Shale Swelling Research Articles

Novel application of citric acid based natural deep eutectic solvent in drilling fluids for shale swelling prevention

Swelling of shale in clastic reservoirs poses a significant challenge, causing instability in wellbores. Utilizing water-based drilling mud with shale inhibitors is preferable for environmental reasons over oil-based mud. Ionic liquids (ILs) have garnered interest as shale inhibitors due to their customizable properties and strong electrostatic features. However, widely used imidazolium-based ILs in drilling fluids are found to be toxic, non-biodegradable, and expensive. Deep Eutectic Solvents (DES), considered a more economical and less toxic alternative to ILs, still fall short in terms of environmental sustainability. The latest advancement in this field introduces Natural Deep Eutectic Solvents (NADES), renowned for their genuine eco-friendliness. This study explores NADES formulated with citric acid (as a Hydrogen Bond Acceptor) and glycerine (as a Hydrogen Bond Donor) as additives in drilling fluids. The NADES based drilling mud was prepared according to API 13B-1 standards and their efficacy was compared with KCl, imidazolium based ionic liquid, and Choline Chloride: Urea-DES based mud. A thorough physicochemical characterization of the in-house prepared NADES is detailed. The research evaluates rheological, filtration and shale inhibition properties of the mud, demonstrating that NADES enhanced the yield point to plastic viscosity ratio (YP/PV), reduced mudcake thickness by 26%, and decreased filtrate volume by 30.1% at a 3% concentration. Notably, NADES achieved an impressive 49.14% inhibition of swelling and improved shale recovery by 86.36%. These outcomes are attributed to NADES’ ability to modify surface activity, zeta potential, and clay layer spacing which are discussed to understand the underlying mechanism. This sustainable drilling fluid promises to reshape the drilling industry by offering a non-toxic, cost-effective, and highly efficient alternative to conventional shale inhibitors, paving the way for environmentally conscious drilling practices.

Swelling damage characteristics induced by CO2 adsorption in shale: Experimental and modeling approaches

Carbon dioxide (CO2) geological sequestration represents a critical technology in mitigating climate change. Shale reservoirs demonstrate a pronounced affinity for CO2, resulting in adsorption-induced swelling that significantly impacts permeability, mechanical strength, injection efficiency, and sequestration safety. For this, we tried to explore the key factors driving the swelling of shale upon CO2 injection and its subsequent impact on reservoir properties. Utilizing a self-developed high-temperature-pressure gas adsorption apparatus, we measured strain in Jurassic shale at 308 K under constant hydrostatic pressure with helium (He) at 1300 psi (1 psi = 6.895 kPa) and CO2 at 850 psi. Next, we investigated the influence of CO2 concentration on swelling protentional while maintaining constant pressure, uncovering the anisotropic deformation in relation to pressure. It shows that CO2 adsorption induces significant swelling in shale, following a Langmuir-type pressure relationship. Deformation is more pronounced perpendicular than that parallel to the bedding plane. At low pressure, vertical swelling is 2.28 times greater than the horizontal; while at high pressure, the vertical compression is 31.26 times greater than the horizontal. It seems that the anisotropic swelling enhances permeability predictions during CO2 injection. Mixed gases under constant compression can prompt gas desorption, stress redistribution, and alterations in pore structure, amplifying He compression effect. The strain induced after replacing CO2 with He exceeds that from pure He injection. The asynchronous response of CO2-induced swelling and mechanical compression can precipitate crack propagation and fracturing. Overall, anisotropic swelling from CO2 adsorption changes pore structure and permeability, affecting fluid flow and storage. Considering CO2 concentration and anisotropic characteristics in reservoir modeling is essential for optimizing injection strategies and enhancing reservoir efficiency.

Improving Shale Stability through the Utilization of Graphene Nanopowder and Modified Polymer-Based Silica Nanocomposite in Water-Based Drilling Fluids

Shale formations present significant challenges to traditional drilling fluids due to fluid infiltration, cuttings dispersion, and shale swelling, which can destabilize the wellbore. While oil-based drilling fluids (OBM) effectively address these concerns about their environmental impact, their cost limits their widespread use. Recently, nanomaterials (NPs) have emerged as a promising approach in drilling fluid technology, offering an innovative solution to improve the efficiency of water-based drilling fluids (WBDFs) in shale operations. This study evaluates the potential of utilizing modified silica nanocomposite and graphene nanopowder to formulate a nanoparticle-enhanced water-based drilling fluid (NP-WBDF). The main objective is to investigate the impact of these nanoparticle additives on the flow characteristics, filtration efficiency, and inhibition properties of the NP-WBDF. In this research, a silica nanocomposite was successfully synthesized using emulsion polymerization and analyzed using FTIR, PSD, and TEM techniques. Results showed that the silica nanocomposite exhibited a unimodal particle size distribution ranging from 38 nm to 164 nm, with an average particle size of approximately 72 nm. Shale samples before and after interaction with the graphene nanopowder WBDF and the silica nanocomposite WBDF were analyzed using scanning electron microscopy (SEM). The NP-WBM underwent evaluation through API filtration tests (LTLP), high-temperature/high-pressure (HTHP) filtration tests, and rheological measurements conducted with a conventional viscometer. Experimental results showed that the silica nanocomposite and the graphene nanopowder effectively bridged and sealed shale pore throats, demonstrating superior inhibition performance compared to conventional WBDF. Post adsorption, the shale surface exhibited increased hydrophobicity, contributing to enhanced stability. Overall, the silica nanocomposite and the graphene nanopowder positively impacted rheological performance and provided favorable filtration control in water-based drilling fluids.

Preparation and Mechanism of Shale Inhibitor TIL-NH2 for Shale Gas Horizontal Wells.

In this study, a new polyionic polymer inhibitor, TIL-NH2, was developed to address the instability of shale gas horizontal wells caused by water-based drilling fluids. The structural characteristics and inhibition effects of TIL-NH2 on mud shale were comprehensively analyzed using infrared spectroscopy, NMR spectroscopy, contact angle measurements, particle size distribution, zeta potential, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The results demonstrated that TIL-NH2 significantly enhances the thermal stability of shale, with a decomposition temperature exceeding 300 °C, indicating excellent high-temperature resistance. At a concentration of 0.9%, TIL-NH2 increased the median particle size of shale powder from 5.2871 μm to over 320 μm, effectively inhibiting hydration expansion and dispersion. The zeta potential measurements showed a reduction in the absolute value of illite's zeta potential from -38.2 mV to 22.1 mV at 0.6% concentration, highlighting a significant decrease in surface charge density. Infrared spectroscopy and X-ray diffraction confirmed the formation of a close adsorption layer between TIL-NH2 and the illite surface through electrostatic and hydrogen bonding, which reduced the weakly bound water content to 0.0951% and maintained layer spacing of 1.032 nm and 1.354 nm in dry and wet states, respectively. Thermogravimetric analysis indicated a marked reduction in heat loss, particularly in the strongly bound water content. Scanning electron microscopy revealed that shale powder treated with TIL-NH2 exhibited an irregular bulk shape with strong inter-particle bonding and low hydration degree. These findings suggest that TIL-NH2 effectively inhibits hydration swelling and dispersion of shale through the synergistic effects of cationic imidazole rings and primary amine groups, offering excellent temperature and salt resistance. This provides a technical foundation for the low-cost and efficient extraction of shale gas in horizontal wells.

Evaluation of a novel paraffin wax microemulsion for improving wellbore stability in shale formations

High-performance shale stabilizers are urgently required to address the concerns of wellbore instability when drilling troublesome shale wells. Herein, a novel paraffin wax microemulsion (PM) containing cationic surfactant was prepared and evaluated for shale formations. The shale stability performance of PM was studied using shale pressure penetration test, shale swelling and dispersion test. The shale stabilization mechanism of PM was investigated by surface tension, contact angle, surface free energy, capillary tube rise and SEM tests. The experimental findings showed that the pressure penetration time in shale after treatment with PM was extended from 13 to 107 min. And PM could decrease the shale swelling rate by 41.5%, and increase the recovery rate to 89.4%. PM exhibited better sealing and inhibition properties than that of commonly used shale stabilizers. The mechanism research revealed that the nano-droplets in PM could freely penetrate into shale pores and cracks of different sizes to form an effective sealing membrane. The water contact angle reached 91.4° after treatment with PM and the surface energy was significantly reduced, effectively inhibiting surface hydration. Through decreasing the surface tension and changing the wettability, the capillary force experienced a noticeable decrease with further enhanced inhibition of shale hydration. Therefore, the application of PM for shale stabilization exhibited promising potential, suggesting its possible effective utilization in shale drilling.

Correction: Experiential investigations for shale–fluid interaction and identification of novel chemical additives as efficient shale swelling inhibitor

Correction: Experiential investigations for shale–fluid interaction and identification of novel chemical additives as efficient shale swelling inhibitor

Experiential investigations for shale–fluid interaction and identification of novel chemical additives as efficient shale swelling inhibitor

Experiential investigations for shale–fluid interaction and identification of novel chemical additives as efficient shale swelling inhibitor

Exploring the role of hydrophobic nanofluids in reducing shale swelling during drilling: A step towards eco-friendly and sustainable practices

This study conducts a comparative analysis between hydrophobic nanosilica (HNS) and potassium chloride (KCl), a widely used shale inhibitor, to better understand how HNS can effectively manage water and shale interactions by restricting mud filtration into the formation. Due to their small size and optimal interfacial properties, nanoparticles emerge as remarkable solutions for addressing this issue. In this work, shale samples were collected from the Kolosh Formation in the Kurdistan Region of Iraq, known for being one of the most challenging formations to drill. Investigations into the properties of drilling fluid were conducted using low pressure and low temperature (LPLT) and high pressure high temperature (HPHT) filter press, alongside analyzing rheological properties at three different temperatures (25, 50 and 75°C). In addition, the impact of the HNS on clay swelling was examined using the liner swelling meter (LSM) test, shale dispersion test (SDT) and capillary suction time (CST) test. The obtaining results revealed that the shale hydration in the drilling fluids was reduced 24.36–15.53% and the shale recovery at high temperatures was improved from 80.2% to 94% by adding 0.4 wt% HNS. Furthermore, HNS demonstrated improved clay suspension in the CST test wherein the suspension time reduced from 303 to 80 sec at the same HNS concentration. Utilizing HNS effectively reduced clay swelling in all experiments and enhanced the rheological properties of the mud, showcasing stability across a range of temperatures and significantly reducing the formation of filter cake and fluid loss. As is obvious, KCl based drilling fluids are prohibited in several parts in the word due to its negative impact on the environment and subsurface activities; thus, it can be substituted by HNS as an active shale inhibitor additive.

Application of graphene oxide/titanium dioxide nanoparticle on the rheological, filtration and shale swelling characteristics in water-based mud system: experimental and full factorial design study

Application of graphene oxide/titanium dioxide nanoparticle on the rheological, filtration and shale swelling characteristics in water-based mud system: experimental and full factorial design study

Sodium dodecyl sulphate-treated nanohydroxyapatite as an efficient shale stabilizer for water-based drilling fluids

Drilling water-sensitive shale formations often leads to wellbore instability, resulting in drilling problems because of the clay's high-water affinity. To solve this problem, different nanoparticles (NPs), such as nanosilica, have been used to formulate water-based muds with potassium chloride (KCl-WBM). Nevertheless, the unmatched pore size of shale pores when using nanosilica fails to completely prevent shale swelling and dispersion. This study discusses the effects of KCl-WBM with sodium dodecyl sulphate-treated nanohydroxyapatite (nHAp/SDS) on shale swelling inhibition through various laboratory techniques. These techniques encompass the linear swell meter (LSM), the dynamic linear swell meter (DLSM), hot-rolling dispersion, suspension stability, and pore structure characterization of shale. The rheological and filtration characteristics of nHAp/SDS and compatibility tests were also studied, and the results were compared with those of nanosilica and KCl-WBM. At all concentrations, the performance of the nHAp/SDS test fluids surpassed that of nanosilica. When compared with KCl-WBM system at 10 cP and 25 °C, the nHAp/SDS and nanosilica concentrations increased the plastic viscosity by 20–90 % and 10–70 %, respectively. The inhibitory effect of nHAp/SDS surpasses that of conventional KCl-WBM and inorganic nanosilica. By adding 2.0 wt% nHAp/SDS to KCl-WBM, the shale swelling decreased from 10.1 to 4.7 % (a 53.4 % reduction). Nanosilica also reduced the swelling to 6.1 % (a 39.6 % reduction) during the LSM test at 25 °C. Under the DLSM test conditions, the shale swelling increased due to the activation of the clay platelet site at an increased temperature of 80 °C. For instance, between 25 and 80 °C, the DLSM test revealed that the shale plug height expanded from 6.1 to 9.8 % for 2.0 wt% nanosilica, 4.7–7.6 % for 2.0 wt% nHAp/SDS, and 10.1–18.8 % for KCl-WBM. Furthermore, the recovery rate of hot-rolled shale plugs with KCl-WBM increased from 89.8 to 96.2 % for nHAp/SDS and 76.6 to 88.8 % for nanosilica from the initial rates of 52.1–63.3 % between 65 and 120 °C. The contact angle results showed that nHAp/SDS is hydrophobic, reducing shale-water attraction. Moreover, the 12 nm nanosilica matches nanopore sizes to partially block shale pores. This research found that nHAp/SDS has the potential to improve wellbore stability.

Thermo-responsive polymer-based Janus biogenic-nanosilica composite, part B: Experimental study as a multi-functional synergistic shale stabilizer for water-based drilling fluids

Wellbore instability caused by shale swelling and dispersion has always been a thorny issue for drilling complex formations. Nanotechnology has offered a revolutionary solution for shale stabilization in water-based drilling fluids (WBDFs). Recent technological advancement in nanomaterials for optimal performance using economically and environmentally sustainable pathway is an utmost desire in oil and gas industries. In this research, Janus nanocomposite (TRJN) with rice husk (RH)-extracted biogenic nanosilica core (RH-NSP) having the shell integrating synergistic benefits of thermo-responsive and amino-based materials, which was reported in our previous work was assessed as a novel shale stabilizer in drilling fluids. The product is anticipated to simultaneously improve the chemical inhibition and nanoplugging performances in shaly formations. TRJN was assessed as an additive in WBDF in comparison with symmetrical thermo-responsive polymer-based nanocomposite (TRN) counterpart and parent RH-NSP. Results from the rheological test revealed that, albeit both nanocomposites (i.e., TRN and TRJN) could provide a certain rheological control above the LCST compared to RH-NSP, but TRJN-blended fluid was less sensitive to increasing temperatures. The inhibitory effects were investigated based on cuttings hot rolling recovery rate, linear swelling rate, pressure penetration rate, tensile strength of shale reduction rate, and high temperatures and high pressures filtration loss. TRJN demonstrated higher chemical inhibition compared to RH-NSP and TRN, driving a better capacity to control pressure penetration. The higher mean free energy of TRJN/Na-Mt (sodium montmorillonite) system than TRN/Na-Mt system was an indication of its stronger interactions with Na-Mt particle, which triggered changes in microstructures, considering the results of zeta potential, FT-IR, surface wettability, X-ray diffraction, and SEM analyses. This, therefore contributing to firmly trap the TRJN into the multi-scale pore structure of the shale and beneficially promoted the construction of a tight hydrophobic plugging layer over the shale surface from the outward face. Lastly, the synergistic enhancement mechanisms of shale inhibition with TRJN was further proposed.

Water-based drilling fluids containing hydrophobic nanoparticles for minimizing shale hydration and formation damage

Wellbore instability is always inevitable in shale formation due to hydration, swelling, and dispersion of clay, especially when using water-based drilling fluids (WBDFs). To mitigate the wellbore instability of shale formation and avoid correlative detriments such as formation damage, various nano-silica particles (nano-SiO2) were employed to plug the nano-sized pores, inhibit water invasion into shale, and prevent shale swelling. Firstly, the influence of various nano-SiO2 on rheological and filtration properties of a set WBDF was evaluated. Then, the linear swelling test, shale recovery test, zeta potential test, imbibition test, contact angle measurement, scanning electron microscopy (SEM) observation, and computed tomography (CT) analysis were conducted to assess the characteristic of nano-SiO2. Experimental results showed that solid phase nano-SiO2 could dramatically increase the viscosity and yield point while liquid phase nano-SiO2 only caused small fluctuations on these parameters. Besides, hydrophobic nano-SiO2 displayed better filtration performance than hydrophilic nano-SiO2. On the whole, the hydrophobic nano-SiO2 dispersion, called as nano-2, showed the best performance in WBDFs. Furthermore, nano-2 exhibited better inhibition than hydrophilic nano-SiO2, KCl, and polyether amine (PA). Mechanism analysis demonstrated that nano-2 could improve the hydrophobic degree of shale surface and prevent water from contacting with the shale. Meanwhile, nano-2 plugged the pores and throats in the shale. As a consequence, water in the drilling fluid was prevented from invading the shale, and the shale was inhibited. Nano-2 could form a thin barrier in the surface of shale, and mitigate the damage degree of shale cores after perforation operation. As a result, nano-2 displayed great potential to stabilize shale and protect formation in WBDFs.

Green nanocomposite synthesis and application: Electrochemically exfoliated graphene-modified biopolymer as an effective clay swelling inhibitor for water-based drilling muds

The expansion of shale formations causing wellbore instability is a costly challenge in drilling operations. To address this issue, researchers have explored the potential of graphene as a shale swelling inhibitor and fluid loss controller. However, the practical application of graphene has been hindered by settling and limited dispersion in drilling muds. In this study, we present a promising solution using low-cost graphene prepared through simple electrochemical exfoliation of graphite. The resulting graphene was further combined with a natural biopolymer to create a nanocomposite. The nanocomposite, known as electrochemically exfoliated graphene-modified Gum Arabic (GrO-ArG), was evaluated as a fluid loss controller and shale swelling inhibitor in water-based drilling muds. To assess its inhibition potential, linear swelling and capillary suction timer tests were employed using different concentrations of the nanocomposite. Additionally, the performance of the drilling mud was examined through rheology and fluid loss tests. The experimental outcomes revealed that modified graphene showed strong dispersion in the water compared to graphene with minimum settling with time. The modified graphene showed stable dispersion in different pH and salinity solutions. GrO-ArG prominently reduced the linear swelling of bentonite clay (Na-Ben). It was observed that the decline in linear swelling was the function of the concentration of GrO-ArG, such as 1 wt% of ArG-GrO-A and ArG-GrO-B reduced the linear swelling by 37.8% and 43.9% correspondingly as compared to deionized water. The zeta potential measurement confirms the adsorption of GrO-ArG with the Na-Ben. The addition of GrO-ArG also revealed a prominent decrease in fluid loss. After the addition of ArG-GrO-A and ArG-GrO-B, the fluid loss declined from 11.3 mL to 8.2 mL and 7.1 mL respectively. A decrease in shear stress was also observed due to the addition of GrO-ArG in the drilling mud. From the experimental findings, it can be inferred that GrO-ArG is a strong candidate that might serve as an alternate green clay swelling inhibitor and fluid loss controller for water-based drilling muds.

Experimental Inspection of the Influence of Chemical Osmosis on Shale Swelling and Subsequent Wellbore Stability

Experimental Inspection of the Influence of Chemical Osmosis on Shale Swelling and Subsequent Wellbore Stability

On the Impact of Temperature on Shale Swelling and Expansion: A Diffuse Double-Layer Perspective

On the Impact of Temperature on Shale Swelling and Expansion: A Diffuse Double-Layer Perspective

Experimental investigation of pyrrolidinium-based ionic liquid as shale swelling inhibitor for water-based drilling fluids

This study evaluated the potential of 1-ethyl-1-methylpyrrolidinium bromide (1E1MPyBr) ionic liquid as a shale swelling inhibitor for water-based mud. Firstly, a linear shale swelling test was conducted to evaluate the ionic liquid's ability to inhibit clay hydration. Moreover, a capillary suction time test was performed to determine the fluid absorbance potential. Besides, particle size distribution analysis and zeta potential were evaluated to determine the ionic liquid effect on the base mud's colloidal distribution and surface charge. Furthermore, the rheological and filtration properties of the ionic liquid-mixed drilling mud were investigated. Finally, The X-ray diffraction analysis was conducted to evaluate the inhibition mechanism. The findings of this study revealed that the incorporation of 0.3 wt% of pyrrolidinium-based ionic liquid into the drilling mud resulted in a 20% reduction in shale swelling behaviour compared to conventional bentonite mud. The observed increase in particle size, decrease in zeta potential, and lower capillary suction timer values demonstrated the clay inhibition potential of ionic liquids. Moreover, adding the ionic liquid to bentonite mixed with water-based mud led to higher fluid loss and decreased rheological properties. These effects were attributed to the intercalation of ionic liquids into the clay layers, which inhibited swelling and hydration and reduced the water absorbance capacity of clay. Besides, the tested ionic liquid showed corrosion inhibition potential. Based on these results, the pyrrolidinium-based ionic liquid is proffered as an efficient shale swelling inhibition additive for water-based mud.

Performance evaluation of different cationic surfactants as anti-swelling agents for shale formations

In this study, three different novel cationic surfactants decyl-trimethyl-ammonium bromide (S1), Octyl-trimethyl-ammonium bromide (S2), hexyl-trimethyl-ammonium bromide (S3) were used to formulate water-based drilling formulations to comprehend the interactions between drilling fluids components and with wellbore formations. The modified drilling formulations were prepared by incorporating novel surfactants in the base mud along with other additives such as bentonite, PAL-C, xanthan gum, and barite. The effect of the surfactant's chemical structure was assessed by rheology and filtration experiments, and colloidal dispersion stability was determined by particle size distribution analysis and sedimentation tests. The shale swelling inhibition characteristics of surfactant-based formulations were accessed by hot rolling dispersion tests, linear swelling rates, and capillary suction time tests. The performance of surfactant-based formulations for shale swelling inhibition was compared with KCl-based and conventionally used base mud formulations. The surface wettability of shale in the presence of different formulations was assessed by a high-resolution optical tensiometer. Shale inhibition properties of surfactant-based formulations depict that shale dispersion recovery increased to 98% for BS1 formulation compared to all other used formulations. Linear swelling of shale pellet show that the swelling rate of BS1 formulation was only 13% compared to all other formulations. The contact angle experiments showed that the BS1 formulation increased the contact angle of a water droplet and reduced the wettability of drilling fluids. The experimental results showed that S1 surfactant has enhanced shale inhibition characteristics compared to other surfactants and conventionally used shale inhibitors.

Epsom Salt-Based Natural Deep Eutectic Solvent as a Drilling Fluid Additive: A Game-Changer for Shale Swelling Inhibition.

Shale rock swelling poses a significant challenge during drilling a well, leading to issues related to wellbore instability. Water-based mud with specific shale inhibitors is preferred over oil-based drilling mud due to its lower environmental impact. Recently, ionic liquids (ILs) have emerged as potential shale inhibitors due to their adjustable properties and strong electrostatic attraction. However, research has shown that the most commonly used class of ILs (imidazolium) in drilling mud are toxic, non-biodegradable, and expensive. Deep Eutectic Solvents (DESs), the fourth generation of ionic liquids, have been proposed as a cheaper and non-toxic alternative to ILs. However, ammonium salt-based DESs are not truly environmentally friendly. This research explores the utilization of Natural Deep Eutectic Solvent (NADES) based on Epsom salt (a naturally occurring salt) and glycerine as a drilling fluid additive. The drilling mud is prepared according to API 13B-1 standards. Various concentrations of NADES-based mud are tested for yield point, plastic viscosity, and filtration properties for both aged and non-aged samples. The linear swell meter is used to determine the percentage swelling of the NADES-based mud, and the results are compared with the swelling caused by KCl- and EMIM-Cl-based mud. FTIR analysis is conducted to understand the interaction between NADES and clay, while surface tension, d-spacing (XRD), and zeta potential are measured to comprehend the mechanism of swelling inhibition by NADES. The findings reveal that NADES improves the yield point and plastic viscosity of the mud, resulting in a 26% reduction in mudcake thickness and a 30.1% decrease in filtrate volume at a concentration of 1%. NADES achieves a significant 49.14% inhibition of swelling at the optimal concentration of 1%, attributed to its ability to modify surface activity, zeta potential of clay surfaces, and d-spacing of clay layers. Consequently, NADES emerges as a non-toxic, cost-effective, and efficient shale inhibitor that can replace ILs and DESs.

On shale swelling: the unrecognized role of diffusion osmosis

ABSTRACT Currently, drilling operators focus on chemical osmosis as a mechanism to extract water out of shale in order to reduce its pore pressure and increase its strength, however, in doing so, the flux of hydrated ions into shale by means of diffusion osmosis and ionic diffusion is increased. Such practice may lead to an increase in shale’s pore pressure and strength reduction which will definitely negate the beneficial impact of chemical osmosis in combatting wellbore stability problems. For the first time, this work investigated the separate impact of diffusion osmosis on shale’s swelling and subsequent wellbore stability issues. The experimental set-up enabled us to isolate chemical osmosis forces which made diffusion osmosis the only force governing water exchange. Making the water activity of shale equals to that of the aqueous solution disabled chemical osmosis forces and activated ionic diffusion and diffusion osmosis owing to the imposed ionic concentration during the interaction. It was found that diffusion osmosis accompanies ionic diffusion since ions travel with their respective water clouds, also known as associated water. The transport of associated water has caused shale’s swelling in the absence of a water activity gradient (chemical osmosis). This was confirmed through gravimetric water and ion measurements conducted at the end of the linear swelling tests. Results showed that the amount of water exchanged by diffusion osmosis was immense, thus one should not ignore it when designing water-based muds for drilling highly sensitive clays. Results also showed that the amount of water exchanged correlated well with the hydrated diameter of the invading ion. Moreover, results confirmed that the swelling magnitude may be related to the mineralogical composition and cation exchange capacity of shale.

Eco-Friendly Drilling Fluid: Calcium Chloride-Based Natural Deep Eutectic Solvent (NADES) as an All-Rounder Additive

Designing an effective drilling mud is a critical aspect of the drilling process. A well-designed drilling mud should not only provide efficient mud hydraulics but also fulfill three important functions: enhancing mud rheology, inhibiting hydrate formation in deepwater drilling, and suppressing shale swelling when drilling through shale formations. Achieving these functions often requires the use of various additives, but these additives are often expensive, non-biodegradable, and have significant environmental impacts. To address these concerns, researchers have explored the potential applications of ionic liquids and deep eutectic solvents in drilling mud design, which have shown promising results. However, an even more environmentally friendly alternative has emerged in the form of natural deep eutectic solvents (NADES). This research focuses on an in-house-prepared NADES based on calcium chloride and glycerine, with a ratio of 1:4, prepared at 60 °C, and utilizes it as a drilling mud additive following the API 13 B-1 standards and checks its candidacy as a rheology modifier, hydrates, and shale inhibitor. The findings of the study demonstrate that the NADES-based mud significantly improves the overall yield point to plastic viscosity ratio (YP/PV) of the mud, provides good gel strength, and inhibits hydrate formation by up to 80%. Additionally, it has shown an impressive 62.8% inhibition of shale swelling while allowing for 84.1% improved shale recovery. Moreover, the NADES-based mud exhibits a 28% and 25% reduction in mud filtrate and mud cake thickness, respectively, which is further supported by the results of XRD, zeta potential, and surface tension. Based on these positive outcomes, the calcium chloride–glycerine NADES-based mud is recommended as a versatile drilling mud additive suitable for various industrial applications. Furthermore, it presents a more environmentally friendly option compared to traditional additives, addressing concerns about cost, biodegradability, and environmental impact in the drilling process for an ultimate global impact.