Rock Surface Area Research Articles

Retention profiles of multiparticle filtration in porous media

A one‐dimensional deep bed filtration model of a polydisperse suspension or colloid in a porous medium is considered. The model includes a quasilinear system of 2n equations for concentrations of suspended and retained particles of n types. The problem is reduced to a closed 3 × 3 system for total concentrations of suspended and retained particles and of occupied rock surface area, which allows an exact solution. The exact solution to the n‐particle problem is derived, the existence and uniqueness of the solution are proven, and the solution in the form of a traveling wave is obtained. The retention profiles (dependence of the deposit concentration on the coordinate at a fixed time) of different size particles and the total profile are studied. It is shown that the profile of large particles decreases monotonically, while the profile of small particles is nonmonotonic. Conditions for the monotonicity/nonmonotonicity of the intermediate particle profiles and the total profile are obtained. The maximum point of the small particles profile tends to infinity with unlimited growth of time, and the maximum points of nonmonotonic profiles of intermediate particles are limited. The asymptotical expansion of the maximum points of nonmonotonic profiles is constructed.

Chemical enhanced oil recovery under Harsh conditions: Investigation of rock permeability and insights from NMR measurements

Injecting surfactant into a hydrocarbon reservoir stands out as a highly effective method for EOR due to its ability to reduce water/oil IFT and alter rock wettability in certain cases. However, the efficiency of this process is compromised in heterogeneous reservoirs, especially carbonates, characterized by significant permeability variations. This study presents findings from three core flooding experiments on heterogeneous carbonate core samples with different permeabilities. The experiments were conducted under representative reservoir conditions of 100 °C, pressures higher than 3000 psi, and seawater salinities and formation water of 57,745 ppm and 213,768 ppm, respectively. In each experiment, seawater was continuously injected followed by continuously injecting a 2500-ppm solution of in-house synthesized Gemini surfactant. Results revealed that the recovery factor was highest in low-permeability rocks and lowest in high-permeability rocks for both seawater and surfactant floods. Surfactant floods yielded additional recoveries of 31%, 23%, and 19% for low, medium, and high-permeability samples, respectively. Nuclear magnetic resonance (NMR) analysis on short analogous core plugs at different flooding stages confirmed these results. Effluent analysis on the produced aqueous phase indicated that dynamic retention was highest (0.467 mg/gm-rock) in the lowest permeability and lowest (0.146 mg/gm-rock) in the highest permeability rock. NMR analysis suggested that the surfactant's recovery performance and dynamic retention were influenced by the larger surface area of low-permeability rocks, facilitating increased contact with the surfactant. Utilizing NMR monitoring in this work enhances EOR insights through integrated studies and coreflooding experiments and establishes a novel framework for complex reservoir conditions.

Full-Scale Pore Structure Characterization and Its Impact on Methane Adsorption Capacity and Seepage Capability: Differences between Shallow and Deep Coal from the Tiefa Basin in Northeastern China

Deep low-rank coalbed methane (CBM) resources are numerous and widely distributed in China, although their exploration remains in its infancy. In this work, gas adsorption (N2/CO2), mercury intrusion porosimetry, and 3D CT reconstruction were performed on five coal samples of deep and shallow low-rank coal from northeast China to analyze their pore structure. The impact of the features in the pore structure at full scale on the capacity for methane adsorption and seepage is discussed. The results indicate that there are significant differences between deep low-rank coal and shallow low-rank coal in terms of porosity, permeability, composition, and adsorption capacity. The full-scale pore distribution was dispersed over a broad range and exhibited a multi-peak distribution, with the majority of the peak concentrations occurring between 0.45–0.7 nm and 3–4 nm. Mesopores are prevalent in shallow coal rock, whereas micropores are the most numerous in deep coal rock. The primary contributors to the specific surface area of both deep and superficial coal rock are micropores. Three-dimensional CT reconstruction can characterize pores with pore size greater than 1 μm, while the dominating equivalent pore diameters (Deq) range from 1 to 10 μm. More mini-scale pores and fissures are observed in deep coal rock, while shallow coal rock processes greater total and connection porosity. Multifractal features are prevalent in the fractal qualities of all the numbered samples. An enhancement in pore structure heterogeneity occurs with increasing pore size. The pore structure of deep coal rock is more heterogeneous. Furthermore, methane adsorption capacity is favorably connected with D1 (0.4 nm < pore diameter ≤ 2 nm), D2 (2 nm < pore diameter ≤ 5 nm), micropore volume, and specific surface area and negatively correlated with D3 (5 nm < pore diameter ≤ 50 nm), showing that methane adsorption capability is primarily controlled by micropores and mesopores. Methane seepage capacity is favorably connected with the pore volume and connected porosity of macropores and negatively correlated with D4 (pore diameter > 50 nm), indicating that the macropores are the primary factor influencing methane seepage capacity.

Scaling effects on arsenic release from excavated hydrothermally altered rocks in column experiments

The excavation of hydrothermally altered rocks from construction sites in Japan has raised concerns over environmental pollution due to the arsenic (As) release beyond the regulatory limit. An accurate assessment of As leaching from these rocks is imperative to understanding potential environmental implications and formulating efficient containment measures. However, the conduction of column leaching experiments to evaluate As leaching from these rocks encounters a lack of well-established protocols primarily due to the ambiguity surrounding scaling effects resulting from alterations in particle sizes and the corresponding column dimensions. Our study aimed to address this critical issue by conducting column percolation experiments on hydrothermally altered rocks of two distinct particle size ranges and rock layer thicknesses. The pH value was found to be proportional to the specific surface area (SSA) of rocks and the rock layer thickness in terms of H+ concentrations. Furthermore, the concentration and leachability of As showed a similar proportionality with the SSA. In contrast, the concentration of As remained relatively unaffected by the increased rock layer thickness, while the leachability of As was noticeably diminished in the column with a thicker rock layer. The absence of elevated As concentration and the decrease in leachability can be attributed to the enhanced As onto Fe/Al oxyhydroxides/oxides within the half-bottom part of the column with a thicker rock layer. Our findings underscore the importance of considering the SSA of rocks and rock layer thickness in the column experiments and help in the design of effective strategies to mitigate environmental contamination.

Influence of Inner Surface Roughness on the Spectral Induced Polarization Response—A Numerical Study

AbstractSpectral induced polarization (SIP) laboratory measurements on water‐saturated rocks show a strong correlation between the electrical polarization strength and the inner surface area of rocks. We investigate the influence of inner surface roughness on the SIP response by simulating the frequency‐dependent complex conductivity of micro‐scale rock models. Starting with smooth grain models, we introduce surface roughness using two different approaches: increasing the surface roughness in a fractal‐like manner, and creating random surface structures, resulting in more natural‐looking surfaces. We find that surface roughness has two distinct effects on the SIP response: (a) a shift in the position and magnitude of the primary relaxation frequency to lower frequencies and lower magnitudes, respectively, and (b) the formation of secondary polarizations above the polarization frequency of the primary polarization. We also compare the relaxation time and normalized chargeability obtained by Debye decomposition and the imaginary conductivity at 1 Hz of our models with mechanistic models and empirical relations. We point out the congruences and offer explanations for the discrepancies between our models and the empirical observations. We conclude that the results of our study are applicable to real rocks and that the SIP method has the potential to detect inner surface roughness. However, the SIP method it not able to discriminate between signals from rough particles and a distribution of smooth particles.

Numerical simulation of rock breaking by PDC cutter with finite-discrete-infinite element method

To better reveal the rock damage evolution law during rock breaking by Polycrystalline Diamond Compact (PDC) cutter, the Finite-Discrete-Infinite Element Method (FDIEM) was adopted to establish the 3D models for rock breaking by PDC cutter pressing and cutting. It was found that the cutter tip was the starting point of crack initiation during rock breaking by PDC cutter pressing. When the pressing depth was about 2 mm, the tensile breaking ratio of the rock was the highest, which was the most conducive to rock breaking. During rock breaking by PDC cutter cutting, the boundary of the area where the cutter contacts with rock was the starting point of micro-crack initiation. The volumetric fracture mainly occurred in the rock surface area in front of the cutter, and the comminuted fracture mainly occurred in the rock in contact with the front of the cutter. A new method based on crack density has been proposed to evaluate rock damage during rock breaking by PDC cutter. The results proved the feasibility and reliability of the FDIEM in simulation of rock breaking by PDC cutter, which can provide a method guidance for the studies on other types of rock breaking tools.

Study on Pore Structure of Shale Reservoir by Low Temperature Nitrogen Adsorption Method

Shale gas is one of the most actively explored unconventional sources of natural gas. There are several types of pores in the shale reservoir, and their structural characteristics are complex. Evaluating the characteristics of the shale pore structure is the basis for understanding the shale reservoir performance and the oil and gas migration mechanism. In this paper, the micro- and nanopores of shale samples from the Yanchang Formation, Hunan basin, are studied by applying the low-temperature nitrogen adsorption method. Several pore structure parameters such as the specific surface area, the pore volume, and the pore size distribution of the analyzed samples are calculated. The predominant characteristics of nanopores that influence hydrocarbon accumulation and control the development of pores are discussed. The results indicate that the shale reservoir rocks from the study area are mainly mesoporous with an average pore size distribution between 2 and 50 nm. A small number of micropores (less than 2 nm) and macropores (more than 50 nm) are also present in the pore network. The development of micropores and mesopores in the shale samples is associated with organic matter content, while the development of macropores is linked to clay minerals content. Total organic carbon (TOC) content is the key element to control the nanopore volume and the specific surface area of the reservoir rocks from the study area. At the same time, the organic matter-enriched pore network also provides extensive space for the accumulation of shale gas.

Recruitment of Postlarval Abalone Haliotis spp. at Santa Catalina Island: Quantifying Natural Recovery

California abalone Haliotis spp., listed as species of concern, have been slow to recover, after 22 years of fishery closure, or are not recovering at all because of low-density populations and recruitment failure. It is not known if there is successful recruitment in populations in the wild in Southern California. This work examines, for the first time, whether newly settled abalones (<3 mm) are present in the wild at Santa Catalina Island to determine if recruitment is occurring. Natural cobbles with crustose coralline algae cover were sampled for recently settled abalones at two sites and at three depths over the reproductive season of green and pink abalone. A total of 128 abalone recruits (Haliotis spp.) were found over a cumulative rock surface area of 7.47 m2, on 325 cobbles, for a total recruitment density of 17.14 recruits per m2. Abalone recruits ranged in size from 220 to 2,120 µm, with an average recruit size of 490 ± 20 µm (mean ± SE, n = 124). Recruitment was similar across depths (2–4, 6–8, and 10–12 m) but differed between the two study sites, and was highest in June and September. Genetic work is needed to confirm species identification of the new recruits; however, they were most likely green abalone which would be consistent with the signs of green abalone recovery at the island. This work quantifies abalone settlement in Southern California, confirming successful recruitment. These methods can aid future restoration efforts empowering managers and restoration practitioners to monitor and quantify recruitment dynamics for abalones in California.

The effect of mineral composition in the compound soil of soft rock and sand on special surface area and cation exchange capacity

The X-ray diffraction method and gas adsorption method were used to investigate the mineral composition and special surface area of different soft rocks, sands, and composed soil. The results showed that (1) Montmorillonite, kaolinite, potash feldspar, calcite, quartz, plagioclase and illite, constitute the soft rock. Quartz, potash feldspar, plagioclase, calcite, montmorillonite, illite, and kaolinite constitute the soft rock in the Mu Us sandy land. There are several types of soft rocks, and there are some differences in the mineral composition of different types. The highest primary mineral content is 94.6% and the lowest 41%; the secondary mineral content is the highest 59% and the lowest is 5.4; (2) The special surface area of different types of soft rock is quite different, and the special surface area is up to 17.14 m2g−1, the lowest is 3.12 m2g−1, and the average content is 9.98 m2g−1. The cation exchange capacity is up to 7.25 cmol(+)/kg, and the lowest is 3.36 cmol(+)/kg; (3) The fitting formula of secondary minerals and specific decomposition of arsenic sandstone, aeolian sandy soil and composite soil is y = 2.423e0.0871x, and the correlation coefficient R2 = 0.8258. The fitting formula for the exchange capacity of secondary minerals and cations is y = 3.105e0.0348x, and the correlation coefficient R2 = 0.9235.

Analyzing the Dynamics of Mineral Dissolution during Acid Fracturing by Pore-Scale Modeling of Acid-Rock Interaction

SummaryHydrochloric acid (HCl) is commonly used in acid fracturing. Given that the interaction between acid and rock affects multiphase flow behaviors, it is important to thoroughly understand the relevant phenomena. The Darcy-Brinkman-Stokes (DBS) method is most effective in describing the matrix-fracture system among the proposed models. This study aims to analyze the impact of acid-rock interaction on multiphase flow behavior by developing a pore-scale numerical model applying the DBS method. The new pore-scale model is developed based on OpenFOAM, an open-source platform for the prototyping of diverse flow mechanisms. The developed simulation model describes the fully coupled mass balance equation and the chemical reaction of carbonate acidizing in an advection-diffusion regime. The volume of fluid (VOF) method is used to track the liquid- and gas-phase interface on fixed Eulerian grids. Here, the penalization method is applied to describe the wettability condition on immersed boundaries. The equations of saturation, concentration, and diffusion are solved successively, and the momentum equation is solved by pressure implicit with splitting of operators method. The simulation results of the developed numerical model have been validated with experimental results. Various injection velocities and the second Damkohler numbers have been examined to investigate their impacts on the CO2 bubble generation, evolving porosity, and rock surface area. We categorized the evolving carbon dioxide (CO2) distribution into three patterns in terms of the Damkohler number and the Péclet number. We also simulated a geometry model with multiple grains and a Darcy-scale model using the input parameters found from the pore-scale simulations. The newly developed pore-scale model provides the fundamental knowledge of physical and chemical phenomena of acid-rock interaction and their impact on acid transport. The modeling results describing mineral acidization will help us implement a practical fracturing project.

Interpreting Groundwater Chemistry and Estimating Residence Time of Groundwater in the Mt. Fuji Area Based on a Dissolution Kinetics-Fluid Flow Model and Chlorofluorocarbons (CFCs) Concentration

Relationships of concentrations of elements (Ca, Mg, Si) in groundwater from the Mt. Fuji area are obtained using analytical data on groundwater. Relationships of Ca, Mg, and H4SiO4 concentrations can be explained in terms of the dissolution of basaltic glass and precipitations of secondary minerals (halloysite, allophane, montmorillonite, and α-cristobalite). The relationship between residence time and H4SiO4 concentration of groundwater is obtained based on dissolution kinetics-piston fluid flow and a perfectly mixing fluid flow model. Using this relationship, the dissolution rate constant experimentally determined in an open system (not in a closed system) (k = 10−10.7 molSi/m2 s) and analytical data on H4SiO4 in groundwater, the residence time of groundwater (Kakitagawa site, southeastern foot and Fuji Yoshida site, northern foot) is estimated to be ca. 20 years for A/M (A: surface area of rock (m2), M: mass of water (kg)) = 20 based on a dissolution kinetics-fluid flow model. This estimated residence time is roughly consistent with other methods (He isotope tritium, chlorofluorocarbons (CFCs) ages (10-40 years), indicating that the dissolution kinetics-fluid flow model using dissolved silica concentration is a potentially useful method for estimating the residence time of groundwater in a young volcanic region. It is also reported that CFCs ages are ca. 30-40 years, which are the first data obtained for the Mt. Fuji area. This suggests that CFCs data are very useful for providing the residence time of groundwater in an area at a high elevation.

Technology of Exposed Rock Surface Insulation against the Influence of Mine Atmosphere

The authors discuss the problem connected with insulation of exposed rock surface areas against the aggressive influence of mine atmosphere and rock falls during mining. The lab-scale tests determine the moisture effect on the strength of rocks in the Orlov Ore Field. The tensile strength of samples of isolation membrane as well as their adhesion to rocks and shotcrete is assessed. The technology of preparation and application of polymer membrane insulation layer on the surface of differently damaged areas on the roof and sidewalls in stopes is justified for the Orlov Mine.

The influence of the structural distribution and hardness of mineral phases on the size and shape of rock drilling particles

Rock drilling is a significant activity widely used in the exploration of marine mineral resources and offshore civil engineering such as marine mining, petroleum and deep-water drilling. The characteristics of size and shape of particles produced during rock drilling influence drilling efficiency and energy consumption. We report a series of drilling experiments on sandstone, limestone and shale to systematically examine particle size distribution and shape and correlate these with original rock structure and composition. Correlations are established via metrics of particle size distribution, average circularity and specific surface area. Impact breakage and contact abrasion of individual particles during rock drilling are the main mechanisms controlling particle size and shape. Impact breakage is controlled by the structural distribution of mineral phases, while contact abrasion is principally related to the hardness of mineral phases. The particle size distribution is affected by the structural distribution of mineral phases. The average circularity of the drilling particles is mainly controlled by the hardness of mineral phases. The specific surface area of rock drilling particles is determined by both structural distribution and hardness of mineral phases – with homogeneous structure and low average hardness of the phases reducing the resulting specific surface area of the drilling products.

The Presence of IUCN Red List Tree Species in Dependence of Site Characteristics in the Vietnamese Cat Ba National Park

Rare or endangered tree species are important components of forest ecosystems and play a crucial role in management and conservation. Understanding what influences their presence is critical for managers, conservationists and planners. This study presents results of a comprehensive inventory of the tree species and site characteristics in the Vietnamese Cat Ba National Park (CBNP). An adaptive cluster sampling technique was applied to study the effect of human disturbance, soil properties, and terrain conditions on the presence of IUCN Red List tree species (all individuals &gt; 5 cm diameter at breast height) in three strictly protected areas in CBNP, which have varying levels of isolation. Data from 239 sample plots (500 m2 each) were analyzed. Tree species recorded during the inventory were assigned to two categories: IUCN Red List and other. Our results showed that site characteristics differed in the three protected areas along with the presence of IUCN Red List tree species. IUCN Red List tree species were more frequently found on less favorable soils (low soil depth) and in terrain with more pronounced slopes and with a higher rock surface area (%). However, there is no indication from existing information on the autecology of the different Red List species that the site conditions hosting the species are the ones favored by the species, even on the contrary for some. Although direct signs of human activity (paths, animal traps) could not be related to the presence of Red List tree species, the data suggest that the accessibility of the sites is a strong negative driver for the presence of Red List tree species. We conclude that protection of the forests of the Cat Ba Island should be stricter to allow the IUCN Red List tree species to grow under more appropriate conditions, which then would allow studying their ecology in more detail. This would further allow deriving more precise recommendations for their future protection.

Impact of asphaltenes and clay interaction on in-situ combustion performance

The increased surface area of reservoir rock due to the presence of clays and the catalytic impact of clays are known to enhance the in-situ combustion (ISC) performance. But the basics behind these mechanisms are still unknown. Six one-dimensional (1-D) combustion tube experiments were conducted on three different crude oil samples. Each crude oil was evaluated with two combustion tube runs; sand-oil and sand-clay-oil mixtures to study the effect of clay on combustion performance. Then, Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) was run at isothermal conditions by ramping up the temperature using the combustion tube temperature. The activation energy and the heat of combustion were calculated empirically. The quality of the produced oil samples was determined through viscosity measurement and saturates, aromatics, resins, and asphaltenes (SARA) fractionation. To better understand the fuel formation mechanism, the compositional variations in SARA fractions have been analyzed through Fourier Transform Infrared (FTIR). Further, asphaltenes surfaces were visualized by Scanning Electron Microscope (SEM) and the Energy Dispersive Spectroscopy (EDS). The combustion tube experimental result shows that saturates fractions have been decreased in displaced oil since saturates are consumed as an ignitor during ISC. The aromatics fraction has been significantly increased in produced oil, which helps to increase the mobility of displaced oil through viscosity reduction. Moreover, the amount of asphaltenes in produced oil decreased due to fuel formation reactions. In the presence of clays, the cribriform structures were formed on asphaltenes surface and aid the combustion process by increasing the surface area of asphaltenes.

What happens to fracture energy in brittle fracture? Revisiting the Griffith assumption

Abstract. Laboratory experiments involving unconfined compressive failure of borosilicate glass cylinders quantified the elastic strain energy released at failure and the size distribution of the resulting fragments. The data were carefully assessed for potential inaccuracies in surface-area calculation, the contribution of energy from the compression machine relaxation during specimen failure, and possible variations in the specific fracture energy of the specimens. The data showed that more new surface area was created during the failures than would be possible if the long-standing assumption, which is that all the energy involved in creating new rock surface area in brittle material is taken up by the newly created surfaces as surface potential energy and is not available to do further work, were valid. We therefore conclude that the assumption is false. This conclusion is supported by independent data from a previous investigation whose authors did not pursue this particular application. Our result does not affect the validity of Griffith fracture mechanics and is significant only when large numbers of very fine fragments are created by brittle fracture, as in rock-avalanche motion and earthquake rupture, and are identified in particle-size distributions. In such situations our result is very significant to understanding fracture energetics.

Energy budget for a rock avalanche: fate of fracture-surface energy

A detailed energy budget of a rock avalanche at Lake Coleridge, New Zealand, included fragments as small as 70 nm in diameter in the debris particle-size distribution, and used ultrasonic disaggregation of agglomerates formed during emplacement of the deposit to properly sample the fine fragments created during the rock avalanche. Using the maximum likely value of potential energy released during the debris fall and runout, and minimum values of energy lost to friction and of energy used in creating new rock surface area by fragmentation, the energy budget showed a substantial energy deficit; the available potential energy almost matched the energy lost to friction, leaving very little energy available for creating the new surface. This deficit was much less prominent if sub-micron fragments were ignored as in earlier energy budgets, because about 90% of total fragment surface area occurred on sub-micron fragments. Close examination of possible sources of error in the calculated budget leads to the conclusion, supported by published data, that only a small proportion of the energy used to create new rock surface transforms to surface energy, while a large proportion of it remains available in the form of elastic body-wave energy.

Produced Flowback Salts vs. Induced-Fracture Interface: A Field and Laboratory Study

Summary The water recovered from hydraulic-fracturing operations (i.e., flowback water) is highly saline, and can be analyzed for reservoir characterization. Past studies measured ion-concentration data during imbibition experiments to explain the production of saline flowback water. However, the reported laboratory data of ion concentration are approximately three orders of magnitude lower than those reported in the field. It has been hypothesized that the significant surface area created by hydraulic-fracturing operations is one of the primary reasons for the highly saline flowback water. In this study, we investigate shale/water interactions by measuring the mass of total ion produced (TIP) during water-imbibition experiments. We conduct two sets of imbibition experiments at low-temperature/low-pressure (LT/LP) and high-temperature and high-pressure (HT/HP) conditions. We study the effects of rock surface area (As), temperature, and pressure on TIP during imbibition experiments. Laboratory results indicate that pressure does not have a significant effect on TIP, whereas increasing As and temperature both increase TIP. We use the flowback-chemical data and the laboratory data of ion concentration to estimate the fracture surface area (Af) for two wells completed in the Horn River Basin (HRB), Canada. For both wells, the estimated Af values from LT/LP and HT/HP test results have similar orders of magnitude (approximately 5.0×106 m2) compared with those calculated from production and flowback rate-transient analysis (RTA) (approximately 106 m2). The proposed scaleup procedure can be used as an alternative approach for a quick estimation of Af using early-flowback chemical data.

Exact Upscaling for Transport of Size‐Distributed Colloids

AbstractThe article investigates one‐dimensional (1‐D) suspension‐colloidal transport of size‐distributed particles with particle attachment. A population balance approach is presented for computing the particle transport and capture by porous media. The occupied area of each attached particle is particle size‐dependent. The main model assumption is the retention rate dependency of the overall vacancy concentration for all particle sizes. For the first time, we derive an exact averaging (upscaling) procedure resulting in a closed system of large‐scale equations for average concentrations of suspended and retained particles and of occupied rock surface area. The resulting large‐scale 3 × 3 system significantly differs from the traditional 2 × 2 deep bed filtration model. However, the traditional model becomes a particular case that corresponds to an equal occupied area for all particles. The averaging yields the appearance of two empirical suspension and site occupation functions, which govern the kinetics of particle retention and site occupation, respectively. One‐dimensional flow problems for the averaged equations are essentially nonlinear. However, they allow for exact solutions. We derive novel exact solutions for three 1‐D problems: continuous injection of particulate colloidal suspension, injection of colloidal suspension bank with particle‐free chase drive, and fines migration induced by high‐rate flows. The analytical model for continuous injection closely matches three series of laboratory tests on nanofluid transport.

Ethylene glycol monoethyl ether (EGME) adsorption by organic matter (OM)-clay complexes: Dependence on the OM Type

The ethylene glycol monoethyl ether (EGME) adsorption method has been used as an available technique for measuring the total specific surface area (TSSA) of soils and clay-rich rocks. However, the existence of organic matters (OM) has recently been proposed to affect the accurate measurement of the TSSA. To explore the effects of OM on the TSSA evaluation of clay-rich samples, EGME adsorption experiments were performed on OM and the OM-clay minerals (OM-clay) complexes that widely exist in soil and clay-rich rocks. Two types of OM, 12-aminolauric acid (ALA) and lauric acid (LA) were used, and montmorillonite (Mt) was selected as the representative clay mineral. OM-clay complexes with OM in interlayer space or OM-clay mixture with OM on the external surface of an expanding clay mineral were prepared to investigate the influence of occurrence sites of OM on the EGME adsorption. The combined methods of X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) were used to study the structural characteristics of the OM-clay complexes before and after EGME adsorption for revealing the EGME adsorption mechanisms. The results showed both the occurrence sites and the functional groups of OM significantly influence the EGME adsorption behaviour and TSSA for OM-clay complexes. As ALA intercalated into interlayer space of Mt, it can occupy parts of adsorption sites of EGME leading to a lower TSSA than that of Mt. While as LA located on the external surface of Mt, it affects access to the interlayer surface by the EGME and occupies parts of EGME adsorption sites of the external surface of Mt, resulting in lower adsorption capability and the slight smaller TSSA than Mt. In addition, EGME reacted strongly with LA producing excess TSSA, which brings about a great difference between LA-Mt and ALA-Mt on EGME adsorption behaviour. These fundamental results demonstrated that OM could strongly affect the EGME adsorption on the OM-Mt complexes and further influence detection of TSSA. The occurrence sites and the functional groups of OM in OM-clay complex must be considered when the EGME adsorption method is used for TSSA evaluation of such clay-rich rocks and soil samples.