Characteristics Of Rocks Research Articles

Mechanical behavior and energy characteristics of red sandstone with different seawater immersion heights under biaxial compression

Rock structures engineered during undersea mining are typically subjected to varying water distributions due to the motion of seawater, which considerably influences their stability. Hence, it is essential to understand the influence of seawater distribution on the mechanical behavior and energy characteristics of rocks. In this study, biaxial compression tests were conducted on red sandstone at various seawater immersion heights, and acoustic emission signals during compression were monitored. The results illustrate that the mechanical properties of the red sandstone deteriorate significantly upon seawater immersion. With an increase in seawater immersion height, the peak strength and elastic modulus of the rock specimens decreased exponentially. When the seawater immersion height was varied from 0 to 1/4 H under lateral stresses of 5, 10, 15, and 20 MPa, the peak strength decreased by 18.94%, 20.29%, 17.47%, and 14.87%, respectively, and the elastic modulus decreased by 4.6%, 8.1%, 11.7%, and 10.9%, respectively. Brittleness also decreased gradually. During compression, the acoustic emission (AE) and accumulated AE counts exhibited a stationary phenomenon, first increasing slowly and then suddenly. However, the AE counts decrease with increasing seawater immersion height. Meanwhile, with increasing seawater immersion height, the proportion of tensile cracks gradually increased and that of shear cracks gradually decreased. As the seawater immersion height increased, both the peak total input strain energy and peak total elastic strain energy decreased, whereas the peak total dissipated strain energy exhibited the opposite trend.

Damage evolution and fracture characteristics of coal rock impacted by self‐excited pulse water jet under different stress loading conditions

AbstractIn this paper, based on smoothed‐particle hydrodynamics‐finite element method, numerical models of plunger squeezing water at a sinusoidal velocity were established to simulate self‐excited pulse water jet (SEPWJ). RHT constitutive model was adopted to describe the damage and failure of coal rock impacted by water jet. The morphological evolutions of broken pits and timeliness of rock‐breaking efficiency of SEPWJ and continuous water jet (CWJ) under the conditions with and without stress loadings were obtained and compared. The evolution laws of damage and stress inner coal rock induced by jet impact, and the failure mechanism were revealed. And the influences of different stress loading magnitudes on the fracture characteristics of coal rock were investigated. The results show that the morphologies of broken pits formed by self‐excited pulse jet undergo changes in a semi‐circular, U‐shaped, V‐shaped, and bullet shaped in sequence under the stress‐free loading condition. When applying one‐dimensional (1D) and 2D stress loadings, the shallow but wide broken pits with laminar main cracks along the stress loading direction and the inverted trapezoidal bowl broken pits are formed, respectively. With the increase of 1D stress, the depth and width of broken pits slightly decrease as a quadratic parabolic function and linearly increase, respectively. And the broken pit width and area both show an exponential slow decreasing trends with the increasing 2D stress. SEPWJ can induce higher stresses to cause the earlier occurrence of initial damage and the shorter duration of damage accumulation to coal rock than CWJ, which leads to a better rock‐breaking effect. The surface and deeper coal rock elements are broken mainly due to compressive shear stresses. The 2D stress loading delays the initial damage occurrence and prolongs the damage accumulation duration due to inhibitory effect of stress loading on jet impact.

Water Quality of Unconfined Aquifer in Universitas Negeri Malang Following the Drinking Water Quality Standard of Indonesian Ministry of Health

The quality of groundwater is naturally determined by water-bearing rock characteristics. However, the progression of civilian activities also negatively affects the groundwater quality. Therefore, this study aims to assess the physical, chemical, and biological characteristics of groundwater in the Universitas Negeri Malang (UM) campus area in Indonesia and evaluate its compliance with drinking water quality standards, particularly the Class A standard. A comparative descriptive strategy was utilized in the study by involving groundwater in the campus area of UM. The focus of the research is water quality in unconfined aquifer. Through purposive sampling, 12 wells were selected to ensure appropriate spatial dispersion. Water samples were collected in sample bottles and tested for physical, biological, and chemical properties. These water quality tests were carried out in the Perum Jasa Tirta I Malang. Water quality data were analyzed qualitatively, descriptively, and comparatively. This study concludes that (1) the groundwater on the UM campus generally meets the physical criteria for drinking water quality standards; (2) the chemical quality of the groundwater on the UM campus still satisfies the drinking water quality standards; and (3) biologically, the free groundwater on the UM campus fails to meet drinking water quality standards. The novelty of this research is that the biggest threat to the quality of free groundwater in the campus area is bacterial contamination from sanitation activities. Accordingly, it is recommended that groundwater is boiled before being utilized for drinking water purposes to neutralize the E. coli bacteria present in all well water samples.Keywords: Water Quality; Unconfined Aquifer; The Drinking Water; Quality Standard

A micro-macro mechanism of hydraulic fracturing with initial stress state effect of brittle rock

The external initial stress state seriously affects the hydraulic fracturing process of rocks. However, the external initial stress effect on the mechanical relationship between the hydraulic pressure and the internal microcrack extension in brittle rocks is rarely studied. This paper proposes a micro-macro mechanical model for predicting the hydraulic fracturing process of brittle rock under compressive stress. Based on the correlation of the stress intensity factor at the tip of the extended micro-cracks, the hydraulic pressure, and the force characteristics of the cracks inside the brittle rock, the evolution law of the hydraulic pressure with the wing crack length is determined. The effects of confining pressure, axial pressure, stress difference, initial crack angle, initial crack length, initial crack density and rock fracture toughness on the hydraulic initiation stress and peak stress are discussed. The rationality of hydraulic fracturing models is verified by experimental comparison. With the increase of axial pressure, stress difference, fracture toughness, initial crack length and initial crack density, the hydraulic initiation and peak stress of rock decrease, and with the increase of confining pressure and fracture toughness, the hydraulic initiation stress and peak stress of rock increase. The study results optimize the parameters such as pre-crack angle, pre-crack length, and external loading conditions based on rock characteristics. It helps to grasp the progress of hydraulic fracturing according to the nature of rock and the degree of hydraulic pressure change, improve the efficiency of hydraulic fracturing, and enhance economic benefits.

Pore-scale study on the permeability characteristics of fractured rock under hydraulic-chemical coupling

Pore-scale study on the permeability characteristics of fractured rock under hydraulic-chemical coupling

Provenance of cretaceous sediments in the West Kunlun piedmont belt and implications for tectonic evolutionary events

The West Kunlun orogenic belt located in the northwestern margin of the Qinghai-Tibet Plateau is an important record of the formation and northward extension of the plateau, but the current research mainly focuses on the tectonic activities of the Cenozoic era, and there is still considerable controversy regarding the formation and evolutionary history of pre-Cenozoic orogenic belts. This study focuses on Cretaceous sandstone samples from the Kedong region in the piedmont belt of the West Kunlun orogenic belt. U-Pb geochronological analysis was performed on 200 detrital zircon grains from the core samples. Combined with stratigraphic data and previous research, the main provenance direction was investigated to constrain the tectonic evolutionary history of the orogenic belt’s peripheral regions. The results show that the detrital zircons are aged from 290 to 208 Ma, 520–310 Ma, 810–580 Ma, 1,400–880 Ma and 2,548–1,730 Ma, reflecting the complexity of provenance in this area. Based on a comprehensive analysis of the characteristics of igneous rocks, zircon age composition and stratigraphic conditions in potential source areas, it is concluded that the primary source regions include the East Kunlun orogenic belt and the North and South Kunlun terranes, with a low likelihood of contributions from within the Tarim Basin. The evolution of the West Kunlun orogenic belt can generally be divided into two opening and two closing phases. The detrital zircon ages predominantly exhibit two peak values at 259 Ma and 459 Ma, respectively representing the ages of transition from oceanic crust subduction to continent-continent collision for the Paleo-Tethys Ocean and the Proto-Tethys Ocean. Additionally, there is a temporal gap between the evolution of the Proto-Tethys Ocean and the Paleo-Tethys Ocean. The Triassic period marks a transitional phase in tectonic evolution, shifting into an intracontinental evolutionary stage. This study provides new geochronological evidence for the early developmental history of the West Kunlun orogenic belt.

Jurassic Source Rock Characteristics and Resource Evaluation in Junggar Basin

Jurassic Source Rock Characteristics and Resource Evaluation in Junggar Basin

Methods of Pore Structural Characterisation of Sedimentary Rocks and Their Constituent Minerals

Pore structural characterisation is important for rocks and their constituent minerals in order to understand physico-chemical processes occurring therein. Rather than a broad general survey of potential pore characterisation techniques, this review focuses on an in-depth discussion of some key current issues in this topic. A so-called ‘brute-force’ characterisation approach involving a single imaging modality is seldom possible for rocks due to their high degree of heterogeneity. This work surveys alternate strategies suitable for rocks. Further, this work addresses some misapprehensions and misunderstandings that have arisen concerning some experimental techniques offering alternate strategies to the brute-force approach, such as gas overcondensation and mercury porosimetry. It also considers some pore structural characterisation techniques, such as cryoporometry, that are seldom used in the context of natural materials and surveys their capabilities.

Damage evolution, acoustic emission and electromagnetic radiation of rock under uniaxial cyclic loading

Uniaxial cyclic loading compression experiments are conducted with synchronous monitoring of acoustic emission (AE) and electromagnetic radiation (EMR). The AE and EMR characteristics of rocks during cyclic loading are analyzed. Subsequently, the Kaiser and Felicity effects of AE and EMR are disclosed. Moreover, the b-value and fractal dimension are calculated to explore the cracking mechanism of rock materials. These results show that the AE and EMR are active during the 1st and 2nd loading cycles, and sparse during the 3rd and 4th loading cycles where the AE and EMR are only generated when the stress exceeds the previous peak stress due to the Kaiser effect. In the 5th loading cycle, AE and EMR accelerate and peak at rock failure. The variation of EMR-based FR is consistent with that for AE under cyclic loading. Hence, the FR associated with EMR is also well correlated with stress memory. The AE and EMR-based FR is greater than 1 in the 2nd-4th loading cycles, and less than 1 in the 5th cycle, indicating that FR can be used to reflect the damage evolution of rocks. The b-value and fractal dimension increase in the 1st-4th loading cycles, and turn to decrease in the 5th loading cycle. This pattern serves as a precursor to identify the rock failure.

Multifractal characteristics on pore structure of Longmaxi shale using nuclear magnetic resonance (NMR)

The efficient exploration and extraction of shale gas is essential for China's energy structure as a replacement for natural gas. In this research, shale samples from the Longmaxi Formation in Changning, Sichuan Province were investigated for their pore structure. To achieve this, X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) experiments were performed on the samples. Fractal theory was employed to characterize the pore structure and fractal features of the shale reservoirs. The fractal characteristics of reservoir rocks were correlated with physical parameters and mineral components to identify the controlling factors for the multifractal dimension. The results indicate the following: ① Quartz predominates in the mineral composition of shale in the study area, while clay minerals are the least abundant. ② The primary pore types observed in the samples are bound fluid pores, primarily controlled by mesopores (2 nm ≤ r ≤ 50 nm). ③ The calculated multifractal parameters show that the heterogeneous pore structure exhibits multifractal characteristics. ④ The low probability multifractal parameters Dmin-D0 and αmax-α0 were found to be negatively correlated with reservoir porosity, permeability, and clay mineral content, while the high probability multifractal parameters D0-Dmax and α0-αmin were found to be positively correlated with them. The comprehensive fractal characterization of reservoir rocks demonstrates the applicability of multifractal dimensions in characterizing the heterogeneity of shale reservoir pore structures, which holds potential promise for coal methane exploration.

Evolution of Pore Structure and Fractal Characteristics in Red Sandstone under Cyclic Impact Loading

Fatigue damage can occur in surface rock engineering due to various factors, including earthquakes, blasting, and impacts. The underlying cause for the variations in physical and mechanical properties of the rock resulting from impact loading is the alteration in the internal pore structure. To investigate the evolution characteristics of the pore structure under impact fatigue damage, red sandstone subjected to cyclic impact compression by split Hopkinson pressure bar (SHPB) was analyzed using nuclear magnetic resonance (NMR) technology. The parameters describing the evolution of pore structure were obtained and quantified using fractal methods. The development of the pore structure in rocks subjected to cyclic impact was quantitatively analyzed, and two fractal evolution models based on pore size and pore connectivity were constructed. The results indicate that with an increasing number of impact loading cycles, the porosity of the red sandstone gradually increases, the T2 cutoff (T2c) value decreases, the most probable gray value of magnetic resonance imaging (MRI) increases, the pores’ connectivity is enhanced, and the fractal dimension decreases gradually. Moreover, the pore distribution space tends to transition from three-dimensional to two-dimensional, suggesting the expansion of dominant pores into clusters, forming microfractures or even macroscopic fissures. The findings provide valuable insights into the impact fatigue characteristics of rocks from a microscopic perspective and contribute to the evaluation of time-varying stability and the assessment of progressive damage in rock engineering.

ANN-based evaluation system for erosion resistant highway shoulder rocks

Highway shoulder rocks are exposed to continuous erosion force due to extreme rainfall that could be caused by global warming to some extent. However, the logical design method for erosion-resistant highway shoulder is not well-researched yet. This study utilized a large-scale UNLETB (University of Nebraska Lincoln–Erosion Testing Bed) with a 7.6 cm nozzle width and a 4000 cm3/sec flow rate to study the erosion characteristics of highway shoulder rocks. Test results showed that different shoulder materials currently used had vastly diverse erosion resistance. However, the clear criteria between the erosion-resistant gradation and other gradation could not be determined easily. Then, this study trained ANN (Artificial Neural Network) with test results to conveniently distinguish the erosion resistance of rocks from other rocks. The ANN predicted the acceptable/non-acceptable erosion characteristics of shoulder rocks with close to 99% accuracy based on the three gradation parameters (D10, D30, and D60).

Integrating μCT imaging of core plugs and transfer learning for automated reservoir rock characterization and tomofacies identification

Traditional methods of core characterization are time-consuming and require the considerable effort of a large number of experts. At the same time, it is quite difficult to readily detect small but important elements in reservoir rocks, especially inside the core volume, that can have a strong impact on assessing reservoir potential and hydrodynamic properties. This research explores the integration of high-resolution micro-computed tomography (μCT) imaging and transfer learning for the automated characterization of reservoir rocks and tomofacies identification. The study involved collecting and marking a dataset containing 66,560 μCT images of 130 standard core plugs containing all major reservoir rock types. Using this dataset of 2D μCT images of core plugs, we applied convolutional neural networks (CNNs) pre-trained on ImageNet and fine-tuned them for rock classification tasks. Applying a transfer learning approach, we trained seven ResNet-50 models, which were able to identify and classify reservoir rock features in μCT images. These features included basic characteristics such as rock type, general texture, the presence of fractures and sulfidization that are common for all reservoir rocks. Further, depending on a specific rock type, individual features such as grain size, individual sedimentological texture and the presence of organic matter zones in the sample could be determined by the specialized model. The results show an average classification accuracy of over 94%, indicating the effectiveness of transfer learning in enhancing rock characterization. The obtained models demonstrated high validation rates and were organized into a workflow for automated rock feature characterization. A case study conducted on a carbonate core from a real oilfield provided a practical demonstration of the automated system's work, whose predictions were validated by traditional analyses such as X-ray diffraction and thin-section petrography. The produced models demonstrated the ability for rapid detection of subtle details that might otherwise have been missed during manual inspection. In addition, the concept of tomofacies resulting from the integration of μCT images and machine learning predictions has proven useful in highlighting different reservoir zones, allowing us to understand their heterogeneity and the ability to separate rock sections despite their apparent monotony. These findings suggest that the integration of μCT imaging and transfer learning is a promising approach for improving the automation and accuracy of reservoir rock characterization. The developed technique represents a significant advance in reservoir characterization, offering rapid and accurate identification of rock properties that can improve exploration and development strategies.

Study on the Damage Evolution and Failure Mechanism of Floor Strata under Coupled Static-Dynamic Loading Disturbance

In the field test, we found that the failure depth of the goaf floor strata tends to be further because the periodic breaking and caving of the immediate roof, upper roof, and roof key stratum has dynamic stress disturbance effects on the floor. To further analyze its formation mechanism, this paper studies the damage evolution and fracture mechanism of goaf floor rock under the coupled static-dynamic loading disturbance caused by roof caving, based on the stress distribution state, the damage evolution equation of coal measure rock, the damage constitutive model, and the fracture criterion of floor rock. The main conclusions are listed as follows: 1. Based on the mining floor stress distribution, the floor beam model establishes the response mechanism of floor rock stress distribution. Also, the equation of stress distribution at any position in floor strata under mining dynamic load is given. 2. Combining the advantages of Bingham and the Generalized-Boydin model, the B-G damage constitutive model is established, which can describe the constitutive characteristics of coal measure rock under the coupled static-dynamic loading disturbance well. Furthermore, the variation law of parameters changing with strain rate is analyzed. 3. According to the twin-shear unified strength yield theory and the B-G damage constitutive model, coal measure rock’s twin-shear unified strength damage fracture criterion is established. Finally, the stress distribution expression of floor strata under concentrated and uniform dynamic loads is introduced, and the fracture criterion of goaf floor strata under a coupled static-dynamic loading disturbance is proposed.

Geochronology, Geochemical Characterization and Tectonic Background of Volcanic Rocks of the Longjiang Formation in the Lengjimanda Plate Area, Middle Da Hinggan Mountains

The Lengjimanda plate is situated in the middle section of the Da Hinggan mountains, in the eastern section of the Tianshan Xingmeng orogenic belt. To determine the formation age of the volcanic rocks in the Longjiang formation in this area, to explore their origin and tectonic background, and to reconstruct the geodynamic evolution of the region, this study conducted petrological, zircon U–Pb geochronological, geochemical, and isotopic analyses of the volcanic rocks in the Longjiang formation. The Longjiang formation’s volcanic rocks are primarily composed of trachyandesite, trachyte trachydacite, and andesite, which are intermediate basic volcanic rocks. They are enriched in large-ion lithophile elements, are depleted in high-field-strength elements, are significantly fractionated between light and heavy rare earth elements, and exhibit a moderate negative Eu anomaly in most samples. The results of the LA–ICP–MS zircon U–Pb dating indicate that the volcanic rocks in this group were formed in the Early Cretaceous period at 129.1 ± 0.82 Ma. The zircon εHf(t) ranges from +1.13 to +43.77, the tDM2 ranges from +655 to +1427 Ma, the initial Sr ratio (87Sr/86Sr)i ranges from 0.7030 to 0.7036, and the εNd(t) ranges from +2.1 to +6.6. Based on the geochemical compositions and isotopic characteristics of the rocks, the initial magma of the volcanic rocks in the Longjiang formation originated from the partial melting of basaltic crustal materials, with a source material inferred to be depleted mantle-derived young crustal. These rocks were formed in a superimposed post-collisional and continental arc environment, possibly associated with the Mongol-Okhotsk Ocean closure and the oblique subduction of the Pacific plate. This study addresses a research gap regarding the volcanic rocks of the Longjiang formation in this area. Its findings can be applied to exploration and prospecting in the region.

A Time-Dependent Damage Constitutive Model for Brittle Rock Materials Based on Subcritical Damage Theory.

In the domain of geotechnical engineering, a profound understanding of the long-term mechanical deformation characteristics of rocks is indispensable for the design and construction of structures, dams, tunnels, and various engineering projects. The deformation behavior of rocks under long-term loads directly impacts the stability and safety of engineering structures. This study employs micromechanical methods to investigate the subcritical extension of microcracks under stress corrosion. By examining the accumulated damage resulting from this phenomenon, the research explores the patterns of aging damage development and establishes a constitutive model for aging that incorporates cumulative damage over the stress history. The accuracy of the proposed model is evaluated through a comprehensive comparison of numerical results with experimental data. The experimental data set encompasses traditional triaxial compression tests, single-stage creep, multistage creep, and single-stage relaxation tests conducted under varying confining pressures. The predicted results exhibit strong consistency with the entire data set. Furthermore, this paper employs crack damage stress as an indicator characterizing the long-term strength of rock. Through frictional damage coupling analysis and derivation, an analytical expression for the long-term strength of rock materials containing microcracks is provided, serving as a theoretical basis for investigating the long-term mechanical performance of brittle rock materials and ensuring the long-term stability of large-scale rock engineering projects.

Quantification of artificially induced microcracks and their effects on hard rock fragmentation performance and mechanical response characteristics

Microcracks have a significant effect on the physical and mechanical properties of rocks. Inducing artificial microcracks in rocks can reduce rock strength and decrease the energy required for rock fragmentation. Nevertheless, few attempts have been made to investigate the effect of microcracks on rock fragmentation performance and mechanical behavior, especially from the perspective of microcrack quantification. For this end, we heated granite samples to induce different degrees of microcracks. However, the parameters of microcracks are difficult to control. For the purpose of accurately characterizing the distribution of microcracks, we measured the microcrack parameters in detail. We visualized microcracks using the fluorescent epoxy method and quantified the microcrack parameters by image processing. Such a method suffered at the expense of losing some of the extremely small microcracks. But, on the other hand, a much larger field of view area is assured, allowing the data to be more representative. After the quantification of microcracks, we performed indentation tests on samples containing microcracks to analyze the mechanical response of tool-rock interaction and crater parameters. The results show that the lengths of individual thermally induced microcracks are distributed between 0.2 and 1.1 mm. At higher temperatures, thermal microcracks are dominated by intragranular microcracks leading to a more uniform distribution. The presence of microcracks can affect the fracture characteristics of rocks and a threshold exists. Compared with the unheated sample, a fivefold increase in the density and total length of microcracks reduces the peak force by 88% and 54%, and the absorbed energy by about 90% and 68%, respectively. Additionally, the comprehensive parameter (i.e., fractal dimension) is not an effective parameter in analyzing microcracks, and a single absolute metric (e.g., crack density, length, number, etc.) is recommended. This study is expected to provide a new perspective to understanding the relationship between microcrack parameters and rock fragmentation, and to provide a reference for applied research on new drilling techniques.Our study enhances the efficiency of drilling in hard rocks for geothermal resources by elucidating the role of microcracks in rock fragmentation. This research aligns with the goals of sustainable and cost-effective subsurface engineering, contributing to a net-zero energy future.

Spatial and temporal evolution of magmatic arcs: Geochemical diversity and tectonic controls

We review the main petrologic and geochemical features of magmatic rocks from continental arcs compared to their intra-oceanic equivalents. Both types share a number of characteristics, including their typical HFSE-depleted incompatible element patterns and isotopic Sr, Nd, Pb and Hf features, intermediate between those of N-MORB and continental crust. They are thought to derive from the partial melting of the mantle wedge metasomatized by fluids emanating from the downgoing plate. They are dominantly hydrous fluids provided by the breakdown of amphibolites and antigorite serpentinites, but a significant role is attributed to felsic hydrous melts derived from oceanic metabasalts and associated sediments. The more enriched character of magmas from continental arcs with respect to those from intra-oceanic arcs is ascribed to their genesis from a less depleted mantle wedge in a milder thermal regime, to the enrichment of their source via subduction erosion of the continental margin, and finally to their contamination during ascent and storage within a thicker crust.

Precise pose control of shaft boring machine considering the characteristic of stratum

The shaft boring machine (SBM) is innovatively applied to shaft engineering with depth and large diameter for the advantages of efficiency, adaptability, and safety. The manual and rough pose control of SBM blocks the improvement of engineering quality and efficiency. This article presents a precise pose control method for SBM considering the characteristics of strata. The kinematic model of SBM and the mechanical-hydraulic-rock coupled dynamic model of grippers actuator are established considering the characteristics of different surrounding rock, respectively. A test rig is established to validate these models. The stratum-adapted double-layer controller is designed for the pose control from the practical aspects, including the deviation and inclination of the SBM center. The upper layer devotes to the kinematic planning between pose and displacement of grippers. The linear active disturbance rejection control (LADRC) method is used to control each gripper in the lower layer. The compensation control strategy is proposed to improve the reliability of the system under the different strata conditions. The stratum-adapted property is validated with the simulation of different surrounding rock characteristics. The control test under hard rock condition is performed with the test rig. The results indicate that the displacement control error of the single gripper cylinder is less than 1.8%, and the corresponding control error of deviation and inclination angle of the SBM center is less than 2.1% and 2.3% respectively. The proposed method can cover the precise pose control under different strata conditions, and it can be applied in the shaft infrastructure construction practically.

Numerical simulation of residual oil distribution characteristic of carbonate reservoir after water flooding

Carbonate reservoirs are characterized by abundant reserves and are currently focal points for development in oil and gas producing regions such as the Ahdab oilfield, Tarim Basin, Sichuan Basin, and Ordos Basin. The primary method for exploiting carbonate reservoirs is waterflooding. However, due to the complex pore structure and pronounced heterogeneity of carbonate rocks, the waterflooding process often leads to an unclear distribution of remaining oil and low waterflooding recovery efficiency, significantly impacting the stable and high production of carbonate reservoirs. This paper presents a two-phase flow model of oil and water in distinct pore structures by integrating fluid flow equations and interface tracking equations. It visually represents the waterflooding process at the pore scale, elucidates the distribution and formation mechanism of remaining oil, and discusses the mechanism of microscopic displacement efficiency change. The study reveals that: 1) After waterflooding, the distribution patterns of remaining oil can be categorized into dead-end remaining oil, pressure balance remaining oil, wall-bound remaining oil, Jamin effect remaining oil, and water-encapsulating remaining oil, which are governed by microscopic pore structure, wettability, and preferential flow paths; 2) From the perspective of actual reservoir displacement efficiency, intergranular pores > intergranular dissolved pores > visceral foramen > mould pore, with this trend being more pronounced under hydrophilic wetting conditions; 3) Given the oil-wet to strong oil-wet wettability characteristics of these carbonate rocks, capillary forces pose significant resistance during waterflooding. The conclusion underscores the importance of leveraging the reservoir’s microscopic pore structure and wettability characteristics for actual oil wells, elucidating the evolutionary law of the mechanical mechanism of oil-water interface advancement, clarifying oil-water percolation characteristics at the pore scale, and understanding the microscopic displacement physical mechanism, all of which are crucial for guiding the design of schemes aimed at enhancing reservoir recovery efficiency.