Applied Clay Science 105–106 (2015) 78–88

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Applied Clay Science

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Research paper

Experimental investigation of the effect of henna extract on the swellingof sodium bentonite in aqueous solution

Aghil Moslemizadeh a, Seyed Reza Shadizadeh a,⁎, Mehdi Moomenie b

a Department of Petroleum Engineering, Ahwaz Faculty of Petroleum Engineering, Petroleum University of Technology, Abadan, Iranb National Iranian Drilling Company (NIDC), Ahwaz, Iran

⁎ Corresponding author at: Abadan Faculty of PetroUniversity of Technology, Northern Bowarde, Abadan 631

E-mail address: shadizadeh@put.ac.ir (S.R. Shadizadeh

http://dx.doi.org/10.1016/j.clay.2014.12.0250169-1317/© 2014 Elsevier B.V. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 31 August 2014Received in revised form 18 December 2014Accepted 19 December 2014Available online xxxx

Keywords:Henna extractClay stabilizersSodium bentoniteConductivitySwellingAdsorption

This paper reports for the first time the effect of Henna extract as a new, naturally occurring, and ecofriendly ad-ditive on swelling of sodium bentonite in aqueous solution. This is performed via a number ofmethods includingdynamic linear swelling test in two distinct temperatures of 28 °C and 82 °C, sodium bentonite inhibition and so-dium bentonite sedimentation tests. The results indicated that inhibition properties of Henna extract are a func-tion of its concentration and are comparable with potassium chloride and polyamine as the two most commonclay stabilizers. Inhibition mechanism was assessed using adsorption measurements obtained by conductivitytechnique, contact angle measurements via the sessile drop method, and scanning electron microscopy (SEM)analysis. Results of adsorption measurements indicated that Henna extract has a lower adsorption isotherm inalkaline medium (pH = 9) compared to natural medium (acidotic). Adsorption of Henna extract increaseshydrophobicity of sodium bentonite particle surface; nevertheless, this adsorption mechanism is slightlyweakened in alkaline medium due to the effect of caustic soda as a pH adjustment agent. SEM analysis demon-strated that sodium bentonite particles have an extended area when exposed to Henna extract solution insteadof distilled water indicating sodium bentonite particle stability. Henna extract has deflocculating properties atlow concentrations (especially up to 0.2 mass%); yet it indicates good inhibition properties to sodium bentoniteswelling at a concentration several times higher than that of deflocculating concentration, about 3 mass%.Inhibition properties could be attributed to the hydrogen bonding between the hydroxyl group of Hennaextract constituents and oxygen atoms available on silica groups of sodium bentonite, especially to the lawsone(2-hydroxy-1,4 napthaquinone) constituent.

© 2014 Elsevier B.V. All rights reserved.

1. Introduction

Wellbore instability is one of the important as well as threateningfactors in raising the cost of drilling operations. According to the statistics(Zeynali, 2012) wellbore instabilities in oil and gas wells could result in awaste of U$$ 1 billion per year worldwide. Roots of wellbore instabilitycan be divided as mechanical and physic-chemical effects (Tan et al.,1996; Osuji et al., 2008). Unlike mechanical effect, physico-chemicaleffects are time dependent (Manohar Lal and Amoco, 1999) and are adirect result of interaction between the rock (especially shale) anddrilling fluids.

Shales can be defined as sedimentary rocks with laminated layeredcharacteristics and high clay content (Diaz-Perez et al., 2007). Theserocks are allocated for about 75% of drilled formations and source of90% of wellbore stability problems (Steiger and Leung, 1992) and areknown as troublesome formations for drilling (Chenevert andAmanullah, 2001; Akhtarmanesh et al., 2013). Non-clay minerals are

leum Engineering, Petroleum8714331, Iran.).

also present in shale but they are generally considered inert makingcontributions. Therefore, swelling and dispersion properties of aparticular shale are functions of the amount and types of clay mineralspresent (Steiger, 1982). Among all the clays, sodiumsaturated smectiteshave attracted a lot of interest, mainly owing to their high swelling po-tential and their occurrence frequencies during drilling operations(Anderson et al., 2010). Exposure of water sensitive shales, especiallysodium saturated smectites, to the conventional water-based drillingfluids results in their hydration and swelling due to water adsorptionwhich in effect leads to more drilling problems.

Clay swelling occurs under two consecutive regimes including theinner crystalline swelling and osmotic swelling (Madsen and Müller-Vonmoos, 1989). The swelling process can be defined as a phenomenonin which water molecules surround a clay crystal structure and positionthemselves to increase the structure's c-spacing, thus resulting in an in-crease in volume (Patel et al., 2007b). Although oil-basedmudshave a su-perior performance such as excellent shale inhibition, wellbore stability,lubricity, anti-accretion properties, contamination resistance and possi-bility of reuse (Chegny et al., 2008), the use of these fluids to controlclay rich shales has been limited due to their high cost and environmentalrestrictions (Clark and Benaissa, 1993; Mody et al., 2002). Up to date,

Nomenclature

AcronymsXRD X-Ray DiffractionXRF X-Ray FluorescenceSEM Scanning Electron MicroscopyPHPA Partially Hydrolyzed PolyacrylamideLOI Loss On IgnitionLSCA Linear Swelling Cap AssemblyPPM Part Per Million

Variablesq Adsorption of Henna extract on sodium bentonite sam-

ple particles, mg/g sodium bentonite samplemtot.solution Total mass of solution in original bulk solutions, gc° Henna extract concentration in initial solution before

equilibrated with sodium bentonite sample, ppmc Henna extract concentration in aqueous solution after

equilibrated with sodium bentonite sample, ppmmclay Total mass of sodium bentonite sample added,

79A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

various drilling fluid additives namely “clay stabilizers” that can inhibitclay swelling have been introduced and utilized to strengthen the clayrich shales compared to water-based drilling fluids. Potassium chlorideknown as a commonly clay stabilizer has been utilized from severalpast decades up to date which has a high performance in controllingthe clay swelling owing to the cationic size and hydrational energy(Pruett, 1987). Presence of potassium ion in water-based drilling fluidsat a concentration above 1 Wt%, fails these fluids according to themysid shrimp bioassay test (Anderson et al., 2010). Therefore, it can beclaimed with certainty that high concentration of potassium chloriderequired to inhibition could yield harmful effects as adversely affectingthe environment including the high disposal costs, high fluid loss due tohigh clay flocculation (Zhong et al., 2011), and higher corrosion rateslike any high salinity aqueous solution (Clark et al., 1976). Setting asidethe aforementioneddrawbacks, the use of potassiumchloride in conjunc-tion of partially hydrolyzed polyacrylamide (PHPA) has been recom-mended to control the water sensitive shales (Clark et al., 1976).Quaternary amine salts have a high inhibition property. However, a num-ber of disadvantages including their toxicity (tetra methyl ammoniumchloride and high molecular weight quaternary amine), flocculation offluids with high solid concentration, and incompatibility with anionicdrilling fluids additives are associated with these salts which restricttheir applications (Patel et al., 2007a). The ability of polyetheraminecomponents in suppressing the swelling potential has already been in-vestigated (Qu et al., 2009; Wang et al., 2011; Zhong et al., 2011).Zhong et al. (2012) indicated the superior inhibitive properties of poly(oxypropylene)–amidoamine, which caused a significant reduction ofhydration and swelling. Recent studies have revealed the high applicabil-ity of dopamine (Xuan et al., 2013) and bis (hexamethylene) triamine(Zhong et al., 2013) in clay swelling reduction.

According to previous discussions, defects of clay stabilizers aremorerelated to their toxicity, high costs, and corrosion. Therefore, finding theappropriate clay stabilizers free from these problems is highly essential.The primary aim of this study is to implement of Henna extract, a naturaldye, as new, naturally occurring, and ecofriendly additive to investigateits effect on swelling of sodium bentonite. Motivations behind thisstudy were the some of the fascinating properties of Henna extractsuch as being a naturally occurringmaterial and thus its environmentallyfriendly characteristics, acting as an anti-corrosion in various metallicmediums (Al‐Sehaibani, 2000; Chetouani and Hammouti, 2003; El-Etre

et al., 2005; Ostovari et al., 2009; Abdollahi and Shadizadeh, 2012),decreasing the hydrophilic properties of sandstone (Abdollahi, 2011;Abdollahi and Shadizadeh, 2013), its low cost and wide availability. Inthe present work, adsorption of Henna extract on non-prehydrated sodi-um bentonite was investigated by conductivity method. The effect ofHenna extract on sodium bentonite swelling was also assessed througha combination of dynamic linear swelling, sodium bentonite inhibition,and sodium bentonite precipitation tests. Wettability of sodium benton-ite film modified with Henna extract was investigated using contactanglemeasurement via sessile dropmethod. Finally, interaction betweenthe Henna extract and sodium bentonite was observed by scanning elec-tron microscopy (SEM) analysis.

2. Experimental

2.1. Materials

2.1.1. Henna extractLawsonia inermis L, which is commonly referred to “Henna” is a

shrub or small tree frequently cultivated in India, Pakistan, Egypt,Yemen, Iran, and Afghanistan (Ali et al., 2009). It has been reportedthat leaves of Henna contain lawsone, gallic acid, glucose, fats, resine,mucilage and traces of alkaloid (Chaudhary et al., 2010). In currentstudy, Henna extract that is obtained from leaves of Henna was pur-chased from Ebnemasouyeh Company, Tehran, Iran. The main consti-tutes of Henna extract are lawsone (2-hydroxy-1,4 napthaquinone,C10H6O3), gallic acid (3,4,5-trihydroxybenzoic acid, C7H6O5), dextrose(α − D -Glocose, C6H12O6), and tannic acid which were characterizedusing gas chromatography, mass spectrometry, and methanolysis bymethanol and sulfuric acid (Fig. 1) (Ostovari et al., 2009). Humanshave employed Henna containing lawsone (principle coloring matter)as hair dye, body paint, and tattoo dye for more than 4000 years(Kirkland and Marzin, 2003). Lawsone can be used as a sensitivecyanide and acetate sensor due to several specifications including capa-bility of hydrogen bonding with anions by the hydroxyl of the enol instructure, containing conjugated ketone that is suitable conjugate or nu-cleophilic addition of strong nucleophiles such as cyanide, and contain-ing naphthoquinone chromophore as a signaling unit (Hijji et al., 2012).Henna extract powder has brown color with special odor, is soluble inwater (with special pH curve as shown in Fig. 2) and alcohol. Propertiesof Henna extract are summarized in Table 1.

2.1.2. Sodium bentoniteSodium bentonitewith highmontmorillonite content and cation ex-

change capacity of 66.5meq/100 g (determined bymethyleneblue test)was obtained fromParsDrilling Fluid Company, Tehran, Iran. X-rayfluo-rescence (XRF) and X-ray diffraction (XRD)were implemented to char-acterize the chemical and semi-quantitative mineral compositions ofsodium bentonite. The chemical and semi-quantitative mineral compo-sitions of sodium bentonite are presented in Table 2. LOI demonstratesloss on ignition that is related to the volatile components.

2.2. Methods

2.2.1. Adsorption measurementsThe adsorption isotherms of Henna extract were determined using

conductivity method both in natural pH and adjusted pH of 9 (usingcaustic soda solution). The adsorption tests were carried out in a num-ber of consecutive steps including: a) preparing different concentra-tions of Henna extract aqueous solution both in natural pH andadjusted pH of 9, b) measuring the conductivity of each series solutionsby Sartorios PP-20 conductivity meter, c) plotting the conductivity ver-sus concentration for each series solutions as a reference conductivitycurve, d) adding 0.5 g of dried sodium bentonite powder (at 105 °C )to 100 ml of each solutions, e) stirring the dispersions by magnetic stir-rer for 24 h to reach equilibrium, f) centrifuging the certain amount of

Fig. 1. Representative chromatogram and corresponding mass spectra of Henna extract. Peaks: 1, lawsone; 2, gallic acid; 3, dextrose; x, unknown (Ostovari et al., 2009).

80 A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

dispersion in centrifuge tube at 6000 rpm for 2 h, g) pouring the upperpart of supernatant in small graduated cylinder, h) measuring the con-ductivity of supernatant. All adsorption tests were performed in 28 °Cand atmospheric condition. The method of Henna extract adsorption onthe sodium bentonite is based on determining the Henna extract concen-tration in aqueous phase before and after adsorption. Amount of Hennaextract adsorption on sodium bentonite using this method can be deter-mined by the following equation (Ahmadi and Shadizadeh, 2013).

q ¼ mtot:solution � c�−cð Þmsample

� 10−3 ð1Þ

where q is Henna extract adsorption on sodium bentonite sample-particles,mg/g-sodiumbentonite sample;mtot.solution the totalmass of so-lution in original bulk solution, g; c° the Henna extract concentration ininitial solution before equilibrium with sodium bentonite sample, ppm;c the Henna extract concentration in aqueous solution after equilibriumwith sodium bentonite sample, ppm; and msample is the total mass of

6.31

4.744.64 4.6 4.61 4.62 4.61

4

4.5

5

5.5

6

6.5

0 1 2 3 4 5 6 7 8 9

pH

Henna extract concentration mass%

Fig. 2. pH of different concentrations of Henna extract in distilled water.

sodium bentonite sample, g. The flow chart of adsorption measurementsis presented in Fig. 3. Thismethodwas found to provide fairly accurate re-sult with an error of less than 4% for all the measurements.

2.2.2. Dynamic linear swelling testsDynamics swelling test was carried out in multiple steps including:

a) compressing 10 g of sodium bentonite powder under a pressure of41 MPa for 30 min using hydraulic compactor, b) placing preparedwafer sample in linear swelling cup assembly (LSCA) located betweenthe stirring hot plate and linear variable differential transducer,c) pouring test fluid in the LSCA, d) inserting thermocouple in theLSCA, e) adjusting stirring hot plate in desired temperature and stir(fluid sample is in agitation condition by magnetic stir designed at bot-tom of LSCA), f) recording linear swelling data as a function of time. Toinvestigate the effect of Henna extract on swelling of sodium bentonite,different concentrations of Henna extract solution were prepared andtheir pHwas subsequently adjusted to 9. Performance of the Henna ex-tract was compared with two most commonly clay stabilizers namelypotassium chloride and polyamine. The tests were conducted at twodistinct temperatures (28 °C and 82 °C) and atmospheric pressurecondition.

Table 1Properties of Henna extract.

Product Total extract powder of Lawsonia inermis (Henna)

Used part LeavesColor BrownOdor Specific odorSolubility in water SolubleSolubility in alcohol SolublePH value See Fig. 2LOD (105 °C/6 h) 5%Total ash ( 550 °C/4 h) 14.36%Description Fine powderMajor applications Anti-corrosion, hair and skin pigments, shampoo

Table 2Chemical and semi-quantitative mineral compositions of sodium bentonite used;obtained from XRD and XRF respectively.

Chemicalcomposition

Mass percentagemass%

Mineralscomposition

Mass percentagemass%

SiO2 58.74 Montmorillonite 61.5Al2O3 14.86 Quartz 9Fe2O3 4.02 Calcite 0.5CaO 1.42 Gypsum 1Na2O 3.86 Anorthite 2K2O 0.31 Cristobalite 10.5MgO 2.58 Feldspar 14.5TiO2 0.641 Muscovite (mica) 1MnO 0.076 – –

P2O5 0.066 – –

SO3 0.061 – –

L.O.I 13.07 – –

81A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

2.2.3. Sodium bentonite inhibition testsThe bentonite inhibition test is used to determine the ability of a

product to prevent bentonite from yielding and tomaintain a low rheo-logical profile (Patel, 2009). This test was carried out by preparing thedifferent concentrations of Henna extract aqueous solutions including0.2 mas%, 1.5 mass%, and 3 mass% (in adjusted pH of 9), treating the400 g of distilled water and each Henna extract aqueous solution with10 g of sodiumbentonite atmedium shear rate (stirring for 30minutes),pouring the fluid sample in aging cell, and finally heating the aging cellat 82 °C for 16h by rolling oven. All sampleswere cooled, their dial read-ings recorded at 60 °C, and then rheological properties including

Fig. 3. A flow chart of adsorption measurements.

apparent viscosity, plastic viscosity, yield point, and gel strength (10-min and 10-sec) were determined. The apparent viscosity, plastic vis-cosity, yield point were calculated from 600 to 300 rpm dial readingsusing the following formula according to the API recommendedpracticeof standard procedure for field testing drilling fluids (API, 1997).

Apparent viscosity AVð Þ ¼ φ600

2cpð Þ ð2Þ

Plastic viscosity PVð Þ ¼ φ600−φ300 cpð Þ ð3Þ

Yield point YPð Þ ¼ φ300−PVð Þ=2 pað Þ ð4Þ

The viscometerwas initially operated at 600 rpm for 10 seconds, andthen followed by a subsequent 10 seconds shut off. The maximumreading attained after starting rotation at 3 rpm is the initial gel strength(10-second gel) in pound per 100 square feet. Fluid sample was re-stirred at 600 rmp for 10 seconds, and after standing for 10 min themaximum reading after starting rotation at 3 rpm was recorded as10-minuts gel strength in pound per 100 square feet. In order to boastan integration in data units being presented, gel strengthwas expressedin Pascal. It should be noted that Henna extract solution of 3 mass%wasalso used in natural pH to investigate the effect of pH of the aqueousme-dium on inhibition performance of Henna extract. A comparison is alsodrawn between the inhibition results of this concentration and those ofpotassium chloride and polyamine solutions in natural pH and similarconcentrations.

2.2.4. Sodium bentonite sedimentation testsSodiumbentonite tends to precipitate in inhibitivemediumandhas a

low potential toward swelling and hydration. Therefore, after a period oftime the clearly visible boundary between the supernatant and the sed-iment became visible. Recording of this boundary as a function of timecould serve as a good indication representing the swelling potential ofsodium bentonite in special inhibitive medium. Sodium bentonite wasused both in prehydrated (sodium bentonite was allowed to hydrate indistilled water for 24 h) and non-prehydrated states. Dispersions ofHenna extract and sodium bentonite were used both in natural pH andadjusted pHof 9 to investigate the effect of pH of aqueousmediumon in-hibition performance of Henna extract. This test is carried out through anumber of steps which are as follows: a) preparing dispersions of Hennaextract and sodium bentonite (in non-prehydrated system, sodium ben-tonite powder was added to Henna extract solution; However, inprehydrated system Henna extract powder was added to prehydratedsodium bentonite solution), b) pouring each dispersion in test tube(with inner diameter of 1 cm and length of 15 cm), c) placing sealedtest tubes in test tube holder, d) recording the sedimentation by h/Hratio (h is height of sediment, cm; H denotes the total height of disper-sion, cm) as a function of time.

2.2.5. Contact angle measurementsStatic contact angle measurements were implemented as a conven-

tional approach to measure the wettability state of sodium bentonite.Theta optical tensiometer equipped to firewall digital camera, environ-mental chamber, and four syringe steel needle was utilized to deter-mine the air–water contact angles. According to the proceduredescribed by Wu (Wu, 2001), contact angle measurements was con-ducted by cleaning the microscope glass slides (2.2 cm × 2.2 cm) withacetone and distilled water, preparing 2 mass% of sodium bentoniteand Henna extract (in different concentrations) dispersions (disper-sionswere used both in natural pH and adjusted pH of 9 using the caus-tic soda solution), covering glass slides with 1.5 ml of prepareddispersions, allowing covered glass slides to dry for 24 h, placing driedglass slides in environment chamber holder of theta apparatus, and de-posing the water droplets on dried glass slides surrounded by air. Theimages of free drop at equilibrium are then captured and saved on the

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80

Swel

ling

(%)

Time (h)

Dis�lled water1 mass% Henna extract3 mass% Henna extract5 mass% Henna extract

Fig. 6. Swelling data of sodiumbentonite exposed to different concentrations ofHenna ex-tract solution at 28 °C.

y = 2382.1x + 189.39R² = 0.997

y = 2950.5x + 191.58R² = 0.9996

y = 1319.9x + 1832.4R² = 0.9978

y = 1549.3x + 2379.3R² = 0.9989

0

2000

4000

6000

8000

10000

12000

0 1 2 3 4 5 6

Con

duct

ivity

(µs/

cm)

Henna extract concentration mass%

Natural pH pH=9

Natural pH pH=9

Fig. 4. Conductivity versus Henna extract concentrations both in natural pH and adjustedpH of 9.

82 A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

computer. Contact angle is obtained afterward via numerically solvingthe Young–Laplace equation for sessile drops and obtaining theLaplacian curve which best matches the drop profile. All the contactangle measurements were performed at 28 °C and atmospheric pres-sure. It should also be noted that themeasurements were repeated sev-eral times for some off-trend samples. All the contact angles measuredaccording to this procedure possessed an error of less than 5%.

2.2.6. SEM observationsInteraction between the Henna extract and sodium bentonite was

observed employing the SEM analysis. Modified sodium bentonite sam-ples were obtained by adding 0.5 g of sodium bentonite to distilledwater and different concentrations of Henna extract aqueous solution,stirring dispersions bymagnetic stirrer for 24 h to reach equilibrium, re-covering the sedimentations after centrifugation of the dispersions at6000 rpm for 2 h, drying the sedimentations at 105 °C for 24 h, andthen sealing dried sedimentations in plastic box. After preparation ofsedimentations, scanning electron microscope model LEO 1455 VPwas implemented to acquire multiple photographs from the samples.Potassium chloride and polyaminewas used for comparison. All the dis-persionswere used in natural pH and tested at temperature of 28 °C andatmospheric pressure.

3. Results and discussion

3.1. Adsorption measurements

The reference conductivity curve of Henna extract aqueous solutionboth in natural pH and adjusted pH of 9 is presented in Fig. 4. Accordingto this Figure, Henna extract solution has higher conductivity curve inthe solution with pH equal to 9 compared to natural pH solution

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6

Ads

orpt

ion

( mg/

g)

Henna extract concentration mass%

Natural pHpH=9

Fig. 5. Adsorption isotherms of Henna extract on non-prehydrated sodium bentonite bothin natural pH and pH adjusted of 9.

owing to the presence of caustic soda added for pH adjustment. Slopeof conductivity curve was changed at approximately 1.5 mass% ofHenna extract both in natural pH and adjusted pH of 9, due to alter-ations in chemical structure of Henna extract constituents when solvingin water. It is generally believed that solution of Henna extract in waterremoves the hydrogen atoms from the chemical structure of the Hennaextract constituents, leading to a consequent reduction in solution pH asindicated in Fig. 2, particularly up to concentrations of 0.2 mass%. Thisphenomenon appears to be retarded significantly at higher concentra-tions upuntil concentrations rangingbetween1 and 2mass% and nearlyvanishes according to the constant pH represented in Fig. 2. The amountof Henna extract adsorbed on non-prehydrated sodium bentonite wascalculated using the Eq. (1). The adsorption isotherms showing the ad-sorption behavior of Henna extract on non-prehydrated sodium ben-tonite both in natural pH and adjusted pH of 9 are presented in Fig. 5.Adsorption of Henna extract on non-prehydrated sodium bentonite in-creases up until concentration of approximately 3mass%, beyondwhichadsorption rate reaches a pseudo plateau. Maximum adsorbed amountsare 92 and 87.08 mg/g-sodium bentonite for natural pH and pH adjust-ed to 9, respectively. Nevertheless, Henna extract has a higher adsorp-tion profile in the solution with natural pH than the solution withmodified pH of 9. This could be attributed to high quantity of causticsoda introduced as alkalinity adjustment agent which adversely affectsthe adsorption of Henna extract on sodium bentonite particles.

3.2. Dynamic linear swelling tests

In the first step, linear swelling of sodium bentonite exposed todistilled water and different concentrations of Henna extract aqueoussolution at two different temperatures of 28 °C and 82 °C was investigat-ed. The results are presented in Figs. 6 and 7 for 28 °C and 82 °C

0

20

40

60

80

100

120

140

160

180

0 10 20 30 40 50 60 70 80

Swel

ling

(%)

Time (h)

Dis�lled water1 mass% Henna extract3 mass% Henna extract5 mass% Henna extract

Fig. 7. Swelling data of sodium bentonite exposed to different concentrations of Hennaextract solution at 82 °C.

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80

Swel

ling

(%)

Time (h)

3 mass% Polyamine

3 mass% Henna extract

3 mass% Potassium chloride

Fig. 10. Swelling data of sodium bentonite exposed to potassium chloride, polyamine, andHenna extract solutions at 82 °C.

0

20

40

60

80

100

120

140

160

180

57.8868.96 67.45

76.990.67

125.09

107.95

160.86Sw

ellin

g (%

)

Fig. 8. Effect of temperature on swelling of sodium bentonite exposed to distilled waterand different concentrations of Henna extract solution after 72 h (cylinders with verticallines: 28 °C; cylinders with horizontal lines: 82 °C).

83A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

temperatures, respectively. For all the samples, swelling curves display asimilar trend with sharp increases within the initial few hours, muchthe same as the swelling behavior reported for montmorillonite in aque-ous solutions (Xuan et al., 2013). Sodium bentonite was observed to fol-low a continuous swelling behavior in distilled water within the wholetest time (72 h)with a swelling degree higher than that of other samples.The swelling rate of sodium bentonite in any concentration of Henna ex-tract was found to be significantly lower than in distilled water at eachtime period and after the accomplishment of each test, revealing the fas-cinatingly favorable impact that Henna extract had on sodium bentoniteswelling. However, at low concentrations of Henna extract (1mass%), so-diumbentonite still continues to swell during thewhole experimental pe-riod even though its swelling rate is lower than that in distilled water. Inother words, the ultimate regime in which swelling rate approaches zerois not observed. On the contrary, swelling curves for higher concentra-tions of Henna extract namely 3 mass%, and 5 mass%, show ultimate re-gime after about 40 h and 25 h for low temperature state (28 °C) andhigh temperature state (82 °C), respectively. Fig. 8 indicates the effect oftemperature on final swelling percentages (after 72 h) of sodium benton-ite exposed to distilled water and different concentrations of Henna ex-tract. Compared with low temperature state, swelling of sodiumbentonite exposed to distilled water and 1 mass%, 3 mass%, 5 mass% ofHenna extract aqueous solution increased by factors of 52.9%, 34.42%,9.45%, and 11.08% at high temperature state, respectively. Therefore, theeffect of temperature on swelling rate of sodium bentonite decreaseswith increases in the concentration of Henna extract in solution(especially for 3 mass%). In much simpler words, the inhibition role ofHenna extract is afflicted by its concentration in aqueous solution forboth test temperatures of 28 °C and 82 °C.

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70

Swel

ling

(%)

Time (h)

3 mass% Polyamine3 mass% Henna extract3 mass% Potassium chloride

Fig. 9. Swelling data of sodium bentonite exposed to potassium chloride, polyamine, andHenna extract solutions at 28 °C.

Continuing, the swelling of sodium bentonite brought into contactwith 3 mass% Henna extract was compared to potassium chloride andpolyamine both in 28 °C and 82 °C, at the same concentration. The re-sults are presented in Figs. 9 and 10 for both temperatures of 28 °Cand 82 °C respectively. In the sameway as of Henna extract, ultimate re-gime for swelling of sodium bentonite exposed to potassium chlorideand polyamine solutions was found to reach earlier for the temperatureof 82 °C as opposed to that of 28 °C. For both temperatures of 28 °C and82 °C, the order of observing the ultimate regime is potassium chloride,polyamine, and Henna extract, respectively. Postponing the swellingphenomenon (i.e. to reach a certain amount of swelling at a longer pe-riod of time) could be thought of as an important factor in wellbore sta-bility of the clay rich shale formations. Figs. 9 and10 indicate clearly thatthe swelling rate of sodiumbentonite exposed toHenna extract solutionin both test temperatures is lower than the other two samples, introduc-ing the Henna extract as an excellent clay stabilizer. In other words,Henna extract delays the swelling of sodium bentonite as the swellingof sodium bentinite reaches to 50% after about 5 h, 11 h, and 21 h forlow temperature state and about 2.5 h, 1.5 h, and 11 h in high temper-ature state when exposed to polyamine, potassium chloride, andHenna extract, respectively. Final swelling percentages of sodiumbentonite exposed to 3 mass% of Henna extract, potassium chloride,and polyamine solutions in both temperatures of 28 °C and 82 °C arepresented in Fig. 11. Swelling of sodium bentonite was increased byfactors of 15.9%, 9.45%, and 7.93% for 3 mass% of polyamine, Hennaextract, and potassium chloride solutions, respectively, at 82 °Ccompared to temperature of 28 °C. It is thus evident that swelling ofsodium bentonite exposed to polyamine solution is more influencedby the temperature than the other two solutions.

Finally, the effect of combination of 3 mass% Henna extract with8.5 mass% potassium chloride (as a routinely used clay stabilizer) was

0102030405060708090

100

60.8868.81 67.45

76.9 75.4

90.49

Swel

ling

(%)

Fig. 11. Effect of temperature on swelling of sodium bentonite exposed to potassiumchloride, Henna extract, and polyamine solutions after 72 h (cylinders with verticallines: 28 °C, cylinders with horizontal lines: 82 °C).

0

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30

40

50

60

70

0 1 2 3 4 5 6 7

Swel

ling

(%)

Time (h)

8.5 mass% potassium chloride8.5 mass% potassium chloride + 3 mass% Henna extract

Fig. 12. Swelling of sodium bentonite exposed to potassium chloride solution and its con-junction with Henna extract at 82 °C.

84 A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

investigated. Fig. 12 indicates that swelling of sodium bentonite ex-posed to this mixture is hindered from the same earliest time leadingto an eventual 22.18% reduction in ultimate swelling after 6 h comparedto sole implementation of the 8.5 mass% potassium chloride solution.

0

20

40

60

80

100

120

0 2.5 5 7.5 10 12.5 15 17.5 20

App

aran

t vis

cosi

ty(c

p)

Sodium bentonite concentration mass%

Dis�lled water (pH=9)0.2 mass% Henna extract (pH=9)1.5 mass% Henna extract (pH=9)3 mass% Henna extract (pH=9)3 mass% Henna extract (Natural pH)3 mass% Polyamine (Natural pH)3 mass% Potassium chloride (Natural pH)

0

20

40

60

80

0 2.5 5 7.5 10 12.5 15 17.5 20

Yie

ld p

oint

(Pa)

Sodium bentonite concentration mass%

Dis�lled water (pH=9)

0.2 mass% Henna extract (pH=9)

1.5 mass% Henna extract (pH=9)

3 mass% Henna extract (pH=9)

3 mass% Henna extract (Natural pH )

3 mass% Polyamine (Natural pH)

3 mass% Potassium chloride (Natural pH)

0

10

20

30

40

50

0 2.5 5 7.5

Gel

stre

ngth

-10

sec

(Pa)

Sodium bentonite

Dis�lledwater (pH=9)

0.2 mass% Henna extract (pH=9)

1.5 mass% Henna extract (pH=9)

3 mass% Henna extract (pH=9)

3 mass% Henna extract (Natural pH

3 mass% Polyamine (Natural pH)

3 mass% Potassium chloride (Natura

A

C

E

Fig. 13. Sodium bentonite inhibition tests results after being rolled at 82 °C for 16 h and read(B) alteration of plastic viscosity with sodiumbentonite concentration; (C) alteration of yield pobentonite concentration; (E) gel strength 10-min with sodium bentonite concentration.

This is attributed to the excellent inhibition properties of Henna extractas compared to two other sample solutions

3.3. Sodium bentonite inhibition tests

The effect of different concentrations of Henna extract on yieldingtendency of sodiumbentonitewas investigated by sodiumbentonite in-hibition test. Results including the apparent viscosity, plastic viscosity,yield point, and gel strength (10-sec and 10-min) versus sodium ben-tonite loading are presented in Fig. 13(a–e).

Plastic viscosity is an indication of high shear rate viscosity and is afunction of the viscosity of the liquid phase and the volume of solidscontained in a mud. The plastic viscosity is increased by addition ofany solid; but solids such as clays, which swelled due to adsorption ofwater, will more increase in plastic viscosity. On the other hand,anything that causes changes in the low shear rate viscosities will bereflected in the yield point. In other words, yield point indicates thetendency of clay layers to linking together and forming a flocculatestructure. Gel strength is a measurement of the shear stress necessaryto initiate flow of a fluid that has been still for a period of time. In

0

20

40

0 2.5 5 7.5 10 12.5 15 17.5 20

Plas

tic v

isco

sity

(cp)

Sodium bentonite concentration mass%

Dis�lled water (pH=9)

0.2 mass% Henna extract (pH=9)

1.5 mass% Henna extract (pH=9)

3 mass% Henna extract (pH=9)

3 mass% Henna extract (Natural pH)

3 mass% Polyamine (Natural pH)

3 mass% Potassium chloride (Natural pH)

0

20

40

60

0 2.5 5 7.5 10 12.5 15 17.5 20

Gel

stre

ngth

-10

min

(Pa)

Sodium bentonite concentration mass%

Dis�lled water (pH=9)0.2 mass% Henna extract (pH=9)1.5 mass% Henna extract (pH=9)3 mass% Henna extract (pH=9)3 mass% Henna extract (Natural PH)3 mass% Polyamine (Natural pH)3 mass% Potassium chloride (Natural pH)

10 12.5 15 17.5 20concentration mass%

)

l pH)

B

D

ing at 60 °C: (A) alteration of apparent viscosity with sodium bentonite concentration;intwith sodiumbentonite concentration; (B) alteration of gel strength 10-secwith sodium

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10 12 14 16

h/H

Time (day)

0.5 mass% Henna extract (pH=9)0.5 mass% Henna extract (Natural pH)3 mass% Henna extract (pH=9)3 mass% Henna extract (Natural pH)

0

0.2

0.4

0.6

0.8

1

0 4 8 12 16 20 24 28

h/H

Time (h)

0.5 mass% Henna extract (pH=9)0.5 mass% Henna extract (Natural pH)3 mass% Henna extract (pH=9)3 mass% Henna extract (Natural pH)

A

B

Fig. 14. Sedimentation behavior of non-prehydrated sodium bentonite in Henna extractsolutions; (A) the whole experimental time; (B) the initial 24 h.

85A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

other words, anything which promotes or prevents the linking of claylayers will increase or decrease the gelation tendency of a dispersion(Annis and Smith, 1996).

In distilled water, sodium bentonite easily adsorbed water andswelled rapidly. This can result in separation of individual unit layersand a consequent increase in the viscosity of the dispersion becausemore separated layers cause an increased resistance to flow (Annisand Smith, 1996). Consequently, the system was too tick to measurerheological dial readings after adding 10 mass% of sodium bentonite todistilled water. For this reasons, distilled water system has a higherrheological profile than other systems. In other systems, rheologicalprofiles changed rapidly in various concentration of sodium bentonite.For Henna extract system, the inhibition power is influenced by its con-centration so that inhibition power increases as with the increases ofHenna extract concentration. Unlike the apparent viscosity (Fig. 13-a),yield point (Fig. 13-c), gel strength 10-sec (Fig. 13-d), and gel strength10-min (Fig. 13-e), Henna extract has an ineffectiveness perfor-mance in reducing the plastic viscosity (Fig. 13-b) at low concentra-tion (0.2 mass%). This can be attributed to the change in chemicalstructure of Henna extract in aqueous medium at low concentration.

It is well known that deflocculants are used to reduce the yield pointand gel strength but, they are not used to reduce the plastic viscosity(Annis and Smith, 1996). In presence of deflocculants, clay separatedunit layers could not be linked together due to neutralization of positiveedges of clay unit layers. This can lead to a decrease in yield point andgel strength, nevertheless being rather ineffective in reducing theplasticviscosity.

Ineffectiveness performance of the Henna extract solution at lowconcentrations (especially up to 0.2 mass%) could be explained by thecreation of negative ions when Henna extract comes into contact withwater molecules. This could be due to separation of hydrogen ionsfrom structure of Henna extract constituents that results in significantreduction in pH value as shown in Fig. 2.These negative ions, neutralizethe positive edges of clay layers leading to a decrease in yield point andgel strength and also ineffectiveness in reducing the plastic viscosity.Thus, it can be pointed out that Henna extract has a deflocculating prop-erty at low concentrations especially up to 0.2 mass% despite having anexcellent inhibition property at higher concentrations preventing sodi-um bentonite from swelling. Because of these reasons, Henna extracthas a lower rheological profile than distilled water at higher concentra-tions. These results could also confirm the findings of Bourgoyne et al.(1991) which state that the deflocculants can have inhibitive mediumin concentration several times greater than those normally requiredfor deflocculation.

In addition, inhibition performance of Henna extract is associatedwith pH value of aqueous medium; therefore, the 3 mass% Henna ex-tract solution in natural pH has a lower rheological profile comparedto the solution with adjusted pH of 9.This may be attributed to the neg-ative effect of relatively high amount of caustic soda required for pH ad-justment of Henna extract solution. Caustic soda acted to increase thegelling rate of sodium bentonite (Browning and Perricone, 1963). Thisnegative effect is due to the formation of a sodium clay (Browning andPerricone, 1963) and high mobility of the hydroxyl ions that intensifyclay cleavage (Browning, 1964). The aforementioned facts could be con-sidered as acceptable reasons for comparable performance of Henna ex-tract in natural pH than potassium chloride and polyamine.

3.4. Sodium bentonite sedimentation tests

The results of sedimentation behavior of sodium bentonite exposedto Henna extract in natural pH and adjusted pH of 9 are presented inFigs. 14 and 15 for non-prehydrated and prehydrated systems,respectively. Both non-prehydrated and prehydrated sodium bentonitecannot form stable dispersions in Henna extract solutions forseveral days. Stable dispersion was only observed in pure water.Non-prehydrated systems are less stable than the prehydrated ones

due to large particle size (Wang et al., 2011). Sedimentation in naturalpH of Henna extract solution is faster than those with higher pH valuesfor both prehydrated and non-prehydrated systems. This is due to neg-ative effect of caustic soda consumed for pH adjustment that was ex-plained in previous sections.

In non-prehydrated systems, precipitation was started immediatelyafter adding sodium bentonite to Henna extract solutions, thereby ini-tial stable point of turbid dispersion for 0.5 mass% and 3 mass% Hennaextract solutions was observed after 2.25 h and 1 h, respectively(Fig. 14B). After these time periods, the ratio of h/H for 0.5 mass%Henna extract was still in reduction until 10 days but, for 3 mass%Henna extract reduction was not occurred after 24 h. This suggeststhat inhibition power of Henna extract is influenced by its concentra-tion. Based on the data obtained for non-prehydrated systems the fol-lowing sequence can be written for inhibition power of differentstates of Henna extract solutions.

3 mass% Henna extract (natural pH) N 3 mass% Henna extract(pH = 9) N 0.5 mass% Henna extract (natural pH) N 0.5 mass% Hennaextract (pH = 9)

In prehydrated system (Fig. 15), the h/H ratiowas gradually reducedfor 0.5 mass% of Henna extract solution so that the initial constant statein the h/H ratio was observed after approximately 18 days as being 0.44(for natural pH) and 0.59 (adjusted pH to 9), respectively. On the otherhand, when concentration of Henna extract reached up to 3 mass%, theh/H ratiowas reduced to around 0.31 and 0.39 for natural pHand pH ad-justed to 9 respectively, within the first seven days; however, no signif-icant changes occurred after this period of time. Based on the resultsobtained for prehydrated system, the aforementioned sequence of inhi-bition power expressed for non-prehydrated system holds true for theprehydrated system as well. Therefore, it can be said that the inhibitionpower of Henna extract both in prehydrated and non-prehydrated sys-tems has been influenced by its concentration. Fig. 16 indicates thephotos of reduction sequence of the h/H ratio captured at differenttimes for both non-prehydrated and prehydrated sodium bentonite

0.2

0.4

0.6

0.8

1

1.2

0 4 8 12 16 20

h/H

Time (day)

Dis�lled water (Natural pH)0.5 mass% Henna extract (pH=9)0.5 mass% Henna extract (Natural pH)3 mass% Henna extract (pH=9)3 mass% Henna extract (Natural pH)

Fig. 15. Sedimentation behavior of prehydrated sodium bentonite exposed to Hennaextract.

86 A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

systemsexposed to 3mass% ofHenna extract at natural pH and adjustedpH to 9.

According to the results obtained for non-prehydrated andprehydrated sodium bentonite systems, inhibition performance ofHenna extract in preventing stable dispersion of sodium bentonite isfully evident.

3.5. Contact angle measurements

The variation of static air–water contact angles for sodium bentonitefilmmodified by various concentration of Henna extract is presented inFig. 17. The air water contact angle for sodium bentonite with the ab-sence of Henna extract is 23.59° and 23.88° degrees for both naturalpH and adjusted pH of 9 respectively. The value of 23.59° is close tothe value of 23.8° measured on smectite film (Shang et al., 2010) and23.9° measured on montmorillonite film (Wang et al., 2011). The hy-drophilic property of sodium bentonite is more affected by Henna ex-tract in natural pH than the solution with its pH adjusted to 9 asshown in Fig. 17. In other words, Henna extract has a higher affinityon alteration of wettability state of sodium bentonite toward the hydro-phobic properties in natural pH. This can be attributed to the negativeeffect of caustic soda that is an intruder agent for adsorption of Hennaextract on sodium bentonite particles, observed in adsorption isotherm.Themaximum alteration of air–water contact angle for sodium benton-ite both in natural pH and adjusted pH of 9 is 26.62°, 23.57° respectivelywhich occurs at 5 mass% concentration. Hydrophilic properties of sodi-um bentonite were reduced after Henna extract modification andreached a pseudo-plateau at Henna extract concentrations between 4

Fig. 16. Sequence reduction in h/H ratio for non-prehydrated (A, B) and prehydrated (C, D) sodiof 9 (B, D): in parts A and B from left to right: initial state, 1 h, 1 day, and 14 days, in parts C an

and 5 mass%, which could be attributed to sodium bentonite particles'complete encapsulation (Wang et al., 2011) by Henna extract. One ofthe common phenomenon that was observed for sodium bentonite isthe lower affinity of Henna extract on wettability alteration at low con-centrations (0.5 mass%) as compared to higher concentrations. Asmen-tioned earlier in sodium bentonite inhibition test, this might be due toinhibition mechanism of Henna extract at low and high concentrationsto prevent sodiumbentonite swelling. At low concentrations, Henna ex-tract hasmore deflocculating role and its adsorption occurs only on pos-itive edges of sodium bentonite particles. Hence, Henna extract has nosignificant effect on wettability alteration of sodium bentonite particlesat low concentrations.

3.6. SEM observations

Thephotos obtained by SEManalysis are presented in Fig. 18. The so-dium bentonite in distilled water has a high potential to hydration andswelling that has result in particles with less extended areas and aphotograph with dense texture (Fig. 18, part A). On the contrary,sodium bentonite in other inhibitive media has particles with large ex-tend areas revealing the stability of sodium bentonite in these media(Qu et al., 2009). Fig. 18 (parts B, C, and D) shows photographs of sodi-um bentonite modified by 0.5 mass%, 2 mass%, and 3 mass% of Hennaextract. Apparently, the hydration and swelling potential of sodiumbentonite decreases with more and more increases in Henna extractconcentration which results in an extended particle area than distilledwater (especially for 3 mass%). Nevertheless, the 0.5 mass% Henna ex-tract solution has no perceivable characteristic which could be due toits weak ability in preventing the sodium bentonite swelling. Compar-ing the Figs. 18 (parts D, E, and F), it is clearly identified that sodiumbentonite modified with Henna extract has a comparable particle areathan potassium chloride and polyamine. Therefore, it can be said thatHenna extract has a comparable inhibition power than potassium chlo-ride and polyamine.

3.7. Probable inhibition mechanism

Description of inhibition mechanism for Henna extract is difficultdue to high number of its constituents. However, the primary aim ofthis section will be to identify a justifiable mechanism for inhibition ef-fect of Henna extract on sodiumbentonite swelling, according to the re-sults obtained in this study and those available in the literature.

As mentioned earlier, themain constituents of Henna extract are in-cluded as lawsone gallic acid, dextrose, and tannic acid (Ostovari et al.,2009). The reduction in pH value occurs due to separation of hydrogenions from hydroxyl groups of Henna extract constituents which leads togeneration of negative ions in Henna extract solution especially at low

umbentonite exposed to 3mass% Henna extract both in natural pH (A, C) and pH adjustedd D from left to right: initial state, 2 days, 4 days, 7 days.

20

25

30

35

40

45

50

55

0 1 2 3 4 5 6

Con

tact

ang

le

Henna extract concentration mass%

Natural pH

pH=9

Fig. 17.Variation of air–water contact angle of sodiumbentonitefilmversusHenna extractconcentration both in natural pH and adjusted pH to 9.

87A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

concentrations (0.2 mass%). At higher concentrations, the separationwas retarded significantly and then almost stopped at concentrationsabove 1.5 mass% resulting in constant pH (Fig. 2) and modification inslope of the conductivity curve (Fig. 4). The negative ions can adsorbon positive edges of clay layers and neutralize them, which in turnleads to deflocculating properties (decrease in gel strength and yieldpoint but ineffectiveness in plastic viscosity reduction).

The results obtained from performed tests indicated that betterinhibition performance of Henna extract to prevent sodium bentoniteswelling was occurred at high concentrations, around 3 mass%. Itseems that inhibition action of Henna extract could be due to theinteraction between the hydroxyl groups of Henna extract constituents

Fig. 18. SEM photographs of sodium bentonite exposed to different aqueousmedia: A: distilled3 mass% potassium chloride, F: 3 mass% polyamine.

and oxygen atom available on silica surface of sodium bentonitethrough hydrogen bonding. This adsorption could be more related tothe lawsone as a principle constituent that is capable of hydrogen bond-ing with anions due to hydroxyl group of the enol (Hijji et al., 2012).This is meanwhile that the effect of other constituents cannot be ig-nored. Therefore, Henna extract is capable of forming inhibitive medi-um at concentrations much higher than that of deflocculatingconcentrations.

3.8. Cost and environmentally aspects

In addition to a technical feasibility for newly introduced clay stabi-lizer, several feasibilities such as performance, toxicity (and subsequentcorrosively), cost, and availability are major factors to applicability ofclay stabilizers in water-based drilling fluids when drilling throughclay rich shales. In south of Iran, the large areas of agriculture landsare dedicated to cultivate Henna trees. The powder of Henna leaveswith an average price of $1/kg ismainly agriculture products of these re-gions. Annually, significant amounts of this product are exported toother countries. Therefore, it can be claimed with certainly that thereis no problem on the availability of Henna. Henna extract that wasobtained from extraction of Henna leaves is natural, commercially avail-ablewith an average price of $10/kg. Generally, Henna extract is expect-ed to be economically viable for drilling operations. This extract is alsocommonly used as a hair and skin dye, thereby not posing any environ-mental problems which is somehow remarkable for offshore drilling.Another fascinating characteristic of Henna extract is its anti-corrosionproperty.

water, B: 0.5 mass% Henna extract, C: 2mass% Henna extract, D: 3mass% Henna extract, E:

88 A. Moslemizadeh et al. / Applied Clay Science 105–106 (2015) 78–88

4. Conclusions

The effect of new plant-based additive (Henna extract) on swellingof sodium bentonite was investigated through implementation of vari-ous methods. The following conclusions can be drawn based on the re-sults obtained from this study:

Adsorption isotherm indicated that adsorption of Henna extract onsodium bentonite in alkaline medium (pH = 9) is lower than naturalmedium (acidotic) that could be due addition of caustic soda as alkalin-ity adjustment agent. The results of dynamic linear swelling tests indi-cate that Henna extract is capable of reducing the swelling of sodiumbentonite in both test temperatures of 28°C and 82°C and also has acomparable performance compared to potassium chloride and poly-amine. Inhibition property of Henna extract is a function of its concen-tration and is little influenced by pH of aqueous medium. Adsorptionof Henna extract increases hydrophobicity of sodium bentonite parti-cles' surface. Henna extract has a deflocculating property at low concen-trations but, it has a good inhibition performancemuch higher than thatof deflocculating concentrations. Inhibition performance could be dueto hydrogen bondingbetween thehydroxyl groupofHenna extract con-stituents and available oxygen atom on silica surfaces of sodium ben-tonite; especially for lawsone (2-hydroxy-1,4 napthaquinone).

Acknowledgment

Weare grateful to theNational IranianDrilling Company (NIDC) andPetroleum University of Technology (PUT) for their laboratory support.

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