A quantitative evaluation method for compaction strength of deep-ultradeep clastic rock

Abstract

The application belongs to the technical field of oil and gas exploration and development, and specifically discloses a deep-ultra-deep clastic rock compaction strength quantitative evaluation method, which comprises the following steps: obtaining basic geological parameters and experimental parameters of a reservoir in a research area, at least including burial depth, initial porosity, overpressure and measured porosity data of a particle coating development horizon; respectively calculating mechanical compaction and chemical compaction porosity change rates and summing them up to obtain ideal porosity; comparing and calculating overpressure contribution value by using overpressure measured data and ideal porosity and correcting, and again comparing and calculating particle coating contribution value by using particle coating measured data and ideal porosity and correcting again to obtain actual porosity; calculating compaction reduction porosity rate and residual porosity retention rate based on initial porosity, actual porosity and burial depth; comparing the two with a double-index three-level classification standard to evaluate the compaction strength grade. The application can accurately and quantitatively evaluate the compaction strength of deep-ultra-deep clastic rocks.

Description

Technical Field

[0001] This application belongs to the field of oil and gas exploration and development technology, and more specifically, relates to a quantitative evaluation method for the compaction strength of deep to ultra-deep clastic rocks. Background Technology

[0002] As oil and gas exploration and development moves towards deeper and ultra-deeper reservoirs, clastic rock reservoirs have become important targets for deep oil and gas exploration. Compaction is one of the core controlling factors leading to reduced porosity and deteriorated physical properties in deep and ultra-deep sandstone reservoirs. The geological background of deep and ultra-deep clastic rock reservoirs is extremely complex. Compared with shallow sand bodies, they are located in a special geological environment with high temperature and high pressure. Compaction is not a simple mechanical compaction process, but is also affected by multiple factors such as formation fluid properties, geothermal gradient, rock mineral composition, and diagenetic evolution stage. Moreover, with increasing burial depth, the dominant type of compaction changes significantly. In shallow layers (burial depth less than 1000m), mechanical compaction is dominant. When the burial depth exceeds 1000m, chemical compaction gradually replaces mechanical compaction as the dominant force controlling reservoir porosity evolution. The dynamic coupling effect of the two determines the final compaction intensity and physical properties of deep and ultra-deep clastic rock reservoirs.

[0003] The compaction of clastic rocks can be classified into two types: mechanical compaction and chemical compaction. Mechanical compaction is the main compaction method in shallow clastic rocks, mainly causing porosity loss through processes such as particle rearrangement, plastic deformation, and rigid particle fracturing. Its mechanism is intuitive and can be semi-quantitatively characterized through burial history, making it the core method for evaluating the compaction of shallow clastic rocks. However, mechanical compaction is only applicable to the shallow burial stage. When the burial depth exceeds a certain threshold (greater than 1000m), the mechanical compaction effect significantly decreases, failing to explain the continuous porosity loss phenomenon under the high temperature and high pressure background of deep to ultra-deep layers, and also failing to consider the modification of the compaction process by factors such as diagenetic fluids and geothermal gradients. Chemical compaction is the dominant type of compaction in deep to ultra-deep clastic rocks. It originates from mineral dissolution, ion migration, and authigenic mineral precipitation at the contact points of clastic particles under high temperature and pressure. It can explain the main control mechanism of deep reservoir porosity evolution and clarify the influence of geothermal gradient and mineral composition on the compaction process. However, most studies analyze the diagenetic effect of chemical compaction in isolation, without combining it with the dynamic evolution process of mechanical compaction. It is also impossible to quantify the contribution ratio of the two at different burial stages, making it difficult to fully characterize the compaction evolution law of the entire burial cycle of the reservoir.

[0004] For quantitative analysis of the intensity of deep to ultra-deep compaction, existing studies mostly rely on numerical simulations, establishing empirical formulas by fitting the porosity characteristics of present-day clastic reservoirs. These formulas treat porosity as a single function of burial depth, failing to comprehensively consider the coupled processes of mechanical and chemical compaction during geological history to establish systematic quantitative calculation formulas. Furthermore, they do not consider the influence of actual stratigraphic factors such as overpressure and particle cladding on the inhibition and modification of compaction, resulting in significant deviations between the evaluation results of compaction intensity and actual geological conditions. In addition, existing compaction evaluation methods are mostly at the qualitative or semi-quantitative level, lacking a systematic and standardized quantitative evaluation system, making it difficult to accurately classify and define the intensity of compaction.

[0005] Therefore, how to accurately and quantitatively evaluate the compaction intensity of deep to ultra-deep clastic rocks is an urgent problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to provide a quantitative evaluation method for the compaction strength of deep-ultra-deep clastic rocks, which can accurately and quantitatively evaluate the compaction strength of deep-ultra-deep clastic rocks.

[0007] To achieve the above objectives, in a first aspect, this application provides a method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks, comprising the following steps: S10, Obtain the basic geological parameters and experimental parameters of the deep-ultra-deep clastic reservoirs in the study area. The parameters include at least the burial depth, initial porosity, measured porosity data of overpressure-developed strata, and measured porosity data of grain-coated reservoirs. S20. Based on the acquired parameters, the porosity change rate of mechanical compaction and the porosity change rate of chemical compaction are calculated respectively, and the two are summed to obtain the total porosity change rate under ideal conditions, and then the porosity under ideal conditions is calculated. S30. The measured porosity data of the overpressure-developed strata are compared with the porosity under ideal conditions to calculate the contribution of overpressure to reservoir porosity. This contribution value is then used to correct the porosity under ideal conditions to obtain the overpressure-corrected porosity. Next, the measured porosity data of the particle-coated reservoirs are compared with the porosity under ideal conditions to calculate the contribution of particle coating to reservoir porosity. This contribution value is then used to correct the overpressure-corrected porosity again to obtain the actual porosity. S40, based on the initial porosity, actual porosity, and burial depth, calculate the compaction porosity reduction rate and residual porosity retention rate; S50 compares the calculated compaction porosity reduction rate and residual porosity retention rate with the three-level quantitative grading standard that uses compaction porosity reduction rate and residual porosity retention rate as dual indicators to evaluate and determine the compaction intensity level.

[0008] As a further preferred embodiment, in step S10, the basic geological parameters and experimental parameters also include geothermal gradient, effective formation stress, consolidation modulus, elastic modulus, initial particle viscosity, initial temperature, particle activation energy, minimum porosity for pure mechanical compaction, and lower limit of residual porosity.

[0009] As a further preferred embodiment, in step S20, the calculation of the mechanical compaction porosity change rate adopts a piecewise function considering the effective stress threshold, and the specific calculation formula is as follows:

[0010] Among them, compaction coefficient Based on whether the effective stress σ exceeds the maximum effective stress Divided into two sections:

[0011] In the formula, t is the geological time; σ is the effective stress of the formation; The initial porosity of the reservoir sand body is dimensionless. The minimum porosity achievable only through mechanical compaction; It is the consolidation modulus; It is the elastic modulus; This represents the maximum effective stress reached by the sediment during its geological history.

[0012] As a further preferred embodiment, in step S20, the calculation of the chemical compaction porosity change rate adopts a functional model that considers the coupling relationship between temperature and particle viscosity, and the specific calculation formula is as follows:

[0013] in, ; In the formula, This represents the current porosity of the reservoir. The viscosity of sand particles at temperature T; To accommodate the residual porosity of the compacted sandstone; The viscosity of the sand particles at the initial temperature To; R is the particle activation energy; T is the gas constant; T is the formation absolute temperature. Z represents the initial absolute temperature; Z represents the reservoir burial depth. This represents the geothermal gradient.

[0014] As a further preferred embodiment, in step S20, the porosity change rate of mechanical compaction and the porosity change rate of chemical compaction are summed to obtain the total porosity change rate under ideal conditions. Then, based on the initial porosity of the reservoir... As an initial boundary condition, the total porosity change rate is integrated over burial time to obtain the ideal porosity corresponding to each burial stage. Thus, the porosity under ideal conditions is obtained, specifically using the following calculation formula: .

[0015] As a further preferred embodiment, in step S30, the specific method for calculating and correcting the contribution of overpressure to reservoir porosity is as follows: the measured porosity data of the overpressure-developed layer is compared with the porosity under ideal conditions to obtain Δ. Then, according to the correction formula +Δ Calculate the porosity after overpressure correction, where Porosity after overpressure correction Calculate porosity for the ideal model.

[0016] As a further preferred embodiment, in step S30, the specific method for calculating and correcting the contribution of particle coating to reservoir porosity is as follows: the measured porosity data of the particle-coated reservoir is compared with the porosity under ideal conditions to obtain Δ. Then, according to the correction formula +Δ Calculate the actual porosity, where The porosity is the porosity after overpressure and particle coating correction, which is the actual porosity of the study area.

[0017] As a further preferred embodiment, in step S40, the specific formulas for calculating the compaction porosity reduction rate V and the residual porosity retention rate P are as follows:

[0018]

[0019] In the formula, Residual porosity retention rate; This represents the actual porosity.

[0020] As a further preferred embodiment, in step S50, the three-level quantitative grading standard specifically refers to: When the compaction porosity reduction rate V < 1% / 100m and the residual porosity retention rate P > 30%, it is evaluated as weak compaction; When the compaction porosity reduction rate V satisfies 1% / 100m ≤ V ≤ 2% / 100m and the residual porosity retention rate P satisfies 15% ≤ P ≤ 30%, it is evaluated as medium compaction; When the compaction porosity reduction rate V > 2% / 100m and the residual porosity retention rate P < 15%, it is evaluated as strong compaction.

[0021] Secondly, this application provides a quantitative evaluation system for the compaction strength of deep-ultra-deep clastic rocks, used to implement the method described in any one of the above, comprising: The parameter acquisition module is used to acquire the basic geological parameters and experimental parameters of the deep-ultra-deep clastic reservoirs in the study area. The parameters include at least the burial depth, initial porosity, measured porosity data of overpressure-developed strata, and measured porosity data of grain-coated reservoirs. The model building module is used to calculate the porosity change rate of mechanical compaction and the porosity change rate of chemical compaction based on the acquired parameters, and sum the two to obtain the total porosity change rate under ideal conditions, and then calculate the porosity under ideal conditions. The correction module compares the measured porosity data of overpressure-developed strata with the porosity under ideal conditions, calculates the contribution of overpressure to reservoir porosity, and uses this contribution value to correct the porosity under ideal conditions to obtain the overpressure-corrected porosity. Then, it compares the measured porosity data of grain-coated reservoirs with the porosity under ideal conditions, calculates the contribution of grain coating to reservoir porosity, and uses this contribution value to further correct the overpressure-corrected porosity to obtain the actual porosity. The index calculation module is used to calculate the compaction porosity reduction rate and the residual porosity retention rate based on the initial porosity, actual porosity, and burial depth. The grading and evaluation module is used to compare the calculated compaction porosity reduction rate and residual porosity retention rate with the three-level quantitative grading standard that uses compaction porosity reduction rate and residual porosity retention rate as dual indicators to evaluate and determine the compaction intensity level.

[0022] The beneficial effects of this application are as follows: This application provides a quantitative evaluation method for the compaction intensity of deep-ultra-deep clastic rocks. This method takes a mechanical-chemical compaction coupling model as its core, incorporates a complete set of quantitative calculation formulas for porosity change rate, and combines actual stratigraphic factors such as overpressure and particle encapsulation to correct the model. At the same time, it establishes a quantitative grading standard for compaction intensity based on compaction porosity reduction rate and residual porosity retention rate. This method can achieve accurate, systematic, and quantitative evaluation of the compaction intensity of deep-ultra-deep clastic rock reservoirs, solving the problems of low evaluation accuracy, large deviation from actual geological conditions, lack of quantitative formula support, and lack of standardized grading system of traditional methods. It provides scientific and reliable technical basis and parameter support for the diagenetic evolution analysis of deep-ultra-deep clastic rock reservoirs, the identification of high-quality reservoirs, and the selection of favorable exploration target areas. Attached Figure Description

[0023] Figure 1 This is a flowchart of the quantitative evaluation method for compaction intensity of deep-ultra-deep clastic rocks provided in this application; Figure 2This application provides an embodiment of the comprehensive compaction evolution curves for the superposition of mechanical and chemical compaction in the deep-ultra-deep clastic reservoirs of the Shawan Depression. Among them, A is the compaction evolution curve under different geothermal gradients, B is the compaction evolution curve under ideal conditions and overpressure development conditions, C is the compaction evolution curve under ideal conditions and grain-coated development conditions, and D is the compaction evolution curve under ideal conditions and actual multi-factor superposition conditions. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0025] This application develops a quantitative evaluation method for the compaction intensity of deep to ultra-deep clastic rocks based on coupled mechanical-chemical compaction calculations, correction for actual formation factors, and quantitative classification of compaction intensity. The overall implementation process is described in [link to implementation details]. Figure 1 This method achieves a full-process quantitative evaluation of compaction intensity through multi-dimensional parameter acquisition, multi-formula coupling calculation, multi-factor comprehensive correction, and multi-index quantitative grading. The specific technical solution consists of three core steps: acquisition and standardized assignment of basic geological and experimental parameters of the study area → construction of a mechanical-chemical compaction coupled porosity evolution model and correction of actual stratigraphic factors → quantitative grading and comprehensive evaluation of compaction intensity. Each step is accompanied by clear quantitative calculation formulas and operating procedures.

[0026] Step 1: Acquisition and Standardization of Basic Geological and Experimental Parameters for the Study Area This step forms the foundation of the entire quantitative evaluation method. Through experimental analysis, geological data collection and processing, and other means, it comprehensively obtains geological experimental parameters of the deep to ultra-deep clastic reservoirs in the study area. Based on the geological characteristics of the study area, it standardizes and assigns values ​​to these parameters, providing a complete and accurate parameter basis for subsequent model construction and formula calculations. The specific implementation content is as follows: First, comprehensive regional geological data, drilling data, logging data, and oil testing data of deep to ultra-deep clastic reservoirs in the study area were collected to determine basic geological parameters such as reservoir burial depth (Z), geothermal gradient (Ga), effective formation stress (σ), and formation pressure coefficient. Then, through core sampling and interactive experiments using a polarizing microscope, initial porosity was calculated based on grain size probability curves, and the residual porosity (φ) of the reservoir sand bodies was measured. The basic rock physics parameters, such as consolidation modulus (Ec) and elastic modulus (Ee), are determined to ensure the accuracy and representativeness of the parameter data. Then, systematic rock and mineral property tests are conducted, using equipment such as polarizing microscopy and laser particle size analyzers to obtain the initial particle viscosity of the sand body. Mineral activation energy ( Key experimental parameters such as chlorite particle coating content, detrital particle composition and content were collected; measured porosity, measured permeability, pressure coefficient and other overpressure-related parameters of overpressure-developed strata in the study area were statistically analyzed, as well as the petrological characteristics of sand bodies of different strata and different sedimentary microfacies, to establish a complete experimental parameter database.

[0027] (Note: Initial porosity calculation formula using the particle size probability curve method:)

[0028]

[0029] In the formula: This is the particle size separation coefficient; , The cumulative content of particles is 25. 75 Corresponding particle size; (This represents the initial porosity.) Subsequently, based on the regional geological characteristics, reservoir petrological characteristics, and diagenetic evolution laws of the study area, the core parameters required for the compaction porosity reduction model were standardized and assigned values, including consolidation modulus (Ec), elastic modulus (Ee), and initial particle viscosity (Ec). ), initial temperature (T°), geothermal gradient (Ga), activation energy ( Based on the parameter variation patterns under different geological conditions, a compaction and hole reduction parameter assignment table (see Table 1) was established for the study area. This clarifies the parameter value standards under different geological scenarios, providing unified and standardized parameter data for subsequent formula calculations and model construction.

[0030] Table 1. Parameter Assignment Table for Compaction Calculation Formula

[0031] Where a, b, and c represent three sets of standardized parameters under low, medium, and high geothermal gradient backgrounds, respectively. Except for the different values ​​of the geothermal gradient (Ga), the initial porosity ( Minimum porosity for pure mechanical compaction ( ), Lower limit of residual porosity ( ), consolidation modulus (Ec), initial particle viscosity ( ), initial temperature (T°), particle activation energy ( The rock physical and mechanical parameters are kept consistent to highlight the control effect of geothermal gradient on chemical compaction and overall porosity evolution. Group a represents the low geothermal gradient parameter group (Ga=20℃ / km), applicable to cold basin areas such as the Shawan Depression in the Junggar Basin; Group b represents the medium geothermal gradient parameter group (Ga=35℃ / km), applicable to oil and gas basins with conventional geothermal backgrounds; and Group c represents the high geothermal gradient parameter group (Ga=50℃ / km), applicable to hot basins and areas with intense tectonic thermal activity. In practical applications, the corresponding parameter group is selected and assigned values ​​based on the actual geothermal field characteristics of the study area. This allows for accurate quantitative calculation of the compaction intensity of deep to ultra-deep clastic rocks under different thermal backgrounds, significantly improving the method's versatility and applicability. Step 2: Construction of a coupled mechanical-chemical compaction porosity evolution model and correction based on actual formation factors. The porosity change rate of mechanical compaction and chemical compaction was calculated separately using a complete set of quantitative calculation formulas. A basic porosity evolution model coupling the two was then constructed. Finally, two actual stratigraphic factors, overpressure and particle coating, were introduced to make multi-dimensional corrections to the basic model, ultimately yielding a porosity evolution curve that closely reflects the actual geological conditions of the study area. This curve accurately reflects the compaction evolution law of deep to ultra-deep clastic reservoirs with burial depth. The specific implementation details are as follows: (1) Construct a basic model for porosity evolution based on mechanical-chemical compaction coupling. Using the total porosity change rate of reservoir sand bodies as the core evaluation index, this paper couples the porosity change rates caused by mechanical compaction and chemical compaction to establish a basic quantitative model for the porosity evolution of deep-ultra-deep clastic reservoirs. The core calculation formula is as follows:

[0032] In equation (1), The change rate of total porosity of reservoir sand bodies is dimensionless. The porosity change rate caused by mechanical compaction alone is dimensionless. The porosity change rate caused by chemical compaction alone is dimensionless.

[0033] ① Quantitative calculation of porosity change rate during mechanical compaction The change rate of porosity during mechanical compaction is calculated using a piecewise function that considers the effective stress threshold, accurately reflecting the intensity of mechanical compaction at different effective stress stages. The calculation formula is as follows:

[0034] In equation (2), t is the geological time, Ma; σ is the effective stress of the formation, MPa; β(σ) is the compaction coefficient related to the effective stress, dimensionless; The effective stress is the rate of change over geological time, expressed in MPa / Ma.

[0035] The compaction coefficient β(σ) depends on whether the effective stress exceeds the threshold ( The maximum effective stress (MPa) reached by sediments during geological history is divided into two segments:

[0036] In equation (3), The initial porosity of the reservoir sand body is dimensionless. The minimum porosity achievable only through mechanical compaction, dimensionless; Here, denoted as consolidation modulus, is expressed in MPa. For elastic modulus, Gpa Ma.

[0037] ② Quantitative calculation of the change rate of porosity during chemical compaction A functional model considering the coupling relationship between temperature and particle viscosity was used to calculate the porosity change rate during chemical compaction, reflecting the controlling effect of the geothermal gradient on chemical compaction. The calculation formula is as follows:

[0038] In equation (4), The current porosity of the reservoir is dimensionless. Let Pa be the viscosity of the sand particles at temperature T. s; The residual porosity of the compacted sandstone is dimensionless. The viscosity of sand particles at temperature T The formulas for calculating the formation temperature T are as follows:

[0039]

[0040] In equation (5), The viscosity of the sand particles at the initial temperature To is Pa. s; R is the particle activation energy, kJ / mol; R is the gas constant, taken as 8.314 J / (mol). K); T is the absolute temperature of the formation; Let be the initial absolute temperature. In equation (6), The reservoir depth is expressed in km. The geothermal gradient is expressed in °C / km.

[0041] ③Quantitative model for overall compaction and reduced porosity By integrating the porosity change rate calculation formulas for mechanical compaction and chemical compaction, a quantitative model for overall compaction porosity reduction applicable to deep-ultra-deep clastic rock reservoirs is obtained. The calculation formula is as follows:

[0042] Equation (7) is the core formula of this application, which enables accurate quantitative characterization of porosity evolution under the coupling effect of mechanical-chemical compaction.

[0043] (2) Correction of actual stratigraphic factors The aforementioned basic model is a porosity evolution model under ideal geological conditions, which does not consider the effects of overpressure and particle coating on the modification and inhibition of compaction in actual strata. Therefore, it is necessary to introduce two core actual strata factors, overpressure and particle coating, to modify the basic model step by step, ensuring that the model calculation results closely match the actual geological conditions of the study area: Overpressure correction: Overpressure is a common geological phenomenon in deep to ultra-deep reservoirs, which can effectively inhibit compaction and slow down the rate of porosity reduction. By comparing and analyzing the measured porosity data of overpressure-developed strata in the study area with the porosity data calculated by the basic model formula, the actual contribution of overpressure to reservoir porosity (Δ) is calculated. Based on this contribution value, the porosity evolution curve of the basic model is corrected to obtain the porosity evolution curve after overpressure correction. The correction formula is as follows: +Δ

[0044] in Porosity after overpressure correction Calculate porosity for an ideal model; Granular coating correction: Granular coatings formed by minerals such as chlorite can create a protective layer on the surface of detrital particles, effectively resisting the compression of particles by compaction and reducing porosity loss. By comparing the measured porosity data of reservoirs with high coating content in the water layer of the study area with the porosity data calculated by the basic model formula, the actual contribution value (Δ) of granular coating to reservoir porosity was determined. Based on this contribution value, a secondary correction is performed on the curve after overpressure correction. The correction formula is as follows: +Δ

[0045] in The porosity is the porosity after overpressure and particle coating correction, which is the actual porosity of the study area.

[0046] After completing the overpressure and particle cladding corrections, the curves calculated by the basic model were superimposed and fused with the curves after the two corrections to obtain the actual porosity evolution curve of the study area. This curve, calculated using quantitative formulas and corrected for actual factors, can accurately reflect the dynamic evolution of porosity with burial depth in deep-ultra-deep clastic reservoirs under the coupled effects of mechanical-chemical compaction and the modification of actual formation factors, providing a core model basis for subsequent evaluation of compaction intensity.

[0047] Step 3: Quantitative Grading and Comprehensive Evaluation of Compaction Intensity This step is the output stage of the entire quantitative evaluation method. Based on the actual porosity evolution curve, it calculates the two core evaluation indicators of compaction intensity using quantitative formulas, establishes standardized quantitative grading standards, completes the grading and comprehensive evaluation of compaction intensity in the study area, and generates relevant result maps. This provides intuitive and specific technical guidance for exploration and development. The specific implementation content is as follows: (1) Quantitative calculation of core indicators of compaction strength Based on the actual porosity evolution curves of the study area, and combined with parameters such as reservoir burial depth (Z) and diagenetic evolution stage, data fitting and rate calculation methods were used to accurately calculate the two core indicators of compaction porosity reduction rate and residual porosity retention rate of clastic rock reservoirs at different burial depths, different stratigraphic positions, and different sedimentary microfacies in the study area using the following quantitative formulas:

[0048] In equation (8), V is the compaction rate for reducing pore size. / km (or / 100m (units can be converted according to research needs); Initial porosity, dimensionless; This represents the actual porosity, which is dimensionless. The depth is measured in km (or 100m).

[0049]

[0050] In equation (9), Residual porosity retention rate ; This represents the actual porosity, which is dimensionless. The initial porosity is dimensionless.

[0051] Among them, the compaction porosity reduction rate (V) reflects the intensity of the compaction effect; the higher the rate, the stronger the compaction effect. The residual porosity retention rate (P) reflects the degree of modification of reservoir properties by the compaction effect; the higher the retention rate, the less damage the compaction effect causes to the reservoir. The combination of the two achieves a comprehensive quantitative characterization of the compaction effect intensity.

[0052] (2) Grading standard for compaction strength Based on the actual needs of exploration and development of deep-ultra-deep clastic reservoirs in the study area, the physical property standards of high-quality reservoirs, and the diagenetic evolution characteristics, this study, through extensive statistical analysis of actual data, geological pattern analysis, and engineering requirement demonstration, determined the compaction porosity reduction rate V (porosity loss per unit depth, reflecting the intensity of compaction) and the residual porosity retention rate P (the ratio of current porosity to initial porosity, reflecting the degree of reservoir modification by compaction). Using the compaction porosity reduction rate (V) and the residual porosity retention rate (P) as dual indicators, a three-level quantitative grading standard for compaction intensity was established, clarifying the threshold values ​​for different levels of compaction, achieving precise grading and definition of compaction intensity. The grading results directly correspond to the physical properties and exploration value of the reservoirs (Table 2).

[0053] Table 2. Quantitative Grading Standards for Three Levels of Compaction Intensity

[0054] (3) Quantitative evaluation of compaction strength Based on the compaction intensity grading standard, and combined with drilling, logging, and geological data of the study area, geological mapping software was used to create a planar distribution map and a vertical evolution profile of the compaction intensity of clastic reservoirs in the study area. This visually demonstrates the distribution patterns of different compaction intensity levels in both the planar and vertical directions. Simultaneously, considering the actual physical properties and oil-bearing characteristics of the reservoirs, the correlation between different compaction intensity levels and the development of high-quality reservoirs was analyzed, clarifying the reservoir exploration value corresponding to different compaction intensity levels, and completing a comprehensive quantitative evaluation of the compaction intensity in the study area.

[0055] The beneficial effects of this application are as follows: The quantitative evaluation method for compaction intensity of deep-ultra-deep clastic rocks provided in this application constructs a complete and standardized quantitative evaluation system, incorporating a full set of quantitative calculation formulas and clear parameter definitions, effectively making up for the shortcomings of traditional methods and demonstrating significant application value. This method, for the first time, incorporates the dynamic coupling process of mechanical and chemical compaction into the evaluation model, establishing a coupling relationship between porosity and multiple parameters to achieve precise quantitative characterization of the compaction process, thus improving the scientific rigor and accuracy of the evaluation. It introduces formation factors such as overpressure and particle coating, and designs correction formulas to make the model results more closely reflect actual geological characteristics. A three-level quantitative grading standard is established, with compaction porosity reduction rate and residual porosity retention rate as the core, achieving a leap from qualitative to quantitative evaluation and providing a standardized evaluation system. Each step is clearly defined and parameters and thresholds can be flexibly adjusted, making it highly versatile and widely applicable to reservoir evaluation in different geological backgrounds. By drawing relevant charts, the spatial distribution of compaction is visually displayed, providing precise guidance for predicting high-quality reservoirs and selecting favorable exploration targets, reducing exploration and development risks. The complete set of formulas can be interfaced with geological numerical simulation software to achieve automated calculation and visual analysis, reducing labor costs and improving evaluation efficiency and accuracy, making it suitable for large-scale regional evaluation work.

[0056] The following is a specific implementation example of this application: This case study focuses on the deep to ultra-deep Permian-Triassic clastic reservoirs in the Shawan Depression, the central part of the Junggar Basin. This area is a typical cold basin with a low geothermal gradient of 20℃ / km. Well A is selected as the representative well. The target layer has a burial depth of 5000~8000m, falling into the deep to ultra-deep category. The reservoir is mainly composed of volcanic-rich lithic sandstone, commonly exhibiting overpressure and chlorite grain coatings, which highly aligns with the applicable scenario of this method. The specific formula application and implementation process are as follows: Step 1: Acquisition and Standardization of Basic Geological and Experimental Parameters for the Study Area Comprehensive geological, drilling, and logging data were collected from the Shawan Depression area. The study identified a geothermal gradient of 20℃ / km, a maximum reservoir depth of Z=7500m, and determined that the effective formation stress σ varies linearly with depth. The initial temperature of 20℃ (absolute temperature 293.15K) and the universal gas constant R=8.314J / (mol·K) were also determined. Laboratory experiments were conducted using core samples to determine the initial reservoir porosity. =45 Minimum porosity of pure mechanical compaction =25 Lower limit of residual porosity =2 Consolidation modulus Ec=10MPa, elastic modulus, initial particle viscosity and particle activation energy =15kJ / mol, and combined with thin section observation and mercury porosimetry, it was determined that the chlorite particle coating content was 0.5%. ~5 The pressure coefficient of the overpressure layer is 1.2~1.5. The measured porosity and permeability data of reservoirs at different depths in Well A are statistically analyzed and a complete parameter database is constructed. Finally, combined with the low geothermal gradient characteristics of the study area, parameter group a in Table 1 is selected to complete the standardized assignment of all parameters, and the units of each parameter are unified to match the constraints of the calculation formula, so as to determine the basis for the quantitative calculation of the subsequent porosity evolution model.

[0057] Step 2: Construction of a mechanical-chemical compaction coupled porosity evolution model (1) Calculation of porosity change rate under ideal conditions of mechanical compaction Set the effective stress threshold for mechanical compaction in the study area =80MPa (corresponding to a burial depth of approximately 4000m), the mechanical compaction porosity change rate is calculated in segments according to formulas (2) and (3): when the burial depth is <4000m, ≤ The compaction coefficient β(σ) = 1 / Ee = 0.1. Substituting this into equation (2) yields: = 0.1 When the burial depth is greater than 4000m, > Compaction coefficient β(σ) = Substituting into equation (2), we get: .

[0058] Using the above formula, the porosity loss caused by mechanical compaction alone at different burial depths was calculated. Mechanical compaction at depths shallower than 4000m is the dominant factor in porosity loss, while the effect of mechanical compaction at depths deeper than 4000m decays rapidly.

[0059] (2) Calculation of porosity change rate under ideal conditions of chemical compaction The chemical compaction porosity change rate is calculated according to equations (4) to (6), taking a burial depth of 6000m as an example: Formation temperature: Substituting into equation (6), =140° (corresponding to an absolute temperature of 413.15K); Particle viscosity: Substitute into equation (5), (413.15K) = 50 The particle viscosity at this burial depth was calculated. ( = 1.26 GPa·Ma; Chemical compaction porosity change rate: Sets the current porosity at this depth. =15 > =2 Effective stress of formation =120MPa, substituting into equation (4) yields: = This clearly demonstrates that deep chemical compaction has become the dominant factor in porosity loss.

[0060] (3) Mechanical-chemical compaction coupled overall model Substituting the above mechanical and chemical compaction calculation results into the core equation (7), the total porosity change rate at different burial depths was obtained, and the porosity evolution curve under ideal conditions was plotted. Calculations showed that under ideal, unmodified conditions, the Shawan Depression reservoir reaches the lower porosity limit at a depth of 7500m, with a residual porosity of only 2%. It basically loses its storage performance, corresponding to Figure 2 The fundamental curve of the ideal model.

[0061] (4) Correction of actual stratigraphic factors Overpressure correction: Measured porosity data from the overpressure-developed strata (6500~7000m) in Well A were selected and compared with the porosity calculated using the ideal model to calculate the contribution value Δ of overpressure to porosity. =5 The initial correction was completed using the correction formula, resulting in the porosity evolution curve after overpressure correction. Figure 2Middle B; Particle coating correction: Measured porosity data from reservoirs with high coating content in the Karamay Formation aquifer were selected and compared with the overpressure-corrected curve to determine the contribution value Δ of chlorite particle coating to porosity. =3 The final correction was completed using a secondary correction formula, yielding the actual porosity evolution curve after double correction by overpressure and particle coating, corresponding to... Figure 2 C.

[0062] By overlaying and fusing the ideal model curve, the overpressure correction curve, the particle coating correction curve, and the final actual porosity evolution curve, the porosity evolution results of the Shawan Depression reservoir throughout its entire burial cycle are obtained. The corrected model predicts that the lower limit of reservoir porosity can be extended to depths of over 8000m. Figure 2 D.

[0063] Step 3: Quantitative Grading of Compaction Intensity Calculation of core evaluation indicators: Based on the final corrected actual porosity evolution curve, the compaction porosity reduction rate V and residual porosity retention rate P of reservoirs at different burial depths are calculated according to Equations 8 and 9. Taking a burial depth of 7000m as an example, the actual porosity at this depth is... =8 Substituting into equation (8), we get (i.e. 0.53) / 100m), substituting into equation (9) yields Compaction strength grading: Based on the physical property standards of high-quality reservoirs in the study area (porosity ≥5). (Permeability ≥ 0.1 mD), establish a three-level classification standard: strong compaction (V > 2) / 100m, P<15 ), medium compaction (1) / 100m≤V≤2 / 100m, 15 ≤P≤30 Weak compaction (V < 1) / 100m, P>30 Evaluations indicate that the shallow reservoirs below 7000m in the Shawan Depression are mainly moderately to weakly compacted, representing a favorable interval for the development of high-quality reservoirs; the overall depth above 7000m is mainly strongly compacted, but the area where overpressure and grain cladding develop simultaneously is still weakly compacted, representing the core exploration target area for ultra-deep reservoirs.

[0064] Step 4: Quantitative evaluation of compaction strength Based on the above full-process formula calculations, parameter corrections, and evaluation results, through Figure 2 Evolution curve of combined compaction effects of mechanical and chemical compaction in deep-ultra-deep clastic reservoirs in the Shawan Depression: Figure 2A represents the compaction evolution curves under different geothermal gradients, reflecting the control process of geothermal gradient on the overall compaction process; Figure 2 B. The evolution curves of compaction under ideal conditions and under overpressure development conditions illustrate the inhibitory effect of overpressure on compaction. Figure 2 The evolution curves of compaction under ideal conditions and under conditions of particle coating development illustrate the inhibitory effect of particle coating on compaction. Figure 2 D represents the compaction evolution curve under ideal conditions and the compaction evolution curve under actual multi-factor superposition conditions (overpressure and particle coating superposition). This application fully presents the deep-ultra-deep compaction process, which can intuitively and quantitatively evaluate the comprehensive compaction intensity, providing intuitive technical guidance for oil and gas exploration in this area.

[0065] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks, characterized in that, Includes the following steps: S10, Obtain the basic geological parameters and experimental parameters of the deep-ultra-deep clastic reservoirs in the study area. The parameters include at least the burial depth, initial porosity, measured porosity data of overpressure-developed strata, and measured porosity data of grain-coated reservoirs. S20. Based on the acquired parameters, the porosity change rate of mechanical compaction and the porosity change rate of chemical compaction are calculated respectively, and the two are summed to obtain the total porosity change rate under ideal conditions, and then the porosity under ideal conditions is calculated. S30. The measured porosity data of the overpressure-developed strata are compared with the porosity under ideal conditions to calculate the contribution of overpressure to reservoir porosity. This contribution value is then used to correct the porosity under ideal conditions to obtain the overpressure-corrected porosity. Next, the measured porosity data of the particle-coated reservoirs are compared with the porosity under ideal conditions to calculate the contribution of particle coating to reservoir porosity. This contribution value is then used to correct the overpressure-corrected porosity again to obtain the actual porosity. S40, based on the initial porosity, actual porosity, and burial depth, calculate the compaction porosity reduction rate and residual porosity retention rate; S50 compares the calculated compaction porosity reduction rate and residual porosity retention rate with the three-level quantitative grading standard that uses compaction porosity reduction rate and residual porosity retention rate as dual indicators to evaluate and determine the compaction intensity level.

2. The method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks as described in claim 1, characterized in that, In step S10, the basic geological parameters and experimental parameters also include geothermal gradient, effective formation stress, consolidation modulus, elastic modulus, initial particle viscosity, initial temperature, particle activation energy, minimum porosity for pure mechanical compaction, and lower limit of residual porosity.

3. The method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks as described in claim 1, characterized in that, In step S20, the calculation of the mechanical compaction porosity change rate adopts a piecewise function considering the effective stress threshold, and the specific calculation formula is as follows: Among them, compaction coefficient Based on whether the effective stress σ exceeds the maximum effective stress Divided into two sections: In the formula, t is the geological time; σ is the effective stress of the formation; The initial porosity of the reservoir sand body is dimensionless. The minimum porosity achievable only through mechanical compaction; It is the consolidation modulus; It is the elastic modulus; This represents the maximum effective stress reached by the sediment during its geological history.

4. The method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks as described in claim 1, characterized in that, In step S20, the calculation of the chemical compaction porosity change rate adopts a functional model that considers the coupling relationship between temperature and particle viscosity. The specific calculation formula is as follows: in, ; In the formula, This represents the current porosity of the reservoir. The viscosity of sand particles at temperature T; To accommodate the residual porosity of the compacted sandstone; The viscosity of the sand particles at the initial temperature To; R is the particle activation energy; T is the gas constant; T is the formation absolute temperature. Z represents the initial absolute temperature; Z represents the reservoir burial depth. This represents the geothermal gradient.

5. The method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks as described in claim 1, characterized in that, In step S20, the porosity change rate of mechanical compaction and the porosity change rate of chemical compaction are summed to obtain the total porosity change rate under ideal conditions. Then, based on the initial porosity of the reservoir... As an initial boundary condition, the total porosity change rate is integrated over burial time to obtain the ideal porosity corresponding to each burial stage. Thus, the porosity under ideal conditions is obtained, specifically using the following calculation formula: 。 6. The method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks as described in claim 1, characterized in that, In step S30, the specific method for calculating and correcting the contribution of overpressure to reservoir porosity is as follows: the measured porosity data of the overpressure-developed layers are compared with the porosity under ideal conditions to obtain Δ. Then, according to the correction formula +Δ Calculate the porosity after overpressure correction, where Porosity after overpressure correction Calculate porosity for the ideal model.

7. The method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks as described in claim 1, characterized in that, In step S30, the specific method for calculating and correcting the contribution of particle coating to reservoir porosity is as follows: the measured porosity data of the particle-coated reservoir is compared with the porosity under ideal conditions to obtain Δ. Then, according to the correction formula +Δ Calculate the actual porosity, where The porosity is the porosity after overpressure and particle coating correction, which is the actual porosity of the study area.

8. The method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks as described in claim 1, characterized in that, In step S40, the specific formulas for calculating the compaction porosity reduction rate V and the residual porosity retention rate P are as follows: In the formula, Residual porosity retention rate; This represents the actual porosity.

9. The method for quantitatively evaluating the compaction strength of deep-ultra-deep clastic rocks as described in claim 1, characterized in that, In step S50, the three-level quantitative grading standard is specifically as follows: When the compaction porosity reduction rate V < 1% / 100m and the residual porosity retention rate P > 30%, it is evaluated as weak compaction; When the compaction porosity reduction rate V satisfies 1% / 100m ≤ V ≤ 2% / 100m and the residual porosity retention rate P satisfies 15% ≤ P ≤ 30%, it is evaluated as medium compaction; When the compaction porosity reduction rate V > 2% / 100m and the residual porosity retention rate P < 15%, it is evaluated as strong compaction.

10. A quantitative evaluation system for the compaction strength of deep-ultra-deep clastic rocks, characterized in that, To implement the method of any one of claims 1 to 9, comprising: The parameter acquisition module is used to acquire the basic geological parameters and experimental parameters of the deep-ultra-deep clastic reservoirs in the study area. The parameters include at least the burial depth, initial porosity, measured porosity data of overpressure-developed strata, and measured porosity data of grain-coated reservoirs. The model building module is used to calculate the porosity change rate of mechanical compaction and the porosity change rate of chemical compaction based on the acquired parameters, and sum the two to obtain the total porosity change rate under ideal conditions, and then calculate the porosity under ideal conditions. The correction module compares the measured porosity data of overpressure-developed strata with the porosity under ideal conditions, calculates the contribution of overpressure to reservoir porosity, and uses this contribution value to correct the porosity under ideal conditions to obtain the overpressure-corrected porosity. Then, it compares the measured porosity data of grain-coated reservoirs with the porosity under ideal conditions, calculates the contribution of grain coating to reservoir porosity, and uses this contribution value to further correct the overpressure-corrected porosity to obtain the actual porosity. The index calculation module is used to calculate the compaction porosity reduction rate and the residual porosity retention rate based on the initial porosity, actual porosity, and burial depth. The grading and evaluation module is used to compare the calculated compaction porosity reduction rate and residual porosity retention rate with the three-level quantitative grading standard that uses compaction porosity reduction rate and residual porosity retention rate as dual indicators to evaluate and determine the compaction intensity level.

Images