Development,sand control mechanism and hydrocarbon accumulation of beach-bar sandstone in a saline lake basin:A case from the Neogene of southwestern Qaidam Basin,NW China

Based on the data of field outcrops,drilling cores,casting thin sections,well logging interpretation,oil/gas shows during drilling,and oil/gas testing results,and combined with modern salt-lake sediments in the Qinghai Lake,the Neogene saline lake beach-bars in southwestern Qaidam Basin are studied from the perspective of sedimentary characteristics,development patterns,sand control factors,and hydrocarbon accumulation characteristics.Beach-bar sand bodies are widely developed in the Neogene saline lake basin,and they are lithologically fine sandstone and siltstone,with wavy bedding,low-angle cross bedding,and lenticular-vein bedding.In view of spatial-temporal distribution,the beach-bar sand bodies are stacked in multiple stages vertically,migratory laterally,and extensive and continuous in NW-SE trending pattern in the plane.The stacking area of the Neogene beach-bar sandstone is predicted to be 3000 km^(2).The water salinity affects the sedimentation rate and offshore distance of beach-bar sandstone,and the debris input from the source area affects the scale and enrichment of beach-bar sandstone.The ancient landform controls the morphology and stacking style of beach-bar sandstone,and the northwest monsoon driving effect controls the long-axis extension direction of beach-bar sandstone.The beach-bars have a reservoir-forming feature of“one reservoir in one sand body”,with thick beach-bar sand bodies controlling the effective reservoir distribution and oil-source faults controlling the oil/gas migration and accumulation direction.Three favorable exploration target zones in Zhahaquan,Yingdong-eastern Wunan and Huatugou areas are proposed based on the analysis of reservoir-forming elements.

Single-factor analysis and interaction terms on the mechanical and microscopic properties of cemented aeolian sand backfill

The use of aeolian sand(AS)as an aggregate to prepare coal mine cemented filling materials can resolve the problems of gangue shortage and excessive AS deposits.Owing to the lack of research on the mechanism of cemented AS backfill(CASB),the response surface method(RSM)was adopted in this study to analyze the influence of ordinary Portland cement(PO)content(x_(1)),fly ash(FA)-AS(FA-AS)ratio(x_(2)),and concentration(x_(3))on the mechanical and microscopic properties of the CASB.The hydration characteristics and internal pore structure of the backfill were assessed through thermogravimetric/derivative thermogravimetric analysis,mercury intrusion porosimetry,and scanning electron microscopy.The RSM results show that the influence of each factor and interaction term on the response values is extremely significant(except x_(1)x_(3),which had no obvious effect on the 28 d strength).The uniaxial compressive strength(UCS)increased with the PO content,FA-AS ratio,and concentration.The interaction effects of x_(1)x_(2),x_(1)x_(3),and x_(2)x_(3) on the UCS at 3,7,and 28 d were analyzed.In terms of the influence of interaction items,an improvement in one factor promoted the strengthening effect of another factor.The enhancement mechanism of the curing time,PO content,and FA-AS ratio on the backfill was reflected in the increase in hydration products and pore structure optimization.By contrast,the enhancement mechanism of the concentration was mainly the pore structure optimization.The UCS was positively correlated with weight loss and micropore content but negatively correlated with the total porosity.The R^(2) value of the fitting function of the strength and weight loss,micropore content,and total porosity exceeded 0.9,which improved the characterization of the enhancement mechanism of the UCS based on the thermogravimetric analysis and pore structure.This work obtained that the influence rules and mechanisms of the PO,FA-AS,concentration,and interaction terms on the mechanical properties of the CASB provided a certain theoretical and engineering guidance for CASB filling.

Suspension mechanism and application of sand-suspended slurry for coalmine fire prevention

North and west China has abundant coal resources, however, such resources make these regions prone to serious mine fire disasters. Although the copious sand and fly ash resources found in these areas can be used as fire-fighting materials, conventional grouting is expensive because of water shortage and loess particles. A new compound material(i.e., a sand-suspended colloid), which comprises a mineral inorganic gel and an organic polymer, is developed in the current study to improve the quality of sand injection and reduce water wastage when grouting. The new material can steadily suspend the sand, through the addition of a small amount of colloid yielding steady sand-suspended slurry. The process of producing the slurry is convenient and quick, overcoming the shortage of sand-suspending thickeners which need heat and are difficult to produce. The space work model based on the theory of the double-electric layer is established to study the suspended mechanism of the solid particles in the sand-suspended colloid.The dispersion effect of the sand-suspended colloid is demonstrated by the incorporation of the electrostatic effect by the double-electric layer and the steric hindrance effect on the sand particles, ensuring the stability of the colloid system and the steady suspension of sand particles in the sand-suspended colloid.Mechanical analysis indicates that the sand is suspended steadily under the condition that the rock sand particles stress on the lower part of the fluid is less than the yield stress of the colloid. Finally, the fireprevention technology of sand suspension was applied and tested in the Daliuta Coal Mine, achieving successful results.

Effect of Lightweight Aggregates Incorporation on the Mechanical Properties and Shrinkage Compensation of a Cement-Ground Granulated Blast Furnace Slag-Phosphogypsum Ternary System

Shrinkage-induced cracking is a common issue in concrete structures,where the formation of cracks not only affects the aesthetic appearance of concrete but also potentially reduces its durability and strength.In this study,the effect of ceramsite sand addition on the properties of a ternary system of cement-ground granulated blast furnace slag(GGBFS)-phosphogypsum(PG)is investigated.In particular,the fluidity,rheology,hydration heat,compressive strength,autogenous shrinkage,and drying shrinkage of the considered mortar specimens are analyzed.The results indicate that an increase in PG content leads to a decrease in fluidity,higher viscosity,lower exothermic peak,and lower compressive strength.However,the shrinkage of the mortar specimens is effectively compensated.The incorporation of internal curing water from ceramsite sand improves fluidity,decreases both yield stress and viscosity,enhances the degree of hydration,and induces mortar expansion.However,the inferior mechanical properties of the ceramsite sand generally produce a decrease in the compressive strength.

Centrifuge model tests of the formation mechanism of coarse sand debris flow

Using the self-developed visualization test apparatus, centrifuge model tests at 20 g were carried out to research the macro and microscopic formation mechanism of coarse sand debris flows. The formation mode and soil-water interaction mechanism of the debris flows were analyzed from both macroscopic and microscopic points of view respectively using high digital imaging equipment and micro-structure analysis software Geodip. The test results indicate that the forming process of debris flow mainly consists of three stages, namely the infiltration and softening stage, the overall slide stage, and debris flow stage. The essence of simulated coarse sand slope forming debris flow is that local fluidization cause slope to wholly slide. The movement of small particles forms a transient stagnant layer with increasing saturation, causing soil shear strength lost and local fluidization. When the driving force of the saturated soil exceeds the resisting force, debris flow happens on the coarse sand slope immediately.

Energy Consumption and Erosion Mechanism of Polyester Fiber Reinforced Cement Composite in Wind-blown Sand Environments

Considering the economic and environmental benefits associated with the recycling of polyester(PET)fibres,it is vital to study the application of fibre-reinforced cement composites.According to the characteristics of the wind-blown sand environment in Inner Mongolia,the erosion resistance of the polyester fibre-reinforced cement composites(PETFRCC)with different PET fibre contents to various erosion angles,velocities and sand particle flows was investigated by the gas-blast method.Based on the actual conditions of sandstorms in Inner Mongolia,the sand erosion parameters required for testing were calculated by the similarity theory.The elastic-plastic model and rigid plastic model of PETFRCC and cement mortar were established,and the energy consumption mechanism of the model under particle impact was analyzed.The experimental results indicate that the microstructure of PETFRCC rafter hydration causes a spring-like buffering effect,and the deformation of PETFRCC under the same impact load is slightly smaller than that of cement mortar,and the damage mechanism of PETFRCC is mainly characterized by fiber deformation and slight brittle spalling of matrix.And under the most unfavorable conditions of the erosion,the erosion rate of 0.5PETFRCC is about 57.69%lower than that of cement mortar,showing better erosion resistance.

Preparation and Properties of Ultra-fine Chromium Carbonization of High Performance Mechanical Activation

The preparation of hydroxyl chromium oxide by hydrogen reduction of disodium chromate and particulate hydroxyl mechanical activation features were studied. Then with self-made hydroxyl chromium as the raw material, a direct reduction and carburization process was used to prepare ultra-fine chromium carbonization. Through SEM and XRD, the high performance mechanical activation, key coefficients, microstructure, hardness and wear-resisting property were investigated. The results reveal that suitable mechanical activation and carbon reducing carbonization temperature, carbonization time, carbon content are beneficial to obtaining ultra-fine chromium carbonization. Typically, when the time of high performance grinding is 5 min, the carbon reducing temperature is 1100 ℃, the carbon reducing time is 1h, the carbon content is 28%, and finally the particle size of chromium carbide powder is 1 μm. Under this condition of preparation of ultra-fine chromium carbide, both the hardness and wear resistance are better than those in the industrialization of chromium carbide coating.

Basic Properties of Concrete Incorporating Recycled Ceramic Aggregate and Ultra-fine Sand

Recycled ceramic mixed sand（RCMS） was obtained by partially replacing ultra-fine sand with recycled ceramic coarse sand（RCCS）. The effects of RCCS replacement rate on the apparent density, workability, compressive strength and splitting tensile strength of recycled ceramic concrete（RCC） were investigated. In addition, the relationship between the water-cement ratio and compressive strength of RCC was also studied. The experimental results indicate that the reusing of recycled ceramic aggregate can improve the cohesiveness and water retentiveness of fresh concrete and benefit the mechanical properties development. When the RCCS replacement rate is not less than 40%, the mechanical properties of RCC are superior to those of the reference concrete. Moreover, when recycled ceramic medium sand was completely used as fine aggregate, the maximum increase in both compressive strength and splitting tensile strength were obtained, comparing with those of reference concrete, the increment ratio was 19.85% and 32.73%, respectively. The microscopic analysis shows that the using of recycled ceramic aggregate can meliorate distinctly the structure of the interfacial transition zone（ITZ） and increase the compaction degree of cement paste. Furthermore, an expression of the compressive strength of RCC and the cement-water ratio is regressed and gains a good linear relativity. It is an effective way to recycle waste ceramic, and the consumption of recycled ceramic aggregate could reach from 26.9% to 47.6% of the total weight of aggregate in producing concrete.

Effect of coral sand on the mechanical properties and hydration mechanism of magnesium potassium phosphate cement mortar

Damaged structures on coral islands have been spalling and cracking due to the dual corrosion of tides and waves.To ensure easy access to aggregate materials,magnesium potassium phosphate cement(MKPC)and coral sand(CS)are mixed to repair damaged structures on coral islands.However,CS is significantly different from land-sourced sand in mineral composition,particle morphology,and strength.This has a substantial impact on the hydration characteristics and macroscopic properties of MKPC mortar.Therefore,in this study we investigated the compressive strength,interfacial mechanical properties,and corrosion resistance of MKPC CS mortar.Changes in the morphology,microstructure,and relative contents of hydration products were revealed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)and X-ray diffraction(XRD).The results indicated that the compressive strength increased linearly with the interfacial micro-hardness,and then stabilized after long-term immersion in pure water and Na2SO4 solution,showing excellent corrosion resistance.Compared with MKPC river sand(RS)mortar,the hydration products of CS mortar were an intermediate product 6KPO2·8H2O with a relative content of 3.9%at 1 h and 4.1%at 12 h.The hydration product MgKPO_(4)·6H_(2)O increased rapidly after 7-d curing,with an increased growth rate of 1100%.Our results showed that CS promoted the nucleation and formation of hydration products of MKPC,resulting in better crystallinity,tighter overlapping,and a denser interfacial transition zone.The results of this study provide technical support for applying MKPC mortar as a rapid repair material for damaged structures on coral islands.

Mechanical Properties and Microstructure of Portland Cement Concrete Prepared with Coral Reef Sand

The feasibility of using coral reef sand（CRS） in Portland cement concrete is investigated by testing the mechanical property and microstructure of concrete. The composition, structure and properties of the CRS are analyzed. Mechanical properties and microstructure of concrete with CRS are studied and compared to concrete with natural river sand. The relationship between the microstructure and performance of CRS concrete is established. The CRS has a porous surface with high water intake capacity, which contributes to the mechanical properties of concrete. The interfacial transition zone between the cement paste and CRS is densified compared to normal concrete with river sand. Hydration products form in the pore space of CRS and interlock with the matrix of cement paste, which increases the strength. The total porosity of concrete prepared with CRS is higher than that with natural sand. The main difference in pore size distribution is the fraction of fine pores in the range of 100 nm.

Mechanical Properties of Sea Water Sea Sand Coral Concrete Modified with Different Cement and Fiber Types

The mechanical properties of modified sea water sea sand coral concrete(SWSSCC)under axial compression were experimentally studied.Two different parameters were considered in this test:types of cement and fiber.An experimental campaign was developed involving uniaxial compression tests and the use of digital image correlation(DIC)method to analyze the strain distribution and crack propagation of specimen.Test results indicated that the compressive strength and elastic modulus of SWSSCC were improved by adding stainless steel fibers(SSF),while polypropylene fibers(PF)enhanced the SWSSCC peak deformation.It was found that the elastic modulus and strength of SWSSCC using ordinary Portland cement(OPC)were higher compared to specimen with low alkalinity sulphoaluminate cement(LAS).Typical strain distribution changed with the variation of fiber types.The propagation and characteristics of cracks in SWSSCC containing PF were similar to those of cracks in SWSSCC.However,the propagation of cracks and the development of plastic deformation in SWSSCC were effectively hindered by adopting SSF.Finally,an analytical stress-strain expression of specimen considering the influences of fibers was established.The obtained results would provide a basis for the application of SWSSCC.

Factors influencing physical property evolution in sandstone mechanical compaction:the evidence from diagenetic simulation experiments

In order to analyze the factors influencing sandstone mechanical compaction and its physical property evolution during compaction processes, simulation exper- iments on sandstone mechanical compaction were carried out with a self-designed diagenetic simulation system. The experimental materials were modem sediments from dif- ferent sources, and the experiments were conducted under high temperature and high pressure. Results of the exper- iments show a binary function relation between primary porosity and mean size as well as sorting. With increasing overburden pressure during mechanical compaction, the evolution of porosity and permeability can be divided into rapid compaction at an early stage and slow compaction at a late stage, and the dividing pressure value of the two stages is about 12 MPa and the corresponding depth is about 600 m. In the slow compaction stage, there is a good exponential relationship between porosity and overburden pressure, while a good power function relationship exists between permeability and overburden pressure. There is also a good exponential relationship between porosity and permeability. The influence of particle size on sandstone mechanical compaction is mainly reflected in the slowcompaction stage, and the influence of sorting is mainly reflected in the rapid compaction stage. Abnormally high pressure effectively inhibits sandstone mechanical com- paction, and its control on sandstone mechanical com- paction is stronger than that of particle size and sorting. The influence of burial time on sandstone mechanical compaction is mainly in the slow compaction stage, and the porosity reduction caused by compaction is mainly con- trolled by average particle size.

Strengthening of HT250 by modified ultra-fine ceramic powders

In this study, three kinds of modified ultra-fine ceramic powders marked A, B and C, which were prepared by each of three different modifiers mixing with a commercial SiC, were added to HT250 cast iron, respectively, and the effects of the modified ultra-fine ceramic powders on microstructure, mechanical properties and wear resistance were studied. Metallographic examination, tensile test, scanning electron microscopy, and three-dimensional surface topography were applied to analyze and compare the samples containing modified powder with the original samples. The results showed that the most obvious modification effect among the powders was seen in the sample containing powder A, with the graphite and eutectic cells being refined, the tensile strength being increased by 36.9%, and the wear resistance being improved by 45.5% and 47.2% under loads of 150 N and 300 N, respectively. The improvements of mechanical properties and wear resistance in the HT250 cast iron with the modified ultra-fine ceramic powders were attributed to the synergistic effect of the grain refinement with the powder acting as a hard particle phase and the lubrication by the graphite.

Effect of upsetting force on microstructure of welds in resistance spot welding of 400 MPa ultra-fine grain steel

The ultra-fine grain （UFG） steel is welded by using resistance spot welding technique with or without requirement of upsetting force. Metallographic inspection shows that the grain size of weld nugget is larger than that of the base metal and the microstructure is altered significantly. In addition, contracting defects such as air holes can be found in the nugget center. The experiments show that the defects can be effectively avoided by the technique of adding upsetting force during the nugget cooling and crystallizing processes. In tensile shear tests, the welding joint starts to crack from the inner edge of the corona bond. The results of micro-hardness tests show that the newly born martensite structure dramatically improves the hardness of the joint. Under the interactions between residual stresses and regenerated fine grains, the micro-hardness of the heat-affected zone （ HAZ ） is lower than that of the nugget, but evidently higher than that of the base metal.

Structural Modification of Sand Cast Eutectic Al-Si Alloys with Sulfur/Sodium and Its Effect on Mechanical Properties

In the present study, the structural modification of sand cast Al-12wt%Si alloy with sulfur/sodium and its effect on mechanical properties were investigated. Different addition levels of sulfur and sodium were used to modify and produce castings of the same shape and size from the alloy. The results indicated that the addition of sodium or sulfur to eutectic Al-Si alloy can modify the Al-Si eutectic morphology from needle-like eutectic silicon structure to fine-scale eutectic silicon structure with significant improvement in mechanical properties of the alloy. The optimum levels of modification by sodium flux (60% NaF and 40% NaCl) and sulfur were found to be 0.6% - 1.0% and 0.02% - 0.05% of the weight of the alloy respectively. The alloy modified with 0.6% Na flux had the best mechanical properties closely followed by the one modified with 0.02% sulfur. Over modification of the alloy with sodium produced over modification band which consisted of aluminum dendrites and coarse silicon particles in the microstructure of the alloy. Increase in concentration of sulfur decreased the degree of fineness of the eutectic silicon structure with significant decrease in mechanical properties of the alloy and this is suggested to be as a result of the presence of a brittle sulfur compound at the grain interfaces of the alloy.

Effect of reclaimed sand additions on mechanical properties and fracture behavior of furan no-bake resin sand

In this work, the effects of reclaimed sand additions on the microstructure characteristics, mechanical properties and fracture behavior of furan no-bake resin sand have been investigated systematically within the temperature range from 25 to 600 oC. The addition of 20%-100% reclaimed sand showed dramatic strength deterioration effect at the same temperature, which is associated with the formation of bonding bridges. Both the ultimate tensile strength(UTS) and compressive strength(CS) of the moulding sand initially increase with the increase of temperature, and then sharply decrease with the further increase of temperature, which is attributed to the thermal decomposition of furan resin. The addition amount of reclaimed sand has a remarkable effect on the room temperature fracture mode, i.e., with the addition of 0-20% reclaimed sand, the fracture mode was mainly cohesive fracture; the fracture mode converts to be mixture fracture mode as the addition of reclaimed sand increases to 35%-70%; further increasing the addition to 100% results in the fracture mode of typical adhesive fracture. The fracture surface of the bonding bridge changes from a semblance of cotton or holes to smooth with the increase of test temperature.

Mechanical property of calcareous sand under action of compaction

Calcareous sand is a kind of special medium which is composed of calcium carbonate and other difficult soluble carbonate substances. Because of its rich in inner pore space and easy crashed,the mechanical property is very different from conventional quartz sand. Based on the compaction test and direct shear test of calcareous sand,by means of data fitting,the coupling relationship between compaction density and mechanical property under different water contents was obtained; meanwhile,the shear strength expression was built on the basis of the relationship between water content and dry density.

An innovative tester system for measuring mechanical property of foundry molding sand

A new intelligent tester system for measuring multiple mechanical properties of foundry molding sand is introduced and has been patented for the invention in China. The testing process can be simultaneously controlled with a build-in chip microcomputer communicating with a PC through a serial port. The testing system applies dynamic testing technology. During the measurement for compression, relaxation, shearing and tensile processes of sand specimens, the corresponding characteristic curves and eight mechanical property parameters can be obtained in a short time, simply by consecutively testing on four sand specimens. The properties and parameters to be measurable by the tester include compressive strength, elastic modulus, plastic deformation threshold, springback potential, shear strength, shear deformation limit, toughness and tensile strength. These properties and parameters for sand specimens can be defined as the corresponding characteristic curves with precise physical meanings, carried out by the tester, Two of them, namely plastic deformation threshold and springback potential, as well as their testing methods, have been invented for the first time. The testing system applying advanced data measurement technology as well as performing excellent functions is an important breakthrough and creativity in foundry molding sand property testing field. The parameters acquired by the testing system are stable, accurate and reliable. The test data can be instantly displayed or printed out or stored in the PC. As evidence, many experimental data obtained by the tester practically from both laboratory and foundry floor tests indicate that the tester system can be widely applied in foundry industry.

Development of a new instrument for measurement of high temperature mechanical properties of resin-bonded sand

The mechanical properties of resin-bonded sand mixtures at high temperatures significantly affect the quality of casting. However, the existing instruments for high-temperature performances testing mainly focus on inorganic binder-bonded sands no matter the test items or the atmospheric protection, while the instrumentss specially designed for resin-bonded sand are not yet available. A new instrument for testing the hightemperature performance of resin sand was designed including the confirmation of the testing parameters, loading, measurement and control systems, and the design of the frame shape and heating furnace. This instrument can test the compressive strength, heat tolerance time and restraining load of phenol-formaldehyde resin coated sand, self-hardened furan resin sand, and trimethylamine(TEA)-based resin bonded sand at high temperatures. The developed instrument has a high accuracy offering smaller than 0.3% deviation at a full scale in the measurement of the high temperature compressive strength and the restraining load over the range of 0-6.8 MPa and 0-2,000 N, respectively. The high temperature heat tolerance time range is 0-300 s and its measurement accuracy is ±1 s.

Loose Sand Cemented by Microbial Cementitious Material:Composition,Microstructure and Mechanical Properties

Through the influence of the dosage of culture solution and calcium source on hardness and compressive strength of samples,the formulation of microbial cementitious materials was optimized and defined.The influence of temperature on composition,microstructure and mechanical properties of loose sand cemented by microbial cementitious material was compared and analyzed systematically.With the increase of temperature,the performance of loose sand was improved remarkably.Calcite with cementitious properties could be induced at higher temperatures,but not at lower temperatures.When the temperature was 30℃,loose sand cemented by microbial cementitious material had more calcite and more dense structure.Moreover,hardness and compressive strength were also superior.The wind tunnel test showed that the wind erosion resistance was improved obviously and the mass loss was lower at high temperature.Engineering properties of loose sand cemented by microbial cementitious material was measured integrally.Through comparative analysis,engineering properties of loose sand were basically unchanged,and there was no negative effect on the later period use of sand.