Carbonate Rock Formations Research Articles

Understanding the processes in a historically relevant thermal and mineral spring water by using mixing and inverse geochemical models.

The thermal mineral water of Peñón de los Baños spa (Mexico City) has been used for over 500years starting in pre-Hispanic times and is famous for the treatment of various pathologies. It has a temperature of 45°C, which is rich in HCO3-, and its main trace elements are B, Li and Fe, which confers healing effects. Concerns about the sustainability of this important spa have motivated this study to understand the thermal system, possible hydraulic and hydrochemical changes over time and its implications. Stable water isotope data indicate that the thermal water sources originate from local precipitation at Sierra de las Cruces with a recharge elevation of approximately 2770m above sea level. The recharged water percolates through volcanic and carbonate rock formations and ascends via fault structure conduits, where it eventually is extracted 25km downstream in Peñon de los Baños. During the gravity-driven deep circulation of up to 4.9km, the groundwater is heated up to 136-160°C. A comparison of past and current water levels and water chemical analyses indicates a water table drop and few variations in the chemical composition, confirming the presence of anthropic impact on water quality. Due to the heavy groundwater extractions in Mexico City, the spring water flow has ceased, and water must be pumped now from a 203-m deep well. In addition, the concentration of bicarbonate, sodium and chloride has been reduced by half since the onset of groundwater development. The therapeutic effects of this thermal mineral water are at risk due to the alteration of the chemical signature. However, new and different therapeutical uses may prevent a future deterioration or closure of this historically important thermal spa. It is crucial to establish a monitoring program of the thermal mineral water and reducing or minimizing nearby urban extractions which tap the regional flow component to preserve the properties of the thermal water.

Discovery of iron orebodies in the Dahalajunshan Formation carbonate rocks in the Beizhan volcanic-hosted iron deposit, Xinjiang and its genetic significance

Discovery of iron orebodies in the Dahalajunshan Formation carbonate rocks in the Beizhan volcanic-hosted iron deposit, Xinjiang and its genetic significance

In situ stress characteristics of the NE Sichuan basin based on acoustic emission test and imaging logging

This study presents the distribution rule of in situ stress in the northeast Sichuan basin and its relationship with fracture. Sixty-seven sets of core samples of 21 Wells from the terrigenous clastic rock formation (Shaximiao, Qianfoya, Xujiahe) and marine carbonate formation (Jialingjiang, Leikoupo, Feixianguan) in the northeast Sichuan basin were tested by acoustic emission experiment. The in situ stress variation with the depth was established and the corresponding regression analysis was done. The horizontal principal stress direction of terrigenous clastic rock formation and marine carbonate rock formation was obtained by combining the dual diameter data of 6 wells and the imaging logging data of 3 wells. The results show that the vertical stress in the northeast of Sichuan basin has a linear relationship with the depth, and there is little difference between the vertical stress and the overburden weight of rocks. The maximum and minimum horizontal principal stress and horizontal shear stress increase with the burial depth. The divergence degree of horizontal shear stress with depth greater than 3000 m is greater than that of the stratum smaller than 3000 m. The horizontal stress plays a dominant role in the northeast Sichuan basin. With the increase in depth, the influence of tectonic stress field decreases and the vertical stress increases. Impacted by Dabashan and Qinling plate tectonic movement, the direction of in situ stress in marine carbonate strata is nearly east–west. The direction of maximum horizontal principal stress in terrigenous clastic rock formation is basically northwest–southeast. The imaging logging data show that the fracture direction is consistent with the horizontal principal stress direction, and the present in situ stress direction is favorable to the secondary reconstruction of natural fractures, and the fractures keep good opening. The distribution law of in situ stress in northeast Sichuan basin shows σH > σV > σh, indicating that the fault activity in this area is dominated by strike-slip type, the tectonic stress field is dominated by horizontal tectonic stress, in addition that the stress state is conducive to reverse fault activity.

Formation and Structures of Horizontal Submarine Fluid Conduit and Venting Systems Associated With Marine Seeps

AbstractMethane‐rich water moves through conduits beneath the seafloor whose surfaces are formed through precipitation reactions. To understand how such submarine fluid conduit and venting systems form and grow, we develop a detailed mathematical model for this reaction‐advection system and we quantify the evolution of an ensemble of similar filaments. We show that this growth can be described by a superposition of advection and dispersion. We analyze analog laboratory experiments of chemical‐garden type to study the growth of a single filament undergoing a precipitation reaction with the surrounding environment. We apply these findings to geological fluid conduit and venting systems, showing that their irregular trajectories can lead to very effective spreading within the surrounding seabed, thus enhancing contact and exchanges of chemicals between the conduit and external fluids. We discuss how this methane venting leads to the formation of marine authigenic carbonate rocks, and for confirmation, we analyze two field samples from the Gulf of Cadiz for composition and mineralogy of the precipitates. We note the implications of this work for hydrate melting and methane escape from the seabed.

Simulation and sensitivity of isotopic alteration and vein development in carbonate rock formations

Isotopic alteration of carbonate rocks during hydrothermal flow is common across a range of geological settings, can be used to identify areas of greater mineralization potential, and is a guide to mineral exploration. To understand potential controls on the variability of this isotopic alteration, we created a series of models to investigate parameter sensitivity. The resulting variograms for δ18O distribution closely matched the variograms for the initial porosity and demonstrate the importance of porosity in controlling isotopic variation. This result shows the utility of variograms for investigating the correlation between hydrologic parameters and isotopic distribution and vectoring toward ore deposits. The mass transfer variables between flowing and stagnant zones within the model were the strongest secondary control on isotopic alteration. The alteration of the carbonate rocks releases 18O, creating a pulse of enriched fluid that flows through the system. The isotopic variation of the solid phase decreases with distance from the inlet because of mixing and the increased size of the 18O-enriched pulse that travels through the system within the fluid phase. The isotopic pulse seen in the model matches isotopic records preserved in zoned calcites from the Upper Mississippi Valley. We also inferred from the model that when sampling isotopic systems, sample intervals taken from large intervals of core can reasonably be used to determine the average alteration but that characterizing the variation is sensitive to sample spacing and frequency.

Geochemical characteristics of rare earth elements (REEs) in soils developed on different parent materials, in the Baoshan area, Yunnan Province, SW China

The geochemistry of rare earth elements (REEs) was studied in rock samples from host formations, ore samples from two mineral deposits (the Hetaoping Cu-Pb-Zn mine: HTP and the Heiyanao Fe-Cu-Pb-Zn mine: HYA) and the overlying or nearby soils to better understand REE concentrations, distributions and behaviour during weathering from different parent materials at the regional scale, Baoshan area, Yunnan Province, SW China. The mudstone and sandstone formations have the highest total REE (ΣREE) contents. Chondrite-normalized diagrams for rocks and ores show significant light REEs (LREEs) enrichments and Eu depletion (except for ores in HYA). Cerium displays an obvious negative anomaly in carbonate rocks (Є-3-R, C-R, D-R, T-1-R and T-2-R). Soils overlying carbonate rock formations (T-1-S, C-S and Є-3-S) have the highest ΣREE contents, while soils overlying basalts have the lowest ΣREE contents. Soils show enrichments in LREEs with negative Eu anomalies and slight Ce anomalies in the studied soils. Soils with high ∑LREE/∑heavy REE (HREE) values may result from the preferential absorption of LREEs by organic matter. Negative Eu anomalies in soils occur for parent materials in the study area lacking feldspar, especially soils developed from carbonates. Compared to the parent materials, most soils show REE enrichment because alkali metals are removed and REEs are concentrated by low mobility in surficial processes and positive Ce anomalies because of weathering dissolution of other trivalent REEs with ionic radii similar to that of Ca 2+ . Supplementary material: Additional data (Tables S1 and S2) and sample locations (Fig. S1) are available at https://doi.org/10.6084/m9.figshare.c.5303140

A new method for wellbore stability evaluation based on fractured carbonate reservoir rock breaking degree

Borehole wall collapse is rare in the drilling of carbonate rock formations. However, several wells in the Maantang–Leikoupo carbonate formation have collapsed and released blocks to varying degrees, which have caused sticking and hindered efficient development of oil and gas resources. Thus, through the study of macroscopic and microscopic characteristics of carbonate rocks in this area, it is concluded that the fractures in this area are developed. In order to facilitate the analysis of formation fracture development, the concept of formation integrity coefficient which is commonly used in rock engineering was introduced. Firstly, the feasibility of using the formation integrity coefficient to characterize the degree of rock fragmentation was verified by the laboratory acoustic experiment. Finally, the empirical formulas were proposed regarding the formation integrity coefficient and the cohesion of carbonate rocks in this area by combining the laboratory mechanical experiment and acoustic experiment, and a calculation model for the collapse density considering formation integrity was established. Results provide guidance for research on carbonate wellbore stability, especially for fractured carbonate strata.

Fate of nitrate during groundwater recharge in a fractured karst aquifer in Southwest Germany

Over the past decades, fractured and karst groundwater systems have been studied intensively due to their high vulnerability to nitrate (NO3−) contamination, yet nitrogen (N) turnover processes within the recharge area are still poorly understood. This study investigated the role of the karstified recharge area in NO3− transfer and turnover by combining isotopic analysis of NO3− and nitrite (NO2−) with time series data of hydraulic heads and specific electrical conductivity from groundwater monitoring wells and a karstic spring in Germany. A large spatial variability of groundwater NO3− concentrations (0.1–0.8 mM) was observed, which cannot be explained solely by agricultural land use. Natural-abundance N and O isotope measurements of NO3− (δ15N and δ18O) confirm that NO3− derives mainly from manure or fertilizer applications. Fractional N elimination by denitrification is indicated by relatively high δ15N- and δ18O-NO3− values, elevated NO2− concentrations (0.05–0.14 mM), and δ15N-NO2− values that were systematically lower than the corresponding values of δ15N-NO3−. Hydraulic and chemical response patterns of groundwater wells suggest that rain events result in the displacement of water from transient storage compartments such as the epikarst or the fissure network of the phreatic zone. Although O2 levels of the investigated groundwaters were close to saturation, local denitrification might be promoted in microoxic or anoxic niches formed in the ferrous iron-bearing carbonate rock formations. The results revealed that (temporarily) saturated fissure networks in the phreatic zone and the epikarst may play an important role in N turnover during the recharge of fractured aquifers.

Comparative Study on Thermodynamic and Geochemical Characteristics between Cemented and Clotted Parts of Thrombolite

Carbonate rocks are widely distributed in nature and are one of the main reservoir rocks for oil and gas. Microbes play an important role in the formation of carbonate rocks. Compared with the cemented part with fewer microorganisms (abiotic minerals), the nucleation and growth of the clotted part with more microorganisms (biotic minerals) are affected by the metabolic activities of microorganisms, so it has a unique morphology and crystal structure. However, there are still some confusing questions such as ones regarding the unique thermal decomposition characteristics and geochemical characteristics, which have rarely been studied. Here, X-ray diffraction (XRD) was used to determine the mineral composition of the cemented and clotted part in the same thrombolite. Then, thermal analysis and stable isotope geochemistry were used to explore the thermal stability and stable carbon isotope. The results of X-ray diffraction (XRD) show that the mineral components of the cemented and clotted part in the thrombolite are calcites, but their crystallinity is different. The crystallinity of the clotted part in the thrombolite is higher than that of the cemented part. Thermal analysis results show that the activation energy and the thermal stability of the clotted part in the thrombolite are relatively higher. In addition, the stable carbon isotope results show that, compared with the chemical precipitated calcite in the cemented part, the microorganisms in the clotted part absorb more 12C through photosynthesis, which results in more 13C in the clotted part, and the carbon isotope δ13C value is higher. This study helps to distinguish the crystallographic, thermodynamic and geochemical characteristics of cemented and clotted parts in thrombolite, and may be helpful to deepen our understanding of abiotic and biotic minerals.

Prediction of Shear-Wave Velocities in Carbonate Reservoirs

The purpose of this paper was to propose a method to predict shear-wave velocities in the process of AVO (amplitude variation with offset) inversion, to interpret seismic converted-wave data, and to match reservoir engineering information with seismic data in regions without shear-wave velocities. During CO2 flooding and sequestration, the shear-wave velocity varies with the pressure that is caused by fluid injection. Predictions of how the shear-wave velocity changes with pressure can be used to interpret 4D seismic monitoring data during different stages of CO2 injection. To verify the calculations, the authors used the characteristic parameters of the Marly dolomite and Vuggy limestone units of the Weyburn Oilfield reservoir in Canada. The Digby’s model and Gassmann’s equation were used to evaluate the dependence of the shear-wave velocity on the pressure in the carbonate rock formation. The authors have developed a new method for calculating the coordination number of the model and supplement the results with a shale correction, enabling the prediction to match the measured shear-wave velocities more closely. Our method is verified by dipole sonic logging data and petrophysical test data from the Weyburn Oilfield. When applied to petrophysical test data, the average error is below 5%. When the method is applied to well log data, the average error in the porous media is 3.014% in the Marly unit and 6.288% in the Vuggy unit.

Petrography of carbonate rocks in the Asmari Formation, Zagros Basin, Dezful Embayment and Izeh Zone, SW Iran

This research aims at studying the Oligo-Miocene Asmari Formation, which is known as one of the best oil reservoirs in Iran. For better understanding and comparing the trend of lithological changes and depositional environment of this formation in a wider area, 5 sections were selected which consist of Lali 20, Karun 3, Masjed Soleyman 186 subsurface, and Asmari anticline surface sections in Dezful Embayment and Gurpi anticline surface section in Izeh Zone. Using polarizing and cathodoluminescence microscopic studies, diagenetic processes affecting the Asmari and their paragenetic sequence in the study areas were interpreted. Index diagenetic processes that have affected the Asmari Formation carbonate rocks include micritization, bioturbation, boring, cementation (such as marine, meteoric, and burial cementation), dissolution (meteoric and burial dissolution), dolomitization (in different phases), pyritization, hematitization, silicification, mechanical and chemical compaction, and fracturing. In general, diagenetic processes such as dissolution and fracturing have increased the reservoir quality, while cementation and compaction have decreased the reservoir potential of this formation. Cathodoluminescence studies indicate three generations of cement of marine, meteoric, and burial based on the color contrast.

Элизионные процессы как основные факторы в формировании высокопродуктивных карбонатных коллекторов венд-кембрийских отложений Восточной Сибири

Элизионные процессы как основные факторы в формировании высокопродуктивных карбонатных коллекторов венд-кембрийских отложений Восточной Сибири

Application of VSP well drive data in the prediction of complex carbonate reservoirs

The qixia formation carbonate rocks in the northwest of sichuan are of great buried depth, thin reservoir thickness and strong heterogeneity. Therefore, VSP data are used to control the seismic data on the surface, VSP well drive data lay a good foundation for interpretation. Then, through waveform clustering analysis, favorable facies zones were developed. Secondly, natural faults are predicted based on maximum likelihood attribute technique. Finally, the reservoir quantitative prediction is carried out by using phase control inversion technique. The drilling well location is optimized based on reservoir and fracture prediction information, and the drilling effect is good, which provides strong technical support for subsequent exploration and development in this area.

Potential of Carbon Stocks and Its Economic Values in Tropical Karst Landscape (Case Study in Biduk-Biduk Karst, East Kalimantan, Indonesia)

Karst especially tropical karst landscape has a potential value to store an amount of both organic and inorganic carbon. Tropical karst landscape can store organic carbon derived from forest ecosystem biomass that covers this karst landscape. While inorganic carbon stocks in tropical karst landscape are stored on carbonate rock (CaCO3). This potential can be calculated to identify the economic carbon value to support carbon trade program in East Kalimantan, Indonesia. This research aims to (1) identify carbon stocks value from organic and inorganic carbon in the study area; (2) calculate economic carbon value in the study area. Organic carbon stocks were measured using field measurement to calculate aboveground, belowground, and litter biomass. Calculation of aboveground, belowground, and litter biomass was measured based on the standard method in SNI 7724: 2011. X-Ray Fluorescence (XRF) method was used to identify the CaO concentration in carbonate rock. This CaO concentration was measured to calculate carbon (C) concentration in carbonate rock formation namely inorganic carbon stocks. Economic carbon value was calculated using cost-benefit transfer method. Biduk-Biduk Karst Region has a big value of organic carbon stocks of 0.007 Pg-C and inorganic carbon stocks of 9.02 Pg-C. Therefore, the total carbon stock in Biduk-Biduk Karst Region is 9.037 Pg-C. Based on the total value of carbon stocks, Biduk-Biduk Karst has a total economic value of US$ 45,171,544,296.

Effect of faults and rock physical properties on in situ stress within highly heterogeneous carbonate reservoirs

This study characterizes the reservoir-scale in situ stress state within a carbonate oil and gas field in the southeast United Arab Emirates (UAE) to further our understanding of the effects of faults and rock property heterogeneity on variations in stress. The in situ stress state was constrained using image-logged wellbore wall stress indicators (i.e., borehole breakouts and drilling-induced tensile fractures) observed within several vertical boreholes penetrating layered carbonate rock formations. The orientation and magnitude of the in situ stress state vary significantly with both location and depth. The azimuth of the maximum horizontal principal stress (SHmax) has diverse orientations that vary significantly with depth and span a ~60° range from NW to NNE. The magnitudes of horizontal principal stresses also vary significantly, meaning that no unique stress–depth relations can be defined. Despite considerable fluctuation in stress magnitudes with depth, the stress state in the reservoir is generally in a strike-slip faulting regime, which is consistent with that prevailing throughout onshore UAE. These widespread variations in stress orientation and magnitude appear to be linked to a combination of geomechanical processes associated with the presence of a set of reservoir-scale faults and the highly heterogeneous mechanical properties of the carbonate reservoir. Our analysis indicates that the SHmax azimuth rotates proximal to faults from the prevailing far-field stress orientation toward the strike of the faults, but the angle of this azimuthal rotation is dependent on the Young's modulus characteristics of individual formations. The gradient of the horizontal principal stress tends to increase with increasing Young's modulus values, indicating that stiffer formations transfer higher magnitudes of stress. The observed stress variations also agree well with the results of three-dimensional finite element modelling. Our study demonstrates that the strong mechanical heterogeneity of carbonate reservoirs controls the in situ stress state in a complex but explainable way.

Geochemistry of surface sediments in parts of Bandipora–Ganderbal areas, Kashmir valley, western Himalaya: Implications for provenance and weathering

Sediment geochemistry is an important tool to understand the sediment provenance and weathering. The present study describes the geochemical distribution, the provenance and the degree of weathering in surface sediments in parts of Bandipora–Ganderbal areas, Kashmir valley, western Himalaya. Following the standard operating procedure of the Geological Survey of India, high-density sediment sampling over an area of 800 km2 of toposheet Nos. 43J/11 and 43J/12 (part) was carried during the Field Season Programme of 2014–2015. A total of 200 stream and slope wash sediment samples collected on a 2 × 2 grid pattern, covering an area of 800 km2 and 10 numbers of duplicate samples were used in this study. An analysis of major and trace element concentrations of the sediment samples revealed significant changes corresponding to different geological formations of the area. The correlation matrix of SiO2, Al2O3, TiO2, Fe2O3, MnO, K2O, Th and Y showed a positive correlation with each other and negative correlation with CaO, MgO and Sr, thereby indicating two dominant geological provenances of the sediments. Two dominant geochemical patterns revealed provenances from basaltic and carbonate rock formations in the area. Furthermore, an analysis of geochemical weathering indices (chemical index of alteration and chemical index of weathering) revealed a poor (27) to moderate (78) degree of weathering in this area. This observation is further substantiated by the immaturity of the soil sediments in the area.

Karst Development Models of Early Plaeozoic Carbonate Rocks on the Southern Margin of North China Platform

This paper analyzes the formation and karst development process of early paleozoic carbonate rocks in the southern margin of North China platform from the aspects of regional stratigraphy distribution, crustal movement and evolution and groundwater recharge and drainage conditions. It is concluded that the karst in the study area is multi-level developed and affected by lithology. Under the control of tectonic movement and groundwater flow, there are three main types of karst development models: bedding karst, water erosive karst, fault zone karst and erosive mining karst.

Increasing confidence in full field modelling and water flood planning for a giant reservoir under primary depletion through Material Balance modelling

One of the principle inputs to project economics and all business decisions is a realistic production forecast and a practical and achievable development plan (i.e. waterflood). Particularly this becomes challenging in supergiant oil fields with medium to low lateral connectivity. The main objectives of the Production Forecast and feasibility study for water injection are:1- Provide an overview of the total expected production profile, expected wells potential/spare capacity, water breakthrough timing and water cut development over time2- Highlight the requirements to maintain performance, suggest the optimum development pattern3- Increasing confidence in business decisions to develop the reservoir in questionThe main tool used for these purposes is a sophisticated reservoir simulation software, namely CMG©, since it can predict reservoir behavior, honor physical constraints and capture the heterogeneity within the reservoir to accurately predict performance. However, the starting point for this kind of complicated studies needs to start from the basics, in order to understand the big picture and be able to plan properly for the scope to be delivered, hence, utilizing analytical tools like MBAL becomes quite necessary, if not crucial, to the success of full field modelling and choosing an optimum water flood pattern and design.This paper covers the methodology for building the reservoir component utilizing a Material Balance model, of which the results will be used as an input to reservoir simulation to evaluate and accurately predict reservoir performance, which directly feeds into planning for water flooding projects and selection of an optimum flood pattern.A Tank model was built at first to assess and understand the driving forces (energies) of the reservoir in question, utilizing pressure and production data from legacy wells, the prepared model is also supported by geological and petro physical studies to give representative results. Acquired Static Bottom Hole Pressures (SBHPs) in wells were used as anchor points for the tank pressure and to test the validity of the history match. Multiple analytical methods to QC the results and STOIIP volume were conducted, e.g. the Havlena-Odeh method.This methodology has been tested successfully in the stated super giant oil field, in which the reservoir in question is a carbonate rock formation. An example of this is covered in the paper. It was concluded that utilizing a history matched and coherent MBAL model before conducting a detailed reservoir simulation study can save a lot of time and effort by providing guidance to the path which needs to be followed, and sheds light on the critical elements to be looked after. This has also helped to uncover the driving mechanisms and energies in the reservoir, hence allowing the engineer to plan for the necessary voidage replacement and water injection rates to sustain the reservoir pressure and pattern development. Another technical advantage of the described method is the higher sustainability of the model.The suggested method, in combination with geological and petro physical information available, can be applied to majority of the reservoirs. This combination is paramount to ensure optimum time and planning that is followed for each reservoir development study that involves water flooding.

Calculating heterogeneity of Majnoon Field/Hartha reservoir using Dykstra Parsons method

One of the principle concepts for understanding the hydrocarbon field is the heterogeneity scale; this becomes particularly challenging in supergiant oil fields with medium to low lateral connectivity in carbonate reservoir rocks.
 The main objective of this study is to quantify the value of the heterogeneity for any well, and propagate it to the full reservoir. This is quite useful specifically prior conducting detailed water flooding or full field development studies and work, in order to be prepared for a proper design and exploitation requirements, which fits with the level of heterogeneity of this formation.
 The main tool used for these purposes is the application of the famous Lorenz coefficient method, in conjunction with the Dykstra Parsons technique for calculating the degree of heterogeneity for any well. 
 The starting point for this kind of complicated studies needs to start from the basics. In order to understand the big picture and be able to plan properly for the scope to be delivered. Utilizing analytical tools like the ones mentioned above becomes quite necessary, if not crucial, to the success of full field modelling and choosing an optimum water flood pattern and design.
 This work covers the methodology for quantifying and calculating the level of heterogeneity in a given reservoir.
 The Dykstra-Parsons Coefficient or the variation of Dykstra Parsons (VDP) is commonly used in calculating permeability variation. The method of calculating begins by sorting the property of interest and make the other property fixed value (to calculate permeability you have to make porosity a fixed value for all calculations) and make permeability in order of decreasing magnitude.
 For each of the values calculate the percentage of values greater or the ‘cumulative probability’, so that the probability of X is P(x≤X). Then plot the original permeability values on a log probability graph with the cumulative probability values. The slope value and the intercept of the line of the best fit, for all data are used to calculate the 50th and 84th probability values or by variation layering system to calculate the variation of P10, P50 and P90, which are used to find VDP.
 This methodology has been tested successfully in the stated super giant oil field, in which the reservoir is a carbonate rock formation. The reservoir is areally extensive reservoir and not of a great thickness.
 The importance of this step is to conclude a utilizing heterogeneity calculation method before conducting any detailed reservoir simulation study. It can save a lot of time and effort by providing guidance to the path, which needs to be followed, and sheds light on the critical elements to be looked after. This also can help to uncover many insights on the reservoir itself, hence allowing the engineer to plan for the necessary voidage replacement and water injection rates to sustain the reservoir pressure and pattern development based on the magnitude of heterogeneity those results from this procedure.
 The suggested method, in combination with geological and petrophysical information available, can be applied to majority of the reservoirs. This combination is paramount to ensure optimum time and planning is followed for each reservoir development study that involves for example water flooding

Chemical Characteristics of Groundwater and Material Sources Analysis in Buckwheat Field, Yunnan Province

In order to study the hydrochemistry characteristics and material sources of groundwater in the Buckwheat basin, we collected 32 groundwater samples in the study area in July 2017. The chemical characteristics of groundwater were analyzed by cluster analysis, factor analysis, and path model analysis. Meanwhile, we qualitatively and quantitatively assessed the sources of groundwater hydrochemistry in the Buckwheat basin. The results showed that the groundwater in the study area was weakly alkaline, and the major ions such as Ca2+, Mg2+, SO42-, HCO3-, and NO3- had high spatial variability. According to the clustering analysis, the groundwater in the study area can be divided into two categories, namely, class A and class B, and these have the following two subsets:A1, A2, B1, and B2. From A to B, the chemical types of groundwater become more complex. The hydrochemistry types of class A were all of the HCO3-Ca type, while those of class B1 were HCO3-Ca, HCO3-Na·Ca, and HCO3-Na·Ca·Mg, and those of class B2 were HCO3-Ca, HCO3-Ca·Mg, HCO3-Na·Ca. In order to further explore the influence factors of groundwater hydrochemistry, we determined that carbonate rocks, human activities, evaporite rocks, and silicate rocks were the main material sources of groundwater through factor analysis and path model analysis. Among all of the above factors, the dissolution of magnesium sulfate evaporite and the actions of human activities were found to be important reasons for the formation of carbonate rocks, which served as the main sources of groundwater chemical components and diverse hydrochemistry characteristics.