth x is: the sedimentary depth required to achieve the aforementioned pressure conditions under a single type 2 lithological sedimentary scenario. Ultimately, the depth will be... By substituting the porosity-depth relationship into the two types of lithology, the corresponding porosity can be obtained. Since the basin is assumed to be a single type of two-lithology sedimentary deposit throughout the process, the porosity-depth relationship of the two types of lithology can be extended vertically to the entire depth. Therefore, the calculated porosity is the corresponding true porosity of the two types of lithology under the pressure conditions.

[0030] Furthermore, in step seven, Similarly, to apply the initial sedimentary porosity value for the target lithology, rather than the object lithology being corrected, The porosity compaction coefficient is used to correct the target lithology.

[0031] The beneficial effects of this invention are as follows: It provides a method for normalizing the physical properties of inter-strata formations, which can be applied to tasks such as recovering erosion from well logging data in basin simulation. On the one hand, by normalizing different lithologies to a preset standard lithology, the compaction characteristics of various lithologies are unified, which can reduce interference such as uneven compaction and inconsistent sonic transit time values ​​caused by lithological mixing, and also make the regularity of compaction trends more significant. On the other hand, when solving the problem of lithological unification, there is no need to discard depth data of non-mudstone sections, which can effectively cover key depth sections that are difficult to cover by traditional methods, and significantly improve the efficiency of data utilization. Moreover, it can effectively identify false structural interfaces caused by lithological factors. Attached Figure Description

[0032] Figure 1 This is an example diagram of the curves showing the physical properties of the lower b stratum before normalization to the a stratum in the embodiment.

[0033] Figure 2 This is an example curve of the lower b stratum's physical properties after normalization and fitting to the a stratum in the embodiment. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] The method for normalizing inter-stratum physical properties includes the following steps:

[0036] Step 1: Determine the basic stratigraphic parameters, and establish the target normalized interface at a depth of 1500m. Also determine the density ρ of the upper stratum a's rock skeleton. s(a) =2.65g / cm 3 The density of pore fluid ρ within the rock f (a) =1.05g / cm 3 The density value ρ of the rock skeleton of the lower b strata s(b) =2.52g / cm 3 The density of pore fluid ρ within the rock in the lower part b f (b) =1.05g / cm 3 The initial sedimentary porosity φ of the upper stratum a 0(a) =34%, initial sedimentary porosity φ of the lower b stratum 0(b)=52%; the porosity of the upper stratum a at the interface is φ=25.19%, and the porosity of the lower stratum b at the interface is φ=17.13%. For example... Figure 1 and Figure 2 As shown, the porosity parameters for each data point are complete, and step three can be performed directly.

[0037] Step 2: If all parameters are complete, proceed directly to Step 3. If physical property parameters are missing, convert them using well logging data. The conversion formula is as follows:

[0038] (1).

[0039] In the formula, These are the measured porosity values ​​matched to the corresponding formation depth measuring points. The data points are the acoustic transit time logging values. This represents the time difference of sound waves in the rock skeleton. This represents the time difference of sound waves in the pore fluid of the rock.

[0040] Step 3: Perform depth projection on the physical parameters of the upper and lower strata at the interface. Using depth as the independent variable, fit the porosity to the natural exponent using an empirical model of strata physical properties to obtain the porosity-depth relationship for the upper and lower strata at the interface. The fitting formula is as follows:

[0041] ;

[0042] ;

[0043] In the formula, The porosity-depth relationship function fitted to the data points of the upper stratum a. The porosity-depth relationship function fitted to the data points of the lower b stratum. The data point embedding depth value.

[0044] Step 4: Based on the porosity-depth relationship fitted in Step 3, and combining the basic parameters such as rock skeleton density from Steps 1 and 2, calculate the density-depth relationships of the upper and lower strata at the interface, as shown in the following formulas:

[0045] ; ;

[0046] In the formula, This is the density-depth relationship function for the upper stratum a. The density-depth relationship function of the lower b stratum is given by , and the meanings of other parameters are the same as those in formula (3).

[0047] Step 5: Invert and fit the burial depth. Eliminate interference from sedimentary discontinuities during later burial processes. Use the physical property parameter data points for inversion and matching to obtain the corresponding fitted burial depth. Here, stratum b is used as the lithology to be corrected, and stratum a is used as the target lithology. The following example uses the data points of stratum b with φ=17.13%. The formula is as follows:

[0048] ;

[0049] In the formula, This represents the initial sedimentary porosity value of the lower b stratum. =52%, The porosity compaction coefficient of the lower b-stratum is given. =–0.0007, For physical property parameters of data points at arbitrary depths in the lower strata, in this embodiment... =17.13%;

[0050] Step Six: Obtain the original fitted formation pressure at the formation correction point through integration. Based on the principle of constant pressure conditions, substitute the density-depth parameters of the target standard lithology, and integrate again to calculate the depth value x corresponding to this pressure. The overall integration formula is as follows:

[0051] ;

[0052] ;

[0053] In the formula, This is the density-depth relationship function for the upper correction target lithological stratum a. The density-depth relationship function for the lower correction target lithological stratum b; Given the conditional pressure depth value, x = 1500m can be obtained by solving the above formula. The meanings of other parameters are the same as those in formula (5).

[0054] Step 7: Substitute the depth value obtained in Step 6 into the physical property-depth formula for the target standard lithology to obtain the final physical property normalized result. The calculation formula is as follows:

[0055] ;

[0056] ;

[0057] In the formula, This represents the initial sedimentary porosity value of the upper stratum a. The porosity compaction coefficient of the upper a stratum; The porosity value is the normalized value of the data point φ=17.13% of the lower b stratum to the lithology of the upper a stratum. The meanings of other parameters are the same as those in formula (6).

[0058] Porosity properties of the original stratigraphic profile, such as Figure 1 As shown ( Figure 1 (This is the graph before normalization), based on the normalization process... Figure 1 The lower mudstone layer was corrected to a sandstone benchmark, and the final processing result is as follows: Figure 2 As shown ( Figure 2 (This is the fitted curve after normalization). After normalizing all remaining data points of the lower stratum b, it was found that the trend fitted line and the fitted line of the upper stratum precisely coincide at the interface, and the overall trend of change is highly consistent with that of the upper stratum. Based on this, it can be determined that the interface is a common lithological interface, not a tectonic interface such as a stratigraphic unconformity.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for normalizing inter-strata physical properties, characterized in that: The method for normalizing inter-stratum physical properties includes the following steps: Step 1: Obtain basic stratigraphic parameters, determine the burial depth of the target normalized interface, and at the same time, sort out the basic lithology and core physical property characteristics of the strata above and below the interface to determine whether porosity physical property parameters are missing. Step 2: If porosity property parameters are missing, use sonic transit time logging data for conversion. The conversion formula is formula (1). If porosity property parameters are not missing, proceed directly to step 3. （1）； In the formula, These are the measured porosity values ​​matched to the corresponding formation depth measuring points. The data points are the acoustic transit time logging values. This represents the time difference of sound waves in the rock skeleton. This represents the acoustic transit time value of the fluid in the rock pores. Step 3: Perform depth projection on the porosity physical property parameters of the upper and lower strata of the interface, and use depth as the independent variable to fit the porosity using the empirical model of strata physical properties to obtain the porosity-depth relationship between the upper and lower strata of the interface. The fitting formula is formula (2). （2）； In the formula, The porosity-depth relationship function for data points. This represents the original sedimentary porosity value of the strata. The porosity compaction coefficient is... The data point burial depth value; Step 4: Based on the porosity-depth relationship fitted in Step 3, calculate the density-depth relationship of the upper and lower strata of the interface respectively. The calculation formula is Formula (3). （3）； In the formula, This is a density-depth relationship function. The data points represent the porosity-depth relationship function values. Density of the rock skeleton Density of pore fluid in rock; Step 5: Invert and fit the burial depth. Eliminate the interference generated by the sedimentary discontinuity during the later burial process, and use the physical property parameter data points to invert and match to obtain the corresponding fitted burial depth, as shown in formula (4). （4）； In the formula, These are the measured porosity values ​​matched to the corresponding formation depth measuring points. This represents the original sedimentary porosity value of the strata. This is the porosity compaction coefficient; Step 6: Obtain the original fitted formation pressure of the formation correction point by integration. According to the principle of constant pressure conditions, substitute the density-depth parameters of the target standard lithology and integrate again to calculate the depth value x corresponding to the pressure. The overall integration formula is formula (5). （5）； In the formula, These are the measured porosity values ​​matched to the corresponding formation depth measuring points. This represents the original sedimentary porosity value of the strata. The porosity compaction coefficient is... To correct the density-depth relationship function of the target lithology, To correct the density-depth relationship function of the target lithology, This refers to the conditional pressure depth value; Step 7: Substitute the depth value obtained in Step 6 into the physical property-depth formula of the target standard lithology to obtain the physical property normalization result. The calculation formula is formula (6). （6）； In the formula, This is the result of normalizing formation porosity. To correct the initial sedimentary porosity value of the target lithology, To correct the porosity compaction coefficient of the target lithology, This represents the conditional pressure depth value.

2. The inter-stratum physical property normalization method according to claim 1, characterized in that: The basic stratigraphic parameters in step one include the density of the rock skeleton. Rock pore fluid density Measured porosity values ​​matched at corresponding stratum depth measuring points Or sonic transit time logging data of corresponding formations .

3. The inter-stratum physical property normalization method according to claim 1, characterized in that: In step six, the depth value used when calculating the conditional pressure corresponding to the rock stratum point to be corrected cannot be the current burial depth.

4. The inter-stratum physical property normalization method according to claim 1, characterized in that: In step six, the left side of the formula is the integrand with the inversion fitting burial depth as the upper limit of integration, which is the density-depth relationship function of the lithology of the correction target; the right side is the depth value corresponding to the conditional pressure. The integrand is the function with the upper limit of integration, which is the density-depth relationship function for correcting the target lithology.

Images