Rock-based Geopolymers Research Articles

Synthesis of sustainable one-part geopolymers for well cementing applications

This work describes the synthesis of a novel one-part granite-based geopolymer mix design for well cementing applications by screening and improving the early-age performance of the geopolymers. The dissolution rate of granite and potassium silicate (K2SiO3) is slightly enhanced when they are blended, compared to the situation when granite was mixed with alkali solution. It was revealed that the chemical composition of granite requires modification. Ground granulated blast-furnace slag (GGBFS) was incorporated up to 90% of total weight (wt.%) within the solid precursor to find out the optimum design, based on its effect on fluid-state and solid-state properties. Pumpability and strength development of the slurries were studied to establish the applicability of the mix designs. To further characterize the final products, the mineralogy and morphology of the specimens were examined. The use of GGBFS, to modify the chemical composition of the granite, reduces the pumping time significantly. Moreover, the use of GGBFS increases the density and initial consistency value of the slurry proportionally to the increase in GGBFS content. Additionally, a threshold effect was observed in the mechanical strength development. The higher the GGBFS content (up to 50 wt%), the higher the early-age compressive strength. The highest measured compressive strength for the neat rock-based geopolymer recipe was around 6 MPa within 1-day to 7-day for a mix of 47 wt% GGBFS to the solid precursor, while its optimized mix was around 12 MPa within the same period.

Development of One-Part Rock-Based Geopolymers for Downhole Cementing Applications

AbstractThe use of geopolymers as a full replacement for cement in oil well cementing applications requires the development of not only environmentally friendly but also user-friendly cementitious materials. This study aims to investigate the early-age mechanical and chemical properties of synthesized one-part geopolymers, which are heat-cured rock-based products. These geopolymers were synthesized from granite-based precursors and were activated by solid powders of potassium silicate, with a small portion of potassium hydroxide (KOH) as an accelerator to enhance the setting time and early strength. The mechanical and chemical properties of the one-part geopolymers were characterized, and the mineralogy of the solidified samples was analyzed through crystallography to better understand their microstructure. The study found that the investigated one-part geopolymer mixes, which were activated by a solid activator with a modulus ratio of 2.4, developed acceptable compressive strength of around 7 to 13 MPa within 24 h and up to 7 days. The use of one-part geopolymers has the potential to provide environmentally- and user-friendly slurries that can facilitate their utilization for large-scale in-situ applications in the petroleum and civil engineering sectors.

Experimental Evaluation of the Effect of Temperature on the Mechanical Properties of Setting Materials for Well Integrity

Summary A fundamental understanding of the mechanical properties of zonal isolation materials is important for predicting well integrity during well operation conditions. Conventionally, the mechanical properties of zonal isolation materials are tested at ambient temperature using uniaxial testing. This study examined the mechanical properties of alternative zonal isolation materials such as rock-based geopolymer, thermosetting resin, and an industrial class expansive cement under realistic well conditions by triaxial testing. Mechanical properties such as Young’s modulus, Poisson’s ratio, cohesive strength, friction angle, and compressive strength of these materials at 30 and 90°C were compared. The effect of confining pressure on the mechanical properties of the materials was also examined. The findings of this study show that all selected materials possess compressive strength at 30 and 90°C and that the compressive strength of all the selected materials is strongly impacted by temperature and confining pressure. The Young’s modulus of all the selected materials was unaffected by confining pressure, while only the Young’s modulus of thermosetting resin was sensitive to temperature. The influence of temperature on the Poisson’s ratio varied from one material to another. In addition, when the test temperature increased, the friction angle of neat Class G and geopolymer decreased.

Effect of Zn2+ and K+ as Retarding Agents on Rock-Based Geopolymers for Downhole Cementing Operations

Abstract Geopolymer material has a potential to function alongside Portland Cement as an efficient cementitious material for well cementing and plug and abandonment applications. Geopolymer material requires retarding agents to be displaced into the well while considering the properties required to maintain efficient zonal isolation through superior mechanical properties. Chemical admixtures affect the material structure and can, in some cases, jeopardize material integrity if not engineered properly to suite downhole conditions. The present article shows the effect of Zn2+ and K+ species have as retarding agents on slurry, mechanical, and microstructural properties. The approach has been carried out to obtain a preliminary overview of how retarding agents can behave in mix design slurries where eventually sealing performance was examined. Samples were cured and examined for periods of 1, 3, 7, 14, and 28 days at downhole conditions. The results obtained confirm a retardation effect by the addition of Zn2+ and K+ species and some shortcomings in early strength development due to a poisoning mechanism by Zn2+ species. This phenomenon indicates the formation of Ca-Zn phase that can hinder the nucleation of the geopolymeric gel structure. No significant effects were observed on the microstructural development throughout the curing period. The effect of Zn2+ species was also observed in increasing threshold for hydraulic sealability. It may be concluded that the tested retarding agents require furthermore development to minimize shortcomings in mechanical properties specifically early strength development.

Impact of Drilling Fluid Contamination on Performance of Rock-Based Geopolymers

Summary Our objective is to present selected rheological and mechanical properties of rock-based geopolymers contaminated with different concentrations of drilling fluids. The possible flash setting and the maximum intake of drilling fluids before seeing a dramatic deterioration of the geopolymers are presented. Rock-based geopolymers designed for cementing conductor and surface casing were prepared and cured for up to 28 days at 22°C and atmospheric pressure. Water-based drilling fluids (WBDFs) and oil-based drilling fluids (OBDFs) were designed in accordance with the recommendations from the petroleum industry. The fluid samples were prepared, and their viscous behavior was characterized before and after hot-rolling. The geopolymeric slurries were mixed and then blended with the prepared drilling fluid volumes. The contaminated geopolymeric slurries were cured and tested at different time intervals. American Petroleum Institute (API) Class G neat cement was used as a reference. These samples were cured and contaminated with the same drilling fluids. The properties of contaminated geopolymer slurries were benchmarked with those of the contaminated Class G cement. The obtained mechanical properties showed that the rock-based geopolymers are more sensitive to WBDFs than to OBDFs. However, for contaminated Portland cement samples, the obtained results were opposite, and the contamination effect of OBDF on cement was more noticeable than WBDF. The impact of geopolymer contamination is a function of curing time. Although geopolymeric samples showed dramatic strength retrogression at the early time, strength buildup of the samples compensated for the impact of contamination.

Alternative setting materials for primary cementing and zonal isolation – Laboratory evaluation of rheological and mechanical properties

Portland cement is the prime zonal isolation material used in hydrocarbon wells and its utilization has been extended to geothermal, carbon sequestration and gas storage wells. Despite the vast quantity of research activities and publications, well integrity reports show shortcomings associated with Portland cement at specific conditions of pressure, temperature, chemical environment and geographical locations. In this experimental study, four alternative barrier materials have been selected for further experiments at laboratory scale: an industrial class of expansive cement, a non-cement pozzolanic slurry, a rock-based geopolymer and an organic thermosetting resin. Neat class G cement was used as reference material for comparing the results.The study includes the rheological behavior of the candidate materials, static fluid-loss and pumpability at both atmospheric and elevated pressures. All of the materials at the liquid phase showed an acceptable viscosity profile at the operational shear rates. The consistency curve of the slurries showed that the barrier materials are pumpable for the desired period with the right-angle set (RAS), except for the pozzolanic slurry, which was not able to make gel up to 24 h at dynamic conditions.Mechanical properties of the candidate barrier materials including uniaxial compressive strength (UCS), modulus of flexibility, sonic strength development and tensile strength of the samples were characterized up to 28 days of curing. The UCS test results showed that the thermosetting resin has an extremely high compressive strength compared to the other materials, while the geopolymer and the pozzolanic slurry are more ductile. The tensile strength of the materials experienced no significant change over time; however, for the neat class G cement, it is reduced after 28 days.

Crushed Rock Geopolymer as a Future Road Construction Material: An Evaluation on Strength Performance and Compaction Characteristics

To be more sustainable in the road construction industry, the rock-based geopolymer concept should be applied with an aim to create a geopolymer-based road structural layer. The research program studied on the geopolymer for road construction was newly established at Chiang Mai University, Thailand. This study concentrated in a preliminarily evaluation of strength performance and compaction characteristics of crushed rock-based geopolymer (CR-GP) to partially or totally replace the usage of ordinary Portland cement (OPC) as a road stabilizing agent. The standard crushed rock (CR), complying with the standard of road base materials, was obtained from a real construction field. The experiment on CR gradation, compaction and compressive strength were carried out. The results showed that CR of a finer grading curve with higher surface areas tended to better react with alkaline activators, resulting in relatively high compressive strength. The mechanical modification with compaction is one of the simplest methods for strength improvement. It found that higher compactive efforts (the modified compaction), higher densification than that of the standard compaction, corresponding to the compaction theory of soil mechanics. CR-GP having an ideal (reconstituted) grading curve achieved higher compressive strength than that of the standard grading one of a well-graded pattern. Overall, it could be concluded CR-GP has intrinsic compaction characteristics of which at its optimum point of compaction, CR-GP could address the minimum requirement for road standard in terms of compressive strength, by which it could be used as an alternative material in replacing the consumption of OPC.

Preliminary Investigation of Crushed Rock-Based Geopolymer for Road Applications

At present, our world is facing environmental issues, which is an increasing amount of carbon dioxide (CO2) generated by the Portland cement (OPC) production. To reduce that carbon dioxide emissions, some researchers have studied the alternative cementitious materials to replace the consumption of OPC, and geopolymer is one of the choices. Geopolymer cement (GP), a green technique for construction material, was applied for the road constructions by using Crushed rock (CR-the typical pavement material) as a starting material of geopolymer synthesis. The results showed that the optimum mixture to achieve both properties and economic aspect was 5M of NaOH concentration, 1.0 SS/SH ratio, 0.5 L/B ratio cured at room temperature. With that mixture, it passed the target compressive strength of Cement-treated base (CTB) for pavement (2.1-5.5 MPa) as well as achieving the CO2 reduction of 45.23% when compared to ordinary Portland cement.

Experimental Evaluation of Geopolymer, Nano-Modified, and Neat Class H Cement by Using Diametrically Compressive Tests

Abstract Cement is the prime barrier material to maintain zonal isolation during wellbore life-cycle. Different types of the cement have different performances on sealability. The primary objective of this study is evaluation of three types of cement systems, neat Class H, nano-synthetic graphite, and rock-based geopolymer cements, on interfacial bond integrity. Diametrical compressive tests are used on casing–cement–formation systems. Cement performances are tested in a conventional configuration (Berea Sandstone). A universal testing system is utilized to analyze the relationship applied load–axial strain and the digital image correlation (DIC) technique is used to generate the strain field maps. Based on the relationship and DIC results, bond strengths in different cement systems are evaluated. Additionally, microscope images provide insight explanations of the bond from micro-view. Based on the experimental results, failures of all cases initiate and propagate from the casing–cement interface. Then, radial cracks develop through the formation. This is because the mechanical interlocking bonds are formed only at the cement–sandstone interface to enhance the bond strength. The comparison of geopolymer and nano-modified cements with the conventional cement (neat Class H) shows that the unconventional cements have a lower maximum load and higher axial strain before failure of the samples. It indicates that both the two kinds of cements are more ductile than conventional cement and can support more deformation before the initiation of cracks.

Effect of nanoparticles on properties of geopolymers designed for well cementing applications

Recently the focus of the oil and gas industry is to find the alternative material for well barrier applications. Geopolymers are among the suggested materials, which could be used in the future to solve the well integrity issues rooted by the properties of Portland cement. Previous study with rock-based geopolymer indicates the potential of geopolymer to be used as a barrier material. However, there are still some shortcomings of geopolymer material, which need to be improved to make it a possible option for well cementing applications. This study aims to improve the properties of the geopolymer. Al2O3 and multi walled carbon nanotubes functionalized with hydroxyl group (MWCNT-OH) nanomaterials were used to study their effect on rheological, filtration loss, and mechanical properties of the geopolymer. Moreover, the effect of nanomaterials on the setting time and microstructure of the geopolymer has been studied. Results obtained from this work indicate that, nanomaterials-based geopolymers have better mechanical properties and setting time compared to the neat geopolymer. Addition of nanomaterials produced a more ductile structure with higher compressive and tensile strengths. Microstructure and element analysis confirmed the formation of a more compact and dense structure with the presence of MWCNT-OH and Al2O3 throughout the structure of the geopolymer.

Experimental study of temperature effects on wellbore material properties to enhance temperature profile modeling for production wells

In a wellbore, transient pressure and temperature behavior occurs as hot reservoir fluids flow upwards and exchange heat with the surroundings. This type of heat transfer happens in drilling, production and injection operations. Wellbore components such as tubings, cement sheets, casings and fluids play a major role in the heat exchange. To estimate and quantify the transferred heat, knowledge on the thermophysical parameters of the wellbore components is essential. This information is important to consider during the planning phase to find the optimal combination of materials used in the well construction to achieve top safety at lowest costs. In this study, experiments were performed using a C-Therm TCi™ thermal conductivity analyzer to measure thermophysical parameters of typical wellbore components (fluids, casings, tubings, cement sheets and formations), specifically, thermal conductivity. The results of the experiments were used to derive temperature-dependent thermophysical correlations, which were applied in a wellbore heat transfer model for oil production scenario by considering a complex well architecture. In simulations, parameter sensitivity tests reveal that as the flow rate of the produced fluid increases, the rate of heat loss of the fluid decreases, and the rate of fluid temperature drop becomes lower as the production time increases. Comparison of simulations’ results for four cementitious materials show that fly ash-based geopolymer has better thermal resistance than other tested materials (Neat class G cement, slag-based- and rock-based geopolymers). When the produced fluid was changed from crude oil to water, it experienced less heat loss from the bottom to the surface. The results of this study provide an idea about thermal behavior of various well components and can be useful for the material selection for geothermal, production and injection wells design.

Laboratory evaluation of rock-based geopolymers for zonal isolation and permanent P&A applications

In this work, we have studied selected rheological properties and mechanical properties of rock-based geopolymers. The geopolymers are suggested for zonal isolation and permanent abandonment of hydrocarbon wells. Our viscosity measurements of the geopolymeric slurries shows a very small yield stress and a nearly constant additional viscosity. To find the effect of mechanical vibration, a rotational viscometer was modified by being equipped with a mechanical vibrator. Consistency of the geopolymeric slurry was measured by utilization of atmospheric and pressurized consistometers to find the impact of pressure and temperature on pumpability. The downhole temperature uncertainty was also studied by using atmospheric consistometers. Static-fluid-loss is an issue, which causes loss of hydrostatic pressure. Therefore, static-fluid-loss test was carried out. Strength development of the geopolymeric slurry was measured directly and indirectly by utilization of uniaxial compressive strength and Ultrasonic Cement Analyzers, respectively. As the pre-defined algorithm could not convert the sonic velocity to sonic strength, a custom algorithm was generated. The elastic shear wave and compressional wave velocities and velocity anisotropies of the samples were tried to be determined experimentally. The measurements were conducted on cube-shaped specimens in a triaxial multi-anvil press using the ultrasonic pulse-transmission technique. As it is necessary to study the bond strength between the geopolymers and pipe, steel pipe was used. The shear bond strength between pipe and the rock-based geopolymer was measured.

Long-term durability of rock-based geopolymers aged at downhole conditions for oil well cementing operations

The long-term integrity of rock-based geopolymers was studied in corrosive environments. The geopolymers were cured for 7 days at ambient conditions. Afterwards, the geopolymers were exposed to crude oil, brine and H2S in brine at 100 °C and elevated pressures. The compressive strength, tensile strength, weight and volume changes were measured prior and after 3, 6 and 12 months of exposure. The measurements showed a turning point after 6 months of ageing. Whereas the compressive strength and tensile strength started to increase when the specimens were exposed to crude oil and brine, the specimens that were exposed to H2S experienced some degradation. Permeability of geopolymers before exposure and after 12 months of exposure to the crude oil and brine was very low. The permeability of the specimens which were exposed to H2S was not measureable. Substantial volume changes were observed for the geopolymers which were exposed to H2S and brine.

Experimental study on the synthesis and characterization of aplite rock-based geopolymers

This paper presents a new method for geopolymer synthesis of ground aplite rock. The resulting geopolymers were easy to manufacture and exhibited promising mechanical properties. Compressive strength testing, X-ray diffraction, and scanning electron microscope analyzes were performed. The results indicated that in manufacturing, the aplite-based geopolymers, potassium-containing systems gave noticeable improvements in comparison with sodium-containing systems. Rheological behavior of the geopolymeric slurry showed non-Newtonian behavior. The Bingham and Herschel–Bulkley models were selected to simulate the viscosities of the slurries. The Bingham model fitted to the measured data with an average deviation of 1.65 (lbf/100 ft2) while the Herschel–Bulkley model showed large deviations from the experimental data.