Influence of Surfactant Structure on the Stability of

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2 Journal of Chemistry, treatments 9 20 Also it is used in well productivity the oil industry for selecting a suitable emulsifying agent. enhancement via asphaltene deposition removal 21 drag for a specific application The industry mainly relies on the. reduction in multiphase flow 10 and for the control of experience and service providers recommendations Too. excessive water production 8 22 Emulsification technique often a series of time consuming laboratory measurements. was introduced in the oil industry through the use of such as phase behaviour and interfacial surface tension are. emulsified acids in 1933 Emulsified acids were invented performed at reservoir condition to select surfactant for an. to address corrosion problems rather than improving the application Commonly the selection of an emulsifier is based. stimulation job 23 Thus many researchers comprehen on a the surfactant solubility b controllable separation. sively studied this technique for further understanding of time thermal stability and c acceptable environmental. advantages and disadvantages of emulsified acids 20 24 26 consideration for a particular region 8 This technique. Moreover for emulsified acids there are many reports on the is founded on Bancroft s rule which is an empirical rule. effect of droplet size water phase volume fraction and the grounded on the surfactant solubility 33 34 more details. concentration of the emulsifier on their stability and rheology are given later Interestingly a more robust method such. see Al Mutairi et al 20 and references within In addition as hydrophobic lipophilic balance HLB which is based. to the well stimulation applications a new application of on the surfactant chemical structure 35 37 is rarely used. emulsification technique in the oilfield is proposed recently in the oilfields at least from surfactant selection point of. as a method for water control with bullhead injection In this view Hence the objective herein is to relate the surfactant. case the emulsion acts as a relative permeability modifier structure to its performance in an attempt to ease the process. RPM The existence of RPM fluids is well known 27 30 In of selecting a surfactant for emulsified W O emulsions for. a patent Stavland and Nilsson suggested an injection of the applications in high temperature high salinity HTHS con. gelant crosslinked polymer as an emulsion for RPM field ditions The performance of the different commercial emul. application 22 In work by Stavland et al 8 an aqueous sifiers is evaluated and correlated to their HLB The usage. polymer gelant is emulsified into an oil and then injected of both Bancroft s rule and HLB as a selection criterion is. as one component Eventually the solution separates into investigated Furthermore the effects of surfactant chemistry. an oil phase and water phase upon reaching the reservoir and concentration temperature oleic phase composition. Afterward the water phase gels up in a water wet pathway of a and water phase salinity on the emulsion stability are studied. pore space to reduce permeability to formation brine and the. oil phase remains mobile to secure a path for hydrocarbons 3 Experimental. to flow 8 22 The control of the gel fraction that occupies. the porous media leads to the control of RPM that is the In this section details about materials equipment experi. reduction in relative permeability of the hydrocarbons and mental procedures emulsion preparation and characteriza. formation brine this is controlled by the water fraction in tion are detailed. the emulsion 8 In a recent publication our group studied. the gelation kinetics of emulsified PAM PEI system using 3 1 Materials The surfactants used in this study were sup. thermal analysis technique 31 plied by Sigma Aldrich AkzoNobel and Capstone as. Undoubtedly the type of emulsion is critical for presented in Table 1 Sea water and brine formation are used. those applications Therefore the emulsifier which will as water phase Water analysis is given in Table 2 Diesel from. be employed to accomplish the emulsification must be local gas stations and refinery waste oil are used for the oleic. cautiously selected to meet the requirements of those phase The Diesel is representative of the oil utilized in the. settings so a fair rate of success could be seized Nowadays field by the industry for preparing emulsified acids All salts. the biggest difficulty with surfactants at least from the used in this study are ACS grade. standpoint of those who have to choose them is the. staggering numbers that are available Each manufacturer 3 2 Equipment The emulsions were prepared in a high. tries to provide one or more of his products that are suitable performance dispersing instrument Ultra Turrax T 50. for every need which makes the selection process difficult Basic provided by VWR International The homogenizer is. The large numbers of surfactants available coupled with the equipped with a variable speed drive with six different speeds. fact that application problems are becoming increasingly in the range 500 10 000 rpm All emulsions were prepared at. difficult is making the need for a suitable process for the room temperature at 2000 rpm mixing speed for 5 minutes. selection of surfactants more and more critical Selection of The mixing speed and time were selected following a separate. surfactants is important for many applications in the oil field investigation A conductivity meter is provided by HACH. such as EOR stimulation and water shut off Our group has CDC401 model the device can handle total dissolved solids. recently conducted a detailed surfactant screening study for in the range 0 to 50 mg L 1 as NaCl The meter is used to. chemical EOR purposes 32 classify the emulsion type whether it is W O or O W GL 18. Forming stable emulsion is not straightforward routine high temperature disposable test tubes and soda lime glass. To emulsify two immiscible fluids a particular emulsifier is 18 180 mm of approximate volume of 32 ml operational. necessary to form a specific type of emulsion Consequently temperature of 180 C were used The high temperature tubes. selecting surfactant emulsifier to do the job is a critical were sealed with a screw cap and a rubber seal case to prevent. subject and it is certainly a very expensive exercise in terms evaporation The fact that no evaporation is taking place was. of both cost and time There is no systemic procedure in assured by comparing the initial and final volumes of the. Journal of Chemistry 3, Table 1 Description of the surfactants used in this study. Surfactant Type Mw g mol 1 HLB Weight ratio, Glycolic Acid Ethoxylate 1 Ether C14 H24 O6 AIS 288 34 12 61 1. Glycolic Acid Ethoxylate 2 Ether CH3 CH2 11 13 OCH2 CH2 OCH2 CO2 H 6 AIS 739 20 7 14 35 7. Glycolic Acid Ethoxylate 3 Ether C55 H112 O8 AIS 901 47 2 9 76. Ethylenediamine Tetrol C3 H6 C2 H8 N2 C2 H4 O N A 3 600 7 35 7. Fluorosurfactant 1 N A N A N A N A,Fluorosurfactant 2 N A N A N A N A. Polyethylene Glycol 1 Ether C58 H109 KO24 S AIS 1260 14 69 8. Polyethylene Glycol 2 Ether C18 H35 OCH2 CH2 OH 2 NIS 356 58 4 20. Polyethylene Glycol 3 Ether C16 H33 OCH2 CH2 OH 2 NIS 330 5 25. Polyethylene Glycol 4 C4 H10 O2 NIS 90 12 N A N A,Amine Acetates 1 IS N A 6 8 34.
Amine Acetates 2 IS 200 10 5 52 5,Amine Acetates 3 IS 263 6 8 34. Ethoxylated Amides 1 Ethomid 1 N A N A 4 85 24 3, Ethoxylated Amides 2 Ethomid 2 N A 340 360 5 1 25 5. AIS anionic surfactant NIS nonionic surfactant IS ionic surfactant Mw molecular weight N A data not available. Table 2 Chemical analysis of water used in the study Lipophilic tail. Water type concentration mg L 1 Hydrophilic,Ion ppm head. Brine formation Sea water, Na 59 300 18 300 Figure 1 Schematic diagram of surfactant emulsifier chemical. Ca2 23 400 650 structure,Mg2 1 510 2 083,SO4 110 4 290.
Cl 137 000 32 200 value of a surfactant Different commercial surfactants with. HCO3 353 120 a broad range of properties are selected as shown in Table 1. Total dissolved solids 221 673 57 642 Conductivity and dilution tests are used simultaneously to. identify the type of emulsions,Determined by addition. Bancroft s Rule The nature of the emulsifying agent controls. sample at the end of the experiment HAAKE FISONS hot the emulsion type rather than the oil water ratio or the. oil bath Model N3 is used to study the emulsion separation method of emulsion preparation 16 17 34 Bancroft devel. separated volume fraction of the phases versus time oped one of the first empirical rules to describe the nature of. emulsion that could be stabilized by a given emulsifier 33. 3 3 Experimental Setup and Procedure The continuous phase is the phase in which an emulsifier. is more soluble as stated by Bancroft s rule Hence O W. 3 3 1 Emulsion Preparation Several emulsions were pre emulsions are formed by the addition of a water soluble. pared systemically to ensure the reproducibility of the results emulsifier On the other hand W O emulsions are formed. All emulsions were prepared at room temperature at a fixed when an oil soluble emulsifier is used 33 34. mixing speed for 5 minutes Enough time was given for the. emulsifier to mix thoroughly in the external phase Then a Hydrophilic Lipophilic Balance HLB Determination HLB. desired volume of the dispersed phase was slowly added to measures the degree to which a surfactant is hydrophilic or. the continuous external phase It is important to control lipophilic HLB offers an efficient way of picking the suitable. the addition of the dispersed phase droplets throughout the surfactant for a specific application as suggested notably by. mixing It is reported that both the addition rate of the Griffin 35 36 A scale of 0 to 20 is proposed HLB value. dispersed phase and mixing intensity govern the type of of 0 represents a completely lipophilic molecule and a value. emulsion a coarse emulsion will be the result of adding the of 20 accounts for a strongly hydrophilic molecule The HLB. dispersed phase to the continuous phase in one step without values for W O emulsifiers are in the range 3 5 6 while those. intensive mixing However a fine emulsion can be produced of O W are in the range 8 18 Wetting agents have HLB values. by adding the dispersed phase in atomized form coupled with in the range 7 9. intensive mixing 20 38 Surfactant HLB value is determined by calculating the. contributions of different constituents of the molecular. 3 3 2 Emulsion Characterization Two methods are used for structure see Figure 1 as described by Griffin 35 36. the surfactant selection namely Bancroft s rule and HLB Another method was suggested in 1957 by Davies 37 It is. 4 Journal of Chemistry, Figure 2 Dilution test a Droplet sinking W O emulsion and b Droplet dispersion O W emulsion. based on the chemical groups of the molecule This method ii HLB founded on the physiochemical properties of the. considers the effect of strong and weak hydrophilic groups surfactant. However it requires more information such as numbers of. hydrophilic and lipophilic groups in the molecule and values 4 1 Results and Discussion To investigate the validity of. of hydrophilic and lipophilic groups Consequently the value Bancroft s rule emulsions were prepared using a number. of HLB for a particular surfactant has been either provided by of surfactants with different solubility Each surfactant was. the supplier or calculated employing Griffin s method Also dissolved in sea water and Diesel at a time wherein 2 vol. the weight ratio of the hydrophilic part to the hydrophobic surfactant concentration was added to an external phase. HLWR is calculated as shown in Table 1 28 vol and then mixed for a one minute at 500 rpm at. room temperature Afterward the mixing speed was raised. Conductivity Test The type of emulsion has been deter to 4000 rpm and a dispersed phase was added to the solution. mined by measuring its conductivity this is a quantitative of a surfactant and an external phase at a specific rate Then. method based on the electrical proprieties of the emul the emulsions were characterized to identify the external and. sion water phase which is highly conductive whereas the dispersed phases The conductivity for each emulsion was. oleic phase is nonconductive It should be pointed out measured periodically in parallel with the drop test in a span. that the external phase dominates the emulsion s conduc of one hour at room temperature see Table 3 to make sure. tivity 20 39 40 Thus O W emulsion is conductive i e there was no inversion taking place. 0 00 S cm 1 whereas W O emulsion is nonconductive When surfactants in Table 3 dissolved in sea water and. i e 0 00 S cm 1 Conductivity measurements for all the Diesel separately to form the emulsion s continuous phase. fluids used in this study were carried out to set a baseline various trends were noted For instance Fluorosurfactant 1. for the conductivity test The recorded conductance val and Glycolic Acid Ethoxylate 2 Ether were dissolved in the. ues at 28 C are as follows standard NaCl buffer solution Diesel oleic phase to form W O emulsion as Bancroft s. 950 S cm 1 deionized water 6 71 S cm 1 sea water 47 2 concept explicitly theorizes However the conductivity and. 103 S cm 1 and field water 1078 S cm 1 dilution tests showed that produced emulsions were O W. as shown in Table 3 which disagrees with Bancroft s rule. Dilution Test This test identifies the emulsion s external phase Conversely Polyethylene Glycol 1 Ether did not dissolve. by dilution in which water can be used to dilute O W in Diesel and formed O W emulsion when dissolved in. ResearchArticle Influence of Surfactant Structure on the Stability of Water in Oil Emulsions under High Temperature High Salinity Conditions AbdelhalimI A Mohamed 1

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