Petrology Of Rocks Research Articles

Conflicting zircon vs. titanite U-Pb age systematics and the deposition of the host volcanic sequence to Kiruna-type and IOCG deposits in northern Sweden, Fennoscandian shield

The Northern Norrbotten region, and in particular the Kiruna area, hosts a number of large apatite iron oxide deposits (e.g. the huge Kiirunavaara ore) of significant economic importance. Age data from rock lithologies hosting these ores, represented by metamorphosed rocks of the Porphyrite and Kiirunavaara Groups, are complex to interpret. This is illustrated by (LA-ICP-MS) data for titanite, and to some extent for rutile, which scatter considerably yielding ages within a span from ca. 2.1 Ga to 1.7 Ga. These analysed hydrothermal minerals, characterized by complex BSE images revealing darker and brighter zones, are located in ore zones and associated with e.g. strong scapolitisation, albitisation and actinolitisation. Previous (TIMS) zircon ages of host rocks, on the other hand, define a more narrower age interval between ca. 1900 and 1870 Ma, and this is supported by new U-Pb zircon results presented here. Furthermore, one coherent set of SIMS data for titanite from the Luossavaara ore favour that crystallization took place at ca 1.88 Ga, although laser ICP data from the same locality are much more complex. An implication arising from published pre-1.9 Ga laser ablation ages for titanites is that the emplacement of host rocks started already at around 2.1 Ga. As the depositional time of these rocks is crucial for the understanding of the overall crustal formation in northern Norrbotten, additional rocks were selected for age dating. New zircon age data (LA-ICP-MS and SIMS) give support to a scenario where host rocks to ores started to develop at around 1900 Ma and this calls for a re-evaluation of published LA-ICP-MS data of hydrothermal mineral phases.Here, we present four models that aim to explain how pre-1.9 Ga titanite ages, believed to have a questionable geological significance, may develop. The principal idea is that ≤2.1 Ga alteration events were not responsible for the crystallization of the hydrothermal minerals, instead it is believed that apparent old age domains carry excess radiogenic lead due to the effect of ≤1.9 Ga hydrothermal processes. Currently, the interpretation of U-Pb isotope data in the study area remains enigmatic, and further radiometric analyses are required.

Peculiarities of Hydrocarbon Generation at Great Depths in the Crust

This article describes the peculiarities of hydrocarbon generation at great depths in the Earth’s crust. It is shown that all the conditions necessary for generation of oil and gas are kept at great depths in the crust in the zones of high pressures and temperatures. However, generation of hydrocarbons in such settings significantly differs from the processes of oil and gas formation at shallow depths. A complex system of mutual thermobaric factors and distribution of the oil and gas potential at great depths was revealed: the start of generation and the phase distribution of hydrocarbons in the section are largely affected by settling of abnormally high pore pressure, as well as by paleotemperatures that could differ considerably from the present-day ones depending on the age of deposits. It is shown that different thicknesses of catagenetic zones are related to the kinetic rate of oil and gas generation, which depends on the type of kerogen, the gradient of temperature change, pressure, lithology, and hydrogeological conditions of the host rocks, the sedimentation rate, and other factors.

Lithology and U–Pb Geochronology of Basement of Cenozoic Yitong Basin in Northeastern China: Implication for Basin Architecture and New Horizon of Deep Natural Gas Exploration

The lithology and formation age of basement rocks are significant for the understanding of the nature of basin architecture, evolution and the potential of hydrocarbons of a basin. In this study, the basement lithology of the Cenozoic Yitong Basin is investigated through the petrological analysis of cores, cuttings, and thin sections. The results suggest that the basement rocks of the Yitong Basin are mostly composed of unique igneous rocks that are different from nearby basins’ sedimentary and metamorphic basement. The igneous rocks are dominated by intrusive monzonite granite and alkali feldspar granite. Additionally, U–Pb zircon geochronology of basement samples by LA-ICP-MS and the geological interpretation of apparent resistivity data indicate that the igneous basement in major part of the basin was mainly formed by a lateral intrusion of granite into the Permian sedimentary stratum in the Yanshanian period from 177 to 170 Ma. The results also reveal the two-layer basin architecture with coal-bearing Carboniferous–Permian strata below the igneous basement covered with Tertiary sediments, thus providing a new geologic horizon for deep natural gas exploration in the older coal-bearing sedimentary rocks beneath the current igneous basement.

Interpretation of 2D-Subsurface Resistivity Data in The Iron Ore Prospect Area of Eastern Binangun Coastal, Regency of Cilacap, Central Jawa

Interpretation of 2D-subsurface rock resistivity data has been carried out in the iron ore prospect area of Eastern Binangun Coastal in ​​Cilacap Regency, Central Java. The background of this research is the potential for abundant iron sand in this area that prospects to be exploited. The research was conducted using a magnetic method in 2017 to map the distribution patterns of the local magnetic anomalies that were interpreted to originate from the distribution of iron ore in the subsurface. In 2018, the research continued using the 2D-resistivity method to find out the lithology section in the subsurface of research area. 2D-resistivity data acquisition is carried out on four tracks consisting of Bng-01 to Bng-04. The resistivity data modeling have produced the true resistivity value for each track in the form of the subsurface resistvity section, which including the Bng-01 track is 2.27 – 44.1 Ωm; the Bng-02 track is 4.5 – 58.6 Ωm; the Bng-03 track is 6.37 – 63.4 Ωm; and the Bng-04 track of 4.98 – 83.3 Ωm. After interpretation process, some models of subsurface rocks lithology section is obtained under the four trajectories. The rocks resulted from interpretation process consists of sand which inserted with gravel (> 58.6 Ωm); sand containing iron ore grains (28.2 – 83.3 Ωm), clayey sand (11.1 – 32.9 Ωm), sandy clay (4.98 – 13.5 Ωm), and fine sand which intruded by saltwater (<6.49 Ωm). Sand containing iron ore grains is main part of the coastal aquifer so that exploitation of iron sand has the potential to reduce aquifer function in storing and flowing of groundwater and causing of abrasion in the Eastern Binangun Coastal area.

Geo-statistical and multivariate analyses of potentially toxic elements' distribution in the soil of Hainan Island (China): A comparison between the topsoil and subsoil at a regional scale

Geo-statistical and multivariate analyses are effective methods to determine the source and influence factors of potentially toxic elements (PTEs) in the soil. Hainan Island, belonging to tropical marine monsoon climate, is a typically individual island with slight industrial activities. In order to study the impact factors on PTEs distribution in the soil at a regional scale, such as impact of lithology, pedogenesis and anthropogenic activities, Hainan Island is an optimal place. For comparison, the topsoil and the corresponding subsoil were sampled and eight PTEs were analyzed respectively. The concentrations of PTEs were counted, such as minimum, maximum, median and mean values. Based on it, the background values and concentration enrichment factors of PTEs were also calculated or illustrated. Exception to Cd and Hg, the concentration of other PTEs in the topsoil were lower than those in the subsoil for all lithological areas since the strong leaching under special climate. By using geo-statistical and multivariate analyses, such as Pearson correlation analysis, principal component analysis, variography and robust biplot analyses, the dominant impact factors are determined for PTEs both in the topsoil and subsoil. Thus, the spatial distribution of PTEs is well explained at a regional scale. Generally, PTEs in the soil represent the components of soil parent materials associated with lithological rocks. Nevertheless, Co, Cr, Cu and Sc elements were dominantly inherited from soil parent materials while Cd, Hg and Pb were greatly superposed by exogenous inputs. On the other hand, elements of As and Zn might be greatly influenced by pedogenesis and weathering process. So, geo-statistical and multivariate analyses are effective methods to discuss the sources or impact factors for PTEs in the soil, and also the comparison between the topsoil and the subsoil provides an opportunity to illuminate the main impact factors on PTEs at a regional scale, including parent materials, weathering process and anthropogenic inputs.

The convective heat transfer of fractal porous media under stress condition

The study of coupled convective heat transfer and deformation behavior in porous media is still a major scientific and engineering challenge, despite major technological advances in both theoretical and computational thermodynamics in the past two decades. Specifically, essential controls on convective heat transfer of porous media under stress condition are not yet definitive. In this paper, meaningful and reasonable quantitative models that manifest the most important fundamental controls on convective heat transfer of porous media under stress condition are proposed. Predictions of the normalized permeability using the theoretical models, derived from Hertzian contact theory and fractal geometry, agree well with available experimental data. The proposed model design specifically accounts for multiple key variables, including the influence of the microstructural parameters of porous media, including elastic modulus and Poisson's ratio, and as functions of rock lithology. The results presented here include (1) the heat transfer rate decreases with the increase of effective stress, and increases with the increased porous media elastic modulus or the increased power law index for a specific effective stress, (2) the heat transfer rate increases with the increase of pore fractal dimension Df0 or the increased ratio rmin0/rmax0 for a specific effective stress. However, the relationship between the convective heat transfer coefficient and effective stress with different pore fractal dimension Df0 is complicated and not monotonic, (3) The heat transfer rate and convective heat transfer coefficient increase as expected with the increase of Nusselt number (i.e. the parameter represents the convective heat transfer in the pore) for a specific effective stress. In general, fractal convective heat transfer models illustrate mechanisms that affect coupled convective heat transfer and deformation behavior of porous media. And, the model proposed here is intended to increase efficacy of reservoir development strategies.

Reservoir characteristics in the Cretaceous volcanic rocks of Songliao Basin, China: A case of dynamics and evolution of the volcano-porosity and diagenesis

To explain the strong spatial heterogeneity of volcanic reservoirs porosity in the Songliao Basin and provide new ideas for predicting good volcanic reservoirs in other similar basins, the relationship between the pore evolution process and lithology of volcanic reservoirs has been described in this article. With the description and interpretation of core, thin section, scanning electron microscope, and the results of mercury injection experiment, this article clarifies the lithology, pore types, and pore structure features of the volcanic reservoirs in the Songliao Basin. The rocks of volcanic reservoirs in study area contain pyroclastic rock and volcanic lavas. The most common lithologies are rhyolite, volcanic breccia, and volcanic tuff. The pore size, morphology, and structure vary greatly between these three lithologies, the reason of which we think is the different volcanic eruption process as well as rock composition and its structure. The digenetic evolution of rhyolite includes gas dissipation of magmatic condensation; vesicles fulfilling by hydrothermal fluid; kaolinization and sericitization of feldspar phenocrysts; carbonation, devitrification, and recrystallization of felsic matrix; and finally, the dissolution of feldspar phenocrysts and felsic matrix. As for volcanic breccia, it usually go through the compaction, quartz and calcite filling the original pores between volcanic breccias, and dissolution of mineral debris together with tuff matrix. Similar with the rhyolite, volcanic tuff also undergoes the carbonation and kaolinization of felsic matrix, the dissolution of feldspar and felsic matrix, and compaction. Due to these comprehensive processes, a comprehensive analysis of volcanic rock lithology, which can indicate lithology distribution vertically and horizontally, is very necessary during volcanic reservoirs evaluation and prediction. These detailed analyses will help explorers to find potential reservoirs by distinguishing the diagenetic evolution and pore characteristic of volcanic reservoirs.

Apparent-Depth Effects of the Dynamic Failure of Thick Hard Rock Strata on the Underlying Coal Mass During Underground Mining

Thick hard rock strata (THRS) are widely distributed among coal-bearing strata in China. The dynamic THRS failure may induce the coal-rock dynamic hazards during underground coal mining. In this study, the size, stress and energy characteristics of dynamic THRS failure were analyzed; the Yangliu coal mine, Huaibei coal basin, China, was taken as a case study. Then the apparent-depth effects of the dynamic THRS failure on the underlying coal mining were researched. The results revealed that the rock roof would be caved, fractured and deformed and even develop the bed separation during underlying coal mining. A large quantity of elastic energy is stored in the bent and compressed THRS, the amount and scope of the vertical stress concentration in front of the working face increases significantly before THRS breaking. THRS generally exhibit the square-form structure failure (SSF), after which the elastic and kinetic energy is attenuated in power form with the energy spreading distance. The shock force and energy effects of the dynamic THRS failure on the underlying coal mass were greater than those observed for the common lithological rock strata. Thus the mining coal mass below THRS bears similar mechanical conditions as the deeper coal mass and is of greater apparent depth, which is called the apparent-depth effects of the dynamic THRS failure. The apparent-depth effects of the dynamic THRS failure significantly influenced the coal-rock dynamic hazards according to in situ measurements of the mine earthquake energy, in situ stress, roof pressure and gas emission parameters. As a result, reasonable measures should be taken to avoid stress concentration and energy accumulation and to reduce the apparent depth of the mining-disturbed coal mass for preventing coal-rock dynamic hazards. The research results provide significant value for the control of coal-rock dynamic hazards below THRS.

Ni-Co enrichment and High-Tech metals geochemistry in the Wingellina Ni-Co oxide-type laterite deposit (Western Australia)

The aim of this study is to evaluate the Ni-Co enrichment and the high-tech metals (REE and Sc) geochemistry in the Wingellina Ni-Co oxide-type laterite deposit (Western Australia). The study has been carried out on two mineralized cores (WPDD0012 and WPDD0019 drillcores) originating from two areas of the deposit. The geochemical assessments have been integrated with the analysis of laterite facies and sample mineralogy. In both the studied laterite profiles Ni enrichment was mostly controlled by the paragenetic evolution of the laterite itself, whereas Co enrichment was related to the formation of Mn-oxy-hydroxide-rich horizons in the limonitic ore-body. Significant REEs concentrations (up to 890 ppm) have been observed within the limonite zones. The correlation between REEs and the major oxides shows a decoupling between Ce and the other REEs, likely reflecting either a variable enrichment process among the different REEs, or a heterogeneous mineralogy of the REEs-bearing phases. Differently from other Ni-Co laterite deposits, Sc is only in limited part correlated with Fe2O3, having been most commonly detected in Ni- and SiO2-rich zones of the saprolitic parts of the profiles. All the geochemical features, the facies characteristics and the Ni-Co, REEs and Sc grades observed in the two studied profiles seems to be the results of the interactions between two main controlling factors: distinct parent rock lithology and diverse degree of serpentinization.

Identification of subsurface basement rock using geoelectrical resistivity method in development area (campus 2 UIN Sunan Gunung Djati Bandung)

The foundation is one of the important elements in the process of building a multistory building, where the foundation serves as the basic building that will support the main building weight above it. The foundation must be built and placed on a hard surface below the ground surface, this aims to avoid the shifting of the foundation which will cause damage to the building above it. One method that can identify hard layers is a type resistivity geolistrik method, which uses different rock resistivity parameters depending on the type of rock. To then be interpreted into a 2D geological section according to the state of the lithology of the area rocks. From the research data obtained, from 3 paths (L.1, L.2, and L.3) using the average Wenner configuration of the identified hard layers starting at a depth of 11.9 meters identified as a tuff stone layer (100-250 Ωm). Tufaan gravel layer and contains a little tufaan sand (250 - 400 Ωm) at a depth of 16.1 - 20.7 m, Tufaan gravel layer with breccia stone insect (400 - 600 Ωm) at a depth of 20.7 - 25.8 m, and the last of the basic constituent layers allegedly dominated by limestone (> 600 Ωm) at depths above 25.8 meters. While the position of the presence of an average hard layer is 96-144 meters from the starting point of measurement for each trajectory.

Geomorphic characteristics of a bedrock river inferred from drainage quantification, longitudinal profile, knickzone identification and concavity analysis: a DEM-based study

An examination of river channels has ability to provide substantial information regarding the geomorphic characteristics, control of lithology, tectonic uplift and geomorphic evolution during the geological past of an area. In this paper, a detailed study of geomorphic and structural investigation has been carried out for Pravara basin, Maharashtra, with the help of 90-m resolution SRTM DEM and geospatial techniques. Drainage network analysis performed in this paper demonstrates the general geomorphic characteristics, while the analysis of longitudinal profile synthesises lithological control over Pravara basin. Pravara is a 6th order drainage basin, encompassing an area of 2637 km2. Bifurcation ratio reveals low to moderate structural control. Due to the hard rock lithology, the drainage density and stream frequency are low, and it indicates higher permeability in the sub-surface layers. The shape parameters denote that Pravara is highly elongated and it is easier to control floods in this basin. Relief parameters show very steep slope and higher vulnerability to the slope failure in some areas. Upstream of Pravara river has shown that series of breaks and knickzones indicate active erosion and acute lithological control on the channel. Major breaks are observed only in the main channel whereas in two major tributaries, no such breaks found, instead these tributaries are characterised by several knickzones which indicate regional variation in the lithological physiognomies. Different lithological stages on knickpoint and channel incision substantiate rejuvenation of Pravara river in several phases during geological past. The geospatial methodology carried out in this study can be pragmatic elsewhere around this world to recognise the geomorphic appearances and lithological control of a drainage basin.

Application of the power mean to modeling the elastic properties of reservoir rocks

The relationship between seismic velocity and porosity is one of the most important research topics in exploration geophysics. A strong correlation, if it exists, can be very useful for quantitative seismic interpretation of direct hydrocarbon indicators. The Voigt and Reuss bounds are often plotted alongside the data for quality control and interpretation. The relative position of the data within the bounds may supply important information regarding the pore shape, stress condition, lithology, and diagenesis of porous rocks. It is found that the Voigt bound and Reuss bound are actually special cases of the weighted power mean, with the power parameters being 1 and −1, respectively. The geometric mean is a special case of the power mean with the power parameter being zero. The power mean is a monotonic function of the power parameter. For the construction of a rock physics template, the region between the Voigt and Reuss bounds can be evenly divided by varying the power parameter between −1 and 1. The power mean can be a very useful tool for modeling the elastic properties of rocks. We have demonstrated the potential applications of the power mean in the studies of velocity-porosity relation, effective media, and pore fluids effect on seismic velocities.

The Impact of Surfactant Imbibition and Adsorption for Improving Oil Recovery in the Wolfcamp and Eagle Ford Reservoirs

Summary Improving oil recovery from unconventional liquid reservoirs (ULRs) is a major challenge, and knowledge of recovery mechanisms and the interaction of completion-fluid additives with the rock is fundamental in tackling the problem. Fracture-treatment performance and consequent oil recovery can be improved by adding surfactants to stimulation fluids to promote imbibition by wettability alteration and moderate interfacial-tension (IFT) reduction. Also, the extent of surfactant adsorption on the ULR surface during the imbibition of completion fluids is a key factor to consider when designing fracture jobs. The experimental and modeling work presented in this paper focuses on the effectiveness of surfactant additives for improving oil recovery in Wolfcamp and Eagle Ford reservoirs, as well as the extent of surfactant loss by adsorption during the imbibition of surfactant-laden completion fluid. Original rock wettability is determined by contact angle (CA) and zeta potential. Then, distinct types of surfactants—anionic, anionic/nonionic, and cationic—are evaluated to gauge their effectiveness in altering wettability and IFT. Moreover, surfactant-adsorption measurements are performed using ultraviolet/visible (UV/Vis) spectroscopy. Next, the potential for improving oil recovery using surfactant additives in ultralow-permeability Wolfcamp and Eagle Ford shale cores is investigated by spontaneous-imbibition experiments, and computed-tomography (CT) methods are used to determine fluid imbibition in real time. Finally, laboratory data are used in numerical simulations to model laboratory results and to upscale these findings to field scale. The results showed that aqueous solutions with surfactants altered rock wettability from oil-wet and intermediate-wet to water-wet and reduced IFT to moderately low values. In addition, cationic surfactant presented the highest adsorption capacity following a Langmuir-type adsorption profile. Spontaneous-imbibition results showed that aqueous solutions with surfactants had higher imbibition, and were better at recovering oil from shale core compared with water without surfactants, which agrees qualitatively with wettability and IFT alteration. However, rock lithology and surfactant type played a key role in adsorption capacity and oil recovery. Our upscaling result showed that, compared with a well that is not treated with surfactant, a 24% increase in the initial peak oil rate and an 8% increase in the 3-year cumulative oil production were observed. For the results obtained, we can conclude that the addition of surfactants to completion fluids can improve oil recovery by wettability alteration and IFT reduction, maximizing well performance after stimulation from Wolfcamp and Eagle Ford unconventional reservoirs.

Predicting aquifer characteristics to enhance hydrogeophysical model in fractured/karstified rocks of Dammam Formation at Bahr Al-Najaf Basin, Iraq

Groundwater represents a major water source in Bahr Al-Najaf basin. So, the knowledge of the aquifer parameters is an essential goal to assess and manage groundwater resources. A comprehensive view of the fractured and karstified aquifers within Dammam Formation at Bahr Al-Najaf basin is very important, because the karstified environments are very complex. This study is an attempt to extract mathematically empirical relationships between the hydraulic parameters and the geoelectrical properties, to improve the construction of a hydrogeophysical model, instead of using the conventional procedures of pumping tests or drill new well which need great effort and high cost. The enhanced hydrogeophysical model shows that the main aquifer has a uniform lithology of carbonate rocks, good water saturation and belongs to M. Dammam member. The correlation between hydraulic conductivity (K) m/day and aquifer resistivity ( $${\rho _0}$$ ) Ωm gave a logical relationship in such kind of aquifer, which has correlation coefficient (R2) equals to 0.737. In addition, the correlation between transmissivity (T m2/day) and both of transverse resistance (Tr) Ωm2 and longitudinal conductance (SL) Ω−1 revealed the similarity in lithological characteristics of middle Dammam aquifer due to the approximately equal values of strong R2 = 0.862 and 0.868, respectively. This may be due to the nature of the studied area as a discharge zone, which has a good porosity ( $$\varphi$$ ) of 22% and a high water saturation (Sw) equals to 1 approximately. The extracted relationship of direct proportionality between T (m2/day) and SL (Ω−1) is an important one. Therefore, this relationship can be used directly to calculate T (m2/day) mathematically. In the present study, the relations between the hydraulic parameters and the geoelectrical properties are expressed as linear equations instead of nonlinear, because we believe that it is mathematically more acceptable and reliable for hard rock aquifers that the M. Dammam aquifer is confined with a fully saturated thickness. In addition, the comparison between R2 of the linear and nonlinear relation of T (m2/day) with Tr (Ωm2) and T (m2/day) with SL (Ω−1) appeared to have little divergence of R2 equal to 0.028 and 0.001, respectively.

Fatigue damage evolution of coal under cyclic loading

The experimental study of fatigue damage to coal under cyclic loading is important for guiding the design of pillars in underground coal mines where the pillars may be affected by repeated mining activity. In this paper, the strength, deformation, energy dissipation, and fatigue of samples of coal from a mine in China are studied using cyclic loading with a servo-controlled rock mechanical test system. The results indicate that coal is more likely to suffer fatigue damage than other, harder, rock lithologies. Under uniaxial cyclic loading, the fatigue failure “threshold value” for the coal samples studied is less than 78% of its uniaxial strength, but there is also a certain amount of fatigue damage when the cyclic loading/unloading experiments are carried out below the threshold value for fatigue failure. Axial deformation during the tests can be divided into three stages: initial deformation, constant steady deformation, and accelerated deformation. Transversal deformation can be divided into two stages: stable deformation and accelerated deformation. During cyclic loading experiments, imminent sample failure is signaled when transversal deformation increases significantly and quickly and the deformation recovers little when the load is removed. With an increasing number of loading/unloading cycles, a graph of energy dissipation per unit volume versus number of cycles presents an L-shaped curve when the coal samples do not suffer fatigue failure. However, for the coal samples that do rupture due to fatigue, the curve is U-shaped. Under cyclic loading, the evolution of compaction, strain hardening, strain softening, and failure of coal can be revealed in great detail by fatigue damage experiments.

Quantitative prediction of seismic rock physics of hybrid tight oil reservoirs of the Permian Lucaogou Formation, Junggar Basin, Northwest China

Tight oil exploration and development in the Jimusar Sag of southeastern Junggar Basin of Northwest China has led to development of two reservoir segments in the Lucaogou Formation. The upper segment is mostly carbonate rocks, while the lower segment consists mainly of fine-grained clastic rocks. Both segments are mixed with clay, sand, and dolomite, which makes it difficult to identify the lithology and predict the porosity using a traditional seismic rock physics template (RPT). We analyzed the trends of ultrasonic P-wave impedance and Vp/Vs of laboratory data changing with lithology, porosity, and total organic carbon (TOC) content. Our data provide parametric sensitivity regarding porosity and TOC content by use of a bi-material-matrix–double-inclusion concentration model. We propose a modified RPT of P-wave impedance versus Vp/Vs with three end members (sandstone, dolostone, and mudstone) to predict porosity and lithology of reservoirs. We also present a new RPT of density versus Poisson ratio with the same three end members to predict TOC content and lithology of source rocks. These were validated by comparisons with laboratory measurements and log data. We inverted the porosity, TOC content, and thickness of the upper reservoir segment in the Lucaogou Formation of the J17 work area of Jimusar Sag by using the new RPT quantitative prediction method. The inversion results were identical to oil testing results, supporting the viability and effectiveness of the new RPTs.

Prediction of coal-bearing strata characteristics using multi-component seismic data—a case study of Guqiao coalmine in China

The longwall mining method has been widely used in underground mining of coal seams. For longwall mining, the stability of coal-seam roofs and hardness of coal rocks in coal-bearing strata are particularly important. High-precision multi-component seismic exploration technology can obtain more parameters for characterizing coalbed reservoirs than conventional methods, and it is gradually replacing conventional P-wave technology in coalfield exploration. We have obtained multi-component seismic data from the central mining area of Guqiao Coal Mine, in the Huainan area, China. Using constraints from logging information, and seismic data, joint PP- and PS-wave inversion and interpretation have been performed. The coal seam 13-1, located in a Permian formation, was studied to determine the lithology of the coal-seam roof and floor, evaluate the stability of the coal-seam roof, and determine the hardness of coal rocks in coal seam 13-1. The distribution characteristics of lithology, roof stability, and hardness of coal rocks in coal seam 13-1 were also investigated. To achieve this, we used P- to S-wave velocity ratios to identify the lithology, evaluated the roof stability with parameters LambdaRho and MuRho, and used Young’s modulus to evaluate the hardness of the coal rocks. Our predicted results are in good agreement with the interpretative results from logging information, which shows the accuracy of our method. The joint PP- and PS-wave inversion and interpretation used in this paper can obtain more accurate information for evaluating coalbed reservoirs than conventional methods, which are valuable in assessing mine safety.

Characteristics of the impedance variation in clastic rock reservoirs and lithology interpretation method for the threshold volume

Abstract An analysis of the petrophysical characteristics of a reservoir demonstrated that the variations in wave velocity were controlled by sedimentary and diagenetic differences, resulting in regular variations in the acoustic impedance. The sedimentary differences are mainly associated with the grain size, sorting and shale content and lead to a slow horizontal change in the wave impedance of the reservoir; the diagenetic differences are associated with compaction, pressure dissolution and cementation and lead to a rapid vertical change in the wave impedance of the reservoir. The classic single threshold method only resolved the vertical variation in the acoustic impedance. As a result, the threshold volume method is proposed. The results of a case study demonstrate that the proposed method yields a more accurate and reliable interpretation of lithology using acoustic impedance than the single threshold method. In particular, the method effectively solves the uncertainty in the sand interpretation using the plane variation of impedance caused by the deposit.

Methylated naphthalenes as indicators for evaluating the source and source rock lithology of degraded oils

Methylated naphthalenes in oils/condensates are relatively resistant to bio- and thermal degradation and can be useful compounds for evaluating the source organic matter and source rock lithology. Assuming that cadinene, abietic acid, and cholesterol are major precursors of methylated naphthalenes in oils and condensates, laboratory hydrous pyrolysis experiments for these possible precursors were performed to understand the precursor/products relationship. The major dimethylnaphthalenes (DMNs) and trimethylnaphthalenes (TMNs) in pyrolyzates of cadinene and abietic acid were 1,2,5-TMN and 1,6- and 1,5-DMNs, whereas those in pyrolyzates of cholesterol were 2,3,6-TMN and 1,3- and 1,7-DMNs. The experimental results suggested that the dimethylnaphthalene ratio (DMR) of [1,5- + 1,6-DMNs]/[1,3- + 1,7-DMNs], and the trimethylnaphthalene ratio (TMR) of 1,2,5-TMN/2,3,6-TMN, can be potential indicators of source organic matter. The relative abundance of TMNs in the pyrolyzates was controlled largely by the maturity level and presence or absence of montmorillonite catalyst. The relative abundance of total TMNs to total MNs (ΣTMNs/ΣMNs ratio) can be a novel indicator for evaluating the clay-catalytic effect in source rocks. A lower ΣTMNs/ΣMNs ratio is related to clay-poor source rocks, such as coal, carbonates, and siliceous rocks, whereas a higher ΣTMNs/ΣMNs ratio suggests shaly (clay-rich) source rocks. The DMR, TMR, and ΣTMNs/ΣMNs ratios of various oils and condensates are very consistent with their source organic matter and source rock lithology, indicating that these indicators are practically useful.

Source Rock Characterictic of The Kızıldere Clays (ARSUZ-HATAY)

Iskenderun Bay is the extension of the Adana Basin and is a convenient place for hydrocarbon exploration in terms of its formation mechanism. It is necessary to find rocks that can display lithological properties of source, reservoir and cover rocks in the mechanism of oil formation. There are formations in reservoir and cover rock lithology in İskenderun basin.Kızıldere formation, which is the main rock, has gray-colored sandstone claystone sequences. Sandstones are 10-50 cm thick and claystones 2-30 cm thick. Stratified gypsium levels are observed at the top of the succession of sandstone and claystone and the thickness of the layers is between 5 and 15 cm. The hydrocarbon production of Kızıldere Formation clay was found by calculating the amount of TOC (Total Organic Carbon) and the average value was 0.56%. In addition, TOC values in the region are higher in the north and north east of the region and decrease in the south. The sandstones in the region where the tectonic fractures are abundant due to MisisAndırın systems are reservoir rocks, and the evaporitic units known as Haymaseki formation are cover rocks.