Diffusion Osmosis Research Articles

Impact of chemical osmosis, diffusion osmosis and ionic diffusion on drilling mud salinity design

ABSTRACT Wellbore stability problems, especially in reactive shale formations, have gained much attention due to their high cost and technical complications. In this work, the blind use of only chemical osmosis to balance reactive shales, while drilling has been challenged through the use of linear swelling technique and water and ions gravimetric test. Moreover, the compatibility of various aqueous solutions with field shale samples was analysed and a proper mud salinity design method was proposed. Using Na+, K+ and Ca+2 and 100 shale samples and cuttings from a drilling site, a mud salinity (ion’s type and concentration) selection method was proposed. A field case was presented and it was shown that KCl solutions were appropriate to drill shale formations up to 9,717 ft. while NaCl solution was suitable to drill a deeper formation that spans from 9,817 to 10,381 ft. Moreover, CaCl2 solutions were not selected to handle these shales due to their high reactivity and excessive water and ions exchange. Besides chemical osmosis, results showed that water transport may occur due to diffusion osmosis and ionic diffusion. Also, the transport of ions by ionic diffusion was found to be a major destabilizing factor.

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.

Experimental analysis of the impact of ionic concentration and type on shale’s stability: dilute vs. concentrated salt solutions

ABSTRACT Wellbore instability in shale formations is one of the most bothersome problems leading to significant changes in shale’s petrophysical, mechanical, and chemical properties, and could cost billions of dollars annually. Drilling fluid’s ionic composition is one of the factors affecting wellbore stability. This paper investigates the impact of chemical osmosis, ionic diffusion, and diffusion osmosis on the stability of shale, identify the critical salt concentration, and examine the impact of ionic type and concentration on shale’s stability. Experimental methods include utilisation of two different shale cores (I and II), in which each core is cut into several samples, to conduct linear expansion and gravimetric measurement tests using different salt solutions (KCl, NaCl, and CaCl2) of various salt concentrations. Results show that the critical salt concentrations of shale I and II is 8 w/w%. Chemical osmosis is found to be a reliable method for water extraction out of shale if the critical salt concentration value is not surpassed. Beyond this value, ionic diffusion and diffusion osmosis in shale I and II were adversely affecting shale’s stability through swelling. The swelling and gravimetric ions and water uptake tests showed that shale is a leaky semi-permeable membrane, and that chemical osmosis could be jeopardised by ionic transport into shale. In this study, the cation type (Na+, K+, Ca+2) that makes up the salt was varied. The impact of cation type on the stability of shale was clear as the anion type was fixed. Since both cations and anions tend to diffuse into shale in the presence of a concentration gradient, it is proposed for future work to study the combined impact of cation and anion types on shale’s stability by varying the anion and cation types.

Reliability of chemical osmosis as a practical method to extract water out of shale and promote shale’s mechanical stability

Wellbore instability in shale formations is one of the most bothersome problems leading to significant changes in shale’s petrophysical, mechanical, and chemical properties, and could cost billions of dollars annually. Drilling fluid’s ionic composition is one of the factors affecting wellbore stability. This paper investigates the impact of chemical osmosis, ionic diffusion, and diffusion osmosis on the stability of shale, identify the critical salt concentration, and examine the impact of ionic type and concentration on shale stability. Experimental methods include utilization of shale I and II through linear expansion and gravimetric measurement tests using different salts. Results show that the critical salt concentration in shale I and II is 8 w/w%. Chemical osmosis is found to be a reliable method for water extraction out of shale if critical concentration value is not surpassed. Beyond this value, the ionic diffusion and diffusion osmosis in shale I and II were adversely affecting shale’s mechanical and chemical stability. The swelling and gravimetric ions and water uptake tests showed that shale is a leaky semi-permeable membrane, and that chemical osmosis could be jeopardized by ionic transport into shale. However, the water transport impact on changes in the thickness of diffuse double layer of clay needs to be investigated. The impact of temperature on water and ions transportation into shale needs to be examined to reflect in-situ conditions. In this study, the cation type that makes up the salt was varied while the anion type was fixed. Since both cations and anions tend to diffuse into shale in the presence of a concentration gradient, it is recommended to vary the anion type to study the combined impact of cation and anion type on shale stability.

Time-Dependent Measurements of Shale's Compressive Strength When Contacting Ionic Solutions.

Time-dependent measurements of uniaxial compressive strength, and ionic and water transport were conducted to analyze the alteration of shale’s strength, as a function of time, when exposed to aqueous solutions. Results showed that the compressive strength of shale is time-dependent, and it relies highly on water activity and ionic concentration differences between shale and aqueous solutions. Data obtained from this work showed that time-dependent water and ion transport into shale correlated well with compressive strength measurements. It was revealed that initial water extraction by osmosis strengthened shale until ions and their associated water clouds invaded shale causing reduction in its strength. It is quite possible that water flow by diffusion osmosis may have counteracted water flow by chemical osmosis rendering ionic diffusion as the primary regulator on shale strength alteration. Furthermore, it was found that alteration of compressive strength when it interacted with aqueous solutions could be adequately explained within the confines of chemical osmosis, ionic diffusion, and diffusion osmosis. Data suggests that the impact of chemical osmosis on compressive strength is observed earlier than ionic diffusion and diffusion osmosis. Data also showed that potassium ions seem to contribute to the enhancement of the compressive strength of shale.

On the consequences of shale desaturation: physicochemical and mechanical perspectives

Adsorption of water by desaturated shale could be misinterpreted as osmotic swelling. If the saturation state of shale is not known, one should not presume that osmosis is responsible for water adsorption and resultant swelling. Such presumption may overlook the fact that spontaneous imbibition could be responsible for most water adsorption and apparent swelling in desaturated shale. This work examines mechanisms responsible for water adsorption by desaturated shale and proposes a superimposing technique that separate water adsorption by imbibition from that by chemical and diffusion osmosis. Also, this work investigates the impact of desaturation on physicochemical and mechanical properties of shale using gravimetric measurements, ASTM methods., X-ray diffraction and pore fluid’s chemical composition analysis. Results show that water transport in desaturated shale is falsely attributed to osmotic swelling and that spontaneous imbibition is the main force driving water transport. In the absence of diffusion osmosis and hydraulic flow, amount of water adsorbed via spontaneous imbibition is 2–3 times higher than that adsorbed by chemical osmosis. For desaturated shale, results revealed that reduction in water activity is non- linearly proportional to desaturation (drying) time. Results also showed that compressive strength and Young’s modulus increased non-linearly as moisture content decreased.

Role of diffusion osmosis on the mechanical and petrophysical alterations of shale when interacting with aqueous solutions

ABSTRACT Several experimental procedures were employed to investigate the impact of salt type and concentration on shale’s effective porosity and compressive strength. The use of a special gravimetric technique made it possible to quantify water and ion transport into shale when interacting with NaCl, KCl, and CaCl2 solutions. Results showed an increase in shale’s effective porosity when dilute solutions (less than 5% w/w) interacted with shale. On the other hand, a decrease in shale’s effective porosity was observed when the concentration of salt increased to 10%, 15% and 20% w/w. It is argued that the increase in porosity at low salt concentrations was due to cementation degradation caused by ionic invasion without loss of grain cohesion and mechanical stability. Decrease in porosity when higher concentrations of salts were used was apparently due to loss of grain cohesion and pore structure integrity caused by the combined effects of ionic diffusion and diffusion osmosis. These observations were confirmed by shale’s compressive strength measurements. The results showed a negligible change in compressive strength of shale when it interacted with 5% NaCl, KCl, and CaCl2 solutions. In contrast, a considerable reduction in shale’s compressive strength was recorded for higher salt concentrations (10%, 15% and 20% w/w).

Development of an interfacial osmosis diffusion method to prepare imine-based covalent organic polymer electrocatalysts for the oxygen evolution reaction

Herein, we report an interfacial osmosis diffusion strategy for sythesising a new covalent organic polymer (COP) at the solvent interface under room temperature ambient conditions. The feasibility of this new approach was first demonstrated by synthesizing a known covalent organic framework (COF) material, TpPa-1. Then, a novel imine-based COP named BEAB (BEA = bis-(2-ethynylaniline), BEB=bis-(2-ethynylbenzaldehyde), BEA+BEB=BEAB) with precisely controlled distribution of nitrogen was prepared using the same method, after which Co, Fe and Ni transition metals were incorporated into the structure to form BEAB-metal complexes, which were then explored as electrocatalysts for the oxygen evolution reaction (OER). Among the various BEAB-metal complexes, BEAB-Co exhibited the best OER performance with a low overpotential of 320 mV at 10 mA cm−2, a Tafel slope of 57 mV dec−1 with only a small potential difference of 7 mV at 10 mA cm−2 after 10 h of continuous electrolysis, indicating the excellent durability and structural integrity of the complex. These promising properties could be attributed to efficient charge transport on the conductive π-conjugated polymeric chain, and the abundant N chelating sites on the BEAB. This work provides a facile and fast way to produce a COP in large quantities in an efficient manner, which would greatly benefit the large-scale practical application of these kinds of functional materials.

Experimental study of the osmotic effect on shale matrix imbibition process in gas reservoirs

Speaking of imbibition, it usually refers to the displacement of the non-wetting phase by the wetting phase in a porous medium by capillary action. Most of the focuses in the technical literature of this area have been given to the factors related to capillarity and viscous forces with or without gravity effect. However, solute (ions/salt)-rock interaction has been overlooked for long, which is also a critical imbibition mechanism as solvent (water)-rock interaction. Moreover, different from conventional sandstone and limestone, shale gas formations exhibited semi-permeable properties due to high clay content and unique pore structure, which result in the osmotic effect. This may explain the low amount of fracturing fluid flowback and the osmosis diffusion-enhanced imbibition could be a critical recovery mechanism from the low permeability rock.Hence, it is important to investigate the imbibition behavior in the fracture network of stimulated reservoir volume which created by hydraulic fracturing. In this study, shale samples from Horn River shale gas formation were used to conduct spontaneous imbibition tests to study the effect of capillarity and osmosis diffusion. To simulate the process during hydraulic fracturing, the fluids with different salinities were used in the experiment.The experimental results showed that the clay content in shale samples determined how capillarity and osmosis diffusion influenced the imbibition process. The linear relationship between imbibition mass and square root of time was observed only in the lower clay content shale samples. The imbibition process in these samples was dominated only by capillarity. That relationship was used to predict the imbibition mass during the water flooding work. On the other hand, in the higher clay content shale samples, due to osmotic effect, the relationship between imbibition mass and square root of time was non-linear.The results of this study can help people understand the imbibition process of the fracturing fluid when fluid contacts with the shale rock during hydraulic fracturing. Adjusting the salinity of the fracturing fluid to change osmotic effect in the shale formation can be used to control fracturing fluid imbibition.

Mechanisms of imbibition during hydraulic fracturing in shale formations

Abstract Hydraulic fracturing technology has been proven to significantly increase production from shale gas and oil formations. However, during a hydraulic fracturing treatment a large percentage of the fracturing fluid usually remains unrecovered. Therefore, the reasons for this low fracturing fluid recovery have become the focus of many studies. Imbibition of fracturing fluid in the shale is believed to be one of the explanations for the low amount of the fracture fluid recovery. The fluid is imbibed by the shale matrix and trapped inside the rock. Capillarity has generally been the primary mechanism considered during imbibition in conventional formations, such as sandstone and carbonate formations. In shale formations osmosis diffusion also exists and cannot be ignored because the clay in the shale rock functions similarly to that of a membrane. It is believed that both capillarity and osmosis diffusion work together to result in imbibition during hydraulic fracturing in shale formations. This paper investigates the effects of both capillarity and osmosis diffusion as the key mechanisms in fluid imbibition through simultaneous imbibition experiments. The results of these tests illustrate that the imbibition process is dominated by both capillarity and osmosis diffusion. This domination is based on the change of water saturation in shale rocks. In addition, the capillary and osmotic pressures, which influence the imbibed rate, can be qualitatively determined by the contact angle and salinity, respectively. Higher capillary and osmotic pressures correlate to faster rates of imbibition. This study, which examines the mechanisms of imbibition and their influences, can improve the understanding of fluid behavior when imbibition occurs during hydraulic fracturing in shale formations. The understanding of this behavior is useful for further simulation research.

The impact of water content and ionic diffusion on the uniaxial compressive strength of shale

Experimental data showed that water content has a profound influence on the uniaxial compressive strength of shale. Testing has shown a great decrease in the uniaxial compressive strength as the water content increases. Regression analysis was used in this work to develop a general equation for predicting uniaxial compressive strength of shale from the available information on its water content and dry uniaxial compressive strength.The impact of ionic diffusion on the compressive strength of shale has been investigated under three saturation conditions: wet shale, dry shale and chemically balanced wet shale. A chemically balanced shale has a water activity (chemical potential) which equals that of the test solution. Results show that, except for potassium ions, ionic diffusion has reduced the compressive strength of all studied shales. It has also been confirmed that diffusion osmosis has a detrimental effect on the mechanical stability of shale by reducing its compressive strength. Furthermore, it was found that when the water activity of shale is slightly higher than that of the test solution, chemical osmosis plays a major role in strengthening the shale by extracting water out of the shale. However, when the water activity of the shale is much higher than that of the test solution, diffusion osmosis weakens the shale. In other words, the detrimental impact of diffusion osmosis overtakes the beneficial effect of chemical osmosis.Moreover, this work shows that compressive strength measurements for completely dried shale could be misleading due to the development of capillary forces that significantly modifies the compressive strength of shale.Finally, the impact of ionic diffusion on the compressive strength of shale was carried out in the absence of both chemical osmosis and capillary forces. Results show that the invasion of sodium and calcium ions into shale reduced its compressive strength considerably while the invasion of potassium ions enhanced its compressive strength.

A Novel Experimental Technique to Monitor the Time-Dependent Water and Ions Uptake when Shale Interacts with Aqueous Solutions

The time-dependent water and ions uptake when shale interacts with aqueous solutions is quantified using a combination of immersion and gravimetric techniques. Results show that when shale interacts with salt solutions, water uptake into shale goes through three distinct stages; water movement out of shale (due to chemical osmosis), water movement into shale (due to diffusion osmosis) and stationary state (equilibrium stage). This work shows that chemical osmosis dominates water movement in early times while diffusion osmosis takes over later. In addition, it is shown that the amount of water movement due to chemical osmosis depends on the chemical potential gradient while the amount of water movement due to diffusion osmosis is highly related to the ionic concentration imbalance. In addition, the amount of ions uptake into shale at equilibrium is shown to depend on the type and concentration of salt solution. Furthermore, this work shows that potassium ion has a strengthening effect on shale while sodium and calcium ions have a weakening effect on shale. Results also show that the shale’s compressive strength alteration is greatly influenced by the type and concentration of the salt solution. Furthermore, the shale’s compressive strength alteration is shown to be time dependent and correlates very well with the time-dependent flux of water and ions. Finally, it is shown that chemical osmosis and diffusion osmosis take place simultaneously when shale interacts with water-based muds. The overall impact on shale stability is governed by the net water flow resulting from chemical osmosis and diffusion osmosis.

An Experimental Investigation of the Impact of Diffusion Osmosis and Chemical Osmosis on the Stability of Shales

Wellbore instability in shales is the most challenging and costly issue in drilling operations. Wellbore instability in shales can be attributed to many factors, some of which have been well studied and documented. However, the physicochemical and mechanical properties alterations in shales that eventually lead to wellbore failure have been largely ignored. Water and ion movements in and out of shales play a major role in the alteration of the physicochemical and mechanical properties of shales, thus leading to wellbore instability problems and possible hole collapse. Water and ions can move in and out of shales by many mechanisms, including, but not limited to, diffusion osmosis, chemical osmosis, convective flow, and capillary suction. This work presents experimental data analyzing the impact of chemical osmosis and diffusion osmosis on water and ion movements when shale interacts with drilling fluids. The adopted experimental work minimized the effect of convective flow and capillary suction. Results show that water movement is not only controlled by chemical osmosis (water activity) as previously thought but is also influenced by diffusion osmosis. This insight provides information and guidelines to optimize drilling fluids to effectively control and mitigate wellbore instability when drilling through troublesome shale.

An Experimental Investigation on the Stability and Reservoir Hydrocarbon Capacity of Shales

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 121451, ’An Experimental Investigation on the Impact of Capillary Pressure, Diffusion Osmosis, and Chemical Osmosis on the Stability and Reservoir Hydrocarbon Capacity of Shales,’ by Talal M. AL-Bazali, U. of Kuwait; Jianguo Zhang, SPE, BP plc; and Martin E. Chenevert, SPE, and Mukul M. Sharma, SPE, U. of Texas at Austin, originally prepared for the 2009 SPE Offshore Europe Oil and Gas Conference and Exhibition, Aberdeen, 8-11 September. The paper has not been peer reviewed. Wellbore instability in shales is the most challenging and costly issue in drilling operations. Wellbore instability in shales can be attributed to many factors, some of which have been well studied and documented. However, the physicochemical- and mechanical-properties alterations in shales that eventually lead to wellbore failure largely have been ignored. Water and ions movement in and out of shales plays a major role in the alteration of the physicochemical and mechanical properties of shales, thus leading to wellbore-instability problems and possible hole collapse. Introduction The unfavorable interaction between shale and drilling fluids is considered to be the primary cause of many wellbore-instability problems. Such interactions are very complicated and include mechanical, chemical, physical, hydraulic, thermal, and electrical phenomena. The overall effect of these interactions mainly is related to the movement of water and ions into or out of shales. The physicochemical and mechanical properties of shale around the wellbore, such as permeability, strength, pore pressure, and elastic modulus, can be altered greatly by such movement. It is well-accepted that the adsorption of water results in shale-strength and elastic-modulus decrease, in swelling, and in pore pressure increase. These changes around the wellbore may cause wellbore instability problems during drilling and completion operations. The magnitude of water movement and the effect of absorbed water on shale properties are influenced by the presence of ions in the solution. Ionic diffusion also may result in the movement of ions into the shale formation, resulting in chemical alteration. Water and ions can move in and out of shales by many complicated mechanisms. These mechanisms include, but are not limited to, chemical osmosis, diffusion osmosis, capillary suction, and convective flow. In the full-length paper, the focus is on the diffusive flow of water and ions. Specifically, the effect of both chemical osmosis and diffusion osmosis on shale alteration was investigated. The experimental setup and procedure were designed to minimize the effect of convective and capillary flow. Shales play a major role in petroleum exploration and production because they commonly are considered to be both source rocks and seals. Their ability to exhibit good sealing characteristics arises from their small, water-wet pores. The small pore throats in shales are responsible for generating high capillary pressures, which exclude hydrocarbons.

Technology Focus: Sand Management and Frac Pack (October 2010)

Technology Focus As our wellbore-integrity- and sand-management-modeling prowess grows from the laboratory to the field, the quest for reliable environmentally responsible energy resources continues to challenge, and in some cases demands, us to accelerate development of new well-system-integrity applications for the field. Well-engineering-systems design benefits from formation-failure-prediction modeling capabilities that can be verified in the field by a more diverse array of measurement techniques in both open- and cased-hole environments, even extending to the overburden by use of geophysical-survey techniques. Still, we are challenged to integrate the formation-failure predictions and observations with well-systems hardware and architecture that define the entire production system, from the completion up to the wellhead, and on through the surface facilities. Papers selected for this month’s feature start with risk-based well integrity for CO2 storage in the subsurface. To ensure CO2 containment over time, well-integrity-modeling technology is pushed to its limits. The risk-based approach is introduced to manage the complexities of long-term storage. A second paper looks at the basics of sand-exclusion-performance evaluation after a change in long-standing completion practice was made to shorten project-payout time. The paper examines this decision from the viewpoint of longer-term production performance. The third paper deals with wellbore integrity in chemically active shale formations. The work experimentally investigates the effects of capillary pressure and osmotic forces on shale-swelling behavior. The study questions the practice of adjusting only the salinity concentrations in the aqueous phase of drilling muds to enhance hole stability by pulling water from the shales into the borehole to retard hydration (chemical osmosis). Could the highest saline concentrations cause associated water to move into the shales through ion transfer by diffusion osmosis? Sand Management and Frac Pack additional reading available at OnePetro: www.onepetro.org SPE 128038 • “Improved Selection Criteria for Sand Control—When Are ‘Fines’ Fines?” by Michael Byrne, SPE, Senergy, et al. SPE 127931 • “State-of-the-Art Screen Selection for Standalone-Screen Applications” by R.A. Chanpura, Schlumberger, et al. SPE 123478 • “A Comprehensive Study of Sanding Rate From a Gas Field: From Reservoir, Completion, and Production, to Surface Facilities,” by Gang Han, Hess Corporation, et al.

An Experimental Investigation on the Impact of Diffusion Osmosis, Chemical Osmosis, and Capillary Suction on Shale Alteration

An Experimental Investigation on the Impact of Diffusion Osmosis, Chemical Osmosis, and Capillary Suction on Shale Alteration

Chemical osmosis in compacted clayey material and the prediction of water transport

Compacted clay membranes are semi-permeable if the double layers of the clay particles overlap, thereby restricting the passage of ions. Semi-permeability is quantified by the reflection coefficient σ. In the design of clay liners for waste contaminant water, transport as a result of coupled transport is rarely taken into account. Where large salt concentration differences exist across natural or man-made clay barriers, water may be transported as a result of chemical osmosis. In a flexible wall permeameter two samples of a commercially available Wyoming Na-bentonite were subjected to a chemical gradient in order to monitor water transport and to obtain values for the reflection coefficient. In both experiments water transport by chemical osmosis was observed, and reflection coefficients of 0.003 and 0.001 were obtained, which are significantly lower than those predicted by the Fritz–Marine model and values obtained from Bolt (1982). However, the values are in good agreement with those obtained by Bresler (1973). Both experiments showed a period of 50 h of linear pressure increase as a result of chemical osmosis, after which the pressure difference dropped, i.e. after reaching a maximum pressure difference the water flow was reversed. The reversal of the water flow is consistent with diffusion osmosis, which is the transport of water as a result of the diffusion of ions in the absence of an externally applied electrical field. However, diffusion osmosis is limited to clays of low cation exchange capacity with high pore water concentrations and porosities.

Approche osmotique de l'hydratation du stratum corneum

Summary An osmotic approach to a study of hydration of the stratum corneum At first Middleton, in his classic studies, explains the water sorption of stratum corneum by osmotic processes. To follow Middleton, and in order to study water osmosis diffusion, we made an osmotic model of stratum corneum (OMSC). The OMSC was constituted by 0.8 g of sheep wool, which was closed in a dialysis bag. When the OMSC was placed in the water, its weight increased, due to water diffusing through the membrane to bind with the protein. The rate of sorption was slow, but the value was about the same as that which Scheuplein has observed for the stratum corneum. At saturation, the weight of 'bound water'was 13 times greater than the weight of keratine. The components of Natural Moisturizing Factor and glycerol enhance the sorption rate and the weight fraction 'bound water'at saturation. The best component is urea. This observation suggests that humectants increase the number of water-binding sites of keratin. The OMSC could allow preliminary tests of water-soluble skin moisturizers.