WAX DEPOSITION IN HORIZONTAL WELLS

ABSTRACT

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.     

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。     

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.     

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.     

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.     

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,纳米粒子的平均粒径为100 nm左右。与现场在用产品相比防蜡率由33.56%提高到88.2%,降黏率由31.06%提高至84.1%,原油凝点由22℃下降至14℃。现场采用连续加药方式实验182口井,使用高效防蜡降凝剂后,油井载荷平均下降0.75 kN,油井平均结蜡周期可延长4倍以上,可有效减少洗井次数,提高油井产油量。     

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.     

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.     

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．     

油基清防蜡剂FLO的研究与应用

FLO油基清防蜡剂主要由1^#、2^#活性剂、降粘剂和有机溶剂组成。室内实验表明，溶蜡速率大于0．02g／min，静态防蜡率大于50％，降粘率大于30％，动态防蜡率大于60％。现场试验表明，采用定期加药方式，可减少洗井次数，提高油井产油量。     

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.     

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。     

宁东油田清蜡、防蜡技术分析

在原油开采过程中,随着温度、压力的降低和气体的析出,溶解的石蜡便以结晶体析出、逐渐长大聚集最终沉积在管壁等固相表面上,即出现所谓的结蜡现象.结蜡会堵塞产油层,降低油井产量,同时也会增大油井负荷,造成生产事故.油井结蜡是影响油井高产、稳产的主要因素之一,清蜡和防蜡是高含蜡油井常规管理的重要内容.通过收集整理现场资料、分析原油性质和综合评价不同清防蜡技术的经济效果,确定宁东油田采用热力清蜡和化学防蜡技术较为合适.     

水溶性防蜡剂FLW的合成与应用

FLW水基防蜡剂主要由1~#、2~#活性剂(用量分别为12.5％)、1％降粘剂和10％助溶剂组成。室内实验表明,防蜡剂加量为100×10~(-6)时,静态防蜡率大于60％,降粘率大于30％,动态防蜡率大于70％。现场试验表明,采用连续加药方式,可减少洗井次数,提高油井产油量。     

NUMERICAL MODEL FOR WAX DEPOSITION IN OIL WELLS

A liquid-solid compositional model that uses an equation of state has been developed to predict the phenomenon of wax deposition in model oil wells. Numerical solutions to the conservation equations for Newtonian-to-non-Newtonian flow regimes show temperature, radial mass flux and wax deposition profiles as a function of time and position in the pipe, using realistic pressure and temperature profiles of a model well. Such rheologic regime changes are dictated by thermodynamic arguments.     

微生物清防蜡技术在低产低效井中的应用

冀东油田高尚堡中深层和柳赞深层原油含蜡量高,区块大部分油井属于低产低效油井,井筒结蜡严重,热洗作业频繁,造成地层污染严重,而且清蜡费用高。从20世纪90年代开始,油田逐步采用了微生物清防蜡技术。室内分析和现场监测表明,微生物能够有效降解石蜡,阻止蜡晶生长;抽油机负荷和回压明显降低,减少检泵次数,延长免修期,对油井的正常生产有较好的维护作用。     

The effect of silica nanoparticle aggregates on wax dissolution in diesel oil

In recent years,silica nanoparticle aggregates(SNPAs) have been used to decrease the injection pressure of wells in low permeability reservoirs achieving good results.In order to study the mechanisms for reduction in the injection pressure of low permeability wells by the SNPA-diesel oil system injection,the microstructure of SNPAs was observed with a transmission electron microscope(TEM).The particle size distribution of SNPAs was also measured by the laser scattering method.The viscosities of diesel oil and SNPA-diesel oil system were measured with a capillary viscometer.The effect of SNPAs on the solubility of wax in the diesel oil was experimentally studied.The influencing factors,including temperature and SNPA concentration in diesel oil,on wax solubility were analyzed.A pore-throat film displacement model(PTFDM) was built for mechanism explanation.The microstructure and size distribution analyses show that the SNPAs are in the nanometer size range.The viscosity of the SNPA-diesel oil system is lower than that of the diesel oil.The solubility of wax in the diesel oil increases greatly due to SNPA addition,the solubility ratio reaches 7.5.The solubility of wax in diesel oil increases with increases in the concentration of SNPAs in the diesel oil and with the temperature.It is proved that the addition of SNPAs to diesel oil helps remove the wax deposited near the wellbore.This maybe one of the main mechanisms for injection pressure decreases in low permeability reservoirs.