WAX DEPOSITION IN HORIZONTAL WELLS

In this research, wax deposition in horizontal well bores was studied. In a horizontal well, the main mechanism for wax appearance is the pressure change rather than the temperature change. Six different thermodynamic models were improved for horizontal wells by adding a pressure function, and a computer program was developed to simulate the precipitation phenomena in horizontal wells. Solid-liquid equilibrium constants for each pseudo-component were calculated. Critical pressures and overall solid mole fractions of the crude oil at different error ranges are determined. In addition to these, the changes in productivity index due to wax deposition for steady state and pseudo-steady state conditions were examined by the addition of a “wax factor”. It was observed that pressure change was slightly effective on wax appearance in horizontal wells.     

MATHEMATICAL MODELLING OF WAX DEPOSITION IN CRUDE OIL PIPELINES (COMPARATIVE STUDY)

ABSTRACT

In this research, wax deposition in different crude oil pipeline systems was studied. In oil pipelines, the main mechanism for wax appearance is the temperature change along the pipeline. A computer program was developed to simulate the wax precipitation phenomena. Temperature profile along the pipeline was determined and solid liquid equilibrium constant, wax mole fraction and wax thickness along the pipeline were calculated. This computer program was applied to different crude oil pipeline systems in Iraq (Baiji-Daura, Rumaila-Zubair-Fao and Hadttha-Rumailia). In Haditha-Rumaila crude oil pipeline system, it was observed that wax thickness after a year is approximately 0.1 mm and temperature declined from 303 K to around 300.5 K. The wax mole fraction after a year is approximately 0.2. The solid-liquid equilibrium constant for the first component around 0.228 and around 165 for the second component after a year. Similar results were observed in other crude oil pipeline systems studied.     

Studies of Wax Deposition Onset in the Case of Indian Crude Oil

Abstract

Before taking any decision regarding strategies for prevention and remediation of wax deposition problems in the production tubing, pipeline, and process equipment, it is essential to identify the conditions of wax deposition and to predict wax deposition rates. In this article a study on the prediction of wax deposition, different factors affecting the deposition, and the practical applications of laboratory results obtained for characterization of the Indian crude oils have been presented. The waxy crude characterization study was performed on both stock tank crude oil and recombined integrated crude oil. The results of it exemplify the influence of composition, temperature, and pressure on the solid behavior of Indian paraffinic crudes.     

Influencing factors governing paraffin wax deposition of heavy oil and research on wellbore paraffin remover

Abstract

Wax deposition is harmful to oil wells, especially for waxy heavy oils at low temperature. The influencing factors on wax deposition of heavy oil were studied and a kind of O/W emulsion type wellbore wax remover was investigated. The results showed that the wax deposition rate of Jinghe heavy oil increased with the increasing wax content and asphaltenes content but decreased with the increasing water content. The oil in water emulsion type paraffin remover was prepared and it showed both good wax dissolution and paraffin prevention ability and can save large quantities of solvent. The results of this study provides a possible way for waxy heavy oils to dissolve wax, to prevent wax deposition and reduce the viscosity of heavy oils by emulsification together, which is helpful to reduce the frequency of hot washing and enhance oil recovery for waxy heavy oils.     

Experimental Investigations of the Mitigation of Paraffin Wax Deposition in Crude Oil Using Chemical Additives

Abstract

Wax deposition from crude oil is a very expensive problem for oil producers around the world. The objective of this study is to understand the characteristics of paraffin wax deposition and to test the effectiveness of solvents in the inhibition of the crystallization and subsequent precipitation of the paraffin wax and to test the most effective concentration of the solvent used. The oil used here is from the Dakota formation from the Fourteen Mile Field in the Big Horn Basin of Wyoming. Two paraffin inhibitors were tested for this crude oil on a horizontal flow system. The inhibitors are mixtures of solvents, pour point depressants, and wax crystal modifiers. These inhibitors were tested at different concentrations and temperatures and the deposition rates were obtained for each. One inhibitor especially designed for this crude oil was relatively successful, reducing the deposition by up to 59% depending on the temperature.     

模拟延长油田CO_2驱油过程原油结蜡特性研究

通过对某CO2驱油区块的不同CO2分压条件下原油结蜡倾向和原油结蜡特性评价,计算出原油的结蜡速率、结蜡率及蜡含量,分析了原油的析蜡曲线特性。结果表明,CO2分压增大时原油的结蜡速率和结蜡率提高,蜡含量降低,蜡析出更明显;经CO2处理作用后原油析蜡点向低温方向移动,其蜡含量也相应地比未处理油样的蜡含量降低。     

An Experimental Study on Wax Deposition of Water in Waxy Crude Oil Emulsions

Abstract

The key factors affecting wax deposition of water-in-oil emulsion were studied experimentally using a cold finger device. Wax deposition characteristics of emulsions were obtained. The results showed that the wax deposition profile of emulsions as a function of temperature parameters was similar to that of single oil. However, the effect of the extent of water cut on wax deposition was obviously different at different temperatures. Furthermore, the relative mass of deposit was proposed and found independent of water cut, from which wax deposition rate at different water cuts could be predicted and the predicted values were in good agreement with experimental data.     

The Effect of Tube Orientation and Pour Point Depressant on Paraffin Wax Deposition

Abstract

A flow loop was used to study wax deposition in the laboratory. Data are presented to demonstrate that the tube orientation and pour point depressants have significant effects on the paraffin wax deposition for oil from the Octh Louie, a Cretaceous formation in the Manderson Field, Wyoming. Changing the tube orientation from horizontal to vertical reduced the amount of wax deposited by 28% for a tube wall (T_wall) temperature of 42°F. The circulating oil temperature (T_bulk) was held constant at 76 ± 3°F. The amount of wax deposited was found to be a linear function of the driving force (T_bulk – T_wall) and the wax appearance temperature (WAT) was estimated by extrapolating this linear relationship to a point of zero wax deposition. The WAT thus obtained (94.5°F) varied considerably with the cloud point (62°F) obtained using the ASTM D2500 method. Change in viscosity with time has also been investigated. Addition of a specific pour point depressant (PPD) at a concentration of 5 mL/gallon reduced wax deposition by 52%; concentrations of 10 mL/gallon of oil reduced the wax by 61%. Changing the flow regime from laminar to turbulent also had a significant effect, reducing the wax deposition by up to 42%. Gas chromatography–mass spectrometry (GC-MS), gas chromatography–flame ionization detection (GC-FID) analyses and other relevant property data pertaining to the oil are also presented.     

延长油田高含水油井井筒结蜡速率预测模型优化

结蜡速率计算是预测油井结蜡的关键参数,目前针对油井井筒的结蜡速率预测模型相对较少,且大多以机理模型为主,计算参数众多,现场应用不便.延长油田油井含水率普遍较高,常用的普适性经验模型预测准确度低.因此,重新考虑含水率对结蜡速率的影响,开展了含水率对结蜡速率影响的室内研究,基于实验数据与简化后的经验公式,拟合了含水率分别为...     

MATHEMATICAL MODELLING OF WAX DEPOSITION IN CRUDE OIL PIPELINES (COMPARATIVE STUDY)

In this research, wax deposition in different crude oil pipeline systems was studied. In oil pipelines, the main mechanism for wax appearance is the temperature change along the pipeline. A computer program was developed to simulate the wax precipitation phenomena. Temperature profile along the pipeline was determined and solid liquid equilibrium constant, wax mole fraction and wax thickness along the pipeline were calculated. This computer program was applied to different crude oil pipeline systems in Iraq (Baiji-Daura, Rumaila-Zubair-Fao and Hadttha-Rumailia). In Haditha-Rumaila crude oil pipeline system, it was observed that wax thickness after a year is approximately 0.1 mm and temperature declined from 303 K to around 300.5 K. The wax mole fraction after a year is approximately 0.2. The solid-liquid equilibrium constant for the first component around 0.228 and around 165 for the second component after a year. Similar results were observed in other crude oil pipeline systems studied.     

Study on Acoustic Cavitation and Magnetic Coupling Wax Control Technology

Abstract

To solve the wax deposition problem of high-pour-point and high-waxy oil wells, a new acoustic cavitation and magnetic coupling shaft wax control technology was proposed. Experimental research and field tests were conducted. This wax control technology can achieve the purpose of freezing point depression, viscosity reduction by emulsification, and wax control through the combined effect of cavitation, acoustic vibration, and magnetic intensification. Laboratory experiments showed that after acoustic cavitation and magnetic coupling treatment, the viscosity reduction ratio of high-pour-point oil was over 25.5% at 30°C; the freezing point was decreased from 32°C to 27°C, a 15.6% reduction; the wax crystal structure of the oil samples was changed from crude, thick, and dense to fine, thin, and sparse. Field tests showed that the acoustic cavitation and magnetic coupling wax control device can significantly extend the well's wax deposit cycle by more than 30 days and reduce the wax thickness (Yumen Oilfield). Using this technology, the flushing period was extended more than two times, with a maximum up to nine times, and the normal production time was also prolonged (Zhundong Oilfield in Xinjiang). The results are useful for the popularization and application of the new shaft wax control technology for high-freezing-point and high-waxy oil wells.     

Experimental study on the regulation of wax deposition

Abstract

Based on the theory of wax deposition dynamics, and the wax deposition rate model of a Tieling–Jinxi insulated crude oil pipeline was established for Daqing–Jilin mixed oil. Based on their physical properties, the sediments removed from the pipeline were mixed into the original oil sample at different proportions. The sediment volume measured by three physical methods in different seasons was compared. The results showed that the error between the value measured by the wax content method and the predicted value by the model was the smallest, which was -5% in winter and -3.9% in summer. Therefore, the wax content method can be used to estimate the sediment in the pipeline and determine the prediction accuracy of the model.     

一种高效防蜡降凝剂的研制与应用

姬塬油田部分区块原油蜡质、胶质含量高,油井结蜡严重,现有防蜡技术在该区块应用效果不佳,针对上述问题利用蜡晶晶格扭曲机理和微乳液机理,将蜡晶改进剂以纳米颗粒的形式均匀分布在水中,制备出一种不易燃烧、防蜡降黏效果好、密度较大、冬季可方便使用的高效防蜡降凝剂.研究结果表明,在最佳的合成工艺条件下制备出的高效防蜡降凝剂,纳米粒...     

Physical properties of wax deposits on the walls of crude pipelines

Wax deposits on the wall of a crude oil pipeline are a solid wax network of fine crystals, filled with oil, resin, asphaltene and other impurities. In this paper, a series of experiments on wax deposition in a laboratory flow loop were performed under different conditions （flow rate, temperature differential between crude oil and pipeline wall, and dissolved wax concentration gradient）, and the wax deposits were analyzed, so quantitative relationships among wax content, wax appearance temperature （WAT）, shear stress, and radial concentration gradient of dissolved wax at the solid/liquid interface were obtained. Finally, a model was established to predict WAT and the wax content of the deposit.     

Effect of drag reducer and pour point depressant on the wax deposition of crude oil pipeline

In this paper, the data of wax precipitation before and after the addition of the additives showed that the addition of the drag reducing agent (DRA) and the pour point depressant (PPD) cannot change the wax appearance temperature (WAT) of crude oil. When the dosage of DRA is small, the DRA cannot increase, stop, or slow down the precipitation of wax crystals. The addition of PPDs has no influence on the amount of precipitated wax crystals. From the GPC analysis, the molecular weight of the wax deposit samples in Linpu pipeline is from 500 to 76,800, which indicates that there is no enrichment of DRA in wax deposit samples. The results of IR show that the C?O group was not detected in the wax deposit sample of the Wei Jing pipeline, which indicates that there is no enrichment of the PPDs in wax deposit samples. The results showed that the DRA and PPD have no obvious effect on crude oil pipeline wax deposition.     

Application of Horizontal Wells to Improve Injectivity During Polymer Flood Processes

Abstract

This numerical study was undertaken to investigate and compare the performances of polymer flood processes through horizontal or vertical wells. To achieve the objective, the author performed an extensive numerical simulation for 3 different well configurations under polymer flood followed by waterflood. The potential for a horizontal well application was assessed through different scenarios in combinations of injection and production wells and reservoir geometry. Other parameters included the length and spacing of horizontal injectors and horizontal or vertical producers. For different parameters of the system, performances were compared in terms of cumulative recovery and water-oil ratio at the production well and pressure drop or injectivity at the injection well. Results demonstrate that additional oil can be recovered and injectivity was significantly improved by utilizing a combination of horizontal wells when the same volume of fluid is injected into the reservoir. The improvement of injectivity through a horizontal injection well was higher when it was combined with a horizontal producer. Parameters such as reservoir thickness, well spacing, and well length are also shown to impact the predicted injectivity. Improvement in injectivity is obtained for thicker and larger reservoirs and longer horizontal wells.     

A Productivity Evaluation Model and Its Application for an Infill Horizontal Well in Different Types of Reservoirs

Abstract

Productivity evaluation for infill horizontal well should take into account the interference of other oil or water wells in the flooding pattern. On the basis of the mirror-image method and source-sink theory, a semianalytical model of productivity evaluation for infill horizontal well in different types of reservoirs was built, in which the effect of boundary, the interference of other wells, the randomicity of flooding pattern, and the pressure drop along the horizontal lateral were taken into account. Application of the novel semianalytical model has demonstrated its reliability and usefulness. It is an effective method for the productivity evaluation for infill horizontal well in different types of reservoirs.     

Artificial Neural Network's Prediction of Wax Deposition Potential of Nigerian Crude Oil for Pipeline Safety

Abstract

Paraffin wax deposition from crude oil along pipeline is a global problem, making preventive methods preferred to removal methods. In this work, a neural network model based on mathematical modeling technique using regression analysis as the statistical tool was developed to predict the wax deposition potential of 11 reservoirs in Nigeria. Using the viscosity-pressure-temperature data obtained from these fields to supervise the model, the model accurately predicted the present real-life situation in each field. Conclusively, the model could be used to predict wax deposition potential of any reservoir that is yet to be explored provided the temperature used during prediction is close to the actual reservoir temperature.     

高含蜡凝析气井石蜡沉积实验研究

国内外研究学者在石蜡沉积研究中对石蜡沉积机理及沉积模型模拟预测等方面进行了大量研究。为了研究某高含蜡气井的析蜡条件及预防措施,针对高含蜡凝析气井的脱气油,进行了石蜡沉积实验研究,发现在模拟研究井筒中油气多次接触过程中,脱气油的析蜡点和溶蜡点以及石蜡的沉积量随着接触次数的增加呈现先下降后上升的趋势。沉积点的测定研究能判断井筒是否结蜡,沉积量的测定研究能够预测井筒析蜡状况,以保证气井正常生产。研究表明该井在地层中不会出现石蜡沉积,同时,井口的温度应不低于42℃,井筒中也不会出现石蜡沉积。     

油井微生物防蜡技术应用

井筒结蜡是影响油井正常生产的普遍问题,常规的热水洗井清蜡不可避免地造成油井怠产,甚至油层伤害。近年来引进微生物防蜡技术,根据油层条件及含蜡原油组分特点,筛选合适的细菌组合注入井筒,利用细菌对石蜡的降解作用、分散作用以及细菌体和其代谢产物的表面效应阻止石蜡结晶,防止或缓解井筒结蜡。微生物防蜡是一种新型、经济、环保、适用性广的油井防蜡技术,应用时应遵循以下程序：选井、取样、室内评价分析、井况落实、施工设计、洗井、施工、资料收集与分析、效果总结。通过几年来的现场试验和推广应用,有效解决了大芦湖和小营油田的井筒结蜡和油层保护问题,提高了油井产量和经济效益．