Core Test Research Articles

Full-scale field test study of bearing characteristics of post-grouting pile for offshore wind turbines

Full-scale load tests were conducted on a combined steel pipe and bored pile foundation used for offshore wind turbine in Fuqing Xinghua Bay. Due to the complex geological conditions of the project, lengthening the bored pile will cause it to exceed the steel pipe pile so much that there are construction risks such as collapsed holes, hence, combined tip-and-side post-grouting was used to improve the bearing characteristics of the pile foundations. The results of double-level O-cell bi-direction tests before and after grouting on test pile SZ32 are reported. Comparing the test results before and after grouting shows that post grouting can significantly enhance the bearing capacity of the pile foundations. Furthermore, the relative displacement required to mobilize the shaft resistance of the test pile is significantly reduced by the post grouting craftwork. Additionally, the core samples obtained from the coring tests showed that the cement grout was distributed from 0.5 D below the pile tip to 5.3 D above the pile tip, respectively. Finally, the results could be applied to similar foundation design used in offshore wind turbine.

Evaluation of the impact of low-salinity water on wettability alteration and oil recovery in Berea sandstones

Low-salinity water (LSW) flooding is an emerging technique to enhance oil recovery from carbonate and sandstone reservoirs. Despite growing interest in the field, significant disparities remain regarding the underlying mechanisms. While most researchers agree that wettability alterations may be the dominant mechanism, their quantitative impact on oil recovery remains elusive. This study quantitatively evaluated the effects of LSW flooding on rock wettability alteration and oil recovery enhancement using a non-polar crude through a series of U.S. Bureau of Mines (USBM) tests and contact angle measurements on synthetic clay-free Berea samples with similar textural properties and pore structures. Experimenting on clay-free samples and non-polar crude evaded the effects of (i) mineral dissolution, (ii) interfacial tension reduction due to in-situ saponification, and (iii) wettability alteration due to multi-ion exchange between clays and the crude-oil polar compounds. When water salinity varied from 85,000 to 4,000 ppm, the USBM index increased from approximately 0.26 to 0.38, thereby confirming a minor change in wettability alteration toward a more water-wet condition. These changes were consistent with a decrease in the contact angle from approximately 55.6° to 35.3°. As water salinity decreased to approximately 5 % of its original value, centrifuge data indicated a drop in the residual oil saturation from 0.247 to 0.202, corresponding to a minor increase (of approximately 4 %) in the oil recovery factor at the end of the forced imbibition cycle. This slight oil recovery enhancement is consistent with the minor wettability alterations observed in this study. However, the relatively large recovery factor values reported in the literature were not reproduced in this experiment. The reported findings of this study concerning the evaluation of wettability alteration and recovery factor improvement caused by LSW flooding are unique because they (i) are based on reproducible measurements obtained using state-of-the-art ultrahigh-speed rock centrifuge and core test system that simultaneously measures capillary pressure, evaluates rock wettability, and generates relative permeability data, and (ii) are focused on clean sandstones.

Effect of Rheological Properties of Polymer Solution on Polymer Flooding Characteristics.

Polymer flooding is an appropriate enhanced oil recovery (EOR) process that can increase macroscopic sweep efficiency. We examined two polymeric superpushers at different salinities (10,000 and 42,000 ppm of NaCl and 18,000 ppm of CaCl2) and temperatures (30 to 75 °C) as polymer-flooding agents for the EOR process. Rheological and thixotropic tests were attempted to find shear viscosity change when the polymer solutions were introduced under different salinity and temperatures, followed by describing the rheological behavior with the two most common rheological models used for polymer solutions, and then a quadratic model with Design-Expert to detect the effective parameters. Core flooding tests were conducted afterward to determine the final proposed fluid. An increase in the concentration of monovalent ions and the addition of divalent ions adversely affected both types of polymers used, which was similar to the effects of a temperature increase. The Flopaam 3630S at 1000 ppm has more stability under harsh conditions and enables 22% and 38% oil recovery in carbonate and sandstone core rocks, respectively. Consequently, Flopaam 3630S can be the perfect polymer agent for different chemical flooding procedures in high-salinity oil reservoirs.

Geomechanical brittleness index prediction for the Marcellus shale exploiting well-log attributes

Geomechanical brittleness of tight formations calculated from Poisson's Ratio with Young's Modulus requires laboratory testing of cores and/or estimation from shear wave acoustic logs. In shale exploitation budgets are not available to provide those measurements in many wells and it is desirable to estimate a geomechanical brittleness index (BIg) from a basic, often limited, suite of available well logs. BIg helps field operators to select the most prospective sections of tight rocks that are likely to benefit most from fracture stimulation. A machine-learning (ML) approach that combines a few recorded well logs with derivative and volatility attributes calculated from that recorded data is applied to two wellbores that penetrate the Middle Devonian formations (Appalachian Basin). This technique is novel as it has not been previously applied to predict BIg. The results demonstrate that ML models involving just two or three recorded well logs plus selected attributes as input variables provide BIg predictions that are as accurate as ML models that involve three and five recorded well logs as input variables, respectively. Moreover, the ML models involving attributes are as generalizable as ML models based only on multiple recorded well logs when applying models trained with data from one well to predict BIg from well log data in another nearby well. Extreme gradient boosting and elastic net models provide the lowest BIg prediction errors when the trained models are applied to log data from another well. Feature importance analysis identifies that the recorded compression sonic log, bulk density and gamma ray, in that order, are the most influential features in the BIg prediction models applied to the two Marcellus Shale wells. However, two of calculated well-log attributes (moving averages of the well-log derivative and volatility) are particularly effective at improving the BIg predictions when used in combination with just those three recorded well logs. The technique is worth testing in other shale basins.

Selecting EOR Polymers through Combined Approaches-A Case for Flooding in a Heterogenous Reservoir.

This work uses micromodel, core floods and Field-Flow Fractionation (FFF) evaluations to estimate the behaviour and key elements for selecting polymers to address heterogenous reservoirs. One of the approaches was to construct two-layered micromodels differing six times in permeability and based on the physical characteristics of a Bentheimer sandstone. Further, the impacts of injectivity and displacement efficiency of the chosen polymers were then assessed using single- and two-phase core tests. Moreover, FFF was also used to assess the polymers' conformity, gyration radii, and molecular weight distribution. For the polymer selection for field application, we weighted on the good laboratory performance in terms of sweep efficiency improvement, injectivity, and propagation. Based on the results, polymer B (highest MWD) performed the poorest. Full spectrum MWD measurement using Field-Flow Fractionation is a key in understanding polymer behavior. Heterogenous micromodel evaluations provided consistent data to subsequent core flood evaluations and were in alignment with FFF indications. Single-phase core floods performed higher injection velocities (5 m/d) in combination of FFF showed that narrower MWD distribution polymers (polymers A and C) have less retention and better injectivity. Two-phase core floods performed at low, reservoir representative velocities (1 ft/d) showed that Polymer B could not be injected, with pressure response staying at high values even when chase brine is injected. Adsorption values for all tested polymers at these conditions were high, however highest were observed in the case of polymer B. Overall, for the polymer selection for field application, we weighted on the good laboratory performance in terms of sweep efficiency improvement, injectivity, polymer retention, and propagation; all accounted in this work.

Are Coal-Hosted Gallium-Rich Ores Elastically Detectable: A Rock-Physics Modeling Perspective

Coal-hosted gallium-rich ores are mainly explored with geochemical analyses, and their elasticities lack research. This paper incorporated core testing, rock-physics modeling, and Monte Carlo simulations to characterize the elastic parameters of gallium-rich cores and discuss whether coal-hosted gallium-rich ores are elastically detectable. The measured cores from No. 6 coal in the Heidaigou mine showed that the gallium contents strongly correlate to the boehmite contents with a 0.96 correlation coefficient. The rock-physics modeling results showed that mineral compositions and contents are critical factors influencing elastic parameters, and elastic parameters in No. 6 coal showed profound heterogeneities as mineral compositions and contents. The preferred parameters for classifying and grouping different mineral-rich cores are the bulk modulus and moduli ratio. Cross-plotting bulk modulus vs. moduli ratio can qualitatively group measured cores and Monte-Carlo simulated realizations into different mineral-rich and saturation states properly. Concerning the factors of boehmite content, porosity, and saturation state, an interpretation template for boehmite-rich coal was proposed and used. As the template interpreted readings close to the measured contents, the built templates can quantitatively interpret boehmite and gallium contents in coal-hosted ores with high precision. In summary, the coal-hosted gallium-rich ores are elastically detectable.

Characterization of the Carbonate Reservoir Unit A of the Upper Triassic Kurra Chine Formation in the well SH-4, Shaikan Oilfield, Iraqi Kurdistan Region, Using Wireline Log Data

Unit A of Kurra Chine Formation has been studied in the well Shaikan - 4 (SH-4) at Shaikan Oilfield in Northern Iraqi Kurdistan Region. The available conventional wireline log data and the existed core test values have been used to characterize the reservoir properties of the studied unit and to determine the flow efficiency of the reservoired fluids. The dolomite and anhydrite dominated lithology of the studied unit contains low percentages of shale except the upper most part of the unit in which shale content exceeds 30%. The porosity is less than 5% in most parts of the unit and secondary porosity comprises less than 4% of the total porosity in some horizons. The shale content consists primly of Illite and Chlorite and distributes in a dispersed pattern. Hydrocarbons are exist almost along the studied unit in saturations exceeding 70% at the middle and lower part of the unit. No effective permeable intervals observed at the upper part of the unit, whereas permeable zones of greater than 70mD are observed at the lower part. Three reservoir units distinguished in Kurra Chine A unit based on variations in shale content, porosity, and permeability. The studied unit contains four distinctive types of Hydraulic Flow Units (HFU) of less than 2.0, 20-5.5, 5.5-10, and greater than 10 Flow Zone Indicator (FZI) values. The calculated net to gross pay ratio for the studied Kurra Chine A Unit appeared to be about 28% representing the collective 52m net pay to the 184m gross thickness of the studied A Unit.

A novel polymer gel with high-temperature and high-salinity resistance for conformance control in carbonate reservoirs

Plugging agents have been widely used to enhance oil recovery in fractured-vuggy carbonate reservoirs. However, the harsh conditions of fractured-vuggy carbonate reservoirs yield a significant challenge in maintaining a long-term stabilization of plugging agents. In this work, we developed an anti-high-temperature and high-salinity polymer gel (APG) with excellent resistance to high temperature (140 °C) and ultra-high salinity (240000 mg/L). The rheology and microstructure of APG were characterized before and after gelation. Core plugging tests on fractured cubic cores were conducted to quantify the plugging performance of the gel system. Experimental results showed that the Sclerglucan and Cobalt (II) Chloride Hexahydrate filled the three-dimensional (3-D) network with various morphologies, providing extra protection to the cross-linking points of the 3D network structure of APG and thus, leading to a prolongation of the dehydration time. The dehydration rate of APG was only 5% within 30 days, and the strength of APG could be maintained at a rigid or near-rigid level over 150 days. Moreover, APG exhibited satisfactory shear and scour resistance. Core plugging tests showed that APG could achieve a plugging rate of 90% and demonstrate ignorable minor damage to the substrate. Our results indicate that APG can serve as a great candidate in channel plugging in fractured-vuggy carbonate reservoirs where fractures are fully developed.

Development of Ternary Inorganic Binder System for Manufacturing High-Functional Ceramic Molds and Core

In existing ceramic mold manufacturing processes, inorganic binder systems (Si-Na, two-component system) are applied to ensure the effective firing strength of the ceramic mold and core. These inorganic binder systems makes it possible to manufacture a ceramic mold and core with high dimensional stability and effective strength. However, as in general sand casting processes, when molten metal is injected at room temperature, there is a limit to the production of thin or complex castings due to reduced fluidity caused by the rapid cooling of the molten metal. In addition, because sodium silicate generated through the vitrification reaction of the inorganic binder is converted into a liquid phase at a temperature of 1,000 °C. or higher, it is somewhat difficult to manufacture parts through high-temperature casting. Therefore, in this study, a high-strength ceramic mold and core test piece with effective strength at high temperature was produced by applying a Si-Na-Ti three-component inorganic binder. The starting particles were coated with binary and ternary inorganic binders and mixed with an organic binder to prepare a molded body, and then heat-treated at 1,000/1,350/1,500 °C to prepare a fired body. In the sample where the two-component inorganic binder was applied, the glass was liquefied at a temperature of 1,000 °C or higher, and the strength decreased. However, the firing strength of the ceramic mold sample containing the three-component inorganic binder was improved, and it was confirmed that it was possible to manufacture a ceramic mold and core via high temperature casting.

Relationship between Cross-Sectional Area and Function of Core Muscles: An MRI Study

Background Particular attention has been paid to the core muscles because they serve as a muscular corset that works as a unit to stabilize the body and spine. Training programs for improving core stability often target improving core strength and endurance. Increased muscle size is also an expected effect of training programs. However, the relationship between core muscle cross-sectional area (CSA) and strength, stability, and clinical core test scores has not been identified. Purpose To investigate the relationship between core muscle CSA and muscle functions (strength, endurance, and stability). Study design A cross-sectional study Methods Fifty healthy participants (24 men, 26 women) participated in this study. The CSA of core muscle was measured using MRI. Maximal isometric trunk flexor strength, endurance, the score of double leg loading test were used to measure core muscle function. The relationship between core muscle CSA and muscle function was examined by Pearson’s correlation coefficient and Spearman rho correlation coefficient. Results Maximal isometric trunk flexor strength and side bridge strength were positively correlated with core muscle CSA. The isometric endurance test scores also showed a positive correlation with core muscle CSA except for the score of trunk flexor endurance test. Conclusions Only core strength showed moderate to excellent correlation with core muscle CSA. These findings indicate that core training to achieve muscle hypertrophy could lead to improved core strength but not core endurance.

Calculation of oil saturation in clay-rich shale reservoirs: A case study of Qing 1 Member of Cretaceous Qingshankou Formation in Gulong Sag, Songliao Basin, NE China

The targeted reservoir, which is referred as the first member of Cretaceous Qingshankou Formation in Gulong Sag, Songliao Basin, NE China, is characterized by the enrichment of clay and lamellation fractures. Aiming at the technical challenge of determining oil saturation of such reservoir, nano-pores were accurately described and located through focused ion beam scanning electron microscopy and quantitative evaluation of minerals by scanning electron microscopy based on Simandoux model, to construct a 4D digital core frame. Electrical parameters of the shale reservoir were determined by finite element simulation, and the oil saturation calculation method suitable for shale was proposed. Comparison between the results from this method with that from real core test and 2D nuclear magnetic log shows that the absolute errors meet the requirements of the current reserve specification in China for clay-rich shale reservoir. Comparison analysis of multiple wells shows that the oil saturation values calculated by this method of several points vertically in single wells and multiple wells on the plane are in agreement with the test results of core samples and the regional deposition pattern, proving the accuracy and applicability of the method model.

Study on Maintenance and Test Method of Primary Equipment in modern substation

In the modern social and economic development, residents and industry more and more high demand for electricity utilization, electricity quality requirements increase, so in order to ensure the safety and stability operation of substation, to strengthen the supervision of power system at the same time, attach importance to an equipment maintenance and test work, and integrate the past problem effective prevention measures are put forward. In substation work state, a device as a foundation for the application of grid design content, practice quality directly affect the efficiency and safety of power grid, so this article in the understanding of modern substation operation condition, on the basis of an equipment and maintenance according to the common sense, key research with computer technology platform as the core equipment maintenance and testing methods, This provides an effective basis for ensuring the long-term development of electric power enterprises.

Tri-level Framework for Realistic Estimation of Concrete Strength Using Bayesian Data Fusion of UPV and Guided Coring

Identification of in situ concrete characteristic strength (CCS) of deteriorating RC structures directly affects their rehabilitation. Contemporary practices lack the ability to yield CCS or at most produce an unrealistic estimate, because: (i) core tests are few due to technical and economic constraints and their positioning is random, inducing bias in the strength estimate, (ii) non-destructive tests (NDT) are themselves not good estimators of project specific strength, (iii) tests are only local indicators and most practising engineers are unaware of how to process the spatial variability. This paper overcomes these limitations with a novel and implementable framework, for an asset manager to make scientific estimates of CCS. This is a tri-level framework: (1) NDT are performed to capture the spatial variability of the investigated concrete; (2) core extractions are guided by the prior NDT information, to avoid bias in test location selection; (3) NDT and coring results are fused via Bayesian NDT test calibration and updating of the probability distribution of the concrete strength. The proposed framework is successfully implemented for the assessment and rehabilitation of a critical hospital complex in India.

From a crisis of results to a crisis of wellbeing – education reform and the declining sense of school belonging in Sweden

ABSTRACT In response to declining results in the Programme for International Student Assessment (PISA) surveys, the then governing Swedish coalition in 2010–2014 introduced earlier grading, more extensive national testing and a new standards-based curriculum. These reforms coincided with a greater emphasis on inclusive’ education understood in the ‘narrow’ sense of placement in mainstream schools. The combination of these two sets of reforms presents an interesting national case where traditional conservative demands for a core curriculum, testing and accountability were combined with calls to increase educational opportunity. Combining different methods and analysis of five separate waves of PISA data, we show that the reforms coincided with a decline in the sense of school belonging among pupils that was exceptional compared to other high-income countries, and especially among marginalised pupils. The study adds to the cumulative work of previous studies on policy effects on wellbeing, concluding that the Swedish compulsory school went from undergoing a mediatised results crisis to a mental health crisis among pupils.

Design, Verification and Testing of Comprehensive Serial Peripheral Interface

Synchronous serial interfaces are frequently employed to offer cost-effective board-level interfaces between various devices, including microcontrollers, DACs, ADCs, and others. Components that are compatible with SPI and Microwire are made by numerous IC makers. An interface called Serial Peripheral Interface (SPI) makes it easier to send synchronous serial data. In master/slave mode, data frames are initiated by the master device. With a separate slave choose line, multiple slave devices are permitted. It is necessary to guarantee that the given hardware design operates as intended and produces the desired outcomes. The design phases would need to be repeated after the functional flaws were discovered. Verification is thus a process that is time and money efficient. Due to this, a strong testbench structure is required, one that includes large broad verification elements that are easily extensible across designs and are extensively reusable. To gain good control over stimulus creation, functional coverage, and other factors, an industry standard verification technique is needed. The primary goal of this work is to design the Master SPI Core and use System Verilog to validate the code. Serial Peripheral Interface of symmetrical structure was synthesized using Cadence genus, and then simulated using Questa IDE. The testing of the SPI core was done by inserting the scan chains using the Cadence Genus tool and finally the code coverage of the SPI core was captured using the Questa IDE. Keywords: SPI, Coverage, Protocol, I2C, Functional Verification

Experimental Study for the Comparison between Core, Schmidt and Cubic Concrete Compressive Strength After Durability Test

Estimating the compressive strength of concrete exposed to different environmental conditions is an essential parameter in judging the quality of concrete and proving its ability to perform as planned. There are various destructive (DT) and non-destructive (NDT) methods for estimating compressive strength. Some NDT and DT procedures, such as Schmidt hammer and core testing, have been used for estimating concrete strength for a long time. These methods consider indirect and predicted tests to evaluate concrete strength in existing structures. Various factors influence these tests, so it is difficult to precisely assess the hardened concrete strength. Thus, this research aims to identify a coherent relationship that connects the results of these tests and correlates them with the results of cube compressive strength by assessing data from laboratory tests conducted under control and durability conditions using statistical techniques. To achieve this purpose, three grades of concrete were considered C250, C450, and C600 Kg/cm2. Six concrete cubes of size (15x15x15 cm) and four concrete columns of size (30x15x50 cm) were cast for each grade and tested to assess the cube, Schmidt hammer, and core compressive strength of concrete. Half of the columns and cubes were cured in drinking water (control condition) and the other half of the samples were subjected to durability cycles for 92 days (durability condition). In the durability condition, the samples were exposed to 10% sodium sulfate solution for a day, placed in a water tank for a day, heated to 100°C at a laboratory furnace for a day and then left at average laboratory temperature for a day to finish one cycle. The results were tabulated and graphed to notice any differences between DT, NDT and cube compressive strength tests. The results showed that the cube strength is higher than the core strength for all grades of concrete under control and durability conditions. The cube test indicates a lower compressive strength than the Schmidt hammer test method at grade C250 under control condition and greater compressive strength in the rest of the grades.

Automatic Inverse Analysis of Asphalt Pavement Field Aging Based on System Identification

Field aging significantly accelerates distresses (fatigue cracking, water damage, etc.) of asphalt pavements due to exposure to the natural environment. Conventional studies explore field aging by laboratory tests of field cores, while little work is devoted to the inverse analysis of aging by nondestructive tests (e.g., falling weight deflectometer (FWD) test). To backcalulate the aging parameters accurately and automatically, an inverse analysis method of asphalt pavement field aging was proposed based on System Identification (SID) in this study. In this inverse procedure, a kinetics-based two-reaction field aging model was employed as the theoretical aging model and the parameter adjustment algorithm was developed based on sensitivity analysis. Fifty sections from four different climate zones in Long Term Pavement Performance (LTPP) database were selected for investigation, where backcalculated moduli from LTPP and field aging temperatures determined by a pavement hourly temperature model were utilized. The results indicated that SID was feasible to inversely analyze the field aging of asphalt pavements automatically with high accuracy and efficiency. To investigate the factors affecting aging parameters, the multiple linear regression analysis and one-dimensional sensitivity analysis were performed. Among those variables, shortwave radiation and cloud cover showed the dominant effects on field aging resistance.

Strength Characteristics and In Situ Stress Measurement of Rock Cores from a Large Section Underground Station: A Case Study

Chongqing is a mountain city in western China with a complex geological environment, which brings many difficulties to the construction of large sections of underground projects. In order to avoid serious problems in the construction of Guobo Station with large sections, intensive coring and laboratory tests were carried out to obtain the rock mass properties in detail. The boreholes reveal that the lithology of the rock mass in the project area consists mainly of mudstone and a small area of sandstone. The uniaxial compressive strength (UCS) and the Brazilian tensile strength (BTS) of mudstone are highly scattered, which are 4.43~42.43 MPa and 0.66~4.30 Mpa, respectively, but they all show a lognormal distribution. The average UCS of sandstone is 65.31 MPa, and the BTS is 3.06 MPa. Meanwhile, the softening coefficients of mudstone and sandstone are 0.33 and 0.73, which indicate that the water content has a great influence on the mechanical properties of the rock. For the in situ stress field, the relationship between the three principal stresses is as follows: the maximum horizontal principal stress > minimum horizontal principal stress > vertical principal stress, and the lateral pressure coefficient is 2.11~5.71. Based on the present experimental results, it is proposed that the potential risks of excavation include: (1) bias pressure (2) high in situ stress; (3) surrounding rock deterioration.

Quantitative evaluation on the effectiveness of fault-block traps in the K Gas Field, Xihu Sag of East China Sea Shelf Basin

Fault-block gas reservoirs are dominated in the K Gas Field, Xihu Sag, East China Sea Shelf Basin. Research on the effectiveness of fault-block traps is lacking. A quantitative method for the evaluation on the effectiveness of fault-block traps has been developed in the study. Based on the core test, logging and geophysical data, detailed depiction and trap effectiveness research were conducted on the pools of the gas field. Anticline traps, lithological traps and mudstone-correspondent traps are effective traps with high probability of reservoir formation, while sandstone-correspondent traps are the least effective with 35% probability of effective traps. Twenty-one drilling wells in the K Gas Field show that when the fault displacement pressure is less than the reservoir displacement pressure, the trap is non-effective, which matches the result 92% of traps without oil and gas. On the contrary, the trap is effective, which matches the result 100% of gas reservoirs. The discrimination diagram of fault-block trap effectiveness can quickly identify trap effectiveness and contribute to fault-block oil and gas exploration in K Gas Field. The method has a wide application potential for the exploration of fault-block reservoirs in other areas.

Study on the evaluation method and application of logging irreducible water saturation in tight sandstone reservoirs

Abstract Taking into consideration the difficulties in predicting the properties of liquid production and evaluating the irreducible water saturation of low-porosity and ultra-low-permeability sandstone reservoirs, the relationships between the irreducible water saturation and logging reservoir evaluation parameters are explored based on a large number of core mercury injection experiment. When the permeability cumulative contribution value reaches 99.9%, the lower limit of pore throat radius is determined as 0.025 μm and the corresponding irreducible water saturation is more accurate. The experimental results of 77 samples in the research area showed that the irreducible water saturation has a good correlation with the median pore throat radius which has a good correlation with the porosity. The irreducible water saturation is consistent with the nuclear magnetic experiment results. Therefore, a new method to determine the irreducible water saturation based on logging data is established. The application results of this method in tight sandstone reservoirs in the Keshen area show that the fluid types identified by the relationship between the calculated irreducible water saturation and total water saturation are consistent with the actual test results, which confirms the accuracy and feasibility of this method. This method solves the problem of irreducible water saturation evaluation in low-porosity and ultra-low-permeability sandstone reservoirs. In the field or other situations where core testing is lacking, accurate irreducible water saturation can be obtained based on only porosity. It also lays a foundation for further improving the prediction accuracy of fluid properties, which has broad application prospects.