Cement Failure Research Articles

Evolution of pore structure and cement composition during weathering of conglomerate at Mogao Grottoes in alkaline and arid regions, NW China

Numerous conglomerate grottoes have been excavated and preserved in the arid and alkaline regions of NW China. After millennia of weathering, these conglomerate grottoes have suffered from various weathering issues (such as seepage and collapse) that are internally governed by the distribution of pore networks and the degree of cementation. However, studies on conglomerate weathering have mostly been reported in humid and tropical climates, where intensive chemical weathering occurs. Additionally, characterizations of pore evolution during conglomerate weathering have been restricted due to limitations in detecting pore size and pore type using a single pore characterization method. To fill this gap, this study jointly used mercury intrusion porosimetry (MIP) and computed tomography (CT) to characterize the pore evolution process during conglomerate weathering at Mogao Grottoes, a world heritage site in NW China. Mineralogical, hydrological, mechanical and microscopic characterization were also conducted to understand the changes in compositions of bulk samples and cements during weathering. Results revealed that the majority of pores in conglomerate are concentrated in macropores > 5 μm, followed by mesopores and micropores. During weathering, volume fraction of macropores significantly increases and that of micropores decreases, with median/average pore diameters experiencing an 8- to 10-fold increase. Permeability, porosity and fractal dimension exhibited strong positive linear correlations with median/average pore diameters. Throughout weathering, the abundances of calcite and clay minerals show notable decrease, particularly in cements, resulting in an enrichment of feldspars. Frequently occurring sand-carrying wind activities and salt weathering in arid regions are inferred to be responsible for the major cement loss and porosity generation through physical processes. Our combined MIP-CT method for pore network characterization is also applicable to other lithologies with a wide range of pore sizes. The proposed mechanism of pore evolution and cementation failure provides a scientific base for protecting stone heritages in arid zones.

Study on the influence of cement slurry viscosity on acoustic emission response and deformation characteristics of slurry-coal cemented body

In the process of grouting sealing, the cementation failure of slurry and coal interface exists in the gas extraction borehole, which leads to unstable and gas leakage in the sealing section and affects the efficient gas extraction in the borehole. In order to study the influence of slurry viscosity on the failure characteristics of slurry-coal cemented body, this paper explores the law of influence of slurry viscosity on the acoustic emission response characteristics and deformation characteristics of slurry-coal cemented body under uniaxial compression through laboratory tests, data analysis and quantitative research of image processing. The results show that: (1) Changing the slurry viscosity can achieve the strength control of the cemented body, which can be increased by up to 42.65 %. (2) In the process of uniaxial compression, the cementation structure of slurry-coal cemented body breaks down successively, and its proportion and strength lead to the distribution difference of AE signals and the fluctuation of b-value. Combined with the phase response characteristics of the two, the change of failure mode can be analyzed to provide a reliable evaluation of crack propagation in the cemented body. (3) The b-value of the sample of slurry-coal cemented body with high-viscosity slurry does not fluctuate significantly, and is relatively stable at a low level near 1.0. The results are helpful to promote the research and development of sealing materials and sealing technology.

Biomechanical Comparative Analysis of Abutment Screw Head Designs on Preload Stability Under Oblique Compressive Forces: An In Vitro Pilot Study.

To examine the impact of abutment screw head sizes on preload stability when secured to a standard external hex implant under oblique compressive forces. Fifteen metal crowns were divided into three equal groups. The first group had five angulated cemented crowns connected to a 3 mm tall straight hexagonal abutment with an external hex abutment screw. The second and third groups each had five straight cemented crowns attached to a tapered abutment with flat slotted and internal hex abutment screws, respectively. Samples were subjected to a static cyclic load until failure. Kruskal-Wallis H, Dunn's, and one-way ANOVA with Tukey HSD tests were performed. Cemented straight crown supported by an angled abutment connected to implants with flat slotted and internal hex abutment screw heads failed at an average of 4.24 x 106 cycles ± 3.31 SD and 12.67 x 106 cycles ± 5.47 SD, respectively. Cemented angled crowns supported by a straight abutment connected to identical implants with an external hex abutment screw survived 18.02 x 106 cycles ± 4.49 SD. Periotest value (PTV) rate of change increased at a higher rate in crowns supported by angled abutments compared to straight abutments (p < 0.05). No cement failure was observed. Under the experimental conditions, larger abutment screw head sizes demonstrated greater stability of the abutment screw joint interface. Based on the in vitro findings, no cement failure was observed between the cemented crown and abutment connection. Future research with standardized comparative setups and larger sample sizes is needed.

Synthetic Clay Application to Reduce the Segregation of Barite-Based Oil-Well Cement.

In the oil and gas industry, cement segregation is a significant concern that can have disastrous consequences, such as the failure of cement. The change of hardened cement's properties is observed, resulting in a decrease in its strength and an increase in its permeability. Therefore, providing some solutions to prevent this is crucial. The objective of this study is to assess the efficacy of synthetic clay in mitigating the problem of segregation in cement having barite. Six concentrations of synthetic clay were used to prepare six heavy-weighted cement samples with a high density of 18 lb/gal using the barite weighting material. The approaches of density distribution and nuclear magnetic resonance (NMR) were employed to characterize the heterogeneity in the hardened cement samples with the aim of identifying the potential of cement segregation. Then, the optimum concentration of the synthetic clay was selected and its effects on the rheological, strength, petrophysical, and elastic properties were evaluated and compared with the properties of the base cement (without synthetic clay). The results showed that 0.4% by weight of cement (BWOC) synthetic clay was the optimum concentration, which yielded the minimum cement segregation as represented by a 61% reduction in the density variation compared to the control specimen. The results obtained from the NMR technique validated the findings of the density distribution method, indicating that the porosity distribution of the synthetic clay cement with a concentration of 0.4% BWOC exhibited uniformity across its top, middle, and bottom sections, with a slight deviation window, while the porosity distribution of the control cement specimen displayed noticeable variation. Moreover, the synthetic clay had better properties than the control cement specimen. For example, the rheological properties were improved as represented by a 22% reduction in plastic viscosity and 42 and 11% increase in the yield point and gel strength, respectively. Compared to the base cement, the compressive and tensile strength were increased by 39 and 43%. The synthetic clay decreased the permeability and porosity by 73 and 24%, respectively. The synthetic clay enhanced the elastic properties as represented by a 1.5% reduction in Young's modulus and a 1.3% increase in Poisson's ratio compared to the base cement sample.

Impact of fault slip induced by water injection on casing deformation: a numerical study

Fluid injection can cause fault reactivation and slip due to weakened cementation strength. The resulting fault slippage poses significant challenges to wellbore and casing integrity. To address this, we developed a multi-scale 3D finite element model, integrating reservoir, and near-wellbore components and applied to an offshore well in China’s ZD Reservoir, an area that has experienced fault reactivations (and casing deformations of wells intersecting reactivated faults) due to routinely water injection in nearby wells. Based on the actual formation’s wellbore-fault angle, a full-size fault is inserted into the model. The traction–separation law (TSL) describes progressive fault damage induced by waterflooding. The model also simulates the impact of fault slippage on cement failure and casing deformation. Research findings indicate that fluid injection reduces friction and shear cementation strength between faults, leading to reactivated fault slippage. The slip process involves three stages: low-level, sharply rising, and high-level stages, each exhibiting reduced fault friction and shear cementation strength. These outcomes provide insights to prevent casing damage during water flooding, optimizing injection points, or using better cement recipes at minimal cost.

Bonding of Composite Cements Containing 10-MDP to Zirconia Ceramics Without Dedicated Ceramic Primer.

To measure zirconia-to-zirconia microtensile bond strength (µTBS) using composite cements with and without primer. Two Initial Zirconia UHT (GC) sticks (1.8x1.8x5.0 mm) were bonded using four cements with and without their respective manufacturer's primer/adhesive (G-CEM ONE [GOne] and G-Multi Primer, GC; Panavia V5 [Pv5]), and Panavia SA Cement Universal [PSAu], and Clearfil Ceramic Plus, Kuraray Noritake; RelyX Universal (RXu) and Scotchbond Universal Plus [SBUp], 3M Oral Care). Specimens were trimmed to an hour-glass shaped specimen whose isthmus is circular in cross-section. After 1-week water storage, the specimens were either tested immediately (1-week μTBS) or first subjected to 50,000 thermocycles (50kTC-aged μTBS). The fracture mode was categorized as either adhesive interfacial failure, cohesive failure in composite cement, or mixed failure, followed by SEM fracture analysis of selected specimens. Data were analyzed using linear mixed-effects statistics (α = 0.05; variables: composite cement, primer/adhesive application, aging). The statistical analysis revealed no significant differences with aging (p = 0.3662). No significant difference in µTBS with/without primer and aging was recorded for GOne and PSAu. A significantly higher µTBS was recorded for Pv5 and RXu when applied with their respective primer/adhesive. Comparing the four composite cements when they were applied in the manner that resulted in their best performance, a significant difference in 50kTC-aged μTBS was found for PSAu compared to Pv5 and RXu. A significant decrease in µTBS upon 50kTC aging was only recorded for RXu in combination with SBUp. Adequate bonding to zirconia requires the functional monomer 10-MDP either contained in the composite cement, in which case a separate 10-MDP primer is no longer needed, or in the separately applied primer/adhesive.

The effect of nitric acid � hydrofluoric acid etching solution on the shear bond strength and mode of failure of resin cement to zirconia (In vitro study)

The effect of nitric acid � hydrofluoric acid etching solution on the shear bond strength and mode of failure of resin cement to zirconia (In vitro study)

Statistical distribution of micro and macro pores in acrylic bone cement- effect of amount of antibiotic content

Aseptic loosening due to mechanical failure of bone cement is considered to be a leading cause of revision of joint replacement systems. Detailed quantified information on the number, size and distribution pattern of pores can help to obtain a deeper understanding of the bone cement's fatigue behavior. The objective of this study was to provide statistical descriptions for the pore distribution characteristics of laboratory bone cement specimens with different amounts of antibiotic contents. For four groups of bone cement (Palacos) specimens, containing 0.3, 0.6, 1.2 and 2.4 wt/wt% of telavancin antibiotic, seven samples per group were micro computed tomography scanned (38.97 μm voxel size). The images were first preprocessed in Mimics and then analyzed in Dragonfly, with the level of threshold being set such that single-pixel pores become visible. The normalized pore volume data of the specimens were then used to extract the logarithmic histograms of the pore densities for antibiotic groups, as well as their three-parameter Weibull probability density functions. Statistical comparison of the pore distribution data of the antibiotic groups using the Mann–Whitney non-parametric test revealed a significantly larger porosity (p < 0.05) in groups with larger added antibiotic contents (2.4 and 0.6 wt/wt% vs 0.3 wt/wt%). Further analysis revealed that this effect was associated with the significantly larger frequency of micropores of 0.1–0.5 mm diameter (p < 0.05) in groups with larger antibiotic content (2.4 wt/wt% vs and 0.6 and 0.3 wt/wt%), implying that the elution of the added antibiotic produces micropores in this diameter range mainly. Based on this observation and the fatigue test results in the literature, it was suggested that micropore clusters have a detrimental effect on the mechanical properties of bone cement and play a major role in initiating fatigue cracks in highly antibiotic added specimens.

Comparing machine learning algorithms for non-invasive detection and classification of failure in piezoresistive bone cement via electrical impedance tomography

At an estimated cost of $8 billion annually in the United States, revision surgeries to total joint replacements represent a substantial financial burden to the health care system and a tremendous mental and physical burden on patients and their caretakers. Fixation failures, such as implant loosening, wear, and mechanical instability of the poly(methyl methacrylate) (PMMA) cement, which bonds the implant to the bone, are the main causes of long-term implant failure. Early and accurate diagnosis of cement failure is critical for developing novel therapeutic strategies and reducing the high risk of a misjudged revision. Unfortunately, prevailing imaging modalities, notably plain radiographs, struggle to detect the precursors of implant failure and are often interpreted incorrectly. Our prior work has shown that the modification of PMMA bone cement with low concentrations of conductive fillers makes it piezoresistive and therefore self-sensing. When combined with a conductivity imaging modality such as electrical impedance tomography (EIT), it is possible to monitor load transfer across the PMMA using cost-effective, physiologically benign, non-contact, and real-time electrical measurements. Despite the ability of EIT for monitoring load transfer across self-sensing PMMA bone cement, it is unable to accurately characterize failure mechanisms. Overcoming this challenge is critical to the success of this technology in practice. Therefore, we herein expand upon our previous results by integrating machine learning techniques with EIT for cement condition characterization with the goal of establishing the feasibility of even off-the-shelf machine learning algorithms to address this important problem. We survey a wide variety of different machine learning algorithms for application to this problem, including neural networks on voltage readings of an EIT phantom for tracking the spatial position of a sample, specifying defect orientation within a sample, and classifying defect types, including cracks and delaminations. In addition, we explore the utilization of principal component analysis (PCA) for pre-treating impedance signals in each of these problems. Within the tested algorithms, our results show clear advantages of neural networks, support vector machines, and K-nearest neighbor algorithms for interpreting EIT signals. We also show that PCA is an effective addition to machine learning. These preliminary results demonstrate that the combination of smart materials, EIT, and machine learning may be a powerful instrumentation tool for diagnosing the origin and evolution of mechanical failure in joint replacements.

Risk of Revision After Vertebral Augmentation for Osteoporotic Vertebral Fracture: A Narrative Review.

Osteoporotic vertebral fractures (OVFs) can hinder physical motor function, daily activities, and the quality of life in elderly patients when treated conservatively. Vertebral augmentation, which includes vertebroplasty and balloon kyphoplasty, is a commonly used procedure for OVFs. However, there have been reports of complications. Although serious complications are rare, there have been instances of adjacent vertebral fractures, cement dislocation, and insufficient pain relief due to cement failure, sometimes necessitating revision surgery. This narrative review discusses the common risks associated with vertebral augmentation for OVFs, such as cement leakage and adjacent vertebral fractures, and highlights the risk of revision surgery. The pooled incidence of revision surgery was 0.04 (0.02-0.06). The risks for revision are reported as follows: female sex, advanced age, diabetes mellitus, cerebrovascular disease, dementia, blindness or low vision, hypertension, hyperlipidemia, split type fracture, large angular motion, and large endplate deficit. Various treatment strategies exist for OVFs, but they remain a subject of controversy. Current literature underscores the lack of substantial evidence to guide treatment strategies based on the risks of vertebral augmentation. In cases with a high risk of failure, other surgeries and conservative treatments should also be considered as treatment options.

Effect of Repressing Lithium Disilicate Glass Ceramics on The Shear Bond Strength of Resin Cements.

A lithium disilicate ceramic (IPS e.max® Press) was first heat-pressed to form rectangular disk specimens. Then, leftovers were used for the second and third presses. A total of 90 specimens were prepared and separated, according to the number of pressing cycles, into three groups: 1st, 2nd, and 3rd presses (n = 30). Each group was further subdivided into three groups (n = 10) according to the type of resin cement used, as follows: Multilink N (MN), Variolink Esthetic DC (VDC), and Variolink Esthetic LC (VLC). All the cement was bonded to the ceramic surface, which was etched with hydrofluoric acid and primed with Monobond Plus. All samples were light-cured and stored for 24 h. Shear bond strength was tested on a universal testing machine. A two-way ANOVA was used to evaluate the influence of repeated pressing cycles and cement type as well as their interaction. The results indicated that cement type has a significant impact (p < 0.001) but not the number of pressing cycles (p = 0.970) or their interaction (p = 0.836). The Bonferroni post-hoc test showed that the SBS of MN was significantly higher than that of VDC and VLC in the first press and second press cycles, respectively. The SBS of MN was significantly higher than that of VDC and VLC cements in the third pressing cycle. There was no significant difference in the SBS between VLC and VDC in all three pressing cycles. The results of the current study did not report a detrimental effect of repeated pressing up to three cycles on the shear bond strength of the IPS e.max® Press. Multilink resin cement showed the highest SBS to IPS e.max® Press at the third pressing cycle. For all types of cement and heat pressing cycles, the majority of cement failures were adhesive. No cohesive failures occurred in any of the tested resin cements, regardless of the cement type or the number of heat pressing cycles tested.

Relationship Between Various Cement Mixture, Cement Fixation and Gait Study for Total Hip Replacement Via Finite Element Analysis (FEA)

To secure the total hip replacement (THR) components, introduced in the 1960s, polymethyl methacrylate (PMMA) bone cement was used as a fixation. The cement polymerizes and becomes firm to hold the implant in place. However, the failure of cement in total hip replacement may lead to hip fractures and dislocations which is detrimental to the patient’s well-being whether in the short-term or long-term. Hence, the aim of this study is to find suitable cement mixtures for total hip replacement compromising of Young Modulus of 2.24 GPa, 0.3129 GPa, 0.03394 GPa and 0.07961 GPa, as reported from prior research. Three separate sorts of proximal cemented techniques were used to deposit the PMMA cement: 40 mm cement reduction, 80 mm cement reduction and full cement (datum). The Titanium Ti-6A1-4V (Ti-41) Charnley hip implant stem model with a Young Modulus of 100 GPa and a Poisson’s ratio of 0.3 was applied in the ANSYS Workbench 2020 R2 software to be analyzed with the three different proximal cemented approaches for each cement mixtures. Subsequently, the total deformation and von Mises stress were simulated under various loading circumstances, including standing, walking, stair climbing and falling. Nevertheless, as shown in the results obtained, all the hip implants consider safe because their von Mises stress does not exceed the yield strength of Titanium Ti-6A1-4V, which is 0.88 GPa. Finally, it may be concluded that, in comparison to the full cement (datum) and 80 mm cement reduction with Young Modulus of 2.24 GPa, 0.3129 GPa, 0.03394 GPa and 0.07961 GPa, the most improvement in the context of total deformation and von Mises stress is the 40 mm cement reduction with Young Modulus of 2.24 GPa.

Low-Level Laser Therapy of Er, Cr: YSGG and Femtosecond on Dentin Adhesion with Bioactive and Resin-Modified Glass Ionomer Cement

Aim: This study examined the shear bond strength (SBS) and mode of failure of bioactive resin cement (BARC) and resin-modified glass ionomer cement (RMGIC) to dentin treated with Er, Cr: YSGG (ECrL) and femtosecond laser (FSL). Methods: 120 non-carious, non-fractured human molars without prior restorations were selected and processed. The teeth were grouped by surface conditioning. Groups 1 and 5 were untreated controls. Groups 2 and 6 had ECrL surface treatment, while Groups 3 and 7 had FSL. EDTA and Tetric N-Bond Universal conditioned Groups 4 and 8. Groups 1–4 (n = 15) employed BARC for bonding, while Groups 5–8 used RMGIC. A universal testing machine (UTM) tested shear bond strength, and a stereomicroscope studied the failure mode. Comparing findings required means, SDs, ANOVA, and Tukey’s post hoc test. Results: Group 1, without conditioning, has the lowest BARC-bonded SBS. In Group 4, EDTA+ Tetric N-Bond Universal-conditioned dentin bonded to BARC had the greatest SBS values. In the RMGIC-bonded groups, Group 5 without dentin conditioning had the lowest bond values, while EDTA+ Tetric NBond Universal-conditioned dentin had the greatest. Conclusion: EDTA and Tetric N-Bond Universal dentin conditioning improves RMGIC and BARC bond strength. This study’s conditioning methods boosted bond strength.

Development of Heavy-Weight Hematite-Based Geopolymers for Oil and Gas Well Cementing.

In the petroleum industry, ordinary Portland cement (OPC) is utilized for different cementing applications. Yet, there are some technical and environmental issues for the usage of OPC in well cementing. The technical problems include gas invasion while setting, instability at corrosive environments, cement failure while perforation and fracturing due to high stiffness and brittleness, and strength reduction and thermal instability at elevated temperatures. Moreover, OPC production consumes massive energy and generates high greenhouse gas emissions. This study introduced the first hematite-based class F fly ash geopolymer formulation that can be used in oil and gas well cementing. Different properties of the designed slurry and hardened samples such as rheology, thickening time, strength, and elastic and petrophysical properties were evaluated. Moreover, mixability and pumpability challenges of heavy-weight geopolymer slurries were investigated. Unlike most of the studies in the literature, this work used 4 M NaOH solution only as an activator that can reduce the overall cost. The results showed that increasing the hematite percentage significantly decreased the thickening time. The developed formulation fell within the recommended fluid loss ranges for some cementing applications without using a fluid loss control additive. A proposed mixture of retarder and superplasticizer was introduced to enhance the thickening time by almost 5 times. The compressive strength increased by 49% and the tensile strength was enhanced by 27.4% by increasing the curing time from 1 to 7 days. The improvement in both compressive and tensile strength with curing time indicated that the geopolymerization reaction continued for extended time but with a smaller rate. The developed slurry acted more like a power law fluid at low temperatures and more like a Bingham plastic fluid at high temperatures. The elastic properties of the developed geopolymer samples proved that they are more flexible than some cement systems.

Deep characterization of heavy-weighted oil well cement segregation by a novel nuclear magnetic resonance (NMR) technique

Oil well cement segregation is one of the catastrophic issues in drilling operations. It changes the properties of hardened cement, such as reducing its strength and increasing its permeability. This can lead to severe consequences, such as cement failure. Therefore, the early identification of cement segregation is crucial to provide some solutions to minimize it. However, conventional techniques that evaluated cement segregation need enhancing. In this work, four heavy-weight cement samples were prepared with a high density of 18 ppg using the four common weighting materials: barite, ilmenite, hematite and Micromax. To identify the potential of cement segregation, a new proposed approach by nuclear magnetic resonance (NMR) was utilized to characterize the cement segregation by measuring the porosity differences and heterogeneity in the hardened cement samples. Moreover, the NMR results were compared with the existing techniques, such as the direct weight and volume method and computer tomography (CT) scan. The results of the conventional direct weight and volume method and CT scan technique showed critical cement segregation of barite, ilmenite and hematite-based cement samples, which can result in several problems related to zone isolation. By applying the evaluation method involving NMR, the NMR approach confirmed the results of the conventional direct weight and volume method and CT scan technique in which severe cement segregation was found in the barite, ilmenite and hematite-based cement samples. To validate the ability of NMR to identify the cement segregation issue, the Micromax cement samples were also examined. The NMR method confirmed the results of the direct weight and volume method and CT scan technique, showing that Micromax had no segregation issue. NMR results showed that the porosity distribution of Micromax weighted cement was mainly the same in which there was no deviation window between its top, middle and bottom sections, while there was obvious variation in the porosity distribution of the barite, ilmenite, and hematite-based cement samples with large deviation window along the cement column. The NMR method allowed a rigorous investigation of the cement segregation in the hardened cement samples. The NMR successfully identified segregation by looking for the pore size distribution and its relation with porosity variation. The novelty of this work is applying a new approach to determine the heavy-weight cement segregation by NMR. Findings from this work have led to an effective method of determining cement segregation for basic laboratory tests of oil well cement.

Prior assessment of CO2 leak rate through cracks sealed by nanoparticle gels

The leakage of hydrocarbon fluids through cracks in the annular cement and CO2 storage is a major concern to the Petroleum Industry. A significant risk is posed when repairing leakage in a micro annuli channel with smaller apertures. A low-viscosity sealant that can generate a long-lasting resilient seal is desired. The solution to sealing these channels might lie in a novel application using nano-silica Gel. In this study, laboratory tests were carried out to examine the capabilities of nano-silica gels to seal the cracks. Analyzing its rheological property, the gel strengths of nano-silica gels were found to increase with an increase in nano-silica concentration. Additionally, it was discovered that as the concentration of nano-silica increases, the sealing and leakage pressures, defined as the pressures before and after water breakthrough, respectively, increase as well. With a typical 15% concentration of nano silica in gel, a sealing pressure gradient of 80.2 psi/in and a leakage pressure gradient of 30 psi/in at a leaking rate of 1 cc/min were noted. To validate the validity of the experimental results, a mathematical model was developed to predict the leakage rate of sealed fractures. The model suggests that the young’s modulus of sealant is a key property of nano-sealants and further investigations are needed to validate the mathematical model for quantitative use. This study suggests a novel strategy for enhancing cement zonal isolation and reducing cement failure in oil and gas sector.

Evaluation of shear peel bond strength and fatigue stress of different orthodontic banding cements – An in vitro study

The purpose of this study were to (1)compare the shear peel bond strength of four different orthodontic banding cements (2) assess the site of cement failure after debanding (3) compare the survival time of the bands cemented with each cement type after simulating mechanical fatigue stress. Eighty teeth were used to assess retentive strength and another forty teeth were used to assess the fatigue survival time. Shear peel bond strength was determined with a universal testing machine. Fatigue testing was conducted in a ball mill machine. The mean shear peel bond strength and survival time of the bands cemented with GC Fuji Ortho band paste pak was significantly greater among all the groups. Bond failure occurred predominantly at the enamel-cement interface. GC Fuji ortho band paste pak orthodontic banding cement required significantly higher forces to deband in comparison with the other cements. GC Fuji ortho band paste pak orthodontic banding cement can be expected to have lower failure rates for band cementation than the other groups in the light of the results of the ball mill test.

THM coupled analysis of cement sheath integrity considering well loading history

The cement sheath is the heart of any oil or gas well for providing zonal isolation and well integrity during the life of a well. Loads induced by well construction operations and borehole pressure and temperature changes may lead to the ultimate failure of cement sheath. This paper quantifies the potential of cement failure under mechanically and thermally induced stress during the life-of-well using a coupled thermal–hydrological–mechanical (THM) modeling approach. A staged finite-element procedure is presented considering sequential stress and displacement development during each stage of the well life, including drilling, casing, cementing, completion, production, and injection. The staged model quantifies the stress states and state variables, e.g., plastic strain, damage, and debonding at cement/rock or cement/casing interface, in each well stage from simultaneous action of in-situ stress, pore pressure, temperature, casing pressure, and cement hardening/shrinkage. Thus, it eliminates the need to guess the initial stress and strain state before modeling a specific stage. Moreover, coupled THM capabilities of the model ensure the full consideration of the interaction between these influential factors.

Review on Oil Displacement Technologies of Enhanced Oil Recovery: State-of-the-Art and Outlook

Despite rapid advances in renewable energy extraction and utilization, global oil demand continues to rise. Oil displacement technologies are widely studied and applied because they can extract more oil in depleted reservoirs or recover unconventional ones. This study introduces research methods and mechanisms of four oil displacement technologies, i.e., water flooding, chemical flooding, gas flooding, and steam flooding. Although oil displacement technologies are helping to meet the growing demand for oil and energy, there are still some challenges for industrial applications. Some agents adopted in the oil displacement have shortcomings in the corrosion of mining equipment and damage to the reservoir structure. Therefore, solutions to the problem are crucial and are investigated widely in the literature using experiments and simulations. For experimental research, a diffusion framework for studying mass transfer in the oil displacement process and an experimental system for simulating oil displacement in offshore reservoirs should be built, which will facilitate the widespread industrial application of oil displacement technology. Therefore, it is necessary to improve the accuracy and expand the application range of the experimental system. As for numerical simulation, reaction kinetics research is essential for selecting displacement agent materials and preventing harmful gas leakage for industrial applications. However, the dynamics of foam flooding and CO2 flooding are not thoroughly studied. Moreover, it is an acceptable research topic that reducing the uncertainty of discrete regions is an effective method to improve the accuracy of numerical simulation results. For the broader application of oil displacement technology to industry, several mechanisms regarding the research field could be studied more thoroughly and comprehensively in the future, i.e., (1) the influence mechanisms of some impurities and complex reservoir physical properties, (2) the method of combining various oil displacement technologies, (3) the T-H-M-C multifield coupling oil displacement mechanism at micro/nanoscale, (4) the cement failure mechanism caused by CO2 and H2S, and (5) the tube brittle fracture mechanism caused by stress corrosion. For the sustainable development and efficient utilization of oil displacement, this review summarizes the extensive information about four oil displacement technologies, thus encouraging and providing research topics for further development and applications.

Assessment of resin systems as solution for well integrity challenge in carbonate reservoirs

Well integrity is defined as technical, operational, and organizational solutions specifically aimed at the reduction of the risk of formation fluids release throughout a well's life cycle. Cement integrity is one of the main aspects that comprises well integrity. Cement integrity must be ensured throughout a well's life cycle as well as after abandonment. If the cement was to lose its integrity, the consequences for the personnel, the equipment, and the environment could be severe. Cement failures might lead to leakages that can seep through the cement pathways; sealant materials are used to plug these pathways. The actual and real-time disputes are mainly dependent on the technical approaches currently available to limit the main causes of well integrity deficiency. These include cementing jobs, substantial design based on downhole conditions, material selection criticality, well construction performance, and technological resources. Additionally, in this specific context, well integrity also refers to the control of the flow inside the wellbore (between different horizons) and the flow from the well (especially in the annulus behind the casing). The worst-case scenario would be the loss of wellbore integrity, and it would be identified as the collapse of the well caused by failure of the construction material. The focal point of the research presented in this paper is the cement quality and its role in developing the most vigorous well casing possible. The focus was centered around resin additives such as microbond, latex, and crystal seal. Microbond is a white mineral cement-based liquid with exceptional performances when combined with cement. Latex is composed of rubber particles dispersed in water, usually found in white liquid form. Crystal seal is a yellow colloidal material highly regarded for sealing properties when mixed with concrete mixtures. These additives were individually incorporated into cement-based samples, in varying concentrations, for testing the changes in properties suitable for well integrity considerations. Highly specialized and sophisticated cement testing apparatuses, such as the ultrasonic cement analyzer (UCA), static gel Strength machine (SGSM), and curing chamber, have been used to perform qualitative and quantitative property gradient tests. Based on the performed experimental tests results, the optimal additive resin for a class G cement slurry is the microbond additive at a concentration of 7.5%. The results highlighted its ability to enhance the cement compressive strength by 52%. Additionally, the transit time showed a 26–42% range decrease in the travel period, indicating that the cement was stronger under increased pressure and temperature. This can clear up the permeable section of the well wherein the cement-resin slurry could efficiently close off wellbore intersecting faults and, therefore, prevent possible connections between the wellbore and water zones in the subsurface. As a result, microbond, latex, and crystal seal, respectively, show the effect of varying controlled conditions as functions of the increase in concentration, curing time, and temperature to its comparable properties such as breakload, compressive strength, and ultimate break force. This study can further support future analysis in improving the reliability of petroleum well constructions.