Thermoplastic Mandrel for Manufacturing Composite Components with Complex Structure

This study was to solve the mandrel demolding problem after curing the composite component with complex structure. In this paper, a reusable thermoplastic mandrel with heating softening characteristics was developed by resin transfer molding (RTM). The glass transition temperature (Tg), surface roughness, and reusability of the mandrel, as well as the shape, surface roughness, thickness uniformity, and internal quality of the formed structure, were tested. The result showed that the Tg of the mandrel was between 80 and 90 °C and the surface roughness was less than Ra 0.5 μm. Additionally, the mandrel can be recycled and can still maintain a good shape after 20 times of deformation. By using this method, the demolding process can be realized by heating and softening the mandrel. The profile error of the formed structure was within 0.5 mm, the surface roughness was less than Ra 0.5 μm, the thickness error was within 0.2 mm, and the average porosity of the upper and lower halves of composite parts was 0.72% and 0.61%. All those data showed that the formed part was in good shape and of good quality. The thermoplastic mandrel can solve the demolding problem of composite materials with complex shapes.

Pore Preservation and Failure Mechanism of Sinian Dengying Formation Carbonate Reservoirs: A Case Study of Two Ultradeep Wells in the Sichuan Basin, Western China

Despite being one of the most important factors in deep oil and gas exploration, the preservation mechanisms of ultradeep carbonate reservoirs remain poorly understood. This study performed thin-section, geochemistry, field emission scanning electron microscopy, fluid inclusion, and basin model analysis of samples from two boreholes over 8,000 m deep in the Sichuan Basin to determine the pore features and preservation mechanism of the Sinian (Ediacaran) Dengying Formation carbonate reservoirs. The reservoir of CS well #1 is characterised by pore diameters larger than a centimetre (average porosity 7.48%; permeability 0.8562 mD), and the pores are mainly filled with dolomite or bitumen. In contrast, the reservoir of MS well #1 is predominantly composed of micron-scale residual pores (average porosity 1.74%; permeability 0.0072 mD), and the pores are typically filled with dolomite, bitumen, and multistage quartz. The burial thermal histories suggest that both reservoirs were subjected to high pressure (i.e., pressure coefficient > 1.5 ) before the Late Cretaceous. However, the pressure coefficient of the reservoir of MS well #1 has decreased to less than 1.0 owing to strong structural adjustment this well since the Late Cretaceous, which allowed other ore-forming fluids to enter and fill the pores, resulting in further compaction of the pores. In contrast, the pressure coefficient of CS well #1 is 1.1–1.2, which effectively prevented other ore-forming fluids from entering and filling the pores. The findings show that the dynamic adjustment of the Dengying Formation palaeo-gas reservoir indirectly affects the preservation or failure of the reservoir. The occurrence and geometry of bitumen in the Dengying reservoir exhibit good consistency with the pressure changes in both boreholes. In particular, bitumen with an annular shape and contraction joints in reservoir pores is widespread in CS well #1, which is attributed to the continuous preservation of palaeo-gas fields. Conversely, bitumen with a broken particle shape is located among the epigenetic minerals widespread in MS well #1, which is attributed to failure and depletion of the palaeo-gas fields.

Study on Mesoscopic Stuctural Damage and Permeability Evolution of Freeze-Thaw Shale

To study the mesoscopic damage and permeability evolution of rock under freezing-thawing (F-T) cycles, freezing-thawing cycle experiments were carried out on shale under different F-T temperatures and cycles, and nuclear magnetic resonance (NMR) and permeability experiments were conducted on shale after F-T. On the basis of the experiment, the pores and permeability of the F-T shale are analyzed, and the existing permeability model is modified and improved; Therefore, the mesoscopic damage evolution characteristics and permeability evolution law of the F-T shale are obtained. It is found that with the increase in the number of cycles, the pore structure of the rock samples changes as the pore size expands and the number of pores increases, and the average porosity also increases correspondingly. It is also found that there is a good positive correlation between the increase in shale porosity and the increase in permeability. Therefore, it is believed that the increase in pore size and pore number leads to an increase in porosity, which in turn leads to an increase in permeability. On the basis of the improved SDR permeability model, the spectral area ratio parameters of large pores and fractures in the T2 spectrum were added for correction, and the number of the F-T cycles and temperature parameters were introduced to obtain the modified permeability evolution model of F-T shale. Compared with the experimental results, it is found that the modified model has good applicability. The damage law and permeability of shale under different F-T conditions are analyzed from the microscopic point of view, which has important reference significance for engineering construction in frozen soil areas.

DEM study of the angle of repose and porosity distribution of cylindrical particles with different lengths

Effect of the length of cylindrical particle on repose angle and porosity of a pile was numerically studied using discrete element method. The variation of repose angle and porosity with coefficient of sliding and rolling friction were also discussed. The results shown that compared with sphere particle, the bottom size of cylindrical pile is smaller, while the height of cylinder pile is larger and the heap is steeper. With the increase of the length of cylinder, the contour line of the pile becomes steep, and the angle of repose increases. The repose angle shows a positive correlation with coefficient of sliding and rolling friction. The porosity increases with the increase of the length of cylinders. The trends of porosity are basically consist with that of repose angle, and with increase of friction coefficient, the average porosity increases.

Petrophysical evaluation of sandstone gas reservoir using integrated well logs and core data for the Lower Cretaceous Kharita formation, Western Desert, Egypt

This study aims to evaluate Kharita gas reservoir to enhance the production. The increase in water-cut ratio reduces the left hydrocarbons’ amount behind pipe. Accurate determination of pore throats, pores connectivity and fluid distribution are central elements in improved reservoir description. The integration of core and logging data responses is often used to draw inferences about lithology, depositional sequences, facies, and fluid content. These inferences are based on petrophysical models utilizing correlations among tools’ responses as well as rocks and fluids properties. Upper Kharita Formation produces gas and condensate from the clastic sandstone in Badr-3 field, western desert of Egypt. It consists mainly of sandstone with shale intercalations. It is subdivided into three sub-units Kharita A, Kharita B and Kharita C that are in pressure communication. Hence, a new further investigation and review for the previously calculated GIIP (gas initially in place) was initiated. The results of this study yielded that the main uncertainty in the volumetric calculations was the petrophysical evaluation; subsequently, a new unconventional petrophysical evaluation approach was performed. The sands thickness in Upper Kharita Formation varies between more than 9 up and more than 61 m with average porosity values range between 0.08 and 0.17 PU while the average permeability values range between 1.89 and 696.66 mD. The average hydrocarbon saturation values range between 46 and 97%. The sands thickness in Upper Kharita Formation varies between more than 9 up and more than 61 m with average porosity values range between 0.08 and 0.17 PU while the average permeability values range between 1.89 and 696.66 mD. The average hydrocarbon saturation values range between 46 and 97%. Reservoir shale cutoff of 55% by using cross-plot between shale volume and porosity (Toby Darling concept) was utilized to discriminate the reservoir from non-reservoir sections. The porosity model was used to calculate reservoir porosity, using the density log. The Archie and saturation/height function models were used to calculate the water saturation and used to calibrate the water saturation in the transition zone. The porosity–permeability (POR-PERM) transform equation was used to estimate the reservoir connectivity (absolute permeability) for the four petrophysical facies (High Quality Reservoir, Moderate Quality Reservoir, Low Quality Reservoir and Highly Shale Reservoir). Core data have shown variations in reservoir quality parameters (porosity and permeability) from one well to the other. Integration of all the reservoir pressures indicated that there are different fluid types (oil, gas and water) in the Upper Kharita Formation level. The saturation/height function model was used to calibrate the saturation in the transition zone. The integration of geological core and geophysical log data helped to conduct a comprehensive petrophysical assessment of Upper Kharita Formation for a better estimation of the reservoir and to achieve a better understanding of the water encroachment in the Upper Kharita reservoir. The big challenge is the determination of the most correct model for calculating porosity, permeability and water saturation in this reservoir of different quality sand. The new petrophysical evaluation resulted in doubling the volumes in Upper Kharita reservoir and so a perforation campaign was performed to confirm the new volumetric calculations, which showed a good match with the model results. Hence, a new well was drilled targeting the low quality sand and found them with high pressure almost near virgin pressure.

Evaluation of Reservoir Fluids Mobility, Mauddud Reservoir (Albian), Khabbaz Oil Field, Kirkuk Area, NE Iraq

The Albian Mauddud reservoir of the Khabbaz Oil Field is consisting of 170 m alternating shelf carbonates and pervasive dolomite horizons of coarse to fine crystalline mosaic. Core analysis and log measurements reveal the occurrence of three electrofacies units (A, B, and C) with variable petrophysical properties. Unit A with good reservoir quality shows average porosity of 18.8 % and average permeability of 27.5 md. The other two units (B and C) are less attractive and have an average porosity of 9.6 % and 9.2 % consequently. Pore size ranges between macro to meso types and related mainly to vugs, fractures and intercrystalline porosity, especially in the dolomite units. The reservoir fluids saturation, bulk volume, and mobility are evaluated using resistivity logs measurements and porosity logs (Neutron-Density porosities) in addition to other reservoir laboratory data. Calculations and cross data plotting of the related petrophysical parameters were applied to the three units of the Mauddud reservoir in seven wells of the field. It shows an overall good reservoir fluids mobility. Results indicate that the formation water of Khabbaz Oil Feld is a non-movable type especially for the crestal wells which make most of these wells produce water-free hydrocarbon. Variability within well’s hydrocarbon mobility is noticed and related to units and subunits lithology and porosity variation. Other variations seem to be related mainly to permeability, pores geometry and variability of water saturation in addition to the location of well with respect to oil pool within the field structure.

Microstructure, Microhardness, Fracture Toughness, and Abrasive Wear of In-Situ Synthesized TiC/Ti-Al Composite Coatings by Cold Spraying Combined with Heat Treatment

TiAl intermetallic compounds, as a new kind of high-performance light-weight structural material, are widely applied in many fields. Titanium carbide (TiC) as the reinforcing phase could improve the mechanical properties, wear resistance, and heat-resistance stability of TiAl intermetallic compounds. Ti(Al, C) mixture powders were deposited by cold spraying at gas temperature of 250 °C, 450 °C, and 550 °C. Then, Ti(Al, C) coatings were annealed at temperatures of 650 °C for different times and following holding at 1100 °C for 3 h. The microstructure, microhardness, fracture toughness, and abrasive wear of Ti-Al composite coatings were investigated. The research results were that the particle size of mixture powders decreased as the ball milling time prolonging. Ti(Al) solid solution appeared in the mixture powders as the milling time increased to 30 h. The average porosity of the coating sprayed at 550 °C was the lowest (0.85%). The as-sprayed coatings exhibited the same phase compositions with the mixture powders. The coating sprayed at gas temperature of 550 °C has the highest microhardness and the lowest weight loss. Ti-Al intermetallic was in-situ synthesized after annealing at 650 °C. The average porosity of the annealed coating (sprayed at 450 °C) was the lowest. The content of Ti-Al intermetallic compounds of the annealed coating sprayed at 450 °C is the highest. The X-ray diffraction (XRD) analysis results are consistent with the EDS analysis of the annealed coatings after annealing at 650 °C. Ti-Al intermetallic compounds were almost completely formed in the three kinds of the coatings after annealing at 650 °C for 20 h and following holding at 1100 °C for 3 h. TiAl and TiAl3 intermetallic phases were in-situ synthesized in the coatings based on the energy dispersive spectroscopy (EDS) and XRD analysis. TiC was also in situ synthesized in the coatings as the annealing temperature increased to 1100 °C. The annealed coating (sprayed at 450 °C) has the highest microhardness, fracture toughness, and wear resistance properties after annealing at 1100 °C for 3 h.

Microscale Mineral and Pore Structure Characterization of the Low-Permeability Sandstone in the Ordos Basin, China

Given the insufficient understanding of the characteristics and controlling factors of the low-permeability sandstone reservoir in the Heshui area, the Ordos Basin, the present study examined the microscale mineral and pore structure of Chang 2 reservoir. It analyzed its major controlling factors using a series of methods, including imaging and indirect methods. The results show that the rocks of Chang 2 reservoir in the study area are dominated by lithic arkose and feldspathic detritus quartz sandstone. The reservoir space develops intragranular pores, feldspar dissolved pores, lithic dissolved pores, and intercrystallite pores. Microcracks can occasionally be found. The average porosity is 10.5%, and the average permeability is 2.2 mD, featuring a low-porosity-ultralow-permeability reservoir. During the reservoir development, traps formed by small-scale nose-shaped uplifts resulting from the tectonic effects provide opportunities for good reservoir space. Sedimentation and diagenetic processes control the degree of development and direction of the evolution of reservoir porosity to a certain degree. Multisegment capillary pressure curve and long missing zone were corresponding to relatively good pore-throat structures. Illite was the predominant diagenetic clay minerals that determine the reservoir quality. These three effects all contribute to the overall development of the reservoir.

High-resolution imaging of depth filter structures using X-ray computed tomography

A multiple length scale approach to the imaging and measurement of depth filters using X-ray computed tomography is described. Three different filter grades of varying nominal retention ratings were visualized in 3D and compared quantitatively based on porosity, pore size and tortuosity. Positional based analysis within the filters revealed greater voidage and average pore sizes in the upstream quartile before reducing progressively through the filter from the center to the downstream quartile, with these results visually supported by voidage distance maps in each case. Flow simulation to display tortuous paths that flow may take through internal voidage were examined.Digital reconstructions were capable of identifying individual constituents of voidage, cellulose and perlite inside each depth filter grade, with elemental analysis on upstream and downstream surfaces confirming perlite presence. Achieving an appropriate pixel size was of particular importance when optimizing imaging conditions for all grades examined. A 3 µm pixel size was capable of representing internal macropores of each filter structure; however, for the finest grade, an improvement to a 1 µm pixel size was required in order to resolve micropores and small perlite shards. Enhancing the pixel size resulted in average porosity measurements of 70% to 80% for all grades. Graphical abstract

Potential-productive intervals determination of the Tutleim formation in the central part of the Krasnoleninsky arch

The article presents the results of the Tutleim formation complex studies of core from 16 wells drilled on an area of 900 km2 near the Kamennaya crest of the Krasnoleninsky arch. The area is characterized by the variability of the structural plan, preserved from the time of deposits sedimentation, that might affect the structure of formation. Regionally traceable lithological units were used to describe different types of sections, which were firmly recorded on the core and on the logs. The article presents the results of the sections correlation, that shows the variability of the Tutleim formation through the area, identifies typical sections for the submerged, slope and crestal parts of the investigated field. The section may contain two reservoir intervals of different types: radiolarite and siliceous-phosphate layers with average porosity values of 7% and 15%, respectively. The radiolarite layers form the main potential-productive intervals, that are found in all types of sections on one or two stratigraphic levels: in the crestal sections only in the third unit, in the slope and submerged sections – in the first, second and third units. The phosphorite layer in the fifth unit is a characteristic singularity only of the crestal sections. The obtained results allow predicting the distribution of the potential-productive intervals of the Tutleim formation and its stratigraphic analogues in different areas with higher accuracy.