Porosity In Carbonate Rocks Research Articles

Accurate Petrophysical Interpretation of Carbonate using the Elemental Capture Spectroscopy (ECS)

Elemental capture spectroscopy (ECS) is an important tool in the petroleum industry for determining the composition and properties of rock formations in a reservoir. Knowledge of the types and abundance of different minerals in the reservoir is crucial for accurate petrophysical interpretation, reservoir engineering practices, and stratigraphic correlation. ECS measures the elemental content of the rock, which directly impacts several physical properties that are essential for reservoir characterization, such as porosity, fluid saturation, permeability, and matrix density. The ability to accurately determine these properties leads to better reservoir mapping, improved production, and more effective resource management. Accurately determining the mineralogy and porosity of carbonate rocks and other materials is the aim of this paper. Calcite, dolomite, quartz, clay (illite), anhydrite, and pyrite, in addition to water as a fluid, are taken into account in the computation. The formation's lithology and porosity can be ascertained from this data. When compared to the core descriptions in the geological report, the results demonstrated a distinct zone of unique lithology with good prediction accuracy.

Karst study of Jinfo Mountain based on image analysis

The KDR (karst development rate) of rocks and their PCR(porosity of carbonate rocks) are common research topics in Jinfo Mountain. The use of traditional carbonate research methods (TCRMs) for karst studies has been shown to be costly and time-consuming. Therefore, this study attempted to find a new, reliable, low-cost, and time-saving method for karst research. The Jinfo Mountain area is a typical carbonate rock area that is suitable for karst research. In this study, many images of rock samples from the Jinfo Mountain were obtained using rock-polarizing microscopes, which provided a good basis for the karst study of Jinfo Mountain. Furthermore, in this study, image analysis technology was used to find the karst development rate of rocks and their porosity. To ensure the accuracy of these research results, we compared the research results obtained using the image analysis techniques with those obtained using TCRM. The comparison showed that the image analysis technology is a feasible research techniques for studying karst in the Jinfo Mountain area. Furthermore, it has good reference significance for other karst study outside the Jinfo Mountain area.

A fast method to infer Nuclear Magnetic Resonance based effective porosity in carbonate rocks using machine learning techniques

A better estimation of the effective porosity of the reservoir rock is a critical task for petrophysicist and well logs analyst. A majority of the current approaches to estimate the effective porosity of the reservoir rocks from well logs are based on the information of the Density-Neutron logs. These approaches usually resulted in the inaccurate estimation of the rock porosity particularly in the naturally fractured carbonates or dolomite rocks. The Nuclear Magnetic Resonance (NMR) based effective porosity is independent of the rock matrix and mineralogy, on contrary it depends on the number of hydrogen nuclei in the pore spaces of the rock. In this study, we have used six machine learning (ML) techniques to predict the NMR based effective porosity in carbonate rocks. The ML models to predict the effective porosity includes deep neural networks (DNN), random forest regressor (RF), decision trees (DT), K-Nearest Neighbors algorithm (KNN), extreme gradient boosting (XGB), and adaptive gradient boosting (AdaBoost). These models were trained on the geophysical well logs such as Gamma ray log (GR), caliper log (Cali), neutron porosity log (NPHI), photoelectric factor log (PE), and bulk density log (RHOB). A total of 4002 data points were obtained from the five wells located in the carbonate field. The tuning of ML models hyperparameters were conducted using a ‘GridSearchCv’ method. Furthermore, the K-fold cross-validation criterion was implemented to improve the accuracy of the ML models. The ML models performances were evaluated using multiple graphical and goodness of fit tests including prediction cross-plots, average absolute percentage error (AAPE), root means square error (RMSE), and coefficient of determination (R2) methods. The prediction results showed that the DNN, RF, and XGB models performed better than the other implemented ML techniques. These methods resulted in a significantly low error and high (R2). The achieved accuracy was above 85% when validated on a blind dataset. This study also offered an empirical model that can be used to quickly estimate the NMR based effective porosity using afore-mentioned well logs. The model can also be used as a standalone package that can be coupled with any logging software for quick evaluation of NMR based effective porosity.

Hyperspectral data as a proxy for porosity estimation of carbonate rocks

Rock porosity is one of the most significant parameters in fluid-flow simulation in the context of carbonate reservoirs. The hydrocarbon industry uses porosity to assess the production potential of oil and gas in carbonate environments. Traditional methods to determine porosity are limited to discrete measurements and generally demand extra resources associated with careful analysis of logs, rock sampling and laboratory analysis. This paper investigates an alternative to estimate porosity in carbonate rocks using pointwise hyperspectral data and machine learning. The method is contiguous, does not require rock sampling and was validated in various rock plug samples collected from two distinct carbonate outcrops. The samples were analysed in the laboratory to determine ground-truth values for the effective porosity and reflectance in visible and infrared regions of the spectra. The supervised regression methods applied were able to estimate a robust relationship between the effective porosity of carbonate rocks and spectral behaviour in characteristic spectral features of carbonate, hydroxyl, molecular water and Fe/Mn. The results obtained here suggest the soundness of the indirect approach to estimate porosity with most of the models trained achieving a coefficient of determination above 0.8 and mean absolute deviation of less than 2%. KEY POINTS Hyperspectral data can be used as proxy for porosity estimation in carbonate rocks. All the tested learners achieved R 2 greater than 0.7. Regularised linear regression can be used to estimate porosity. Support vector regression estimation of porosity achieves a mean absolute error of 1.0249 in our dataset.

Porosity of the porous carbonate rocks in the Jingfengqiao-Baidiao area based on finite automata.

This study is based on the processing of computed microtomography images of rock samples. In this study, a finite automation is constructed using the grey value, red-green-blue (RGB) value and Euler number of polarized images of carbonate rocks from the Jingfengqiao–Baidiao area. The finite automaton is used to perform black and white binary processing of the polarized images of the carbonate rocks. The porosity of the carbonate rock is calculated based on the black and white binarization processing results of the polarized images of the carbonate rocks. The obtained porosity is compared with the carbonate porosity obtained by use of the traditional carbonate research method. When the two porosities are close, the image processing threshold of the finite automata is considered to be credible. Based on the finite automata established using the image processing threshold, the black and white binary images of the polarized images of the carbonate rocks are used to establish a rock pore image using ImageJ2X. The polarized images of the carbonate rocks are classified according to their RGB values using the finite automata for the porosity classification, and the obtained images are used as textures to paste onto a cube to construct a three-dimensional data model of the carbonate rocks. This study also uses 16S rDNA analysis to verify the formation mechanism of the carbonate pores in the Jingfengqiao–Baidiao area. The results of the 16S rDNA analysis show that the pores in the carbonate rocks in the Jingfengqiao–Baidiao area are closely related to microorganisms, represented by denitrifying bacteria.

Creation of Secondary Porosity in Dolostones by Upwelling Basement Water in the Foreland of the Alpine Orogen

Creation of secondary dissolution porosity in carbonate rocks during deep burial has the potential to improve reservoir properties for hydrocarbons, gas storage, and geothermal applications. However, the occurrence and mechanisms of such porosity enhancement are controversial. Here, we present compelling evidence for generation of deep burial porosity from the Swiss Molasse Basin, where dissolution of eogenetic anhydrite nodules in dolostones of the Middle Triassic Muschelkalk increased the matrix porosity by up to 15 vol.%. We reconstruct the genesis and evolution of the anhydrite-dissolution porosity based on petrography, porosity determinations, analyses of stable and radiogenic isotopes (δ2H, δ18O, δ34S, and 87Sr/86Sr), fluid inclusion studies, and laser U–Pb geochronology of secondary calcite. The results show that modified meteoric waters derived from the Variscan crystalline basement ascended via basement–cover cross-formational faults into the overlying Muschelkalk, where they dissolved the anhydrite nodules throughout an area of at least 55 km2 at 700–2300 m depth and 40–160°C. Secondary calcite in anhydrite moulds yields Late Eocene to Middle Miocene U–Pb ages, which coincide with the timing of basement uplift in the foreland bulge of the Swiss Alpine Orogen. This uplift provided the hydraulic gradients to drive meteoric water deep into the adjacent Molasse basin. Similar enhancement of reservoir properties can be expected in dolostones in other foreland basins that are bordered by a foreland bulge in which fractured basement rocks are exhumed.

Ultrasonic velocity as a tool for mechanical and physical parameters prediction within carbonate rocks

Physical and mechanical properties of rocks are of interest in many fields, including materials science, petrophysics, geophysics and geotechnical engineering. Uniaxial compressive strength UCS is one of the key mechanical properties, while density and porosity are important physical parameters for the characterization of rocks. The economic interest of carbonate rocks is very important in chemical or biological procedures and in the field of construction. Carbonate rocks exploitation depends on their quality and their physical, chemical and geotechnical characteristics. A fast, economic and reliable technique would be an evolutionary advance in the exploration of carbonate rocks. This paper discusses the ability of ultrasonic wave velocity to evaluate some mechanical and physical parameters within carbonate rocks (collected from different regions within Tunisia). The ultrasonic technique was used to establish empirical correlations allowing the estimation of UCS values, the density and the porosity of carbonate rocks. The results illustrated the behavior of ultrasonic pulse velocity as a function of the applied stress. The main output of the work is the confirmation that ultrasonic velocity can be effectively used as a simple and economical non-destructive method for a preliminary prediction of mechanical behavior and physical properties of rocks.

Quantification of sub-resolution porosity in carbonate rocks by applying high-salinity contrast brine using X-ray microtomography differential imaging

Characterisation of the pore space in carbonate reservoirs and aquifers is of utmost importance in a number of applications such as enhanced oil recovery, geological carbon storage and contaminant transport. We present a new experimental methodology that uses high-salinity contrast brine and differential imaging acquired by X-ray tomography to non-invasively obtain three-dimensional spatially resolved information on porosity and connectivity of two rock samples, Portland and Estaillades limestones, including sub-resolution micro-porosity. We demonstrate that by injecting 30 wt% KI brine solution, a sufficiently high phase contrast can be achieved allowing accurate three-phase segmentation based on differential imaging. This results in spatially resolved maps of the solid grain phase, sub-resolution micro-pores within the grains, and macro-pores. The total porosity values from the three-phase segmentation for two carbonate rock samples are shown to be in good agreement with Helium porosity measurements. Furthermore, our flow-based method allows for an accurate estimate of pore connectivity and a distribution of porosity within the sub-resolution pores.

New Digital Methods of Estimation of Porosity of Carbonate Rocks

Carbonate stones consist of about 60% of the global reserves of hydrocarbons. The structure of pore space of carbonate rocks considerably differs morphologically and genetically from such one in clastic stones. In the carbonate rocks interconnected and unconnected voids can be equally important. There exists 3D estimation of porosity by the method of liquid saturation, mainly, aimed at interconnected void volume. Digital methods of thin section estimation of porosity make it possible to fix both types of voids and reveal the importance of one or another type in formation of reservoir properties of rocks. It is considered the possibilities of using the program Cluster Image as alternative and express way for estimation of 2D advantages from thin areas of carbonate stones reservoirs by example of Tournasian oil-bearing deposits, penetrated by the well in the southern slope of the South Tatar crest. The program Cluster Image allows avoiding application of estimated percentage of unclassified pixels in the process of estimating photographs of thin porosity carbonate reservoir rocks with significantly lockable voids in the image. It has been determined the specific variations of porosity by well profile depending on lithotypical rocks and structure of void volume. These variations correspond to the zonal structure of natural carbonate oil-saturated reservoir.

2D multifractal analysis and porosity scaling estimation in Lower Cretaceous carbonates

The study of scaling porosity in carbonate rocks has great importance because (1) porosity measurements are usually made at scales that are different from the one of interest and (2) carbonate formations contain most of the hydrocarbon reservoirs and aquifers in the world. Despite these facts, scaling porosity in heterogeneous media, such as carbonate rocks, is still an open problem. The heterogeneity of carbonate rocks mainly resides in their complex texture. We have extended previous studies on carbonate multifractal behavior in pore space morphology at different scales, and we have developed a new equation based in fractal geometry that could be used to scale the porosity. In our methodology, we (1) perform a multifractal analysis in thin-section images of a set of complex carbonate rocks from the Lower Cretaceous, (2) review the effect of magnification in scanning-electronic-microscope and thin section images, (3) deduce a new scaling equation for porosity, and finally (4) evaluate this equation in the studied samples. We found that this new equation could be used under the approximation that the majority of the pores have a similar size, equivalent to the maximum pore size found in thin-section images. However, it must be applied carefully because the fractality/multifractality of pore spaces in carbonates could be present only in certain parts of the rocks and in a limited range that might not include the targeted scale. In fact, multifractality in the studied carbonate rocks seemed to be more complex than that found in previous studies. It was noticed that the proposed equation brought the benefit of fractal geometry formalism taking into account the physical scaling of pore space heterogeneities, and it indeed has the potential to estimate porosity at different spatial scales as an alternative method to find porosity when measurements are not available.

Detecting vuggy porosity in carbonate reservoirs by well logs

Vuggy porosity is a type of porosity in carbonate rocks. This kind of porosity significantly affects the permeability, pressure drop and recovery factor in the reservoir. Therefore, their identification and modeling is important for the reservoir characterization and history matching. Image logs, RCAL and SCAL tests are main tools to determine vugs, though all are costly and sometimes unavailable. Thus, development of a generalized approach to recognize vugs in reservoirs will be significant. In this paper, a combined majority voting-Parzen–wavelet based algorithm is developed using gamma ray (GR), neutron porosity (NPHI), bulk density (RHOB) and sonic (DT) logs for identification of vugs in frequency domain. The agreement between the core tests results and the results of this newly developed method confirms the application of proposed new method.

Pore-scale modeling of elastic wave propagation in carbonate rocks

The relationship between P-wave velocity and porosity in carbonate rocks shows a high degree of variability due to the complexity of the pore structure. This variability introduces high uncertainties to seismic inversion, amplitude variation with offset analysis, porosity estimation, and pore-pressure prediction based on velocity data. Elastic wave propagation in porous media is numerically modeled on the pore scale to investigate the effects of pore structure on P-wave velocities in carbonate rocks. We built 2D models of porous media using pore structure information and the similarity principle. Then, we simulated normal incidence wave propagation using finite element analysis. Finally, the velocity was determined from received modeled signals by means of crosscorrelation. The repeatability and accuracy of this modeling process was verified carefully. Based on the modeling results, a simple formulation of Sun’s frame flexibility factor ([Formula: see text]), aspect ratio (AR, the ratio of the major axis to the minor axis), and pore density was developed. The numerical simulation results indicated that the P-wave velocity increases as a power function as the AR increases. Pores with small AR ([Formula: see text]) or large [Formula: see text] created softening effects that decrease P-wave velocity significantly. The P-wave velocity of carbonate rocks was dispersive; it depends on the ratio of the wavelength to pore size ([Formula: see text]). Such scale-dependent dispersion was more evident for carbonate rocks with higher porosity, lower AR, and/or lower P-wave impedance of pore fluids. The P-wave velocity of carbonate rocks with complicated pore geometries (low AR, high [Formula: see text], small [Formula: see text]) was much lower than that of rocks with simple pore geometries (high AR, small [Formula: see text], large [Formula: see text]) at low and high [Formula: see text]. The pore-scale modeling of elastic wave properties of porous rocks may explain the poor velocity-porosity correlation in carbonate rocks.

A combined Parzen-wavelet approach for detection of vuggy zones in fractured carbonate reservoirs using petrophysical logs

Abstract Vuggy porosity which is the most important type of porosity in carbonate rocks, significantly affects permeability, pressure drop and recovery factor of the rocks. As a result, its identification and modeling are essential for reservoir characterization and history matching. Image logs as well as RCAL and SCAL tests are main methods to determine vugs. However, these methods are costly and usually unavailable. Therefore, developing a generalized approach for recognizing vugs appears to be necessary. In this paper, a combined Parzen-wavelet based algorithm is developed for identifying vuggy zones in wavelet coefficient domain using gamma ray (GR), neutron porosity (NPHI), bulk density (RHOB) and sonic (DT) logs. Compatibility between core tests and the results of the developed method revealed the capability of the method.

A Reservoir Rock Porosity Estimation through Image Analysis and Fuzzy Logic Techniques

Petrophysical properties of petroleum reservoir rocks are usually obtained by laborious core laboratory measurements. The present study investigates the capability of petrographic image analysis applied on thin sections of reservoir rock and fuzzy logic for predicting porosity in carbonate rocks. The proposed methodology comprises two steps: first, the petrographic parameters, including porosity type, grain size, mean geometrical shape coefficient of grains, and texture type, were extracted for each thin section based on image analysis techniques. Consequently, the petrographic parameters were formulated to core porosity using a Takagi and Sugeno fuzzy inference system. Petrographic image analysis is an emerging technology, which provides fast and accurate quantitative evaluation from reservoir rock. The results of single petrographic image analysis showed inaccurate estimation of total porosity in all rocks except those that have an extremely isotropic pore structure. A quantitative evaluation of thin section images and fuzzy model was successfully used to improve the accuracy of porosity prediction and the results of thin section analysis were generalized to core plug analysis. The mean square error and correlation coefficient between two-dimensional measurements and core plug were obtained at 0.0262 and 86.3, respectively, which shows acceptable prediction of three-dimensional porosity from two-dimensional thin sections. Therefore, the results confirmed the validity of the propounded methodology.

Potential for increasing oil Recovery from Polish oil-fields by applying EOR methods / Analiza Możliwości Zwiększenia Efektywności Wydobycia Ropy Naftowej Z Polskich Złóż W Oparciu Metody Eor

Streszczenie Jednym ze sposobów zwiększenia efektywności wydobycia ropy naftowej jest zastosowanie zaawansowanych metod wydobycia (EOR - Enhanced OilRecovery). W odróżnieniu od pierwotnych i wtórnych metod wydobycia, celem metod zaawansowanych jest dostarczenie do złoża dodatkowego źródła energii wspomagającego naturalne procesy lub je zastępującego, a także modyfikacja składu i właściwości fizycznych płynów złożowych w celu minimalizacji oporów przepływu w złożu. Metody te znajdują szczególnie zastosowanie w przypadku złóż w znacznym stopniu sczerpanych. Znaczenie tych metod w światowym wydobyciu rośnie, a dominującą rolę zaczynają odgrywać metody zatłaczania gazów w tym dwutlenku węgla. Polskie złoża ropy naftowej są obecnie eksploatowane z wykorzystaniem metod konwencjonalnych, co stwarza możliwości podniesienia efektywności wydobycia przez zastosowanie metod zaawansowanych. Proces doboru optymalnej metody do złoża jest złożony i wieloetapowy. W fazie wstępnej opiera się na podstawowych informacjach o złożu i stopniowo przechodzi do etapów zaawansowanych, kończących się opracowaniem szczegółowego projektu najefektywniejszej metody. W pracy przeanalizowano możliwości zastosowania tych metod na polskich złożach wykorzystując technikę opartą na podstawowych kryteriach ich stosowalności i logikę dwuwartościową. Przeanalizowano 49 złóż ropy naftowej z całego obszaru Polski występujących zarówno w skałach węglanowych jak i piaskowcowych. Z punktu widzenia kryteriów stosowania metod EOR, analizowane obiekty to złoża ropy o średniej gęstości i lepkości, niskiej przepuszczalności (w przypadku skał węglanowych podwójna porowatość), zalegające stosunkowo płytko lub na średniej głębokości. Uzyskane wyniki wskazują, że najszersze zastosowanie w warunkach polskich znaleźć mogą metody zatłaczania gazów, w tym dwutlenku węgla lub azotu. Wymaga to jednak przeprowadzenia szeregu badań i testów pilotażowych, gdyż doświadczenia amerykańskie nie mogą być bezpośrednio przenoszone ze względu na odmienne warunki złożowe, technologiczne i ekonomiczne.

X-ray microtomography application in pore space reservoir rock

Characterization of porosity in carbonate rocks is important in the oil and gas industry since a major hydrocarbons field is formed by this lithology and they have a complex media porous. In this context, this research presents a study of the pore space in limestones rocks by x-ray microtomography. Total porosity, type of porosity and pore size distribution were evaluated from 3D high resolution images. Results show that carbonate rocks has a complex pore space system with different pores types at the same facies.

Carbonate rocks and petroleum reservoirs: a geological perspective from the industry

Abstract Carbonate oil reservoirs are sometimes regarded with apprehension in the petroleum industry since it can be difficult to predict the quality of, and ensure high recovery factors from, this rock family. Particular problems are the complex and heterogeneous nature of porosity in carbonate rocks, often leading to large ranges in permeability for any given porosity, and the organization of carbonate successions most commonly as vertically heterogeneous, but laterally persistent, layers. Important issues that arise time and again in carbonate reservoir description include (a) predicting reservoir quality at inter-well scales and in uncored wells, (b) recognizing problematic high-permeability layers, (c) determining the permeability component to allocate to fractures and connected vug systems, and (d) populating reservoir models with representative physical parameters. Because porosity in carbonate rocks generally presents as diverse and heterogeneous, conventional core plugs are seldom representative of large rock volumes and significant issues remain in terms of the scale-compatibility of the various datasets for measured physical parameters that are used in carbonate reservoir description. Many of the world's largest carbonate reservoirs were discovered and developed shortly after the Second World War and are now showing signs of maturity, expressed variously as poor pressure support, water or gas breakthrough and stranded resources. The proportion of the world's ‘conventional’ petroleum that is reservoired in carbonate rocks is commonly estimated at around 50–60% and many large carbonate reservoirs are likely to have a production lifetime beyond 50 years. It is no coincidence then that the petroleum industry has been the primary source of funding of and promotion of research into carbonate rocks and depositional systems, often with impacts extending well beyond oil and gas exploitation.

Dominant Microbial Populations in Limestone-Corroding Stream Biofilms, Frasassi Cave System, Italy

Waters from an extensive sulfide-rich aquifer emerge in the Frasassi cave system, where they mix with oxygen-rich percolating water and cave air over a large surface area. The actively forming cave complex hosts a microbial community, including conspicuous white biofilms coating surfaces in cave streams, that is isolated from surface sources of C and N. Two distinct biofilm morphologies were observed in the streams over a 4-year period. Bacterial 16S rDNA libraries were constructed from samples of each biofilm type collected from Grotta Sulfurea in 2002. beta-, gamma-, delta-, and epsilon-proteobacteria in sulfur-cycling clades accounted for > or = 75% of clones in both biofilms. Sulfate-reducing and sulfur-disproportionating delta-proteobacterial sequences in the clone libraries were abundant and diverse (34% of phylotypes). Biofilm samples of both types were later collected at the same location and at an additional sample site in Ramo Sulfureo and examined, using fluorescence in situ hybridization (FISH). The biomass of all six stream biofilms was dominated by filamentous gamma-proteobacteria with Beggiatoa-like and/or Thiothrix-like cells containing abundant sulfur inclusions. The biomass of epsilon-proteobacteria detected using FISH was consistently small, ranging from 0 to less than 15% of the total biomass. Our results suggest that S cycling within the stream biofilms is an important feature of the cave biogeochemistry. Such cycling represents positive biological feedback to sulfuric acid speleogenesis and related processes that create subsurface porosity in carbonate rocks.

A Novel Plasma Technique to Stimulate Tight Carbonate Rocks

Tight formations are normally fractured using different fluids under high pressure to improve well permeability and consequently improve productivity. In this paper, a new sophisticated technique is proposed to treat tight formations, especially those containing large deposits of heavy oil. The technique consists of exposing the wellbore to an argon plasma jet to insure instantaneous and efficient heat transfer to the surrounding wellbore rocks. The high temperature associated with the plasma jet changes the basic properties of the rock, resulting in a significant increase in its porosity and permeability. In this study the effect of high temperature on the carbonate rock porosity and permeability is investigated. Limestone rocks were subjected to high temperatures ranging from 800 to 1200°C. At temperatures beyond 600°C, the carbonate rock decomposes to form calcium oxide and carbon dioxide. Thermogravimetric analysis (TGA) of carbonate samples indicated that the rate of decomposition at atmospheric pressure depended mainly on reaction temperature. At low temperatures, the rate of reaction was so slow that only 5% of the carbonate converted to calcium oxide in a period of 1 h, while at 1000°C complete conversion was achieved in 5 min. The changes of the pore structure under different temperatures were also observed using scanning electron microscope (SEM). Porosity and permeability analysis of heated carbonate samples indicated that the porosity and permeability increased by 100% and 4500%, respectively, at 1000°C.

Skarns Related to Porphyry-Style Mineralization at CaicayenHill, Neuquen, Argentina: Composition and Evolution of Hydrothermal Fluids

Located in the Main Cordillera of northwest Neuquen, Argentina, the Caicayen district shares the following features with Cu skarn–porphyry copper deposits in other parts of South, Central, and North America, as well as Asia and the South Pacific: (1) alteration and mineralization are related to I–type, magnetite series, calc–alkaline porphyritic sills of intermediate composition with stockwork veining, brittle fracturing, and brecciation; these are features indicative of a relatively shallow environment of formation (~500 bars); (2) skarns have an oxidized mineralogy dominated by garnet (Ad 45–97 ), clinopyroxene (Hd 18–60 ), epidote, and hematite–magnetite; (3) skarns contain up to 15 percent sulfides (pyrite >> pyrrhotite–chalcopyrite) and locally are associated with distal massive magnetite and hematite lodes; (4) massive silica–pyrite bodies replace prograde skarn and marble; (5) pyroxene–skarn and silica– pyrite alteration distal to the potassic core are Fe and Zn enriched, respectively; (6) mineralized igneous rocks exhibit characteristic early potassic–propylitic and late phyllic alteration that in the skarns can be correlated with prograde garnet–pyroxene and retrograde silica–pyrite, respectively; and (7) Cu–Au anomalies occur in exposures within the potassic and phyllic halos. Fluid inclusions from igneous rocks record multiple fluid events: (1) a hypersaline inclusion population (up to 67 wt % NaCl equiv for halite + sylvite–bearing inclusions, 2–36 wt % KCl equiv, and 31–45 wt % NaCl equiv) that homogenized by salt dissolution between 355° and 400°C, interpreted to have been trapped at a lithostatic pressure of approximately 500 bars; (2) a second hypersaline inclusion population that homogenized by vapor bubble disappearance at 215° to 385°C and may have been trapped at similar temperatures but lower pressures relative to the first population; and (3) a population of coexisting NaCl–saturated inclusions (average salinity of 35 wt % NaCl equiv) and vapor–rich inclusions in igneous rocks close to skarn homogenized at similar temperatures (326°–360°C) that may have formed from boiling of a low–salinity fluid (up to 8 wt % NaCl) at hydrostatic pressures of 120 to 170 bars. Skarn minerals also record hypersaline fluids with similar homogenization temperatures to those measured in nearby igneous rocks but have slightly lower salinities (23.3–26 wt % NaCl equiv). Inclusions from limestone next to skarn have similar homogenization temperatures and salinities (33 wt % NaCl equiv) to skarn and igneous rock inclusions. As evidenced by boiling fluids in the phyllic zone and supercritical fluids in silica–pyrite, hydrostatic regime dominated during retrograde alteration of skarn and porphyry–style alteration. The vapor phase formed by boiling fluids in igneous rocks nearby skarn produced a vapor plume that may be responsible for retrograde alteration and also of cavernous porosity in carbonate rocks at the skarn front. Overall, Caicayen is similar to worldwide copper skarn systems emplaced at shallow levels, but it lacks multiple intrusive phases and successive fluid pulses; thus, resulting in lower copper grades than mined in other copper skarns.