Ceramic Proppants Research Articles

Preparation and characterization of quartz ceramic proppant replacing natural quartz sand by solid waste silica fume

AbstractThe improper disposal of industrial wastes will cause environmental pollution and economic losses due to the loss of active ingredients. Solid waste silica fume and pyrolusite powder were used to synthesize quartz ceramic proppant by pelleting and sintering to replace natural quartz sand for unconventional oil and gas exploitation. The effects of pyrolusite powder content and sintering temperature on the apparent density, breakage ratio, and acid solubility of the proppant were thoroughly studied. The phase composition and microstructure of the proppant were characterized by X‐ray diffraction and scanning electron microscopy, respectively. The results revealed that the main crystal phase of the proppant prepared without pyrolusite was cristobalite, while that with pyrolusite was cristobalite and quartz, and the content of quartz phase increased gradually with increasing the pyrolusite content. The addition of pyrolusite remarkably increased the density and improved the performance of the proppant due to the resulting glass phase at high temperatures and the presence of andradite. As adding 20% pyrolusite, the apparent density of the proppant sintered at 900°C was 2.26 g/cm3, while the breakage ratio under 28 MPa closed pressure and acid solubility reached the minimum, 9.89% and 5.3%, respectively, meeting the industrial standard requirements.

Preparation and Properties of Lightweight Amphiphobic Proppant for Hydraulic Fracturing.

The wettability of the proppant is crucial in optimizing the flowback of fracturing fluids and improving the recovery of the produced hydrocarbons. Neutral wet proppants have been proven to improve the fluid flow by reducing the interaction between the fluid and the proppant surface. In this study, a lightweight amphiphobic proppant (LWAP) was prepared by coating a lightweight ceramic proppant (LWCP) with phenolic resin, epoxy resin, polytetrafluoroethylene (PTFE), and trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (TMHFS) using a layer-by-layer method. The results indicated that the LWAP exhibited a breakage ratio of 2% under 52 MPa (7.5 K) closure stress, with an apparent density of 2.12 g/cm3 and a bulk density of 1.21 g/cm3. The contact angles of water and olive oil were 125° and 104°, respectively, changing to 124° and 96° after displacement by water and diesel oil. A comparison showed that the LWAP could transport over a significantly longer distance than the LWCP, with the length increasing by more than 80%. Meanwhile, the LWAP displayed notable resistance to scale deposition on the proppant surface compared to the LWCP. Furthermore, the maintained conductivity of the LWAP was higher than that of the LWCP after displacement by water and oil phases alternately. The modified proppant could minimize production declines during hydrocarbon extraction in unconventional reservoirs.

Secondary utilization of self-suspending proppant's coating polymer: Enhance oil recovery

Fracturing is associated with significant economic costs, and the loss of the utility of the self-suspending proppants' coating polymer after fracturing appears highly wasteful. To enhance the utilization of the self-suspending proppant's coating polymer, we propose a novel concept: the secondary utilization of coating polymer, enabling the coating polymer to gel-breaking within the reservoir and generate surface-active substances, thereby enhancing the oil recovery efficiency. To realize this concept, this study designed and synthesized a hydrophobic associative polymer, which was combined with ceramic proppant to form self-suspending proppant. Using the surface-active monomer octadecyl dimethyl allyl ammonium chloride (DMDAAC-18), acrylamide (AM), acrylic acid (AA), and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) via aqueous free-radical copolymerization synthesized the PAAAD (Polymer (AM/AA/AMPS/DMDAAC-18)). PAAAD has demonstrated excellent thickening properties, with a viscosity of 240.01 mPa s at a concentration of 6 g/L in shear rate 170s−1. Its solution exhibits high viscoelasticity, and a loss factor (tan δ) < 1 over the frequency range of 0–20 Hz at a shear stress of 0.56 Pa indicates that it behaves like a viscoelastic solid with gel-like characteristics, which is beneficial for proppant suspension. The gel-breaking solution of PAAAD reduced surface tension (29.33 mN/m at a PAAAD concentration of 6 g/L), converted oil-wet rocks to water-wet conditions (reducing the contact angle of oil-wet shale to 46.7° and of oil-wet sandstone to 19.9°), and enhanced shale imbibition oil recovery efficiency in 16.5%. The basic properties of self-suspending proppants meet the Chinese Petroleum Industry Standard SY/T 5108-2014 and exhibit good suspension properties, with sedimentation of 1.7 mm in 40 min at a sand ratio of 15%. This study is the first to propose the secondary utilization of the self-suspending proppant's coating polymer, significantly enhancing their utilization value.

Optimization of ceramic proppant properties through an innovative coating approach

In this current research endeavor, a comprehensive exploration into the properties of ceramic coatings has been undertaken, utilizing bauxite, talc, and kaolin clay. The primary focus lies in the meticulous analysis of the mechanical strength of ceramic proppants. The proppant raw material employed is kaolin clay, treated through a dry coating technique and subsequently sintered at 1300°C. Evaluation of sample performance is based on the establishment of coating and substrate shrinkage. Shrinkage and density assessments are separately conducted for the coating mixtures and substrate. X-ray diffraction (XRD) is employed to discern the crystalline phases within the coatings, while structural characterization is facilitated through scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX). Density and mechanical strength of proppants are meticulously investigated using picnometry and crush tests. The performances of the coated and uncoated samples were compared and investigated. Interestingly, the coated proppants demonstrate slightly higher density than their uncoated counterparts. Remarkably, the specimen featuring a coating composition of bauxite (72wt%)+clay (25wt%)+talc (3wt%) yields optimal results for mechanical strength. The sole crystalline phase detected in the coating is mullite, with a minimum coating thickness of 10μm.

New model to evaluate the impact of quartz sand crushing on fracture conductivity in a proppant monolayer

The formation of a complex fracture network with sufficient proppant conductivity is crucial for the efficient development of deep shale gas. Due to cost considerations, quartz sand has commonly replaced ceramic proppant in the field. However, the significant crushing of quartz sand and its distribution as multiple particle sizes both before and after crushing, termed as particle size redistribution, raises concerns about its ability to meet the demands of the fracture network. Based on contact mechanics, we developed an evolutionary equation for fracture width that considers particle size redistribution. The particle crushing is described using a fragmentation replacement method, and changes in specific surface area before and after crushing are used to correct the permeability model of the fracture. By integrating models of fracture width and permeability evolution, we have established an analytical model for proppant conductivity that accounts for quartz sand crushing and its particle size redistribution. Numerical simulations further validate the predictive accuracy of our model. Sensitivity analyses investigate the impact of quartz sand degree of crushing, compressive strength, particle size, particle combination ratio, and closure pressure on fracture conductivity, demonstrating the reliability of quartz sand as a substitute for ceramic proppant in deep shale applications.

Reused green glass for the production of low-density ceramic proppants

The reuse of waste to promote manufacturing processes that are respectful of the environment is a fundamental requirement in circular economy practices. In this work, it is assessed the feasibility of manufacturing ceramic proppants from a commercial red clay, sodium and potassium feldspars, and significant amounts of green bottle glass recovered from urban wastes.Different ceramic mixtures were formulated, and the sintering conditions were defined considering optical dilatometric, differential thermal, and thermogravimetric analysis. The obtained granules were characterised following the international standard for proppants, and also using X-ray diffraction, scanning electron microscopy, and individual diametral compression tests.The results show that competitive proppants are obtained, due to their low-density (2.5 g/cm3) and good breakage ratio (7.8 % at 5000 psi, or 34.5 MPa), but also considering the involved low-cost processing route and raw materials.

Steady-state two-phase relative permeability measurements in proppant-packed rough-walled fractures

Understanding multiphase flow in fractures filled with minerals and proppants is vital in various subsurface applications. Limited experimental data have led to reliance on correlations lacking physical basis. We conducted experiments to characterize relative permeability in rough-walled fractures packed with unconsolidated porous media. We tested fractures packed with water-wet 40/70 sand (silica) and surface-coated ceramic proppants. Brine and mineral oil were used as the wetting and non-wetting fluid phases, respectively. Steady-state (SS) drainage (non-wetting-phase displacing wetting-phase) and imbibition (wetting-phase displacing non-wetting-phase) tests were performed under a wide range of saturation histories (full-cycle and scanning-curves) to study relative permeability hysteresis of the propped fractures. Every SS drainage or imbibition test consisted of several discrete points at which fluid saturations and the corresponding relative permeability were measured by varying the fractional flow rates of fluids whilst maintaining a constant total flow rate. We analyzed residual non-wetting phase saturations and relative permeability trends to understand two-phase flow behavior in each proppant pack. High-resolution x-ray microtomography was used to understand the pore-scale topology, wettability, and to provide insights about the pore-scale displacement mechanisms involved in this study. The results showed that commonly used models to estimate relative permeabilities of fractures significantly overestimated the SS brine and oil relative permeabilities (denoted as krw and kro) measured in this study. Further analysis unveiled that the kro values during imbibition exceeded their drainage counterparts in both proppants, the ceramic proppant exhibited a lower initial water saturation and a higher end-point kro permeability at the end of the drainage displacement, as well as higher krw across all flooding processes. Updated fitting parameters for a Brooks-Corey-type relative permeability correlation are introduced. This study presents improved insights, extensive experimentally generated relative permeability data, and an updated relative permeability correlation, which can be collectively utilized to reduce uncertainties associated with continuum-scale forecasts of multiphase flow behavior in fractured subsurface formations.

Surface corrosion mechanism of ceramic proppant caused by formation water

AbstractThe performance of ceramic proppant tended to deteriorate during service, and one of the main reasons was the formation of water corrosion on the proppant surface. The proppant was isothermally soaked in formation water and the proppant immersed for different times was characterized by X‐ray fluorescence spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, Fourier‐transform infrared spectroscopy, and scanning electron micrscopy. It is found that Cl− in the formation water can migrate to the proppant surface by diffusion and cause corrosion, which degrades its performance. Silica of the proppant can react with Cl− of formation water to form SiCl4, which will rapidly hydrolyze to produce opaque silica gel or silicic acid gel coating the proppant surface. With the extension of immersion time, the gel becomes thicker and more, promoting the degradation of the proppant. This will provide some theoretical guidance for alleviating the degradation of proppant.

Low-temperature preparation of lightweight ceramic proppants using high-proportioned coal-based solid wastes

Lightweight ceramic proppants are prepared using coal gangue, fly ash, and bauxite as raw materials, and a mixture of manganese dioxide and magnesium oxide is used as composite additives. The total content of the coal gangue and fly ash in the raw materials reaches up to 70 wt%. The effects of coal gangue and fly ash precalcination, sintering temperature, and composite additive content on the phase compositions, microstructures, and performances of the resulting ceramic proppants are studied in detail. The ceramic proppant prepared at 1285 °C using 1 wt% of the composite additive is composed of quartz, corundum, and mullite. It also presents the desired sphericity, roundness, and microstructure. The apparent density, bulk density, and breakage ratio of the ceramic proppant described above are 2.55 ± 0.06 g/cm3, 1.03 ± 0.02 g/cm3, and 8.30 ± 0.68% at 35 MPa, respectively. This ceramic proppant belongs to lightweight ceramic proppants and meets the requirement of the 5K grade in the standards of SY/T 5108-2014 and API STD 19C-2018.

Preparation and characterization of high-performance ceramic proppant from recycling utilization of oil-based drilling cuttings pyrolysis residues

Oil-based drilling cutting pyrolysis residues (ODCPRs), bauxite, and sintering additives were applied to manufacture ceramic proppants with low density and high strength in this work. The effect of ODCPRs ratio, sintering temperature, holding time, and the content of additives on the performance of the proppants was comprehensively investigated, respectively. And the sintering mechanism of proppants was also discussed according to the phase, microstructure, and thermal behavior analyses. The results revealed that at the best sintering condition (1280 °C, holding for 60 min), and a mass ratio (ODCPRs: bauxite: MnO2 at 3:7:0.1), the well-developed granular corundum and acicular mullite formed inside the proppants and interspersed with each other to form a dense structure. The proppants presented low density and high strength as the bulk density of 1.48 g/cm3, the apparent density of 2.94 g/cm3, a breakage ratio of 5.25% under 52 MPa closed pressure, and the acid solubility of 4.80%, which could well meet the requirement of the standards of SY/T 5108-2014. This work provided a new pathway for recycling ODCPRs and the fabrication of high-performance proppants.

Evaluation of sintered bauxite proppant for binary enhanced geothermal systems

Solid granular proppant particles are widely used in oil and gas development to sustain permeability through fractures after hydraulic stimulation. Similar proppants are of interest for geothermal applications where the goal of sustaining permeability is the same, but the harsh geothermal environment risks rapid proppant degradation that will reduce fracture permeability. Here, we present proppant conductivity experiments using saw cut granite, tensile fractured granite, and aluminum control specimens packed with sintered bauxite ceramic proppants at concentrations of 0.0, 0.1, and 1.0 kg/m2. Simulated geothermal conditions included temperatures up to 130 °C and normal closure stresses up to 60 MPa. Compared to unpropped specimens, peak fracture conductivity enhancement was up to 6 orders of magnitude. At simulated geothermal conditions, proppants were able to sustain fracture conductivity over 60 h, but chemical dissolution and decreasing permeability over time were evident. Irreversible conductivity reductions with crushing and embedment of proppants during loading stages were also observed. Overall, sintered bauxite proppant remains a promising option for low-temperature binary-cycle enhanced geothermal systems.

In situ mullite whisker network formation for high strength and lightweight ceramic proppants

In this study, a facile in situ sintering method has been proposed for fabricating high strength lightweight mullite whisker network reinforced proppants. The effect of TiO2 on the microstructure, properties and fracture behaviours of the mullite whisker network was researched in detail. The addition of TiO2 promoted the formation of a modified mullite whisker network structure, which effectively improved the flexural strength. The sample containing 4 wt.% TiO2 exhibited an excellent flexural strength of 215.25MPa and low bulk density of 1.53 g/cm3 at 1400 ?C. The TiO2-added mullite whiskers mostly exhibited rod-like crystals with about 0.5- 0.8 ?m in diameter and 10-15 ?m in length. The as-prepared ceramic proppant showed excellent properties, such as low breakage ratio (2.19%under 52MPa), low density (1.36 g/cm3) and low acid solubility (2.28 wt.%).

MAGNESIUM AND IRON OXIDES INFLUENCE ON SINTERING PROCESSES AND PHASE FORMATION OF ANORTHITE CERAMICS BASED ON NATURAL RAW MATERIALS

Ceramic proppants based on silicates and aluminosilicates with various structures are used in the hydrocarbons mining with hydraulic fracturing method. The disadvantage of these known proppants is their high apparent density. Anorthite CaO∙Al2O3∙2SiO2 is a prospective material for proppants production. However, its wide application in this field is restricted due to insufficient knowledge of the MgO-CaO-Fe2O3(FeO)-Al2O3-SiO2 system. Consequently, the physical and chemical processes in the mixes of kaolin and chalk with magnesium oxide and iron(III) oxide additives during firing for anorthite ceramics were studied. It was found that adding of 5 – 10% magnesium oxide in batch for anorthite synthesis leads to obtain ceramics with near-zero water absorption at 1250 °C. Increasing the firing temperature to 1300 °C leads to overfiring of the ceramic and a decrease in its strength. Magnesium oxide reacts with the kaolin to form spinel and forsterite. The highest compressive strength (350 – 390 MPa) is achieved for ceramics with 5% MgO in the batch. The ceramics has fine-grained structure with the grain sizes less than 5 μm. Iron(III) oxide is a weak mineralizer for anorthite synthesis, and its mineralizing effect occurs during the formation of gehlenite-based solid solutions. The sintering process of anorthite ceramics is intensified at 1350 °C due to the melting of the anorthite – iron(III) oxide eutectic. This leads to decrease the water absorption of ceramics with 5 – 10% Fe2O3 in batch to about 2 – 3%. The compressive strength of this ceramics is about 230 – 250 MPa.

Study on aging mechanism of ceramic proppant soaked in formation water

The quality of ceramic proppant directly affects the recovery efficiency of unconventional gas reservoirs. Two types of proppant were isothermally soaked in formation water and the proppant soaked for different time was characterized by XRF, XPS, XRD, SEM, EDS, TEM and FT-IR. The characterization results show that H+, Cl−, CO32− and HCO3− ions in the formation water can migrate to the proppant surface by diffusion and chemically react with the proppant components. The acidic environment of formation water can make alumina of the proppant change into Al3+ ions, and then react with the CO32− or HCO3− ions of formation water to generate Al(OH)3, precipitating in the formation water. Silica of the proppant can react with the Cl− ions of formation water to form SiCl4, which meets water to produce silica gel on the surface of proppant. Therefore, these reactions will undoubtedly destroy the dense structure of proppant and reduce its conductivity and crushing resistance. This study provides some theoretical direction for preventing the aging of proppant.

The solidification and volatilization behavior of heavy metal ions in ceramic proppant made from fly ash

As a type of silica-alumina solid waste, fly ash can be utilized to prepare ceramic proppants by partially substituting bauxite due to a similar chemical composition. However, the heavy metal elements in fly ash including Zn and Cd are subjected to be released during high-temperature calcination, causing harm to some extent. In this study, migration, transformation, solidification, and volatilization of heavy metals in proppant at elevated temperatures are systematically studied by various experimental characterization methods. The results show that the solidification effect of the prepared ceramic proppant on the Zn and Cd elements is favorable, with solidification ratios up to 77.16% and 74.34%. The addition of Cd improves the bulk density and strength of the ceramic proppant, while the addition of Zn significantly reduces the strength and increases the water absorption. Additionally, the majority of doped Zn will combine with Al2O3 to form a new phase, zinc spinel ZnAl2O4, which hinders the formation of the inherent mullite phase. On the contrary, the addition of Cd does not change the phase composition, and the Cd element is mainly solidified in the form of lattice substitution. Finally, the distributions of volatile Zn and Cd in gas- and solid-phase were quantitatively determined by the in situ continuous collection system. In addition, a mathematical model was used to predict the volatilization of heavy metals during the proppant calcination process.

Preparation of drilling cuttings-coal fly ash based ceramic proppants: The roles of barite

This study presents the feasibility of preparing ceramic proppants (CPs) using drilling cuttings (DCs) and coal fly ash (CFA) via high-temperature sintering. The reaction behavior of barite in ceramic proppant precursors originating from DCs during the sintering process was investigated. The breakage ratio of the CPs (optimal group S3) met the requirements of Chinese standard SY/T 5108-2014 (2 K grade). The primary chemical reactions (7–8 in Table 4) between the barite and silica/alumina components resulted in a reduction of the eutectic point of the mixtures and the formation of aluminosilicates containing barium. However, these interactions also released gases (SO2 and O2), which created pores and weakened the CPs strength. The ideal temperature range for sintering is between 1170 and 1200 °C, during which there should be a gradual weight loss and minimal gas generation. This range will also ensure that the appropriate amount of liquid phase is present, which will have a moderate viscosity and aid in the densification of the ceramic proppants, as well as the formation of a dense enamel layer. The composite reactions of barite in the S3 sample follow a one-and-a-half-order chemical reaction mechanism within the temperature range of 950–1200 °C. The average activation energy and pre-exponential factor were 583.304 kJ mol−1 and 5.81 × 1020 min−1, respectively. The kinetic and reaction rate equations for the composite reactions were (1 − α)−1/2–1 = (5.81 × 1020 × e−5.83 × 10^5/RT) × t and dα/dt = (2(1 − α)3/2) × (5.81 × 1020 × e−(5.83 × 10^5)/RT)), respectively. This study provides a theoretical basis and guidelines for large-scale production of CPs using DCs and CFA.

Basic principle, progress, and prospects of coal gangue ceramic proppants

AbstractCeramic proppants are preferred in hydraulic fracturing because of their high strength, good sphericity, and excellent acid corrosion resistance. Bauxite is the main raw material of ceramic proppants, but with the increasing depletion of bauxite resources, substitutes for bauxite need to be sought. Coal gangue is a solid waste that is rich in SiO2 and Al2O3, making it a potential substitute for the preparation of ceramic proppants. The use of coal gangue to prepare ceramic proppants can reduce the cost of ceramic proppants and benefit environmental protection. Studies on using coal gangue to prepare ceramic proppants have been conducted and achieved progress, but further improvement can still be obtained. Here, the basic principle, progress, and prospects of coal gangue ceramic proppants are reviewed. First, coal gangue ceramic proppants are divided into two categories, namely, proppants prepared using coal gangue as an auxiliary material and proppants prepared using coal gangue as the main material. Second, the progress of research of coal gangue ceramic proppants is summarized from the perspective of additives, and the influence of different kinds of additives on the sintering temperature and performance of proppants is discussed. Lastly, the future prospects of coal gangue ceramic proppants are presented.

Preparation and performance study of coated sand fracturing proppants based on three of resin

Oil and gas resources are becoming increasingly difficult to extract owing to long-term exploitation. Therefore, hydraulic pressure technologies, such as fracturing proppants, are needed to stimulate production. In this study, the strength and corrosion resistance of quartz were increased by modifying quartz sand and preparing high-performance coated-sand-based oil-fracturing proppants. Although many resins play crucial roles in the process of preparing fracturing proppants, their performances differ considerably. Chemical structural compositions and microstructures were investigated through infrared spectroscopy and scanning electron microscopy. The modification mechanism of quartz sand and the bonding mechanism between quartz sand and different types of resin proppants were analyzed by systematically investigating the flexural strength, corrosion resistance of the proppants as a function of resin contents, and curing temperature. The results show that the performance of the coated proppants is superior to those of conventional quartz sand and ceramic proppants. The flexural strength of modified quartz sand improved by 5.3%. The best performance was obtained using an 8% polyimide resin film and a curing temperature of 180 °C, achieving a coated sand proppant with a breakage ratio of 2.89% under 55.2 MPa.

Study on Salt Dissolution Law of High Salinity Reservoir and Its Influence on Fracturing

For the high-salt reservoir of the Fengcheng Formation in the Mahu area, the production decreases rapidly due to the conductivity decrease after fracturing. The analysis shows that this has a great relationship with the special salt dissolution characteristics of the High salinity reservoir. In order to study the problem of salt dissolution pattern, the effect of different temperatures, the salt concentration of fracturing fluid, the viscosity of fracturing fluid, and injection rate on the rate of salt dissolution was evaluated by using the dynamic experimental evaluation method of salt dissolution. Through the grey correlation analysis of salt rock dissolution rate, it can be found that the degree of influence is from large to small which the influence of temperature is greater than fracturing fluid velocity, followed by fracturing fluid viscosity and, finally, fracturing fluid salt concentration. The results of compressive strength tests on salt-bearing rocks after dissolution show that the compressive strength is greatly reduced after salt dissolution by more than 60%. At the same time, the test results of proppant-free conductivity showed that the conductivity increased first and then decreased sharply after salt dissolution. This shows that in the early stage of salt dissolution, the flow channel will increase through dissolution. The rock strength decreases greatly with the increase of salt dissolution. As a result, collapse leads to a sharp reduction in the facture conductivity. Therefore, it is necessary to choose saturated brine fracturing fluid. In the proppant conductivity experiments, by optimizing the use of saturated brine fracturing fluid with 30/50 mesh or 20/40 mesh ceramic proppant with a sand concentration of 5 Kg/m2, a high facture conductivity can be achieved under high closure pressure conditions. Based on the above study, directions and countermeasures for improving high saline reservoirs are proposed, which point the way to improve the fracturing conductivity.

Synthesis of forsterite with high strength and low acid solubility using magnesite tailings

The synthesis of forsterite from magnesite tailings is beneficial to the secondary resource utilization of tailings and maintaining ecological balance. And the synthetic forsterite multiphase material can be used as the raw material of ceramic proppants instead of natural forsterite ore. In this study, forsterite multiphase material was synthesized via a solid-state reaction method using magnesite tailings and silica. Furthermore, the phase composition, microstructure, apparent porosity, bulk density, mechanical properties, and acid solubility of the synthetic material were characterized. The results show that the densification and forsterite phase content of the synthetic forsterite multiphase material gradually increase as silica is added. Additionally, the excess silica generates enstatite and quartz phases, which increase the glass phase in the material and decrease the forsterite phase. Forsterite multiphase material with optimal mechanical properties was synthesized from 83 wt% magnesite tailings and 17 wt% silica. The acid solubility of the synthetic forsterite multiphase material was as low as 4.33%.