Hasil untuk "Petrology"

P. Birkeland

Xiangchun Zhang, Xin Zhang, Bing Liu et al.

Abstract Improving oil recovery from ultra-tight reservoirs remains a critical challenge due to their inherently low permeability, restricted pore connectivity, and poor sweep efficiency. This study presents a systematic experimental investigation of water-based enhanced oil recovery (EOR) techniques applied to core samples from the Tarim Basin. Coreflooding tests were conducted using conventional methods (waterflooding, CO₂ injection), hybrid strategies including Water Alternating Gas (WAG), Gas Alternating Water (GAW), and Alkali–Surfactant–Polymer (ASP), and advanced chemical-assisted schemes, including four Carbonated Water Alternating Gas (CWAG) variants and a novel Active Carbonated Water Alternating Gas (ACWAG) method. Results showed that ACWAG achieved the highest oil recovery (85.3%) and the lowest residual oil saturation (15.7%), outperforming all other techniques. Key performance indicators such as pressure behavior, wettability alteration, and slug size sensitivity confirmed the importance of injection sequencing and chemical formulation. This study provides new insights into the design of EOR strategies for ultra-tight formations and introduces a promising hybrid approach that could be scaled for field application.

Vali Mehdipour, Ahmad Reza Rabbani, Ali Kadkhodaie et al.

Abstract The primary purpose of this study is to identify the high reservoir quality area for drilling and perforation of new wells using interrelated geological, petrophysical, and seismic data. Various datasets such as, core analysis data (two wells), petrophysical logs (twenty wells) and 3D seismic cube were used to consider different scenarios for optimum well placement based on the availability and accuracy of the data. Considering four criteria (structure, reservoir property, fracture network, and heterogeneity), various data were combined to assess reservoir potential. A static reservoir model was constructed to reduce the uncertainty of the well location determination. A range of scenarios were implemented based on this static reservoir model or by relying only on the available seismic data. Electrofacies analysis was conducted to establish representative facies with which to guide the forecasting of locations suitable for drilling the new wells. Six facies were determined based on multi-resolution graph-based clustering (MRGC) method. In parallel, 3D seismic data was applied to determine seismic facies and seismic attributes to identify high-quality reservoir areas for well placement. As high fracture intensity is an essential feature required for high oil/gas production rates, a continuous fracture model (CFM) was constructed, and average intensity fracture maps were developed to determine the best production locations and to avoid low-productivity (or potential loss-of-circulation zones) from a drilling perspective. Some structural issues, such as distances from transition zones and/or faults, were also considered for well-placement purposes. Coefficient of variation (as a heterogeneity criteria) was also taken into account for well-placement decision-making. The results indicate that applying the developed integrated approaches reduces well-placement uncertainty and delineates high-quality reservoir zones (or sweet spots) with more confidence.

Majid Safaei-Farouji, Thomas Gentzis, Bo Liu et al.

Abstract To understand variations in geochemistry, organic petrology, and chemical composition of crude oil and byproducts, an immature sample from the Cretaceous Qingshankou Formation in the Songliao Basin, China, was analyzed by anhydrous and hydrous pyrolysis (AHP/HP) at a wide range of temperatures ranging from 300 °C to 450 °C. The geochemical parameters: TOC, S2, HI, and Tmax obtained from Rock–Eval pyrolysis showed both a decrease and an increase as thermal maturity progressed under HP and AHP conditions. Gas chromatography (GC) analysis showed the presence of n-alkanes in the C14 to C36 range in both expelled and residual byproducts, a Delta-shaped configuration although many samples had a gradually reducing (tapering) trend toward the high range. Gas chromatography-mass spectrometry (GC–MS) analysis revealed both an increase and a decrease in biomarker and very small changes in aromatic compound variations with increasing temperature during pyrolysis. To be more specific, C29Ts biomarker increased with temperature for the expelled byproduct, while the opposite trend was observed for the residual one. Next, The Ts/Tm ratio initially increased and then decreased with temperature while the C29H/C30H ratio fluctuated for the expelled byproduct but increased for the residual. Moreover, the GI and C30 rearranged hopane to C30 hopane ratio remained unchanged whereas the C23 tricyclic terpane/C24 tetracyclic terpane ratio and the C23/C24 tricyclic terpane ratio showed varying trends with maturity alike the C19/C23 and C20/C23 tricyclic terpane. Ultimately, based on organic petrography observations, increasing the temperature resulted in higher bitumen reflectance (%Bro, r) and optical and structural alterations in the macerals. The findings of this study provide valuable insights for future exploration endeavors in the studied region. Moreover, they contribute to our understanding of the significant role of water in the generation and expulsion of petroleum and associated byproducts, thereby facilitating the development of updated models in this field.

Nasrolah Kalantari, Zahra Sajadi, Abbas Charchi et al.

Proper water resources management requires recognizing and evaluating the factors that affect the quantity and quality of water resources. The Ilam-Sarvak (Upper Cretaceous) and Asmari (Oligocene to Miocene) limestone- dolomite formations in the Zagros structural belt have formed a promising karst groundwater horizon. In the present study, the hydraulic relationship between the karst structures of the Izeh territory in the northeast of Khuzestan province was investigated using hydrogeochemical and isotopic information of springs and wells. The results enabled to understand various components influencing the recharge of water resources. In this study, samples were collected from the karst springs and wells of Mongasht, Shavish-Tanosh and Kamarderaz anticlines and Naal-e-Asbi (Horseshoe) syncline and meteoric water to understand the hydrochemical and isotopic characterization, and hydrogeological and hydraulic behavior of the Izeh karst system. The meteoric and groundwater samples were analyzed to determine major and minor ion concentrations and δ18O and δ2H isotope ratios. Isotopic content ranged from -31.6 to -2.9‰ and from -6.32 to -1.87‰ for δ2H and δ18O, respectively, and d-excess values were high and positive. The study of the isotopic content of water samples of springs and wells in the region shows three groups of water sources. The first group, related to the Mongasht anticline springs, has lower isotopic values, indicating that it is recharged by rainfall at high altitudes and snow melting. The isotopic value of the second group is richer than that of the first group, indicating rainfall recharge as well as groundwater mixing (ex­amples of Naal-e-Asbi syncline and Shavish-Tanosh anticline). The highest value in the third group (samples of Kamarderaz anticline) is attributed to evaporation and longer distance from the recharge site to the discharge point, as well as to the diffu­sion system. The trend of decrease in Sr+2 and increase in Ba+2 in the samples of dolomitic limestone formations (Shavish Ta­nosh and Mongasht anticlines) compared to the water samples of Kamarderaz anticline and Naal-e-Asbi syncline indicates the possibility that karst aquifers of the region are recharged from the Mongasht anticline and that there is a hydraulic relation­ship between these structures. D-excess and δ18O show a linear trend, illustrating the effect of altitude difference on isotopic content and recharge sources. The major and minor changes in the concentration of ions, the isotopic content of groundwa­ter and the relationship between TDS and δ18O and d-excess and δ18O indicate the mixing and recharging of karst aquifers (Shavish-Tanosh, Kamarderaz and Naal-e-Asbi aquifers) from the Mongasht karst aquifer and their hydraulic connection.

Ahmed Farid Ibrahim, Ruud Weijermars

Abstract Accurate estimation of fracture half-lengths in shale gas and oil reservoirs is critical for optimizing stimulation design, evaluating production potential, monitoring reservoir performance, and making informed economic decisions. Assessing the dimensions of hydraulic fractures and the quality of well completions in shale gas and oil reservoirs typically involves techniques such as chemical tracers, microseismic fiber optics, and production logs, which can be time-consuming and costly. This study demonstrates an alternative approach to estimate fracture half-lengths using the Gaussian pressure transient (GPT) Method, which has recently emerged as a novel technique for quantifying pressure depletion around single wells, multiple wells, and hydraulic fractures. The GPT method is compared to the well-established rate transient analysis (RTA) method to evaluate its effectiveness in estimating fracture parameters. The study used production data from 11 wells at the hydraulic fracture test site 1 in the Midland Basin of West Texas from Upper and Middle Wolfcamp (WC) formations. The data included flow rates and pressure readings, and the fracture half-lengths of the 11 wells were individually estimated by matching the production data to historical records. The GPT method can calculate the fracture half-length from daily production data, given a certain formation permeability. Independently, the traditional RTA method was applied to separately estimate the fracture half-length. The results of the two methods (GPT and RTA) are within an acceptable, small error margin for all 5 of the Middle WC wells studied, and for 5 of the 6 Upper WC wells. The slight deviation in the case of the Upper WC well is due to the different production control and a longer time for the well to reach constant bottomhole pressure. The estimated stimulated surface area for the Middle and Upper WC wells was correlated to the injected proppant volume and the total fluid production. Applying RTA and GPT methods to the historic production data improves the fracture diagnostics accuracy by reducing the uncertainty in the estimation of fracture dimensions, for given formation permeability values of the stimulated rock volume.

Xiangdong Guo, Min Lv, Hongjun Cui et al.

Abstract Based on static geology and dynamic production of typical wells in Yan'an gas field, a convenient method of the wells controlled reserves was established combining with material balance method (MB). The method was applied to 88 wells in Yan'an tight gas field. The results show that: ①Controlled by pore structure, wells are divided into three types based on the morphology of the capillary pressure curve and the analysis of the parameter characteristics, and their productivity is evaluated, respectively. ②The flow material balance method (FMB) ignores the change of natural gas compressibility, viscosity and Z in the calculation. After the theoretical calculation of 30 gas samples, the slope of the curve of the relationship between bottom hole pressure and cumulative production and the slope of the curve of the relationship between average formation pressure and cumulative production are not equal. ③Compared with the results of the MB, the result of the FMB is smaller, and the maximum error is 34.66%. The consequence of the modified FMB is more accurate, and the average error is 2.45%, which has good applicability. The established method is simple, only requiring production data with high precision, providing a new method to evaluate well-controlled reserves of tight gas sandstone. This method with significant application value can also offer reference values for other evaluating methods of well-controlled reserves.

H. Y. Hu, R. J. Stern, Y. Rojas‐Agramonte et al.

Abstract The Greater Antilles islands of Cuba, Hispaniola, Puerto Rico and Jamaica plus the Virgin Islands host fragments of the fossil convergent margin that records Cretaceous subduction (operated for about 90 m.y.) of the American plates beneath the Caribbean plate and ensuing arc‐continent collision in Late Cretaceous‐Eocene time. The “soft” collision between the Greater Antilles Arc (GAA) and the Bahamas platform (and the margin of the Maya Block in western Cuba) preserved much of the convergent margin. This fossil geosystem represents an excellent natural laboratory for studying the formation and evolution of an intra‐oceanic convergent margin. We compiled geochronologic (664 ages) and geochemical data (more than 1,500 analyses) for GAA igneous and metamorphic rocks. The data was classified with a simple fourfold subdivision: fore‐arc mélange, fore‐arc ophiolite, magmatic arc, and retro‐arc to inspect the evolution of GAA through its entire lifespan. The onset of subduction recorded by fore‐arc units, together with the oldest magmatic arc sequence shows that the GAA started in Early Cretaceous time and ceased in Paleogene time. The arc was locally affected (retro‐arc region in Hispaniola) by the Caribbean Large Igneous Province (CLIP) in Early Cretaceous and strongly in Late Cretaceous time. Despite multiple biases in the database presented here, this work is intended to help overcome some of the obstacles and motivate systematic study of the GAA. Our results encourage exploration of offshore regions, especially in the east where the forearc is submerged. Offshore explorations are also encouraged in the south, to investigate relations with the CLIP.

Alireza Almasi, amir mahdavi, Jingwen Mao

Porphyry Cu deposits are typically oxidized. Oxygen fugacity (fO2) is a key factor, which controls the formation of porphyry Cu deposits. Trace element compositions of Cretaceous magmatic zircon grains (65.9-65.1 Ma) were determined from ore-bearing intrusive rocks of Gazu porphyry Cu deposit in the Tabas block. Then Ce4 +/Ce3+ of zircons were calculated, and estimated the oxygen fugacity of their parental magmas. The values of Ce4 +/Ce3+ in Gazu magmatic zircons are medium to low (range from 10 to 385 with an average of 110) which indicate a small deposit. The low oxygen fugacity values (average ∆FMQ ~ +1) of Gazu magma indicate that during the crystallization of magmatic zircons, the magma did not show high oxidized state (above hematite-magnetite buffer (HM) and ~ ΔFMQ + 4), which is not favorable for porphyry mineralization. This is confirmed by evidence such as magma generation due to metasomatized lithospheric mantle peridotite melting with low involving of the slab and mineralogy of deposit (lack of hematite-magnetite intergrowth and anhydrite). The contamination process during the ascent and emplacement had a decreasing effect on the oxygen fugacity of the Gazu emplaced bodies.

Weiwei He, Zhiqiang Liu

Abstract Understanding the formation damage surrounding the well during the drilling operation is the key to predict damage degree and protect the formation in oil/gas reserviors. Based on the core drainage results, we obtained an empirical relationship between the invasion volume of drilling fluid and permeability reduction of formation. Furthermore, the equation is incorporated into a commercial reservior numerical simulation simulator to characterize the behaviors of drilling fluid invasion process. The results show that, although the invasion depth in low permeability reservoirs is short with the range of 1.7–2.5 m, the effect on recovery factor is significant due to the narrow seepage area in the near fracture region. When considering the formation damage, the pressure in the near-fracture damage region drops sharply, leading to a three-stage shape in pressure distribution curve. In addition, we found that high viscosity and low density oil-based slurry and shorter soaking period are conducive to decrease the formation damage during drilling operation. This work reveals the fundamental mechanisms of formation damage in low permeability reservoirs, which is a theoretical basis in formulation drilling fluids and optimization operation parameters.

Tamara de Riese, Paul D. Bons, Enrique Gomez-Rivas et al.

Crustal-scale fluid flow can be regarded as a bimodal transport mechanism. At low hydraulic head gradients, fluid flow through rock porosity is slow and can be described as diffusional. Structures such as hydraulic breccias and hydrothermal veins both form when fluid velocities and pressures are high, which can be achieved by localized fluid transport in space and time, via hydrofractures. Hydrofracture propagation and simultaneous fluid flow can be regarded as a “ballistic” transport mechanism, which is activated when transport by diffusion alone is insufficient to release the local fluid overpressure. The activation of a ballistic system locally reduces the driving force, through allowing the escape of fluid. We use a numerical model to investigate the properties of the two transport modes in general and the transition between them in particular. We developed a numerical model in order to study patterns that result from bimodal transport. When hydrofractures are activated due to low permeability relative to fluid flux, many hydrofractures form that do not extend through the whole system. These abundant hydrofractures follow a power-law size distribution. A Hurst factor of ~0.9 indicates that the system self-organizes. The abundant small-scale hydrofractures organize the formation of large-scale hydrofractures that ascend through the whole system and drain fluids in large bursts. As the relative contribution of porous flow increases, escaping fluid bursts become less frequent, but more regular in time and larger in volume. We propose that metamorphic rocks with abundant veins, such as in the Kodiak accretionary prism (Alaska) and Otago schists (New Zealand), represent regions with abundant hydrofractures near the fluid source, while hydrothermal breccias are formed by the large fluid bursts that can ascend the crust to shallower levels.

S. Philippo, F. Hatert, Y. Bruni et al.

<p>Luxembourgite, ideally <span class="inline-formula">AgCuPbBi₄Se₈</span>, is a new selenide discovered at Bivels, Grand Duchy of Luxembourg. The mineral forms tiny fibres reaching 200&thinsp;<span class="inline-formula">µ</span>m in length and 5&thinsp;<span class="inline-formula">µ</span>m in diameter, which are deposited on dolomite crystals. Luxembourgite is grey, with a metallic lustre and without cleavage planes; its Mohs hardness is 3 and its calculated density is 8.00&thinsp;g&thinsp;cm<span class="inline-formula">⁻³</span>. Electron-microprobe analyses indicate an empirical formula <span class="inline-formula">Ag_1.00(Cu_0.82Ag_0.20Fe_0.01)_Σ1.03Pb_1.13Bi_4.11(Se_7.72S_0.01)_Σ7.73</span>, calculated on the basis of 15 atoms per formula unit. A single-crystal structure refinement was performed to <span class="inline-formula"><i>R</i>₁=0.0476</span>, in the <span class="inline-formula"><i>P</i>2₁∕<i>m</i></span> space group, with <span class="inline-formula"><i>a</i>=13.002(1)</span>, <span class="inline-formula"><i>b</i>=4.1543(3)</span>, <span class="inline-formula"><i>c</i>=15.312(2) <i>Å</i></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi mathvariant="italic">β</mi><mo>=</mo><mn mathvariant="normal">108.92</mn><mo>(</mo><mn mathvariant="normal">1</mn><mo>)</mo><msup><mi/><mo>∘</mo></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="73pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="4d920107eb4a98473050fd7bdaf16dee"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-32-449-2020-ie00001.svg" width="73pt" height="13pt" src="ejm-32-449-2020-ie00001.png"/></svg:svg></span></span>, <span class="inline-formula"><i>V</i>=782.4(2) <i>Å</i>³</span>, <span class="inline-formula"><i>Z</i>=2</span>. The crystal structure is similar to that of litochlebite and watkinsonite and can be described as an alternation of two types of anionic layers: a pseudotetragonal layer four atoms thick and a pseudohexagonal layer that is one atom thick. In the pseudotetragonal layers the Bi1, Bi2 ,Bi3, Pb, and Ag1 atoms are localised, while the Cu2 and Bi4 atoms occur between the pseudotetragonal and the pseudohexagonal layers. Bi1, Bi2, and Bi3 atoms occur in weakly distorted octahedral sites, whereas Bi4 occurs in a distorted 7-coordinated site. Ag1 occupies a fairly regular octahedral site, Cu2 a tetrahedral position, and Pb occurs on a very distorted 8-coordinated site.</p>

Nur Aqilah Ahad, Morteza Jami, Stephen Tyson

Abstract Sand production is a problem that affects hydrocarbon production from unconsolidated sandstone reservoirs. Several factors, such as the strength of the reservoir, its lithification and cementation and reduction in pore pressure, may cause sand to be separated from the rock and transported by hydrocarbons to the well. Producing sand commonly causes erosion and corrosion of downhole and surface equipment, leading to production interruptions and sometimes forces operators to shut-in wells. Several different methods of sand control are available to reduce the impact of sand production. The reviewed papers suggest that the most suitable methods for unconsolidated sandstone reservoirs are stand-alone screens and gravel packs. Because of the cost and complexity of gravel packs, stand-alone screens are usually the first choice. These screens have different geometries, and selection of the most suitable screen depends on the particle size distribution of the grains in the formation and other reservoir and production parameters. A screen retention test, run in a laboratory with screen samples and typical sands, is often used to ensure that the screen is suitable for the reservoir. This paper reviews the main causes of sand production, the properties of unconsolidated sandstones that predispose reservoirs to sand production problems and the selection criteria for the most suitable mitigation method. The process of selecting a screen using experimental screen retention tests is reviewed, and the limitations of these tests are also discussed. Some numerical simulations of experimental tests are also reviewed, since this represents a very cost-effective alternative to laboratory experiments.

Hai-Gang Wang, Yong-Lei Lin, Wu-Qiang Yang

Abstract In the pharmaceutical industry, fluidized beds are typically used for pellets drying, coating and granulation. The gas–solids flow characteristic in the process plays an important role to control the heat and mass transfer as well as the end-point product quality. Therefore, it is necessary to investigate the flow characteristics based on advanced measurement technologies. In this research, electrical capacitance tomography (ECT) sensor with eight electrodes was used to investigate the pharmaceutical fluidized bed drying process with different operation conditions. Key process parameters including solids concentration, particle moisture and capacitance signals in the process are given and analysed based on the ECT sensor. In addition, the fluidized bed process with Wurster tube is also investigated based on this ECT sensor. The effect of Wurster tube on the hydrodynamic behaviour and the dominant frequency spectrum distribution in the chamber were analysed based on fast Fourier transform. Test results reveal that process moisture change can be addressed from the raw capacitance of adjacent electrode pair combined with calibration model. Experimental result also indicates that ECT technology can provide useful information for process monitor in a fluidized bed dryer.

Vladimir Sova, Abdul-Gapur Kerimov

Abstract Stavropol Region is one of the oldest petroleum provinces on South of Russian Federation. Today, most of its fields are depleted and prospects for the discovery of new large hydrocarbon deposits considered exhausted. However, our studies allow us to talk about the possibility of the existence of previously undiscovered oil reservoirs, clamped in the source rocks associated with North-Stavropol tectonic element. In the middle of the last century, similar deposits have been identified within Prikumsk-Tyulenevskiy (Praskoveyskoe, Achikulakskoye, Ozek-Suat and a number of other fields) and Chernolesskiy (Zhuravskoye, Vorobyevskoye) tectonic elements. However, these findings were largely spontaneous due to lack of approved and unified approach to the petrophysical evaluation of dedicated reservoirs from well logs. At the same time the experience of shale reservoirs studies, as well as the results of its implementation to evaluation of deposits of Zhuravsky-Vorobyevsky petroleum accumulation zone, allows to revise existing well log materials for deep wells of explorational and depleted structures, and to identify promising intervals for further re-exploration and testing. In this work, Paleocene sediments of Blagodarnenskaya explorational structure of the Stavropol Region were studied. Despite the approval of the oil bearing of these deposits within the Prikumsk-Tyulenevskiy tectonic element and the positive signs of hydrocarbon saturation from initial well logs data, its evaluation and testing within Blagodarnenskaya structure associated with North-Stavropol tectonic element, were not conducted. However, the results of well logs analysis performed by us with the use of interpretation technique approved on reservoirs of Zhuravsky-Vorobyevsky petroleum accumulation zone, as well as the core tests indicate the presence of oil-saturated reservoirs in the Paleocene sediments of Blagodarnenskaya structure.

Xiao Guo, Pengbin Du, Peng Wang et al.

Abstract The water coning phenomenon leads to decrease the wellhead pressure with moving of water into gas production zone, which is regarded as one of most serious problems during gas production. It has been shown that water breakthrough time plays an important role in analyzing the water coning phenomenon and production of water. However, the existing prediction models of water breakthrough time are very scarce and need to be discussed. In this work, a novel model for water breakthrough time in high-sulfur gas reservoir with edge water is developed based on flow law and sulfur precipitation model in porous media. The effect of irreducible water saturation, residual gas saturation, and the distance between gas well and edge water, sulfur saturation and gas non-Darcy flow on water breakthrough time was involved in this model. The validity of the proposed model is verified by comparing the existing models available. A good trend is found between them. In addition, the influence of the distance between gas well and edge water, sulfur saturation and gas non-Darcy flow on water breakthrough time was detail discussed further.

Jo De Waele

Orosejski zaliv je eno najpomembnejših obalnokraških območij v Italiji. Številne nove meritve jam so omogočile boljše razumevanje speleogeneze na območju zaliva. Razvoj krasa na tem območju smo raziskovali z različnimi geomorfološkimi raziskavami na površju in pod morjem, ter spelološkimi raziskavami v jamah. Glavni faktorji morfoloških procesov so litologija, tektonika, paleoklima in nihanja morske gladine. Študija nekaterih pomembnih jamskih sistemov je pokazala kompleksen geološki razvoj, kjer so kraški procesi igrali pomembno vlogo od zgodnjega terciarja in dosegli višek v pliokvartarju. In the past ten years cave surveying has allowed better understanding of speleogenesis in the Orosei Gulf (Central-East Sardinia, Italy), one of the most important coastal karst areas of Italy. Surface geomorphologic research has been accompanied by subterranean and submarine landform analysis in order to try and understand the evolution of this coastal karst since its emersion in Upper Eocene. The main factors influencing the geomorphic processes are lithology, tectonics, palaeo-climate and sea level changes. The study of several important cave systems demonstrates a complex geological history with karst processes that started in Early Tertiary and accelerated during Plio-Quaternary.

J. Moore

J. Papike, S. Simon, J. Laul

M. Duke, L. Silver