Petrology Of Rocks Research Articles

Organic Matter of Domanik Deposits of the Timan–Pechora Basin: the Oil Window Conditions

Abstract —A comprehensive study of Domanik deposits of the Timan–Pechora Basin has been carried out. The examined composition of hydrocarbon biomarkers, chemical structure of kerogen, carbon isotope composition, and rock lithology, the Rock-Eval pyrolysis data, and the contents of bitumen and Corg in the rocks give an insight into the geochemical processes in the oil window in the Domanik deposits, which took place at Tmax = 435–450 °C. The bitumen coefficient βCB is maximum in this temperature interval, reaching 30%. The obtained data on the distribution of polycyclic biomarkers in the Domanik rocks and the bitumen and Rock-Eval pyrolysis data allowed determining the boundary values of biomarker maturity coefficients in the study of the maturation of organic matter of the rocks. The carbon isotope composition of bitumen fractions in the Domanik rocks is considered, and the bimodal distribution of the δ13C values of the bitumen is shown.

Impact of Chelating Agent Salt Type on the Enhanced Oil Recovery from Carbonate and Sandstone Reservoirs

In this paper, chelating agents were introduced as standalone fluids for enhancing the oil recovery from carbonate and sandstone reservoirs. Chelating agents such as glutamic acid di-acetic acid (GLDA), ethylene-diamine-tetra acetic acid (EDTA), and hydroxyl-ethylethylene-diamine-tri-acetic acid (HEDTA) were used. Chelating agents can be found in different forms such as sodium, potassium, or calcium salts. There is a significant gap in the literature about the influence of salt type on the hydrocarbon recovery from carbonate and sandstone reservoirs. In this study, the impact of the salt type of GLDA chelating agent on the oil recovery was investigated. Potassium-, sodium-, and calcium-based high-pH GLDA solutions were used. Coreflooding experiments were conducted at high-pressure high-temperature (HPHT) conditions using carbonate and sandstone cores. The used samples had porosity values of 15–18%, and permeability values were between 10 and 75 mD. Seawater was injected as a secondary recovery process. Thereafter, a GLDA solution was injected in tertiary mode, until no more oil was recovered. In addition to the recovery experiments, the collected effluent was analyzed for cations concentrations such as calcium, magnesium, and iron. Moreover, dynamic adsorption, interfacial tension, and contact angle measurements were conducted for the different forms of GLDA chelating agent solutions. The results of this study showed that incremental oil recovery between 19% and 32% of the Original Oil in Place (OOIP) can be achieved, based on the salt type and the rock lithology. Flooding carbonate rocks with the calcium-based GLDA chelating agent yielded the highest oil recovery (32% of OOIP), followed by that with potassium-based GLDA chelating agent, and the sodium-based GLDA chelating agent yielded the lowest oil recovery. The reason behind that was the adsorption of the calcium-based GLDA on the rock surface was the highest without reducing the rock permeability, which was indicated by the contact angle, dynamic adsorption, and flooding experiments. The outcome of this study will help in maximizing the oil recovery from carbonate and sandstone reservoirs by suggesting the most suitable salt type of chelating agents.

Testing Landscape, Climate and Lithology Impact on Carbon, Major and Trace Elements of the Lena River and Its Tributaries during a Spring Flood Period

Transport of carbon, major and trace elements by rivers in permafrost-affected regions is one of the key factors in circumpolar aquatic ecosystem response to climate warming and permafrost thaw. A snap-shot study of major and trace element concentration in the Lena River basin during the peak of spring flood revealed a specific group of solutes according to their spatial pattern across the river main stem and tributaries and allowed the establishment of a link to certain landscape parameters. We demonstrate a systematic decrease of labile major and trace anion, alkali and alkaline-earth metal concentration downstream of the main stem of the Lena River, linked to change in dominant rocks from carbonate to silicate, and a northward decreasing influence of the groundwater. In contrast, dissolved organic carbon (DOC) and a number of low-soluble elements exhibited an increase in concentration from the SW to the NE part of the river. We tentatively link this to an increase in soil organic carbon stock and silicate rocks in the Lena River watershed in this direction. Among all the landscape parameters, the proportion of sporadic permafrost on the watershed strongly influenced concentrations of soluble highly mobile elements (Cl, B, DIC, Li, Na, K, Mg, Ca, Sr, Mo, As and U). Another important factor of element concentration control in the Lena River tributaries was the coverage of the watershed by light (for B, Cl, Na, K, U) and deciduous (for Fe, Ni, Zn, Ge, Rb, Zr, La, Th) needle-leaf forest (pine and larch). Our results also suggest a DOC-enhanced transport of low-soluble trace elements in the NW part of the basin. This part of the basin is dominated by silicate rocks and continuous permafrost, as compared to the carbonate rock-dominated and groundwater-affected SW part of the Lena River basin. Overall, the impact of rock lithology and permafrost on major and trace solutes of the Lena River basin during the peak of spring flood was mostly detected at the scale of the main stem. Such an impact for tributaries was much less pronounced, because of the dominance of surface flow and lower hydrological connectivity with deep groundwater in the latter. Future changes in the river water chemistry linked to climate warming and permafrost thaw at the scale of the whole river basin are likely to stem from changes in the spatial pattern of dominant vegetation as well as the permafrost regime. We argue that comparable studies of large, permafrost-affected rivers during contrasting seasons, including winter baseflow, should allow efficient prediction of future changes in riverine ‘inorganic’ hydrochemistry induced by permafrost thaw.

Internal architecture and earthquake rupture behavior of a long-lived intraplate strike–slip fault: A case study from the Southern Yangsan Fault, Korea

Deciphering the internal composition of large-scale fault zones helps to better understand the various geologic factors that govern their seismic rupture behavior. We used new detailed geologic, structural, and geomorphic map of an excellent natural laboratory in the Southern Yangsan Fault (SYF) in the southeastern part of the Korean Peninsula to elucidate the fault zone architecture and its controls on the rupture processes of neotectonic earthquakes. The Yangsan Fault is a major strike–slip fault, and a subsidiary fault within the fault zone ruptured during the 2016 ML 5.8 Gyeongju earthquake which is the largest instrumental record in the intraplate Korean Peninsula. The 12-km-long study area in the SYF shows along-strike variations in wall rock lithology and fault zone architecture. At the south of the study area, the fault zone surrounded by crystalline rocks consists of a single major fault core. In contrast, at the north, the fault zone is sandwiched between crystalline rocks and sedimentary rocks and exhibits multiple major fault cores bounding broken-up wall rock blocks. The width of the across-fault damage zone, which was estimated from the cumulative fracture frequency with the distance from the major fault core, widens northward, indicating the distributed deformation of the northern fault zone over a long history of fault evolution. The geometry of paleoearthquake surface ruptures traced by the geomorphic and stratigraphic evidence of deformed young deposits diverge to multiple strands in the northern fault zone but converge to a single strand in the southern fault zone, directly reflecting its internal architecture. We propose that the long-lived rupturing patterns have been primarily controlled by intrinsic discontinuity- and mineralogy-dependent deformation processes in terms of strain-hardening vs. strain-weakening, along with propagation arrest and rupture tip damage due to a fault-bend geometry (geometric barrier) and an abrupt change in wall rock lithology (relaxation barrier).

Geochemistry of the Yumen picrites-basalts from the Emeishan large igneous province: Implications for their mantle source, PGE behaviors, and petrogenesis

Olivine compositions are often used to infer the source lithology of basaltic rocks, but the effect of source melting conditions on olivine chemistry remains poorly studied. Here we present mineral chemistry, whole-rock major and trace elements, SrNd isotopes, and platinum-group element (PGE) concentrations for high-Ti picritic-basaltic rocks from Yumen area. These data provide new constraints on the source lithology and petrogenesis of these high-Ti rocks in the Emeishan large igneous province (ELIP). The picrites have primitive compositional features (e.g., high Mg# values, depleted SrNd isotopic compositions, no PGE depletions and/or fractionations). Some basaltic rocks have negative NbTa anomalies, enriched SrNd isotopic compositions, and depleted and/or fractionated PGE contents, indicative of fractional crystallisation, variable degrees of crustal contamination, and magmatic sulfide segregation. Combined with published data for the ELIP, the compositions of the primitive magmas and 10000Zn/Fe and FC3MS (FeO/CaO − 3 × MgO/SiO2, all in wt%) values of the ELIP high-Ti picrites are similar to those of garnet peridotite-derived experimental melts. Based on the primitive magma compositions, the ELIP high-Ti melts could have been produced by mantle melting at 4.0–5.4 GPa and 1620–1660 °C, and started to crystallise olivine at 1410–1550 °C, based on the Al-in-olivine thermometer, which are higher temperatures than for mid-ocean ridge basalts and ELIP low-Ti magmas. The high-Ni and low-Mn olivine phenocrysts in the ELIP high-Ti samples crystallised from peridotite-derived, MgO-rich melts at high temperatures. Variations in the physicochemical source melting conditions was enough to explain the differences in olivine Ni and Mn contents in the ELIP high- and low-Ti picrites-basalts. Additionally, the almost constant Pd, Pt, and Rh contents with decreasing Mg# values indicate intermediate partition behaviors in the ELIP magmas. No correlations exist between whole-rock 10,000 × Pd/Yb and Mg#, (Th/Nb)N, and εNd(t) values, implying that selective assimilation of crustal sulfur resulted in magmatic sulfide saturation. We propose that the ELIP high-Ti magmas were derived from a deep-sourced garnet peridotite, and experienced various igneous processes during ascent through the continental lithosphere to form different types of ELIP high-Ti basaltic rocks.

Predicting the Rock Sonic Logs While Drilling by Random Forest and Decision Tree-Based Algorithms

AbstractThe sonic data provide significant rock properties that are commonly used for designing the operational programs for drilling, rock fracturing, and development operations. The conventional methods for acquiring the rock sonic data in terms of compressional and shear slowness (ΔTc and ΔTs) are considered costly and time-consuming operations. The target of this paper is to propose machine learning models for predicting the sonic logs from the drilling data in real-time. Decision tree (DT) and random forest (RF) were employed as train-based algorithms for building the sonic prediction models for drilling complex lithology rocks that have limestone, sandstone, shale, and carbonate formations. The input data for the models include the surface drilling parameters to predict the shear and compressional slowness. The study employed data set of 2888 data points for building and testing the model, while another collected 2863 data set was utilized for further validation of the sonic models. Sensitivity investigations were performed for DT and RF models to confirm optimal accuracy. The correlation of coefficient (R) and average absolute percentage error (AAPE) were used to check the models’ accuracy between the actual values and models’ outputs, in addition to the sonic log profiles. The results indicated that the developed sonic models have a high capability for the sonic prediction from the drilling data as the DT model recorded R higher than 0.967 and AAPE less than 2.76% for ΔTc and ΔTs models, while RF showed R higher than 0.991 with AAPE less than 1.07%. The further validation process for the developed models indicated the great results for the sonic prediction and the RF model outperformed DT models as RF showed R higher than 0.986 with AAPE less than 1.12% while DT prediction recorded R greater than 0.93 with AAPE less than 1.95%. The sonic prediction through the developed models will save the cost and time for acquiring the sonic data through the conventional methods and will provide real-time estimation from the drilling parameters.

Characteristics of coal-measure source rock and its controlling effect on gas-water distribution of tight sandstone of He8 Member in Sulige Gas Province, Ordos Basin

Characteristics of complex gas-water distribution affect the efficient exploration of tight gas. The paper aims at tight sandstone gas-water distribution characteristics of He8 Member in Sulige Gas Province (SGP), describes thickness and TOC of source rocks from Benxi Formation in Carboniferous to the Second Member of Shanxi Formation in Permain, evaluates its hydrocarbon generation potential, discusses its controlling effect on tight sandstone gas-water distribution, and determines the threshold values of Ro and HGI of commercial gas flow wells. Research shows that the coal-measure source rock has the characteristics of extensive and superimposition. The coal seam and dark mudstone is the lithology of source rock, and its Ro is chiefly distributed 1.2% ∼ 2.1% in the stage of high mature thermal evolution, which is mainly type III kerogen. Among them, the thickness of coal seam is mainly ranged from 5 ∼ 15 m with an average of 9.32 m, and its average TOC is 64.08% and the distribution of HGI is (1∼36) ×108 m3/km2. No.8 and No.5 coal seams are relatively stable. The extent of thickness of dark mudstone is mainly between 10m and 30m with an average of 21.2m, and its average TOC is 2.11%, HGI is between (0.2∼10)×108m3/km2. Gas reservoir of He8 Member is tight sandstone lenticular reservoirs with the large-area quasi-continuous distribution. When the gas testing production is less than 1 × 104m3/d, the controlling effect of Ro and HGI are relatively obvious, and its controlling effect is obviously weakened with the increase of gas production. When Ro is more than 1.6%-1.7%, or HGI is larger than 15 × 108m3/km2, the decreasing trend of water/gas ratio is evident, especially in commercial gas flow wells (including high producing gas flow wells). In comparison, the controlling effect of HGI is stronger than Ro. 1.33% and 8 × 108 m3/km2 are the threshold values of Ro and HGI for commercial gas flow wells, respectively.

Pengelolaan Air Asam Tambang dari Batuan Sisa di Pit Barani dan Ramba Joring serta Aplikasi Model Enkapsulasi pada Bendungan Tailing di Tambang Emas Martabe

Acid mine drainage is one of the significant negative impacts of mining activities that can result in environmental degradation. Waste rock is mine waste that is found in large quantities and can produce acid mine drainage (AMD). This study aims to identify waste rock which has the potential to generate acidity (PAF) and do not generate acidity (NAF) in the Barani and Ramba Joring pits and the application of the encapsulation model in tailings dams. The research method with the encapsulation model is a simple method designed in tailings dams to encapsulate the PAF with the NAF. Rock characterization and geochemical analysis will result in the rock being classified as PAF and NAF in both wells . The data used for this study are drilling data (cutting) data that include rock lithology and chemical quality (NAPP and NAG) data. The results identified that the PAF was dominant relative to the NAF both wells and the waste rock in the Barani pit was at a higher risk of producing acidity than the Ramba Joring pit. Measurements of oxygen diffusion and surface water quality indicated that encapsulation of waste rock in the tailings dam may prevent the formation of acidic mine drainage

A column study of the impact of layering the different Lac Tio mine waste rock lithologies on drainage water quality

In the mining industry, the extraction of waste rocks (WR), without economic value, is needed to access ore deposits. The amount of WR are very large in the case of open pit mines. They are usually stored at the surface in waste rock piles. The presence of reactive minerals such as sulphides in waste rock can lead to the contamination of drainage water that come-out from these waste rock piles. In order to limit the production of contaminants and the volume of drainage water, an innovative method of construction of waste rock piles has been developed. In this context, an experimental waste rock pile was constructed at the Lac Tio mine near Havre-Saint-Pierre (Quebec, Canada) to evaluate the performance of this approach in field conditions. To understand the geochemical mixing between the leachate from the hemo-ilmenite and anorthosite waste rock layers constituting this experimental pile, tests using lab columns that were filled with layers of these two types of materials were run. The anorthosite and hemo-ilmenite waste rock subjected to column tests generated near-neutral drainage (pH ~7) containing up to 4.5 mg/l of nickel, and 1500 mg/l of sulphate. The nickel and sulphate release rates varied from one to two orders of magnitude depending on the type of waste rocks and their configuration (pure or mixed with each other). The drainage water quality was affected by changes in the volume of rinsing water, by the precipitation/dissolution of secondary minerals, and by Ni sorption within anorthosite waste rock. This study demonstrates that the storage of hemo-ilmenite waste rock over anorthosite waste rock is an effective way to reduce Ni levels in drainage waters from the Lac Tio mine materials.

STUDY OF GENESİS OF PRODUCTİVE SERİES SEDİMENTS BY PETROPHYSICAL PARAMETERS

It is known that over than 90% of oil produced in Azerbaijan is extracted from the South Caspian Basin. The South Caspian basin is one of the largest deeply buried basins. Sedimentation process here is characterized by high rate as 25 km for 150-170 mln. years (0.6-0.7 km/mln.years). Last year’s due to acceleration in search and exploration works and assessment of the outlook for oil and gas deposits research of the genesis of Productive Series attracts a lot of attention. İn this paper “Quantitative and qualitative models of log facies” on the basis of well logging data the analysis of lithology, facies and genesis of sedimentary rocks in Pirallahi structure have been done and results were derived. Within the framework of the study by use of Neuralog software based on LL, SP, GL, NGL and other log types the data have been transformed into the LAS format, then the, porosity, bulk clay coefficient and thickness of facies alteration models have been designed by use of Petrel software. Study of sedimentation environment constantly draws the interest of geoscientists due to the direct dependence of structure and identification of oil and gas traps on sedimentation environment. This paper deals with study of genesis of Productive Series deposits based on quantitative and qualitative analysis of logging curves. The study target is Kirmaky suite across Pirallahi field of Absheron oil-gas bearing region. Study of sedimentation environment constantly draws the interest of geoscientists due to the direct dependence of structure and identification of oil and gas traps on sedimentation environment. This paper deals with study of genesis of Productive Series deposits based on quantitative and qualitative analysis of logging curves. The study target is Kirmaky suite across Pirallahi field of Absheron oil-gas bearing region. Keywords: facies analysis, log facies, genesis, flow, bar, coastal plain.

Differentiating between hydrothermal and diagenetic carbonate using rare earth element and yttrium (REE+Y) geochemistry: a case study from the Paleoproterozoic George Fisher massive sulfide Zn deposit, Mount Isa, Australia

Carbonate minerals are ubiquitous in most sediment-hosted mineral deposits. These deposits can contain a variety of carbonate types with complex paragenetic relationships. When normalized to chondritic values (CN), rare-earth elements and yttrium (REE+YCN) can be used to constrain fluid chemistry and fluid-rock interaction processes in both low- and high-temperature settings. Unlike other phases (e.g., pyrite), the application of in situ laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) data to the differentiation of pre-ore and hydrothermal carbonates remains relatively untested. To assess the potential applicability of carbonate in situ REE+Y data, we combined transmitted light and cathodoluminescence (CL) petrography with LA-ICP-MS analysis of carbonate mineral phases from (1) the Proterozoic George Fisher clastic dominated (CD-type) massive sulfide deposit and from (2) correlative, barren host rock lithologies (Urquhart Shale Formation). The REE+YCN composition of pre-ore calcite suggests it formed during diagenesis from diagenetic pore fluids derived from ferruginous, anoxic seawater. Hydrothermal and hydrothermally altered calcite and dolomite from George Fisher is generally more LREE depleted than the pre-ore calcite, whole-rock REE concentrations, and shale reference values. We suggest this is the result of hydrothermal alteration by saline Cl--rich mineralizing fluids. Furthermore, the presence of both positive and negative Eu/Eu* values in calcite and dolomite indicates that the mineralizing fluids were relatively hot (>250°C) and cooled below 200–250°C during ore formation. This study confirms the hypothesis that in situ REE+Y data can be used to differentiate between pre-ore and hydrothermal carbonate and provide important constraints on the conditions of ore formation.

Typical Zone Division of Karst Kevelopment in China

Determining the typical area of karst development in China would provide positive reference for theoretical research of engineering geology in karst areas in China. By quantitative or semi-quantitative analyzing on the distribution characteristics, climatic conditions and formation lithology of carbonate rocks in China, regional difference characteristics of karst development in carbonate rock regions in China is evaluated, and finnally the representative karst zone in China is reasonably and theoretically delineated and demonstrated. Results show that: the pure Carbonate rocks in southwest of China in tropical and subtropical climate zone which are very favorable for karst development, distributes continuously and massively, and therefore can be considered as the most typical karst area,. this is also a very explanation that karst morphology develops completely. Especially, karst in the zone including Guangxi Zhuang Autonomous Region, southeast and north-east of Guizhou province, and southeastern of Chongqing Municipality, is the most representative karst region in southwest of china because of its the purest carbonate rocks.

WITHDRAWN: Different methods for lithology and mineralogy recognition

Abstract Formations lithology determination is very important for formations properties, because the chemical and physic rock properties contains water or hydrocarbons effect on response of tools used to estimate reservoir characterization. To get the most accurate results, it is better to use the different methods for determining the rock lithology, which are: Neutron-Density Cross Plot, Sonic-Density Cross Plot, M−N Mineral Plot and the Matrix Identification plot (MID). The results of the selected methods show the excellent way to identify the rock formation, while relying on only one method in determining the magma does not achieve accurate results. In addition, there is consistency in the results of these methods which gives confidence in the results obtained. When these four methods were used in our study of the Jeribe formation in a field in northern Iraq, it was found that the rock formation is limestone and dolomite, but that the limestone is more than dolomite with little sandstone.

Investigation of Groundwater Potential Based On Vertical Electrical Sounding Methode On Gosoma District In North Halmahera

Population growth has encourage an increasing of clean water needs as a basic human necessity, both in terms of quality and quantity. River water and rain water are sources of raw materials for these elementary needs, however global climate change has indirectly affected the hydrological characteristics of the last few decades. Thus, the use of ground water is a solution in meeting these needs. The research aims to identify the potential presence of ground water that can be used as a source of fresh water in the village of Gosoma, Tobelo, North Halmahera Regency. This potential fresh water investigation was carried out using a Mc Ohm Mark-2 OYO resistivity meter, while the Schlumberger configuration was the measurement method used. The length of the track geoelectric extends as far as 1,060 m, while for transverse profiles as far as 560 with a total number of measurement points of 6 points. The results of geoelectric measurements show that there are 2 layers that have the potential as deep aquifers. First groundwater layers predicted at a depth that varies between 21.10 m - 83.00 m and secondary groundwater layer may exist deeper than 95.90 m above the surface. This result were indicated by resistivity values measured at the observed points, where the values varies from 18.10 ohms to 91.30 ohms. Those resistivity value illustrates that lithology of the soil layer were indicated as a layer of sand and sandy tuff, where both of the rock lithologies layer have a potential as a layer of ground water.

The Implementation of Machine Learning in Lithofacies Classification using Multi Well Logs Data

Lithofacies classification is a process to identify rock lithology by indirect measurements. Usually, the classification is processed manually by an experienced geoscientist. This research presents an automated lithofacies classification using a machine learning method to increase computational power in shortening the lithofacies classification process's time consumption. The support vector machine (SVM) algorithm has been applied successfully to the Damar field, Indonesia. The machine learning input is various well-log data sets, e.g., gamma-ray, density, resistivity, neutron porosity, and effective porosity. Machine learning can classify seven lithofacies and depositional environments, including channel, bar sand, beach sand, carbonate, volcanic, and shale. The classification accuracy in the verification phase with trained lithofacies class data reached more than 90%, while the accuracy in the validation phase with beyond trained data reached 65%. The classified lithofacies then can be used as the input for describing lateral and vertical rock distribution patterns.

Correlation of lithofacies and depositional environment using Markov chain analysis in Sambipitu formation at Ngalang river, Gunungkidul, Yogyakarta, Indonesia

The research area is located at Ngalang river, Gedangsari sub-district, Gunungkidul Regency, Special Region of Yogyakarta. The research area is part of southern mountain area which is composed of lithology of Sambipitu calcareous sandstone. The depositional process phase in the Sambipitu formation has a unique pattern and is relevant to the previous lithology. As a result, the stratigraphic position and lithological repetition pattern were reviewed using the statistical method (Markov chain). The aim of this research is to use geostatistics to examine the sedimentation trend in order to predict the existence of rock facies in the Sambipitu Formation. In each unit of lithology cycle, geostatistics is expected to assist, to predict and to interpret the significance of subsequent lithology appearances. The research method used was measured stratigraphy, determination of rock age and depositional environment based on fossil identification. In addition, this research used probability matrix in Markov chain analysis. The results of the Markov chain analysis showed that lithology of rock in the upper Sambipitu formation had a non-random transition pattern. The results of statistical calculation showed that the calculation value was greater than the Chi-square table value (333.9>34.38) that the H0 component was rejected. Lithofacies and depositional environment are correlated to several geological aspects such as distribution of rock facies, source of rock, paleobtahymetri, trace fossils and sedimentation process.

Multiple Influence Factor Sensitivity Analysis and Height Prediction of Water-Conducting Fracture Zone

To explore the influence law and sensitivity of various factors on the height of the water-conducting fracture zone, and further predict the development height of the water-conducting fracture zone, taking the field survey and collected actual measured data as the research foundation, establishing mathematical model, regression analysis, and field measurement were adopted comprehensively. Based on the Data Processing System (DPS), influence factors of the development height of the water-conducting fracture zone were analyzed. By introducing sensitivity coefficient, a sensitivity quantification mathematical model was established, and sensitivity ranking was obtained. The regression relationship between each factor and the height of the water-conducting fracture zone was obtained by single factor analysis. Based on this, the prediction formula was proposed and successfully used in the field practice. Results show that the sensitivity coefficient of mining thickness, ratio coefficient of hard rock lithology, mining depth, and length of working face was 0.75, 0.69, 0.66, and 0.58, respectively. The dispersion degree of working face length and mining depth was greater than that of ratio coefficient of hard rock lithology and mining thickness. To some extent, it also reflects that the sensitivity of working face length and mining depth to the height of the water-conducting fracture zone was the weakest, which was consistent with the previous conclusions. Using the multiple regression mathematical model, a nonlinear statistical relationship between the height of the water-conducting fracture zone and ratio coefficient of hard rock lithology, mining thickness, working face length, and mining depth was obtained. This research provides some scientific basis and guidance for safe and efficient underwater mining.

Precipitation/dissolution and precipitants movement mechanisms effects on injectivity variations during diluted produced water re-injection into a layered reservoir - experimental investigation

ABSTRACT Permeability reduction is one of the significant problems in the water injection process. Several mechanisms may be involved in permeability reduction including scale formation, suspended particle invasion and fines migration. On the other hand, rock dissolution may also lead to permeability improvement of carbonate rocks. In this research, effect of rock lithology along with incompatibility of injection and formation brines, scale formation and plugging of pores by particles in the injection water for a layered reservoir were examined. Diluted formation brine (produced from desalination unit) was considered as injection water. Simulation of scale formation due to thermodynamic conditions and mixing of formation and injection brines were performed to investigate amount and types of scales. Simulation and jar tests showed that Scale precipitation decreased with increasing the mixing ratio of injection water to 75%. For core flooding tests, both carbonate and sandstone core samples from a layered candidate reservoir were selected for monitoring of formation damage and permeability variation due to incompatibility of fluids. SEM and EDX analysis were used for static and dynamic tests. Carbonate core sample showed sever damage and competition between scale precipitation and rock dissolution. Higher flow rates contribute to permeability enhancement of carbonate rocks by prevention of scale sedimentation (less scale formation) and acceleration of carbonate rock dissolution. As a pressure difference increasing of 60% was shown in the first stage of water injection process into the carbonate rock. Eventually, after increasing and decreasing the injection rate, the pressure difference decreased to 30 presences. Scale formation mechanism is dominant in sandstone rock samples and can be removed by backflow. As pressure difference decreased 27% in sandstone rock sample, which resulted in permeability decrease from 365 to 265 mD.

Detection of water seepage in lake body using ground penetrating radar method

Ground Penetrating Radar (GPR) is a geophysical method used to identification subsurface condition at a certain depth, using a source of electromagnetic waves in the form of radar. Geoscanners Akula A9000C and Antenna Gecko 60 with 60 MHz antenna frequency were used for data acquisition for this study. Survey data was conducted as many four lines, located on the south and east sides of the lake, with the distance range from 0 to 145 m. This paper reports basic signal processing GPR data using matGPR for the analysis and modelling. The results show that there is anomaly which is suspected as water seepage appear on depth of 2 m. On the lengthwise line, anomalies show on a distance of 20 m and 35 m (line A) and 125 m and 135 m (line B), while on the crosswise line anomalies show on a distance of 35 m and 50 m (line C), 25 m and 95 m (line D). Water seepage can be found in this area as it is formed by alluvial depositional environment, remembering that the characteristics and rocks lithology in this area can stimulate water infiltration process. Water seepage will cause erosion of the lake and can collapse the lake’s structure.

Probabilistic analysis of Vette fault stability in potential CO2 storage site Smeaheia, offshore Norway

Reliable assessment of fault stability is key for safe CO2 storage in a saline aquifer in fault-bounded structures. The Alpha structure located in the Vette fault's footwall in the Smeaheia area, offshore Norway, is one of the potential CO2 storage sites with a fault-bounded three-way closure. Assessing fault stability in the Smeaheia area is challenging because of the uncertainties associated with the subsurface fault properties (i.e., fault rock lithologies, strength and geometry of faults, etc.). Besides, CO2 injection-related pore pressure changes is another critical factor for mechanical deformation and potential failure. We employed a stochastic analytical approach to assess the probability of Vette fault failure using the Monte Carlo Simulation (MCS) and First Order Reliability Method (FORM). The possible fault smear scenarios of the Vette fault zone are evaluated by interpreting the seismic section and the detailed geological understanding. Each scenario's likelihood and the corresponding probability of failure are then integrated stochastically using an event tree method. Overall, Vette fault's system reliability shows a good to average performance range, which has a system probability of failure between 10−3 to 10-4. This finding suggests that the Vette fault will likely act as a potential barrier during CO2 injection into the Alpha structure. Moreover, the sensitivity study reveals that the stresses (both horizontal and vertical) and fault rock strength (i.e., cohesion and friction angle) are the most crucial parameters to characterize uncertainty reduction.