File Name: crude oil waxes emulsions and asphaltenes .zip
These deficiencies are in part the result of the non-polar and hydrophobic nature of the paraffinic hydrocarbon base oils which are part of slack wax emulsions. The present invention provide a wax emulsion having thixotropic properties comprising a wax; an emulsifier; and a naphthenic oil. According to one embodiment, the wax is slack wax, preferably derived from waxy lube distillates, preferably having an inherent oil content of not more than 10 percent by weight.
Solid deposition during production, transport, and storage of crude oils leads to significant technical problems and economic losses for the oil and gas industry. The thermodynamic equilibrium between high-molecular-weight components of crude oil, such as asphaltenes, resins, and waxes, is an important parameter for the stability of crude oil. Once the equilibrium is disturbed due to variations in temperature, pressure, and oil composition during production, the solubility of high-molecular-weight waxes decreases.
This results in a decrease in the wax appearance temperature WAT and the deposit of wax onto solid surfaces. The role of waxes during the asphaltene aggregation and deposition has not been appropriately explained yet. The objective of this research study is to describe the interaction of asphaltenes and waxes and subsequently address the specific example of an asphaltenic oil commingled with a wax inhibitor-containing oil during the combination of different oil streams. In this work, the quartz crystal microbalance QCM technique has been used for the first time to investigate the effect of waxes and related chemicals, which are used to mitigate wax deposition, on asphaltene aggregation and deposition phenomena.
This study confirms that the different wax inhibitor chemistries result in significant differences in the pour point decrease and viscosity profiles in crude oil. Different wax inhibitors also showed different outcomes regarding the asphaltene deposition tendency. A comprehensive modeling study has also been conducted for mechanistic investigation of experimental results. Organic solid deposition is a serious challenge in the oil industry, from production to oil transportation and storage operations.
Asphaltenes are heavy and highly polar molecules found in crude oil, which contain polycondensed aromatic sheets and aliphatic chains along with various polar functional groups such as pyridine, pyrrole, hydroxyl, sulfoxide, carboxyl, and carbonyl. Additionally, it can lead to increased viscosity, decreased flow, and an increase in operational costs.
The role of asphaltenes during wax crystallization has not yet been well understood. The influence of asphaltenes has been explained contradictorily. Some researchers noted no significant interactions between wax and asphaltenes, but that asphaltenes may result in smaller interspersed wax crystals. Some asphaltene properties, such as molecular mass distribution, density, and solubility parameters, are fitted and adjusted using the aforementioned experimental data of asphaltene precipitation yield curves.
This observation is consistent with solubility parameters observed for smaller short-chain alkanes. This suggests that the precipitating potency of the n -alkanes decreases with an increase in the carbon number up to a maximum value and then increases beyond this value. This observation is mainly due to the entropy of the mixing of molecules with various sizes. The Flor—Huggins theory is widely employed to illustrate the phase behavior of asphaltenes.
Despite a uniform change in the viscosity and solubility parameter, the asphaltene aggregation rate did not differ uniformly with the carbon number of n -alkane. Their model also successfully estimates the asphaltene aggregation rates in the presence of various n -alkanes and depicts that the most unstable fraction of asphaltenes with the highest solubility parameter is able to precipitate in the presence of greater n -alkanes.
Although the effect of different light n -paraffin solvents on the asphaltene phase behavior has been extensively investigated, the potential effects of heavy paraffins and their related chemicals on both asphaltene precipitation and deposition phenomena in the presence of gas have not yet been unveiled.
The aim of this study is to shed some light on the effect of waxes and related chemicals on asphaltene solubility and stability in crude oil. First, the performance of various wax inhibitors in pour point decrease and WAT changes was evaluated by viscosity measurements using a rheometer. Then, a long-chain paraffin, as the main constituent of paraffinic crudes, and wax inhibitors at various concentrations were separately blended with crude oil, and their effects on the precipitation and deposition of asphaltenes of the treated oils were studied using a QCM-based technique.
A modeling investigation was also conducted for the mechanistic understanding of observations from the experiments. The efficiency of each additive was evaluated based on the decrease in the non-Newtonian viscosity when it was added to the system.
Results of rheometer tests with atmospheric geometry and shear rate of 10 s —1 using blank crude oil and blended with various wax inhibitors. The viscosity changes have been observed due to decrease in temperature for the blank crude oil and in the presence of various inhibitors at specified concentrations. As the cooling process started well above the wax appearance temperature, the viscosity gradually increased. This behavior continued following the Arrhenius temperature dependence of Newtonian fluids until the wax started to precipitate out from the crude oil.
Equation 1 explains a linear Arrhenius relationship for the Newtonian range A sudden deviation in the viscosity was then observed owing to the formation of wax crystals.
The point at which a non-Arrhenius behavior began is considered as the WAT. As the temperature decreased further below the WAT, wax crystals grew causing the oil sample to become more non-Newtonian, and therefore the viscosity increased at a higher rate.
It was also observed that the viscosity in the non-Newtonian region decreased in the presence of all inhibitors, particularly the polymeric ones. Typically, the performance of wax inhibitors can be categorized in one of three classes: 1 decrease in high viscosity, 2 moderate decrease, and 3 no significant change or slight increase. As an overall ranking, INH-3 and 6 were found to be better viscosity modifiers compared to the other tested inhibitors.
The efficiency of wax inhibitors can also be evaluated based on their capability to reduce the pour point. The decrease in pour point may lead to higher production rates and therefore lower production costs for the operators. The liquid-like behavior of the reservoir fluid is identified by the loss modulus viscous response , while the solid-like behavior is identified by the storage modulus elastic response. When the wax—oil mixture was at a temperature above the pour point, the loss modulus was at a higher value than the storage modulus.
When temperature decreased, both moduli values increased until the test fluid reached the pour point. At the pour point, the storage modulus is equal to the loss modulus. The storage modulus increased if the mixture was subjected to further cooling. All of the chemicals decreased the pour point with almost keeping a similar efficiency as they had for decrease of viscosity. The asphaltene aggregation and deposition experiments were conducted at and above the natural gas contents of the precipitation onset point.
A HPHT-QCM has been utilized in this study to investigate the effectiveness of paraffin wax and different wax inhibitors on the asphaltene precipitation and deposition rate at elevated pressure and temperature conditions in the presence of natural gas. The change in RF increases as a result of a decrease in both viscosity and density of the fluid due to gas injection and decreases when asphaltenes start precipitating out of the crude oil.
INH-9 is actually neutral with respect to changing asphaltene precipitation tendency at concentrations of and ppm and has shown some limited effects in suppressing asphaltene precipitation at ppm. The results obtained clearly show that all employed wax inhibitors, with the exception of INH-9, have a positive effect on the asphaltene rate decrease on the QCM surface after exceeding the AOP. In addition, there is a drastic change in deposition rate curves between the blank oil and with , , and ppm of inhibitors INH-6, 3, and 4, respectively.
A dramatic change in RF can be seen during the first 2 h of the experiment without an inhibitor, compared to the test with wax inhibitors. However, it cannot properly curb further interaction between nanoaggregates since it does not have any strong surface-active functional group to interact with asphaltene molecules through hydrogen bonding, acid—base, or van der Waals interactions.
The enhanced performance of INH-6 in this study may be due to the influence of this steric repulsion on AOP and the resultant decrease in deposition rates. On the other hand, it is worth noting that generally INH-3, 4, and 6 in the presence of an aromatic solvent show superior performance in decreasing asphaltene precipitation and deposition. This is due to the ability of the solvent to control the phase behavior of the asphaltenes, which is dominated by dispersion forces.
The AOP- and QCM-based deposition rates were considered as representative performance criteria for the ability of waxes to act as an inhibitor or promoter.
Hence, the addition of whole waxes appears to improve the solubility of asphaltene nanoaggregates in crude oil and the stability of asphaltenes increases with the increasing wax concentrations used in this study. Asphaltene precipitation is therefore affected by an ensemble of waxes with long aliphatic chains. It is proposed that waxes with various aliphatic chains might form synergies when acting on asphaltene precipitation and aggregation.
Waxes containing large aliphatic chains interact with asphaltene and inflict steric interferences during asphaltene nucleation. This could cause the formation of more contorted asphaltene aggregates with less tendency to interact and show self-association phenomenon. The influence of paraffin wax on asphaltene stability zones in the crude oil at different system compositions i.
As can be seen, for all modified crudes with different wax contents, the model predictions are in good agreement with the experimental results. A probable explanation for the variation between the model prediction and the QCM experimental data at high wax content may be the generalizations made in the properties of the crude oil fraction utilized as well as the uncertainties in the asphaltene structure and onset point determination in high paraffin wax-modified crude oil samples.
PC-SAFT modeling results of the effect of wax addition to the crude oil on asphaltene stability at various concentrations of 1. This could be explained by the presence of heavier hydrocarbons in the crude oil and the significantly higher 56 solubility of asphaltene in hydrocarbons with a higher carbon number. In addition, this increased solubility of asphaltene widens the asphaltene stability range. The effects of different wax inhibitors on WAT and the decrease in the pour point were evaluated first.
Subsequently, the crude oil compositional modifications made as a result of the addition of several wax inhibitors and various paraffin wax content in crude oils and their influence on the asphaltene stability were investigated by monitoring changes in the asphaltene precipitation onset point and the deposition behavior of asphaltene nanoaggregates.
The results indicate that it may be possible to find an optimum dosage at which the wax inhibitor can reduce both wax and asphaltene deposition problems. A wax inhibitor that is highly efficient in decreasing the viscosity might not be an appropriate chemical solution in addressing the challenge of organic deposition.
Some wax inhibitors can hinder asphaltene aggregation and deposition and some of them aggravate these phenomena. This may be attributed to the higher solubility of asphaltenes in hydrocarbons with higher carbon number compared to those with lower carbon number.
These predictions were compared with the experimental results. However, for modified crudes with lower paraffin wax concentrations, more satisfactory predictions have been attained.
Experiments were conducted with an additive-free crude oil from the North Sea. Table 1 presents the properties and characterization analysis of the crude oil. Four different wax inhibitors, which were commercially sourced and denoted as INH. Table 2 shows the composition and application of each inhibitor in the oilfield chemical industry.
These chemicals were chosen based on their applications and contributions in mitigating wax challenges in the industry and used as received from suppliers. For each chemical, the effective optimum concentration suggested by the suppliers as mentioned in Table 2 has been employed in this study. Based on the distribution of representative paraffin waxes from generic paraffinic oils, the paraffin carbon number of C 30 was chosen. Hence, the paraffin carbon number is in agreement with the reported distribution of native paraffins from typical paraffinic crude oils.
Then, the paraffin was gently added to the crude oil sample and homogenized for at least 1 h to eschew the local concentration of the paraffin waxes or the respective chemicals. The rheological properties of the studied crude oil were determined by temperature sweeps utilizing a stress-controlled rotational-type rheometer purchased from Anton Paar Ltd.
Physica MCR The setup comprises two circular plates with space in between, in which the reservoir fluid is placed. The bottom plate is fixed in rotational terms while the top is fitted to a shaft, floated on a sophisticated air bearing to keep friction to a very low level. The gap between the lower and upper test plates is set to be 0.
The main reason in selecting this geometry is due to its capability to make a uniform shear rate on the thorough measuring surface area. Hence, it could generate a homogeneous flow and eliminate particle migration alongside the measuring system.
Thermal equilibrium is reached easily due to the small sample volume requirement of 22 cm 3 of the setup geometry. The base plate temperature was accurately controlled within 0. After performing primary experiments, it was illustrated that a shear rate of 10 s —1 would provide reproducible curves for the tested fluid.
The capability of the Anton Paar, Physica MCR rheometer using oscillatory mode at atmospheric conditions allows the determination of the pour point with different applied stresses.
These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric. Find more information on the Altmetric Attention Score and how the score is calculated.
Wax- and asphaltene-related problems include solid deposits, stabilization of a water–oil emulsion, and sludge production. Determination of.
By Erika C. Nunes Chrisman, Angela C. The waxes in petroleum can precipitate and form unwanted gels and deposition when exposed to low temperatures. The idea of this chapter is to approach methods of quantification and physicochemical and morphological characterization of waxes and how this information can help in understanding this deposition.
The interface connects the central large droplet and the surrounding small droplets tightly. The results also indicate the size of the central droplet, and the indistinct interface can be enlarged with increasing temperature and increasing stirring rate. Compared to resin, it is noted that the larger asphaltene molecules have stronger connection because of their stronger intermolecular force, larger IFV, and less IFT. In conclusion, the stability of water in heavy oil emulsion is mainly related to the large interfacial viscosity of the interface with much more heavy components such as asphaltene and resin compared to thin oil.
The author and publisher assume no liability whatsoever for any loss or damage that results from the use of any of the material in this book. Use of the material in this book is solely at the risk of the user. Includes index. ISBN 1. Title TP
Kokal, Sunil, and Jamal Al-Juraid. The precipitation of asphaltenes during crude oil production can cause a number of problems. One problem is the agglomeration of asphaltenes at the water-oil interface and formation of tight emulsions. These asphaltenes can form a thick pad in the dehydration equipment, which can significantly reduce the demulsification rate or increase the demulsifier dosage. The paper discusses the emulsion problem in these GOSPs.
Ahn, S. This laboratory investigation considers the effects of emulsions via adding surfactants and the formation and deposition of paraffin wax. This study relates the properties of added surfactant and emulsion characteristics with their wax deposition tendency. Parameters considered include the surfactant HLB Hydrophilic Lipophilic Balance , molecular weight, and surfactant concentration.
Composition and molecular mass distribution of n -alkanes in asphaltenes of crude oils of different ages and in wax deposits formed in the borehole equipment were studied. In asphaltenes, n -alkanes from C 12 to C 60 were detected. The peculiarities of the redistribution of high molecular paraffin hydrocarbons between oil and the corresponding wax deposit were detected. In the oils, the high molecular weight paraffinic hydrocarbons C 50 —C 60 were found, which were not practically detected in the corresponding wax deposits. Waxes and asphaltenes are the most important constituents of crude oils because they have a great influence on crude oil properties. Waxes are a complex mixture of solid at ambient temperature hydrocarbons which consist mainly of paraffin hydrocarbons with a small amount of naphthenic and aromatic hydrocarbons as well as polar compounds. There are two general classes of petroleum waxes.
Solid deposition during production, transport, and storage of crude oils leads to significant technical problems and economic losses for the oil and gas industry. The thermodynamic equilibrium between high-molecular-weight components of crude oil, such as asphaltenes, resins, and waxes, is an important parameter for the stability of crude oil. Once the equilibrium is disturbed due to variations in temperature, pressure, and oil composition during production, the solubility of high-molecular-weight waxes decreases. This results in a decrease in the wax appearance temperature WAT and the deposit of wax onto solid surfaces. The role of waxes during the asphaltene aggregation and deposition has not been appropriately explained yet. The objective of this research study is to describe the interaction of asphaltenes and waxes and subsequently address the specific example of an asphaltenic oil commingled with a wax inhibitor-containing oil during the combination of different oil streams. In this work, the quartz crystal microbalance QCM technique has been used for the first time to investigate the effect of waxes and related chemicals, which are used to mitigate wax deposition, on asphaltene aggregation and deposition phenomena.
Oil-in-Water Emulsions and Environmental Concerns Water-in-Oil Emulsions and Environmental Concerns Field Application of.Jodie C. 18.12.2020 at 05:43
PDF | Composition and molecular mass distribution of n-alkanes in asphaltenes of crude oils of Heat flow curves of asphaltenes from wax deposits 3 (green line), 4 (red solid line), and 5 (dashed line) emulsion, and sludge production.