High-temperature Formation Research Articles

Oxidative decomposition of dimethyl methylphosphonate on rutile TiO2(110): the role of oxygen vacancies.

The decomposition of dimethyl methylphosphonate (DMMP, (CH3O)2P(O)(CH3)), a simulant to the toxic nerve agent Sarin, on the rutile TiO2(110) surface has been studied with temperature programmed desorption (TPD) and density functional theory (DFT) calculations. The reactivity of the TiO2(110) surface for DMMP decomposition is shown to be low, with mainly molecular desorption and only a small fraction of methanol and formaldehyde decomposition products seen from TPD at around 650 K. In addition, this amount of products is similar to the number of O vacancies on the surface. DFT calculations show that O vacancies are key for P-OCH3 bond cleavage of DMMP, lowering the barrier by 0.7 eV and enabling the reactive process to occur at around 600 K. This is explained by the closer position of DMMP with respect to the surface in the presence of O vacancies. Calculations show that the produced methoxy groups can transform into gas phase formaldehyde and methanol at the considered temperature (600 K), in agreement with experiments. O-C bond cleavage of DMMP is also a viable pathway at such a high temperature (600 K) for DMMP decomposition on r-TiO2, even in the absence of O vacancies, but the formation of a gas phase product is energetically unfavorable. O vacancies hence are the active sites for decomposition of DMMP into gas phase products on r-TiO2(110).

Recent development in catalyst and reactor design for CO2 reforming of alcohols to syngas: A review

Global energy demand has had a significant impact on the Green House Gases (GHGs) emission, which have harmful effects on the environment and human health. Catalytic CO2 reforming of biomass-derived alcohols converted into syngas is regarded as a viable option for reducing GHGs. Even though this is sustainable and ecologically beneficial for utilizing value-added biomass, little research has been done on the topic. Due to the high reaction temperature, metal sintering and coke formation have been widely reported as the major challenges in the CO2 reforming process. These conditions could reduce the catalyst efficiency and cause the reactor system to shut down. To address these issues, this article provides a review of the current catalyst and reactor design development for CO2 reforming of methanol, ethanol, glycerol, and butanol to generate synthetic gas. Thermodynamic analysis, catalyst performance, optimizing reaction parameters, and future potential catalyst design are also covered.

Impact assessment of nanoparticles on microstructure and rheological behaviour of VES fracturing fluid formulated with mixed surfactant system

The nature and type of fracturing fluid play a vital role in a successful hydraulic fracturing job. The desired fracturing fluid should have non-damaging characteristics and an effective proppant carrying capacity. Though viscoelastic surfactant (VES) fluid has started to replace the polymer-based fluids for the fracturing of specific formations owing to its non-damaging characteristics; however, its wider application to high-temperature formation is still a challenge to the operators. Incorporation of nanoparticle has been able to extent the thermal stability of VES fluid. The current study examined the impacts of different nanoparticles at different concentrations on rheological and structural properties of VES fluid prepared from mixed surfactant system which is composed of NaOA/tween 80, Co-surfactant, oil and water. Nano-enhanced VES fluids were formulated using SiO2, Fe2O3, MgO, and ZnO nanoparticles at varied concentrations, ranging from 250 ppm to 1000 ppm. The rheological and morphological variations of VES fluids were studied at different shear rates and temperatures. MgO and Fe2O3 enhanced VES at 500 ppm concentration fluid showed excellent rheological characteristics with 3529 cp and 2817 cp viscosity at a shear rate of 100 S−1, temperature 35 °C, which is much above the required viscosity value. Zeta potential and surface area of nanoparticles both play an important role in the rheological enhancement of VES fluid. MgO enhanced VES fluid with a surface area (83.7 m2/g) and zeta potential (−15.9, mV) of MgO nanoparticles showed better rheological properties than silica enhanced VES gel with surface area (127.8 m2/g) and zeta potential (–33.8, mV). It was also observed that increasing the nanoparticle concentration improved VES fluid's rheological properties; however, the rate of increment decreased after 500 ppm concentration. The cryo-FESEM images clearly indicate the distict change in the lamellar structure of VES fluids on the addition of nanoparticles compared to that of in its absence. The dynamic rheology tests further confirmed the compact structure and stronger entanglement of micelles in the presence of nanoparticles.All the developed nano-enhanced VES fracturing fluids showed desired viscosity up to the temperature of 150 °C. Among all nano-enhanced fracturing fluid, MgO enhanced VES fracturing fluid showed excellent viscosity (i.e., 200 cP) with respect to time at 100 °C temperature and a shear rate of 100 S−1. All the nano-enhanced VES fluid was miscible with formation water & there were no residues observed. A static column test was also done to check the proppant carrying capacity of VES gel. The MgO enhanced VES gel has also showed lowest proppant settling velocity of 0.305 cm/min which is much lower than the maximum permissible proppant settling velocity of 5 cm/min. The findings of this study can help for a better understanding of nano-enhanced VES fracturing fluid in mitigating the constraints associated with hydraulic fracturing jobs in formation with high temperatures. Thus, the knowledge about the functional characteristics of different nanoparticles in enhancing the fracturing fluid properties will help us to select suitable nanoparticle-surfactant combinations for a particular field.

A simulation experiment method for HTHP gas well productivity

In recent years, a series of major natural gas exploration discoveries and breakthroughs have been achieved in deep and ultra-deep carbonate gas reservoirs in the Sichuan Basin, and all discovered gas reservoirs are characterized by great burial depth, complex pore structures and high formation temperature and pore pressure. In order to accurately predict the gas flow rate of single well in high temperature and high pressure (HTHP) gas reservoirs and clarify the gas flow characteristics under formation conditions, this paper establishes a productivity simulation experimental device and method based on the formation temperature and pore pressure of carbonate gas reservoirs in the Middle Permian Qixia Formation of northwestern Sichuan Basin and the Upper Sinian Dengying Formation of central Sichuan Basin. Then, the cores of above mentioned gas reservoirs are selected to carry out the productivity simulation experiment under HTHP. Finally, the gas flow characteristics are studied. And the following research results are obtained. First, the newly established productivity simulation experimental device and method suitable for the conditions of 160 °C formation temperature and 100 MPa pore pressure is used to predict the natural gas AOF (absolute open flow) of Well S-1 in the Qixia Formation gas reservoir of northwestern Sichuan Basin. And the prediction result is better accordant with the calculation result of theoretical model, with a relative error of only 2.12%. Second, based on the Klinkenberg permeability under surface conditions, the single-well gas flow rate calculated from the productivity simulation experiment is better accordant with the gas flow rate from field completion testing; while based on the Klinkenberg permeability under formation conditions, the single-well gas flow rate calculated from the productivity simulation experiment is better accordant with the AOF. Third, the change of formation temperature and pore pressure has a significant influence on rock permeability, and the permeability is more sensitive to stress than to temperature. Fourth, to carry out the reservoir stress sensitivity experiment and the productivity simulation experiment, it is required that core samples be recovered to the formation conditions for aging, or the experimental results may have characteristics of strong stress sensitivity and cannot be used for reservoir engineering evaluation directly. In conclusion, the production rate and AOF of HTHP gas wells can be predicted accurately by means of productivity simulation experiment, based on drilling core samples. In addition, the Klinkenberg permeability under formation conditions can be evaluated by using the relational expression between surface or Klinkenberg permeability under formation conditions and single-well gas flow rate, combined with gas well testing data.

Geochemical Investigation of CO2 Injection in Oil and Gas Reservoirs of Middle East to Estimate the Formation Damage and Related Oil Recovery

The injection performance of carbon dioxide (CO2) for oil recovery depends upon its injection capability and the actual injection rate. The CO2–rock–water interaction could cause severe formation damage by plugging the reservoir pores and reducing the permeability of the reservoir. In this study, a simulator was developed to model the reactivity of injected CO2 at various reservoir depths, under different temperature and pressure conditions. Through the estimation of location and magnitude of the chemical reactions, the simulator is able to predict the effects of change in the reservoir porosity, permeability (due to the formation/dissolution) and transport/deposition of dissoluted particles. The paper also presents the effect of asphaltene on the shift of relative permeability curve and the related oil recovery. Finally, the effect of CO2 injection rate is analyzed to demonstrate the effect of CO2 miscibility on oil recovery from a reservoir. The developed model is validated against the experimental data. The predicted results show that the reservoir temperature, its depth, concentration of asphaltene and rock properties have a significant effect on formation/dissolution and precipitation during CO2 injection. Results showed that deep oil and gas reservoirs are good candidates for CO2 sequestration compared to shallow reservoirs, due to increased temperatures that reduce the dissolution rate and lower the solid precipitation. However, asphaltene deposition reduced the oil recovery by 10%. Moreover, the sensitivity analysis of CO2 injection rates was performed to identify the effect of CO2 injection rate on reduced permeability in deep and high-temperature formations. It was found that increased CO2 injection rates and pressures enable us to reach miscibility pressure. Once this pressure is reached, there are less benefits of injecting CO2 at a higher rate for better pressure maintenance and no further diminution of residual oil.

In situ trace elements of magnetite in the Bayan Obo REE-Nb-Fe deposit: Implications for the genesis of mesoproterozoic iron mineralization

The giant Bayan Obo REE deposit bears a large amount of iron resources as well. However, the genesis of iron mineralization is still highly controversial with limited research. In this study, new data of trace elements of magnetite from Bayan Obo ores, Eastern contact zone skarn and Heinaobao BIF are obtained by Laser ablation (LA) ICP-MS analyses, revealing the genesis of Bayan Obo iron resources through comparing study. The Bayan Obo deposit contains disseminated, banded and massive ores, and in which magnetite is associated with REE minerals, fluorite, aegirine, riebeckite, and biotite. Euhedral magnetite in the skarn of Eastern contact zone is usually associated with pyrite, biotite, fluorite, and bastnaesite. There are two types of magnetite in the Heinaobao BIF: (1) euhedral to subhedral magnetite associated with quartz and a small amount of amphibole; (2) anhedral magnetite associated with quartz, garnet, plagioclase, amphibole and biotite.Magnetite in the Bayan Obo is enriched in Ni, but depleted in Mg, Al, Ti, Ge, Mn, Ga and Zn, showing low and variable concentrations, which is similar to the hydrothermal magnetite. The contents of some trace elements (e.g. Ti, Mn, Sc, Zn, Nb and REE) of magnetite from the skarn ores are generally higher, indicating a relatively high formation temperature. Magnetite in the Heinaobao BIF is generally characterized by low and uniform trace element contents, except for the abnormal values of Ti, Al, Cr and Mn, suggesting the involvement of terrigenous clastic materials. Compared with Bayan Obo magnetite, the skarn magnetite has the highest Sn/Ga, Co/Ni, Nb/Ta, La/Yb, Ti/V and Ti/Al ratios, while magnetite in the BIF has the highest Al/Co and lowest Nb/Ta ratios. The significant difference in mineralogical and trace element characteristics among the three types of magnetite indicates that the iron resources in Bayan Obo deposit are unlikely to be a skarn Fe deposit nor a BIF deposit. However, the Bayan Obo magnetite shows similar geochemical characteristics to hydrothermal magnetite related to carbonatite, both of which are depleted in high field strength elements, such as Zr, Hf and Ta, and show strong positive anomalies of Mn and Zn and negative anomalies of Co and Ga. In addition, in the diagrams of Ti vs. Nb + Ta and Ti vs. Zr + Hf, the Bayan Obo magnetite falls into the field of hydrothermal magnetite associated with carbonatite. In conclusion, it is recommended that the Bayan Obo iron deposit is a typical hydrothermal deposit related to carbonatite. In this contribution, the skarn magnetite formed at high temperature and the BIF magnetite was contaminated by terrigenous materials deviating from the expected region in discriminant diagrams. It is therefore proposed that the validity of these diagrams depends on a full understanding of mineralogical characteristics of samples and magnetite precipitation environment, and that multiple discrimination diagrams should be used in combination.

Enhanced oil recovery mechanism by surfactant-silica nanoparticles imbibition in ultra-low permeability reservoirs

Due to the low permeability, small pore throat and poor pore connectivity of ultra-low permeability reservoirs, the development technology of ultra-low permeability reservoirs is different from the stimulation techniques of conventional oil reservoirs, making development more difficult. In recent years, nanoparticles have been widely used in the oil industry and have shown great potential in oil exploitation. However, the application of nanofluids in high temperature and high salinity formation is still facing great challenges. In this work, a new type of nanofluid was prepared by mixing silica nanoparticles with anionic surfactant. The nanofluids were stored at high salinity (30,000 mg/L) and high temperature (80 °C) for 3 weeks without any aggregates. The particle size and zeta potential of nanofluids with different concentrations and ratios were measured. The microscopic structure of nanofluids was characterized by transmission electron microscope (TEM). By measuring and comparing the oil–water interfacial tensions between different concentrations and ratios of nanofluids and crude oil, as well as the contact angles between high salinity simulated water (30,000 mg/L) and nanofluids, the application potential of nanofluids in oil exploitation is discussed. Compared with high salinity (30,000 mg/L) simulated water, the interfacial tension decreases by 99.98% after adding nanofluids. The contact angle increases by 20° with the addition of nanofluids comparing with single surfactant, and the rock surface changes from oil wet to water wet. The recovery of nanofluids with different concentrations and ratios was measured by spontaneous imbibition experiment. The imbibition recovery of high salinity (30,000 mg/L) simulated water was only 8.9%, and that of surfactant was 14.33%. With the addition of nanofluids, the imbibition recovery is significantly improved, up to 29%. The possible mechanism of nanofluids for enhanced oil recovery (EOR) is proposed and analyzed, which proves that nanofluids have great potential in EOR. The findings of this study can be helpful for better understanding of the flooding mechanism of nanoparticles and the mechanism of enhanced oil recovery by nanofluid imbibition.

Experimental investigation on the PDC cutter penetration efficiency in high-temperature granite

Hot dry rock (HDR) is a renewable and clean energy resource, its efficient exploration has attracted widespread attention from scholars. However, the rock encountered during drilling is characterized by poor drillability, high abrasiveness and great hardness, which aggravates the wear of bits and increases drilling costs. To address such an issue, much research has been conducted to investigate the failure mechanism of high-temperature rocks. But most of them focused on the rock cutting process by PDC cutters and the penetration of rocks was ignored. In the present study, a series of experiments were performed to determine the penetration efficiency of PDC cutters under different temperatures and back rake angles. The penetration force and 3D topography of penetration pits were measured to analyze rock failure characteristics. Besides, uniaxial compressive experiments were carried out to study the effects of temperature on rock properties. The results indicate that as the rock is heated from 25 to 240 ℃, its properties change slightly. Analogous rock failure characteristics can be found in rock indentation process, where chipping and crushing of rocks, on following another, are presented, respectively. Moreover, the occurrence of chipping is the major contributor to the increase in penetration efficiency. The further increase in rock temperature (greater than 360 ℃) results in a sharp decrease in the strength of rocks, which is accompanied by the enhancement of rock plasticity. At his moment, the plastic failure dominates rock indentation process under different back rake angles. The induced horizontal force cannot promote brittle failure and the penetration efficiency is hard to be improved, significantly affecting the performance of conventional PDC bits in high-temperature formations. Based on the results, the low penetration efficiency at high temperatures is a major obstacle that restricts the exploration of HDR. Increasing the cutting depth should be an important target in optimizing drilling parameters and the arrangement of PDC bits.

Petrology of Granitoids of the Selennyakh Ridge (Verkhoyansk-Kolyma Orogenic Belt)

The Verkhoyansk-Kolyma orogenic belt is characterized by intense Late Mesozoic granitoid magmatism. Numerous granitoids plutons form longitudinal belts, elongated parallel to the boundaries of major tectonic structures (Main and Northern), and transverse belts, oriented across or at an angle to them. The Main belt is dominated by massifs of granodiorite-granite composition, accompanied by tin-tungsten, boron-tin, and gold mineralization of various scale. Therefore, understanding their petrological and genetic characteristics and crystallization conditions leading to the generation of mineralization is of not only theoretical but also practical interest. The aim of the research was a detailed study of petrography, geochemical features and crystallization conditions of granodiorite-granite massifs of the Selennyakh block of the Omulevka terrane of the Kolyma-Omolon microcontinent that forms part of the Verkhoyansk-Kolyma orogenic belt. It was found that the formation of granitoids took place in an active continental margin setting and was long-term and complex. During the evolution of magmatism, the homodrome character of development (granodiorites → granites → leucogranites and aplites) was replaced by the antidrome one (granite-porphyries and granodiorite-porphyries). The Rb-Sr isotopic age of the rocks varies from 136 to 122 Ma. The generation of the parent melts for the granitoid massifs occurred within the lower crust at the boundary between amphibolite and dacite-tonalite substrates at temperatures of 1070–990° C and a pressure of 1.1–0.9 GPa. These parameters are comparable to those of the melt that formed the granodiorite-porphyry dikes: 990° C and 0.94 GPa. Maintaining high temperatures of the melt formation from initial to final derivatives at deeper levels of the magma chamber with a simultaneous increase in their fluid saturation requires the supply of juvenile heat and fluids. The main mineral in the territory is tin. The formation of mineralization is associated with late fluid-saturated derivatives of the granitoid melt. During the crystallization of leucogranites and pegmatites, fluorine was the main Sn-extracting agent. With depth, in the course of crystallization of granite and granodiorite porphyries, boron and then sulfur became the major extractants of tin.

Change of physical and chemical properties of asphaltene-resin-paraffin deposits deposits in tubing

The paper analyzes the geological and physical characteristics of the White Tiger field, deep and estuary samples of oil and asphaltene-resin-paraffin (ARP) deposits, which revealed the main factors leading to the intensive accumulation of asphaltenes on tubing surface during oil production. First of all, these are high formation temperatures (80-120°C) in combination with high paraffin separation temperature (57°C) and a relatively large oil depth (up to 4,500 m). Experimental studies were carried out and chemical reagents consisting of a mixture of polyvinyl acetate and organic solvents were selected (naphthalene, toluene, aromatic derivatives), which affect paraffin separation, which, in turn, leads to a decrease in viscosity and dynamic shear stress at the same temperature, as well as a decrease in oil congelation temperature thereby promoting the inhibition of asphaltene-resin-paraffin deposits by interacting with an activator for gel formation, adsorption on the surface of rocks, i.e. preventing the formation of asphaltene during oil production.

Waterproof, flexible field-effect transistors with submicron monocrystalline Si nanomembrane derived encapsulation for continuous pH sensing

To understand the physio-pathological state of patients suffering from chronic diseases, scientists and clinicians need sensors to track chemical signals in real-time. However, the lack of stable, safe, and scalable biochemical sensing platforms capable of continuous operation in liquid environments imposes significant challenges in the timely diagnosis, intervention, and treatment of chronic conditions. This work reports a novel strategy for fabricating waterproof and flexible biochemical sensors with active electronic components, which feature a submicron encapsulation layer derived from monocrystalline Si nanomembranes with a high structural integrity due to the high formation temperature (>1000 °C). The ultrathin, yet dense and low-defect encapsulation enables continuous operation of field-effect transistors in biofluids for chemical sensing. The excellent stability in liquid environment and pH sensing performance of such transistors suggest their great potential as the foundation of waterproof and scalable biochemical sensors with active functionalities in the future. The understandings, knowledge base, and demonstrations for pH sensing reported here set the stage for the next generation long-term biosensing with a broad applicability in biomedical research, food science, and advanced healthcare.

Mechanical Properties and Microstructure of Shotcrete under High Temperature

High temperature is recognized as one of the extreme environments in the application of shotcrete which significantly deteriorate the performance of shotcrete. This paper reviews the mechanical properties and microstructure of shotcrete under high temperature. First of all, this paper reviews the cause of formation of high ground temperature. Based on these causes, the author establishes a heat transfer model with a spiral shape by introducing a multidimensional morphological formula into the heat conduction process. Then, the paper reviews the influence of high temperature on the mechanical and micro properties of shotcrete, the cooling technology under high temperature, and the optimization research technology of shotcrete. The author discusses the influence of high temperature on the thermal parameters and the deformation of shotcrete from the perspective of thermodynamics. Multiple studies have shown that the irregular movement and disorderly overlapping of molecules in the shotcrete caused by the high temperature environment result in the premature termination of the hydration reaction of cement in shotcrete. Finally, the author suggests the challenges of high-temperature shotcrete in term of the process structure, performance optimization, and application in special engineering fields. The research in this paper intends to give guidance to those conducting shotcrete research under high temperature, and to promote the further development of shotcrete technology.

Key Technologies for Deep Horizontal Well Drilling of Shale Gas in Luzhou of Sichuan Basin

The drilling of deep shale gas horizontal wells in Luzhou block of Sichuan Basin has been chanllenged by long drilling cycle, low rate of penetration (ROP), high drilling tool vibration, poor drillability of special lithological formations, horizontal wellbore instability, high formation temperature, and high friction torque and sticking risk etc.. To solve these problems and to ensure operation safety and increase cost-efficiency, technological research was carried out on casing program design of horizontal wells, wellbore trajectory control and optimization of horizontal sections. As a result, the optimal parameters of the radical drilling method were recommended, and shock absorption, speed-up, and high efficient rock breaking technologies for special lithological formations were preferentially adopted. In addition, drilling fluid system and performance parameters were recommended based on pilot tests of ground cooling equipment. In this way, key drilling technologies with high operation safety and efficiency were formed for the deep shale gas horizontal wells in Luzhou block. Through the application of the key technologies in four wells in Luzhou block, the experimental results show that the drilling cycle was redcued by 14.5% and no downhole failure was reported for average well depth of 5,601.00 m and the horizontal section length of 1,884.00 m. So these technologies can meet the requirement of safe and efficient drilling as well as wide application scope in Luzhou.

A holistic approach to determine the enhanced oil recovery potential of hydroxyethylcellulose, tragacanth gum and carboxymethylcellulose

Several polymers have been investigated for their potential as an enhanced oil recovery process. In general, polymer dispersion in an injection fluid increases its sweep efficiency and mobility ratio leading to an increase in oil recovery rate. Though, harsh reservoir heterogeneous environment, lowers performance of different polymers under high formation salinity and temperature. Therefore, to achieve a profitable operational decision to recover crude oil, the oil and gas industry relies heavily on predicting various enhanced oil recovery (EOR) fluid performance in advance. Decisions on such recovery strategies should be taken at the lab scale before practical field job planning. In this study, we propose a holistic approach for analyzing and assessing tragacanth gum (TGU), hydroxyethylcellulose (HEC), and carboxymethyl cellulose (CMC) potential as an EOR fluid in three stages of screening methods, depending on the criteria that are well-established in the literature. We perform a comprehensive study based on the polymer rheological characteristics as first stage examination, wettability alteration features as second stage examination, and evaluation of additional oil recovery potential using oil reservoir simulating bioreactors (ORSBs) in the final stage. We integrate all the practical screening principles involving the reservoir characteristics through this innovative approach. The first stage screening showed better rheological characteristics of HEC and TGU, and the existence of wettability alteration capacities in these polymers was observed during the second stage screening. The final stage demonstrated that both these polymers (HEC – 7.38% and TGU – 6.71% of Residual Oil in Place) had higher additional oil recovery potential than polyacrylamide polymer (5.83%), a widely used commercial EOR polymer.

Application of the Mineralogy and Mineral Chemistry of Carbonates as a Genetic Tool in the Hydrothermal Environment

The mineralogy and mineral chemistry of carbonates from various hydrothermal deposits, including volcanic-hosted Au-Cu epithermal, “Chilean Manto-type” Cu(-Ag), stratabound Mn, and Ag-Ba vein deposits from Spain and Chile, were investigated. Dolomite-ankerite (±siderite) was found in variable amounts within the epithermal deposits and associated hydrothermal alteration, whereas calcite was found either within barren veins or disseminated within the regional alteration. Calcite is the major gangue phase within the stratabound deposits, which tend to lack dolomite/ankerite and siderite. Carbonates precipitated from hydrothermal ore fluids are typically Mn-rich, up to 3.55 at. % in siderite, 2.27 at. % in dolomite/ankerite, and 1.92 at. % in calcite. In contrast, calcite related to very low-grade metamorphism or regional low-temperature alteration is Mn-poor but sometimes Mg-rich, possibly related to a higher temperature of formation. Chemical zonation was observed in the hydrothermal carbonates, although no unique pattern and chemical evolution was observed. This study suggests that the chemical composition of carbonates, especially the Mn content, could be a useful vector within ore-forming hydrothermal systems, and therefore constitutes a possible tool in geochemical exploration. Furthermore, Mn-poor calcites detected in some deposits are suggested to be linked with a later episode, maybe suggesting a predominance of meteoric waters, being not related to the main ore stage formation, thus avoiding misunderstanding of further isotopic studies.

Thermal Characteristics of Borehole Stability Drilling in Hot Dry Rock

Due to high temperature of formation and low temperature of the drilling fluid while drilling in the hot dry rock, thermal stress around the borehole is easy to appear. The thermal stress causes cracks in the borehole wall. In severe cases, the cracks caused borehole instability and lost-circulation. Based on the theory of transient heat transfer in formation, the method of Bessel infinite series is adopted to analyze the distribution of temperature around the borehole. The results showed that the specific heat of rock and the coefficient of heat conduction changing with temperature fiercely influences the transient heat conduction in the rock and had no significant effect on the heat conduction velocity in the rock. The crack propagation is related to the stress intensity factor at the crack tip and the crack opening width. Compared with the thermal conductivity coefficient and elastic modulus, the linear expansion coefficient has a stronger effect on the peak value of thermal stress. The deeper the crack around the borehole, the weaker the influence of the drilling fluid temperature on it. The temperature gradient of the borehole wall changes gently in space. The stress intensity factor of the crack tip around the borehole is far higher than the fracture toughness of the rock, and the crack opening width near the crack tip is more than 1 mm. Therefore, the rock around the borehole while drilling in the hot dry rock would almost inevitably crack and expand, influenced by the thermal stress.

Filtration and structure of bentonite-β-cyclodextrin polymer microspheres suspensions: Effect of thermal aging time

Effective filtration loss control is a challenge for water-based drilling fluid when drilling high temperature and high pressure (HTHP) formations. After thermal aging at 200 °C for varying times, the static filtration loss controlling capabilities of β-cyclodextrin polymer microspheres (β-CDPs) and synthetic polymer Driscal-D in bentonite suspensions were compared in this study. A comprehensive physicochemical characterization was presented using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), particle size distribution, zeta potential, electrical conductivity and scanning electron microscope (SEM). The results indicated that when exposure to thermal aging of 200 °C, the filtration loss of bentonite suspension increased with the initial 6 h of aging, after that it increased slightly. While for synthetic polymer Driscal-D, the filtration loss increased gradually with thermal aging time until to 36 h. In contrast for β-CDPs, the filtration loss increased firstly and then decreased and maintained relatively stable after thermal treatment for 6 h. High temperature destroyed the hydrated structure of bentonite particles and induced the increase of filtration loss volume. In viewing of Driscal-D, degradation of the polymer in combination with dehydration of bentonite particles led to the gradual losing of suspensions stability. For β-CDPs, after aging of 6 h, the hydrothermal carbonization reaction generated numerous nano and micro carbon spheres and bentonite-carbon sphere composited structures, which fill in the gaps between the larger particles and contribute to reducing the filter cake permeability. This result identified that β-CDPs are superior to synthetic polymer Driscal-D in filtration control when subjected to long term high temperature environments.

Prediction Model and Distribution Law Study of Temperature and Pressure of the Wellbore in drilling in Arctic Region

The low temperature condition of permafrost in Arctic region affects the rheology of drilling fluids and the distribution of temperature and pressure in the wellbore during drilling. In order to understand the influence law of permafrost in Arctic region on the temperature and pressure distribution in wellbore and provide a basis for the design and construction for drilling in Arctic region, a model to predict the wellbore temperature and pressure of drilling in Arctic region was built. It was based on the analysis of the influence of low temperatures on the rheology of water-based and oil-based drilling fluids, considering the coupling between permafrost and wellbore. By comparing the measured and test results, it was verified that the prediction accuracy of the proposed model met the requirements of drilling in Arctic region. The model was used to simulate the temperature and pressure distribution in a wellbore in Arctic region under the conditions of no circulation or pump function. The results showed that the drilling fluids absorbed the heat of the high-temperature formation and returned to the annulus transferring the heat to the permafrost in shallow part of the wellbore during the circulation. This process thawed the permafrost near the wellbore and the wellbore temperature was lowered due to the heat consumed by thawing. The circulating friction in annulus increases with the increase of circulation time. The longer the pump shutdown lasts, the closer the temperature of drilling fluid to the formation temperature in the wellbore. The larger the annular circulation pressure loss, and the higher the pump pressure. The research results can provide a basis and guidance for design and construction of drilling in Arctic region.

Atomic-scale structure and non-stoichiometry of meteoritic hibonite: A transmission electron microscope study

Abstract Hibonite (CaAl12O19) is a common refractory mineral in Ca-Al-rich inclusions (CAIs) in primitive meteorites. Transmission electron microscope (TEM) studies have identified enigmatic planar defects in different occurrences of hibonite in the Allende meteorite that give rise to strong streaking along c* in electron diffraction patterns. Atomic resolution high-angle annular dark-field (HAADF) imaging and energy-dispersive X-ray (EDX) analyses were used to determine the nature and origin of these planar features. HAADF images of hibonite grains reveal lamellar intergrowths of common 1.6 nm spacing, and less commonly 2.0 and 2.5 nm spacings, interspersed in stoichiometric hibonite showing 1.1 nm (002) spacing. Stoichiometric hibonite consists of alternating Ca-containing (“R”) and spinel-structured (“S”) blocks stacked in a sequence RS. In contrast, the 1.6 nm layers result from a doubled S block such that the stacking sequence is RSS, while in the widest defect observed, the stacking sequence is RSSSS. These intergrowths are epitaxial and have coherent, low-strain boundaries with the host hibonite Meteoritic hibonite shows common Ti and Mg substitution for Al in its structure. Atomic-resolution EDX maps of hibonite grains in the Allende CAI confirm the preferred site occupancy of Mg on tetragonal M3 sites in S blocks and of Ti on trigonal bipyramidal M2 and octahedral M4 sites in R blocks. Mg is highly concentrated, but Ti is absent in the planar defects where wider S blocks show Al-rich compositions compared to stoichiometric MgAl2O4 spinel. Therefore, Mg likely played the major role in the formation and metastability of planar defects in hibonite. Electron energy loss spectroscopy data from the Ti L2,3 edge show the presence of mixed Ti oxidation states with ~15–20% of Ti as Ti3+ in hibonite, suggesting a direct substitution of Ti3+ ↔ Al3+ in hibonite. The remaining ~80–85% of Ti is present as Ti4+ and corresponding EDX analyses are consistent with the well-known coupled substitution 2Al3+ ↔ Ti4+ + Mg2+ being the major mechanism for Ti and Mg substitution in hibonite. The formation of planar defects in hibonite occurred during high-temperature nebular condensation or melting/crystallization processes. The occurrence of non-stoichiometric hibonite in the Allende CAI deviates from the mineral formation sequence predicted from equilibrium condensation models. Overall, our atomic resolution TEM observations signify non-equilibrium, kinetic-controlled crystal growth during the high-temperature formation of refractory solids in the early solar nebula.

Characteristics of an Extreme Dusty Star-forming Galaxy at z = 4.5

Abstract We present new physical properties for an extreme (L IR > 1013 L ⊙), unlensed dusty star-forming galaxy at z = 4.531, G09-81106. We compile fluxes from the literature, and include new Hubble Space Telescope data to generate SED models under various assumptions. G09-81106 has a number of physical characteristics that far surpass the average data for DSFGs, including high dust temperature (∼70 K) and star formation rate ( > 2 × 103 M ⊙ yr−1). While barely within the average star-forming main sequence region, G09 is already an order of magnitude more massive and more star-forming than most star-forming galaxies at similar epochs. Visual inspection suggests these exceptional properties may be due to an ongoing merger, though future work with spatially resolved imaging and spectroscopic analysis will reveal its true nature.