油田固体和油包水乳化稳定性Oilfield solids and water-in-oil emulsion stability.docx

Oilfield solids and water-in-oil emulsion stability 油田固体和油包水乳化稳定性D.M. Sztukowski, H.W. Yarranton. Journal of Colloid and Interface Science 285 (2005) 821-833Abstract 摘要Model water-in-hydrocarbon emulsions consisting of toluene, heptane, water, asphaltenes, and native solids were used to investigate the role of native solids in the stability of oilfield emulsions. The solids were recovered from an oil-sands bitumen, a wellhead emulsion, and a refinery slop oil. The solids were clay platelets and fell into two size categories: (1) fine solids 50 to 500 nm in diameter and (2) coarse solids 1 to 10 pim in diameter. Emulsions stabilized by fine solids and asphaltenes were most stable at a 2:1 fractional area ratio of asphaltenes to solids. It appears that when the asphaltene surface coverage is high, insufficient solids remain to make an effective barrier. When the solids coverage is high, insufficient asphaltenes remain on the interface to immobilize the solids. Treatments that weaken the interface, such as toluene dilution, are recommended for emulsions stabilized by fine solids. Emulsions stabilized by coarse solids were unstable at low solids concentrations but became very stable at solids concentrations greater than 10 kg/m3. At low concentrations, these solids may act as bridges between water droplets and promote coalescence. At high concentrations, layers of coarse solids may become trapped between water droplets and prevent coalescence. Treatments that flocculate the solids, such as heptane dilution, are recommended for emulsions stabilized by high concentrations of coarse solids. It is possible that emulsions containing both types of solids may require more than one treatment, or even process step, for effective water resolution.采用甲苯、庚烷、水、沥青质和天然固体组成的模拟烧包水乳化，研究油田乳化稳定 性中天然固体的作用。从油-砂沥青、井口乳化和炼油污油中回收了固体。固体是粘土片晶， 分为两种尺寸类别：(1)直径为50至500 nm的细固体和(2)直径为1至10 pim的粗 固体。沥青质与固体面积比为2:1时，细固体和沥青质稳定的乳化最稳定。沥青质外表覆 盖率高时，似乎剩余固体缺乏以形成有效的屏障。固体覆盖率高时，界面上剩余的沥青质 缺乏以固定固体。对于细固定稳定的乳化，推荐弱化界面的处理，如甲苯稀释。粗固体稳 定的乳化在低固体浓度下不稳定，但是，固体浓度大于10 kg/m3时变得非常稳定。低浓2.2.3. Refinery emulsion炼厂孚L化Solids (fraction of asphaltene-solids)固 体(沥青质-固体的分数)1.24710.7The refinery emulsion contained 43 vol% water in the form of an emulsion. However, unlike the wellhead emulsion, the IOL sample destabilized after five minutes of centrifugation at 4000 rpm into four distinct phases: (1) a continuous phase free of water; (2) a rag layer consisting of 51 vol% water; (3) a free water phase; (4) a solids slurry consisting of 48 vol% water. The rag layer and solids slurry made up only 9 and 7 vol%, respectively, of the total emulsion. Note that, on average, approximately 80% of the water was resolved as a free water phase from the IOL emulsion after this initial centrifugation.炼油厂乳化含43 vol%的乳化形态的水。但是，与井口乳化不同，IOL样品在以4000 rpm离心5 min后脱稳，分为4个不同的相：(1)无水的连续相；(2)由51 vol%水组 成的老化层；(3)游离水相；(4)由48 vol%的水组成的固体浆体。老化层和固体浆体分 别仅占总乳化的9和7 vol%。注意初始离心后，平均约80%水从IOL乳化中别离为游 离水相。Each phase was decanted from the centrifuge tubes. Asphaltene-solids from the continuous phase were precipitated as described for Athabasca bitumen. Since only small volumes of both the rag layer and the solids slurry were recovered from the refinery emulsion, the solids were recovered directly from these samples rather than asphaltenes first being precipitated. Toluene was added to either rag layer or solids slurry in a 25:1 (cm3/g) ratio. The mixture was sonicated for 20 min and then left to stand for 1 h. After settling, the mixture was sonicated briefly for 10 min and then transferred into centrifuge tubes for 6 min of centrifugation at 4000 rpm. The supernatant was decanted and the solids remaining in the centrifuge tubes were allowed to dry until their mass was invariant. The solids yields from the continuous phase, rag layer, and solids slurry are given in Table 3. The asphaltene content was not determined because the yields of both the rag layer and solids slurry were too small. However, the asphaltene-solid yield from the continuous phase was 7.6 wt%. Solids made up 1.7 wt% of the continuous phase asphaltene- solids.从离心管中倒出每一相。如沥青所述，从连续相中沉淀出沥青质-固体。由于从炼厂乳 化中仅回收了少量老化层和固体浆体，因此，直接从这些样品中回收固体，而不是首先沉 淀沥青质。甲苯以25:1 (cr"/g)的比例加入老化层或固体浆体中。混合物超声处理20min, 之后静置lh。沉降后，混合物短暂超声处理lOmin,之后转移到离心管中，以4000 rpm 速度离心6 min。倒出上清液，留在离心管中固体干燥，直到质量不变。表3是给出了连 续相、老化层和固体浆体的固体产率。由于老化层和固体浆体产率都太小，没有确定力质 含量。但是，连续相的沥青质-固体产率为7.6 wt%o固体占连续相沥青质-固体的1.7 wt%。Table 3 Solid yield of each phase of the IOL refinery emulsion 炼厂乳化的每一相组成2.3. Particle shape and size analysis 颗粒形状和尺度分析omponent 成分Continuous phase 连续 相(wt%)Rag layer 老 化层(wt%)Total总计 (wt%)omponent 成分Solids (fraction of phase) 固体(相的分数)0.111.811.8Solids (fraction of bitumen) 固 体(沥青的分数)0.090.291.72.1Dry solids were examined with a Philips/FEI field emission transmission electron microscope at an accelerating voltage of 200 kV, as described elsewhere 29. The particle size distribution of dry solids was obtained with a Malvern Instrument Model 2000 Mastersizer particle size analyzer. The detection range of the instrument varies from 0.020 to 2000 |im and all measurements must be performed in an aqueous environment. The solutions were prepared by dispersing 100 to 200 mg of solids in 10 ml of water. This mixture was shaken by hand and sonicated until it appeared to be free of any clumps of solids and all solids had migrated from the air/water interface to the water. The mixture was then introduced into the 2000 Mastersizer apparatus.如其他地方所述，以200kV的加速电压下，采用Philips/FEI场发射透射电子显微镜, 分析干燥固体。采用粒度分析仪，取得干固体的粒度分布。仪器的检测范围从0.020到 2000 |im不等，所有测量都必须在水环境中进行。将100至200 mg固体分散在10 mL 水中，制备溶液。用手摇动混合物，并进行超声处理，直到看起来没有任何固体团块，且 所有固体都从空气/水界面迁移到水中。之后将混合物引入2000 Mastersizer设备中。2.4. Emulsion preparation 乳化制备Model emulsions were prepared with heptane, toluene, water, and one of either asphaltene- solids, asphaltenes, or a mixture of asphaltenes and wet solids. The procedure for preparing emulsions stabilized by asphaltenes, AS, or recombined mixtures of asphaltenes and solids has been described previously 29,52 and is summarized here briefly.采用庚烷、甲苯、水和沥青质-固体、沥青质或沥青质和湿固体混合物中的一种，制备模拟乳化。之前描述了制备由沥青质、AS或沥青质和固体重新混合混合物稳定乳化的程 序，这里简要总结。A known mass of asphaltenes and solids was dissolved and dispersed, respectively, in toluene, after which heptane was added to make up a mixture of 25 vol% heptane and 75 vol% toluene (25/75 heptol). The total volume of emulsions was 50 ml. The mixture was sonicated for 5 min after the addition of heptane to ensure mixture homogeneity. Water in a 40 vol% ratio was added dropwise to the hydrocarbon phase while the mixture was homogenized with a CAT-520D homogenizer at 18,000 rpm for 5 min. After 1.5 h of settling, a continuous phase and a concentrated emulsion phase had separated. For the emulsions stabilized by asphaltenes or asphaltenes and fine solids, the drop size distribution did not change during the settling period, nor did any water separate from the emulsion 50. The drop size distribution did change during the settling period when AEC coarse solids were used as stabilizers, but no free water was observed.将质量的沥青质和固体分别溶解和分散在甲苯中，之后加入庚烷，制成25 vol% 庚烷和75 vol%甲苯(25/75罐醇)混合物。乳化的总体积为50 mL。加入庚烷后，混合 物超声处理5 min,保证混合均匀。将40 vol%比的水逐滴加入煌相中，同时用CAT-520D 均质器以18000rpm均化混合物5 min。沉降1.5 h,连续相和浓缩乳化相别离。对于由沥 青质或沥青质和细固体稳定的乳化，沉降期间液滴尺寸分布没有变化，也没有任何水从乳 化中别离出来。当AEC粗固体用作稳定剂时，沉降期间液滴尺寸分布确实发生了变化, 但没有观察到游离水。O asphaltenes AS recombined - dry solids in heptol recombined - dry solids in uater recombined - wet solids in beptolIt was found that dried solids were not suitable for emulsion stability experiments. Chen et al. observed that drying the solids extracted from bitumen froth led to a change in the three-phase contact angle between solid tablets, water, and mixtures of heptane and toluene 53. A change in wettability would change how the solids in an emulsion were distributed between the bulk phases and the interface and hence would likely affect emulsion stability. Fig. 1 compares the free water resolution after 8 h of treatment (see next section) for model emulsions stabilized by Athabasca Bitumen 1 asphaltenes, asphaltene-solids, and asphaltenes and dry or wet solids recombined in 100 their original ratios. The stability trends show that, 4 80 if dry solids are utilized, the original emulsion 1 60 号40 £200010203040Asphaltene Equilibrium Concentration (ke/m31 stability (free water resolution) cannot be restored whether the solids are dispersed in the continuous hydrocarbon phase or in the aqueous phase. In fact, these solids appear to have no effect on the emulsion stability, since the free water resolution is the same as when only asphaltenes are used as stabilizers. However, if wet solids are used, the resulting emulsions have the same stability as the original emulsion. Therefore, in this work, all the emulsion recombination experiments have been performed with freshly extracted wet solids.Fig. 1. Emulsion stability after 8 h for (a) asphaltenes, (b) AS, (c) recombined asphaltenes and dry fine solids in heptol, (d) recombined asphaltenes and dry fine solids in water, (e) recombined asphaltenes and wet fine solids in heptoL Athabasca Bitumen 1, 25/75 heptol, 40 vol% water. The lines are visual aids. 8 h 进乳化的稳定性(a)沥青质，(b) AS, (c)凄醇 中重新混合的沥青质和干燥细固体，(d)水中重新混合的沥青质和干燥细固体，(e)凄醇中 重新混合沥青质和湿细固体。Athabasca沥青1、25/75庚醇、40 vol% 7j<o线辅助观察。发现干燥固体不适乳化稳定性实验。观察到干燥从沥青泡沫中提取固体导致固体片晶、 水以及庚烷和甲苯混合物之间的三相接触角发生变化。润湿性的变化会改变乳化中固体在 体相和界面之间的分布，因此，可能影响乳化稳定性。图1比照了 Athabasca沥青1沥 青质、沥青质-固体和沥青质以及按原始比重新混合的干或湿固体稳定的模拟乳化处理8 小时后(见下一节)游离水别离。稳定性趋势说明，如果使用干固体，无论固体分散在连 续烧相还是水相中，都无法恢复原来的乳化稳定性(游离水别离)。实际上，由于游离水 的别离与仅使用沥青质作为稳定剂时相同，这些固体似乎对乳化稳定性没有任何影响。但 是，如果使用湿固体，所得乳化具有与原始乳化相同的稳定性。因此，在这项工作中，所 有乳化重新混合实验都是采用新提取的湿固体进行。2.5. Assessment of emulsion stability 乳化稳定性评价Emulsion stability was gauged by measuring the water resolved from the emulsion as a function of time. After 1.5 h of settling at room temperature, samples of the concentrated emulsion phase were transferred into 12-cm3 graduated centrifuge tubes and capped to prevent evaporation. The tubes were centrifuged for 5 min at 4000 rpm (1640 RCF) and placed in a water bath maintained at 60 °C. After 2 h, the tubes were removed from the water bath and centrifuged for 5 min and the volume of separated water was measured. The tubes were returned to the heating bath for another 2 h, after which they were centrifuged for 5 min and the free water was measured. This procedure was repeated for a total treatment time of 8 h. The amount of resolved water was reported as the percentage of total water volume contained in the given emulsion sample. The relative stability of all the emulsions was assessed by comparing the percentage ofseparated water at a given destabilization time.通过测量作为时间函数的乳化中别离水，测量乳化稳定性。在室温下沉降1.5 h后， 浓缩乳化相的样品转移到12-cm3带刻度的离心管中，并盖上盖子，防止蒸发。以4000 rpm (1640 RCF)离心管5 min,之后置于保持在60的水浴中。2小时后，管从水浴中 取出，离心5 min,测量别离水的体积。试管放回加热浴中，再放置2h,之后离心5 min, 测量游离水。重复这一过程，总处理时间为8 ho别离的水量报告为给定乳化样品中所含 总水量的百分比。通过比照给定脱稳定时间的别离水的百分比，评估所有乳化的相对稳定 性。2.6. Asphaltene and solids surface coverage 沥青质和固体外表覆盖Previous studies indicated that for model emulsion systems in which the asphaltene concentration varied from 1 to 40 kg/m3, asphaltenes adsorbed at the interface as a monolayer 52. The monolayer mass surface coverage is given by之前的研究说明，对于沥青质浓度从1到40 kg/m3变化的模拟乳化系统，界面处吸 附的沥青质为单层。下式给出单层质量外表覆盖率(1)where nu is the total mass of asphaltenes in the emulsion, d32 the Sauter mean diameter of the emulsion droplets, Vw the total volume of the water phase, C eq a the asphaltene equilibrium concentration, and C0a the initial asphaltene concentration.其中mA是乳化中沥青质总质量，d32是乳化液滴的Sauter平均直径，Vw是水相总 体积，Cet>A是沥青质平衡浓度，C°A是初始沥青质浓度。The same procedure can be applied to emulsions containing both asphaltenes and solids, except now, if solids are adsorbed at the interface, the asphaltene surface coverage will be less than the monolayer coverage. The fractional surface coverage of asphaltenes (0A) at a water/oil interface was given by the ratio of the asphaltene mass surface coverage to the monolayer mass surface coverage 29:相同程序可用于同时含沥青质和固体的乳化，只是现在如果固体吸附在界面上，沥青 质外表覆盖率将小于单层覆盖率。沥青质在水/油界面的外表覆盖率(9A)由沥青质外表覆 盖率与单层质量外表覆盖率之比给出：(2)For model emulsions stabilized solely by asphaltenes and solids, the solids are assumed to occupy the remainder of the interface, so that the fractional area of solids on the interface, 0s, is equal to 1 -0a.对于仅由沥青质和固体稳定的模拟乳化，假设固体占据界面的其余局部，因此，界面 上固体的分数面积9s等于1"a。The variables required to calculate surface coverage from Eq. (1) are the initial asphaltene concentration, C°a , the total volume of water, Vw, the Sauter mean diameter, d32, and the asphaltene equilibrium concentration, C eq a. The initial asphaltene concentration and the water volume were experimentally controlled parameters. The Sauter mean diameter was found from drop size distributions of samples taken from a settled emulsion. A Carl Zeiss Axiovert S100 inverted microscope equipped with a video camera and image analysis software was used to gather and analyze the drop size distributions. Approximately 400-500 drops were used, giving an expected error of 5-10%, according to Dixon and Massey 54.根据上式(1)计算外表覆盖率所需的变量是初始沥青质浓度，c%,水的总体积，Vw， Sauter平均直径d32和沥青质平衡浓度C四a。初始沥青质浓度和水量是实验控制参数。 Sauter平均直径是由沉降乳化中提取的样品液滴尺寸分布中找到。配油摄像机和图像分析 软件的Carl Zeiss Axiovert S100倒置显微镜用于采集和分析液滴尺寸分布。采用大约 400500液滴，预期误差为5-10%oThe asphaltene equilibrium concentration is determined from a gravimetric analysis of the separated continuous phase. After 1.5 h of settling at room temperature, the continuous phase was decanted from the top of the settled emulsion and its volume measured. The solvent was allowed to evaporate and the residual mass of remaining asphaltenes or asphaltene-solids was determined gravimetrically. For emulsions stabilized solely by asphaltenes, the equilibrium asphaltene concentration is simply the residual mass divided by the volume of the decanted continuous phase. For emulsions containing asphaltenes and solids, the solids in the residual asphaltene-solids mixture were dispersed in toluene at a 100:1 toluene to asphaltene-solids (cm3/g) ratio and separated using the procedure described for Athabasca bitumen. The mass of asphaltenes remaining after solids removal was then determined gravimetrically and the equilibrium concentration of asphaltenes calculated as before. Note that, for initial asphaltene concentrations less than 10 kg/m3, the equilibrium concentration was on average 30% smaller than the initial concentration. For initial asphaltene concentrations greater than 10 kg/m3, the equilibrium concentration was on average 15% smaller than the initial concentration.沥青质平衡浓度根据别离连续相的重量分析确定。在室温下沉降1.5 h,潍出沉降乳 化上方的连续相，并测量其体积。溶剂蒸发，通过重量法测定剩余沥青质或沥青质-固体的 剩余质量。对于仅由沥青质稳定的乳化，平衡沥青质浓度只是剩余质量除以浅水出的连续 相体积。对于含沥青质和固体的乳化，剩余沥青质-固体混合物中固体分散在100:1的甲 苯与沥青质-固体（cm3比的甲苯中，采用描述的沥青程序别离。之后通过重量法测定去 除固体后剩余沥青质质量，去按前述计算沥青质的平衡浓度。注意对于小于10 kg/m3的 初始沥青质浓度，平衡浓度平均比初始浓度小30%o对于大于10 kg/m3的初始沥青质浓 度，平衡浓度平均比初始浓度小15%。The mass of solids in the