Oil and gas fields encounter issues associated with clay minerals through drilling and production. Depending on the types of clay minerals, they pose the danger of swelling and migration upon exposure to incompatible water. Drilling introduces water through drilling mud, and production introduces water through different treatments such as acid stimulation and hydraulic fracturing.The recovery of oil and gas from subterranean formations has been troublesome in formations that contain water-sensitive minerals, e.g., water-swellable clays, such as clays in the smectite group, and fines capable of migrating when disturbed, such as silica, iron minerals, and alkaline earth metal carbonates.It has been common practice to add salts to the treatment fluids. The salts adsorb to the clay surfaces in an ion exchange process that can temporarily reduce the swelling and/or migration of the clays. Another method used is to coat the area with a polymer in order to physically block the surface of the clays. This paper will mention the types of clays related to the oil industry, describe the structure of clays, mention the mechanisms behind swelling and migrating, and compare the different developments in the field of clay inhibition.

Borate crosslinkers are the most commonly used crosslinker in fracturing fluids. However, they exhibit lower performance at high temperature, high pressure, high water salinity, and low pH applications. Consequently, zirconium crosslinkers are utilized to address these limitations. Zirconium crosslinking chemistry is complex and depends on many factors such as pH, metal to ligand ratio, ligand order, ionic strength, and type of polymer used, which in turn influence the delay time, thermal stability and shear resistance performance. This work evaluates the rheological performance of four different zirconium crosslinkers with a biopolymer and a synthetic polymer. The tested crosslinkers are manufactured in different chemical structures. The two polymers tested are 40 lb/1,000 gal CMHPG and 40 lb/1,000 gal synthetic polymer. The rheological performance was measured through HPHT rheometer (100 s−1 shear rate) at 200-400°F for 2 hours. The shear tolerance performance was also evaluated under a custom shear rate schedule (100-1000 s−1). The results show significant variation in crosslinking performance due to the changes in crosslinker chemical structure and type of polymer used. Zirconium lactate and propylene glycol crosslinker shows the highest enhancement in shear and thermal stability with CMHPG based fracturing fluids. Surprisingly, the same crosslinker performed the least with synthetic polymer-based fracturing fluids. However, Zirconium triethanol amine and lactate showed significant enhancements in shear and thermal stability with synthetic polymer-based systems. The results also show and discuss the influence of systematically changing crosslinker ligand order in CMHPG and synthetic polymer-based fracturing fluids. The work studies the influence of the zirconium crosslinker chemical structure on the rheological properties of both biopolymer and synthetic polymer-based fracturing fluids. The performance evaluation shows that delay time, shear and thermal stability can be enhanced by manufacturing the appropriate crosslinker chemical structure, thus reducing additional additives required used and saving cost.

Hydraulic fracturing technology has grown popular with the rapidly increasing development of tight conventional and unconventional reservoirs. A major concern with this technique is the use of large amounts of water in these treatments. The use of water causes many potential damaging issues in the formation and limits the amount that can be saved for future generations. One solution is waterless fracturing treatments, which were developed to reduce or eliminate the need for water in hydraulic fracturing. Hydraulic fracturing treatments consume at least 200,000 gallons of water in conventional wells and up to 16,000,000 gallons of water in unconventional wells. The pumped water must include clay stabilizers to deal with the sensitive clays in the formation. Additionally, using water poses a risk of inorganic scale precipitation near the wellbore. Water can also cause severe emulsions that can lead to emulsion blockage cases. Moreover, there are significant reports of water blockage cases in tight gas wells. Only a mere 10-30% of pumped water flows back after the treatment, with the rest attached to clays, or stuck in the pores due to high capillary pressures. Water-based fluids can also cause alterations to relative permeability, and liquid holdup cases in many gas wells. These issues can certainly increase near wellbore skin and reduce production rates. At the end of the treatment, water still causes issues related to disposal and separation prior to diverting it to the plant. The main challenges in developing waterless fluids include feasibility, environmental friendliness, and effectiveness to stimulate the reservoir. This review will cover the various waterless fracturing methods such as hydrocarbon-based, liquid CO2, energized, and foamed fluids (CO2 and N2 foams) as well as their advantages and disadvantages. Studies into the properties of these fluids, such as rheology, solubility, compatibility, will also be discussed. Field trials will be examined where applicable. This literature review examines various waterless alternatives to traditional fluids for hydraulic fracturing. From this paper, readers can better understand the nature of waterless technologies and be able to better evaluate these technologies for fracturing purposes.

The action of anodic glow discharge electrolysis (gde) on ethanol in neutral aqueous phosphate buffer gave acetaldehyde, butan-2,3-diol, hydrogen peroxide, and acid. The yields of these products were found to vary substantially with the presence or absence of oxygen and in particular with oxygen flow rate and substrate concentration. A mechanism has been proposed for the reaction of substrate in both the presence and absence of oxygen.Ethanol vapor and water vapor, over aqueous ethanol solutions, were subjected to glow discharge electrolysis (gde).by Klemenc (1), who examined the gaseous products only. Gde has been performed also on pure methanol (2), with a variety of supporting electrolytes; products were a complex mixture of simple breakdown species. Scholes and co-workers (3) studied the effects of x-rays (200 kV) on ethanol in aqueous solution and found that in the presence of oxygen the products were hydrogen peroxide and acetaldehyde alone. Using deaerated solutions they found acetaldehyde and butan-2, 3-diol, with traces of hydrogen peroxide (under acid conditions). Seddon and Allen (4) studied the hydrogen yields arising from the 7-radiolysis of neutral aqueous solutions of ethanol both in the presence and in the absence of oxygen. Recently Schultze and Schulte-Frohlinde (5) studied the effects of the v-irradiation of dilute aqueous ethanol under a gaseous mixture of oxygen and nitrous oxide. The products were acetaldehyde, acetic acid, glycolaldehyde, ethylene glycol, and hydrogen peroxide.A careful study was made of the total yields in the present work to determine the ultimate fates of all the radicals generated by gde: As will be seen, we have accounted for G(OH) in terms of our products. We also studied carefully the proportion cf acetaldehyde and hydrogen peroxide since this gives valuable evidence about the reaction possibilities, and we were able to show that in gde under oxygen flow rates high enough to scavenge all the 1-hydroxyethyl radicals (CHsCHOH) and at ethanol concentrations high enough to scavenge all the hydroxyl radicals, there is a particularly straightforward interaction between the 1-hydroxyethylperoxyl radicals (CH3 CI-IOH) 02 yielding acetaldehyde and hydrogen peroxide in 2:1 proportions. ExperimentalThe ethanol solutions were prepared by dissolving the correct amounts of pure absolute ethanol in neutral phosphate buffer solution, except for runs on acid determination under oxygen where very dilute alkali was used. The solutions after gde were analyzed for hydrogen peroxide (6), acetaldehyde (7), butan-2, 3-diol, and acid. since these compounds were the products of x-irradiation of phosphate buffer/ ethanol solutions (3). Other species sought by the wor]~ers who used x-irradiation were acetic acid, ethylene glycol, glycolaldehyde, ethyl hydroperoxide, diethyl peroxide, peracetic acid, and ethyl acetate, but no evidence was found for any of these. The acetaldehyde determination is essentiM]y co]orimetric: the absorbance, which declined rapidly, was recorded as Key words: glow disc...

Commonly used borate crosslinkers produce weak fracturing fluids at high temperature, high pressure, high salinity, and low pH conditions. Accordingly, zirconium crosslinkers were developed to address these shortcomings. Zirconium crosslinking chemistry is complicated and depends on many factors such as pH, ionic strength, ligand type, ligand order, and ligand to metal ratio. This work evaluated the rheological performance of four commercial zirconium crosslinkers with a polysaccharide and a polyacrylamide. The tested crosslinkers are manufactured with similar zirconium content but differ in ligand type and ligand order, producing different crosslinker chemical structures. The rheological performance was assessed using an HPHT rheometer at 93–204°C for 1.5 h. Shear tolerance performance was evaluated under shear rates of 40 s−1–1000 s−1. The results showed substantial variation in crosslinking performance due to the differences in the crosslinker chemical structure and type of polymer used. Zirconium lactate and propylene glycol crosslinker exhibited the greatest enhancement in shear and thermal stability with the polysaccharide‐based fracturing fluid. Remarkably, the same crosslinker performed the least with the polyacrylamide‐based fracturing fluid. However, Zirconium triethanolamine and lactate demonstrated considerable improvements in shear and thermal stability with the polyacrylamide‐based system. The work unravelled the influence of the zirconium crosslinker ligand type and ligand order on the rheological properties of both tested polymers. The performance evaluation showed that shear resistance, crosslinking delay, and thermal stability could be improved by utilizing the appropriate crosslinkers. The enhancements ultimately reduce additional additives required, prevent screenouts, and save cost during field treatments.

The increasing demand for energy has extended the development horizon towards relatively tighter formations all over the world. In Saudi Arabia, hydrochloric and organic acids have been extensively used to enhance well productivity or injectivity in low permeability formations. However, the use of these acids was associated with severe formation damage, which is attributed to acid/oil emulsions and/or asphaltene precipitation in some of the low permeability carbonate reservoirs. Consequently, a detailed study on different factors that influence the acid/oil emulsion and asphaltene precipitation mechanism was carried out for these reservoirs. Several compatibility studies were conducted using representative crude samples and different acid systems such as HCl and formic acid. The experiments were conducted at various temperatures up to 240°F using HP/HT aging cell for both live and spent acid samples, where some of the experiments included anti-sludge, iron control and demulsifier chemical additives. In addition, another set of experiments was performed in the presence of ferric ions (Fe3+). The total iron concentration in these experiments varied between 0-1,000 ppm. The results obtained from this study have revealed that the acid systems were not compatible with several representative oil field samples. The amount of asphaltene precipitation and the stability of formed emulsions increased significantly in the presence of ferric ions. Several wells have already been acidized and damaged prior to initiating this study. This paper discusses different tests conducted to identify, quantify and treat acid-oil emulsions/asphaltene precipitation in tight carbonate reservoirs. It also provides details of a special solvent treatment fluid recommended to revive dead wells which were damaged by acid-induced emulsion and asphaltene precipitation.

Gas injection is amongst the oldest and most used enhanced oil recovery (EOR) methods in the petroleum industry. Nevertheless, gas EOR is subject to poor macroscopic sweep efficiency due to the higher mobility and lower density of gas compared to reservoir fluids. Foamed-gas injection can regulate the mobility of gas by trapping a large fraction of the gas inside the porous medium, thereby increasing its apparent viscosity and reducing its relative permeability. However, the poor stability of foam at harsh reservoir temperature and salinity conditions is a major limitation that hinders the effectiveness of the foam flood. A combination of surfactant and nanoparticles (NPs) provides a novel solution to foam stability challenges. This study evaluates the role of NPs on enhancing foam stability. Static and dynamic laboratory tests were conducted along with particle size and zeta potential measurements to capture the foam stability and strength in porous media for a cationic surfactant combined with surface modified silica NPs. The static bulk foam stability was determined by measuring the foam half-life over time. The dynamic foam stability was determined through the mobility reduction factor (MRF) using a micromodel apparatus. The tests were carried out on a variety of NPs concentrations and fixed surfactant concentration. The results from the experiments show that the use of surfactant combined with NPs enhances the stability and strength of the generated foam when compared to the use of surfactant alone. The foam static tests show that the mixture of NPs and surfactants produces foams with smaller bubbles and longer half-life when compared to those in the absence of NPs. The results also demonstrate that the concentration of surfactant and NPs is a crucial parameter for foam stability and that there is an optimal concentration of NPs for strong foam generation. In porous media, the addition of NPs to surfactant solutions results in larger pressure differences across the micromodel chip and, accordingly, greater reduction of gas mobility when compared to those using surfactant solution alone. The results also reveal that the generation of NPs flocs is the main mechanism of foam stabilization enhancement. This work shows that using NPs at carefully selected concentrations in combination with surfactant can improve the foam static and dynamic stability in porous media, effectively lowering the mobility of the injected fluids and, eventually, improving the sweep efficiency of gas compared to the typical application of using surfactant alone.

Hydraulic fracturing technique, using water-soluble polymers, has been extensively used to improve the productivity of oil and gas wells, especially in low-permeability formations. However, the production enhancement by hydraulic fracturing can be hindered by the fracture conductivity damage and/or fracture face skin. This paper describes an approach to establish a suitable fracturing fluid cleanup process by analyzing the performance of different gel breaker types, especially in sours environments. In addition, the interaction of clay stabilizers with different gel breakers is investigated.Several experiments were conducted to assess the effect of different gel breakers on high temperature fracturing fluid as a function of time. Most commonly used breakers-inorganic oxidizers (bromate and persulfate salts), specific enzymes and acids-were used in this evaluation. The effectiveness of each breaker was evaluated using various techniques, such as Zeta Potential, Gel Permeation Chromatography (GPC), High-Pressure/High-Temperature (HP/HT) aging cells, H 2 S compatibility tests and Environmental Scanning Electron Microscope (ESEM). All experiments were performed on borate and zirconate crosslinked carboxymethyl-hydroxypropyl guar (CMHPG) guar gum system with loading up to 45 lb/1,000 gals in addition to clay control agents potassium chloride and polymer-based clay stabilizers.The results obtained from this study have shown that amount and size of the residual gel polymer chains, after its breakage, were mainly dependent on the type and loading of used gel breaker. Furthermore, it was found that both KCl and polymer-based clay stabilizers were effective in preventing clay-induced formation damage. However, laboratory tests have revealed that some gel breaker types may negatively affect the performance of polymer-based clay stabilizers. Additionally, this paper will highlight other negative interactions of common gel breakers, especially in sour environments.