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Study on the effect of CH_(4) dissolution on the microstructure of wax crystal in Waxy crude oil

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Petroleum Science 2022年第4期19卷 1853-1865页

作者： Bing-Fan Li Man-Ping Yang Gang Liu Li-Ming Zheng Chao Yang School of Vehicles and Energy Yanshan UniversityQinhuangdao066004HebeiChina University of Petroleum(East China) Shandong Provincial Key Laboratory of Oil&GasStorage and Transportation SafetyQingdao266580ShandongChina Technology Inspection Center of Shengli oilfield SINOPECDongying257000China

In this work, the influence of the dissolution of methane(CH_(4)) gas on the wax crystal of Waxy crude oil and the effect on the rheology of crude oil by dissolved CH_(4) were studied comprehensively. A self-deign high-pressure micro visualization device was developed to analyze wax crystals before and after gas dissolution. The crude oil from Shengli and Nanyang was tested by the device under various gas pressures. Results showed that the viscosity, maximum shear stress and equilibrium shear stress of Shengli crude oil decreased with the increasing pressure of the dissolved CH_(4). Due to the supersaturation of dissolved gas, the viscosity, maximum shear stress and equilibrium shear stress of Nanyang crude oil decreased initially and increased with the increasing pressure of dissolved CH_(4). The change in rheology of the dissolved gas crude oil can be a combined influence of gas pressure and dissolution mechanisms caused by CH_(4). Additionally, the wax precipitation point of Shengli crude oil decreased at the saturated dissolution of CH_(4), while Nanyang crude oil showed an increasing wax precipitation temperature.Notably, the wax precipitation area, number of wax particles, and average diameter of wax crystal in both crude oils gradually decreased with dissolution. However, a saturation of CH_(4) caused a small amount of precipitation of wax crystals in Nanyang crude oil, and the small wax crystals were aggregated to form the large wax crystals. The dissolution of CH_(4) gas can affect the wax crystallization process, crystallization ability, and morphology of wax crystals that resulted in significant variation in the rheology of crude oil.

关键词： Waxy crude oil CH_(4)dissolution Wax crystal Rheology Mechanism

Study on the thixotropy and structural recovery characteristics of Waxy crude oil emulsion

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Petroleum Science 2021年第4期18卷 1195-1202页

作者： Li-Ping Guo Xue Han Yun Lei Lei Wang Peng-Fei Yu Shuang Shia Key Laboratory of Enhanced oil Recovery Ministry of EducationNortheast Petroleum UniversityHeilongjiang163000China Jiangsu Key Laboratory of oil and Gas Storage&Transportation Technology Changzhou UniversityJiangsu213164China Exploration and Development Research Institute Daqing Oil Field Company LtdDaqingHeilongjiang163712China

Waxy crude oil emulsion has thixotropic properties at the temperature near gel point,which is a macromechanical characterization of the structure failure and recovery of Waxy crude oil emulsion.In this paper,the thixotropic behaviors of Waxy crude oil emulsion near gel point were studied using hysteresis loop formed by stress linear increase and decrease,as well as the structural recovery characteristics.The influence of the loading conditions and water content on the thixotropy of Waxy crude oil emulsion were analyzed with hysteresis loop area.The concept of"structural recovery"was introduced to study the degree of structural recovery after different stewing,and influencing factors were taken into account.Results have shown that for Waxy crude oil emulsion,the failure to fully restore of the structure after lysis is the cause of the formation of hysteresis loop,and the loading conditions will not affect the strength of thixotropy and the degree of structural recovery.Additionally,the dispersed phase droplets weaken the thixotropy and structure recovery characteristics of Waxy crude oil emulsion,and the greater the water content,the weaker the thixotropy.The findings can help to better understand the safe and economic operation of Waxy crude oil-water pipeline transportation.

关键词： Waxy crude oil Emulsion Thixotropic properties Structural recovery Hysteresis loop

Prediction Model of Wax Deposition Rate in Waxy crude oil Pipelines by Elman Neural Network Based on Improved Reptile Search Algorithm

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Energy Engineering 2024年第4期121卷 1007-1026页

作者： Zhuo Chen Ningning Wang Wenbo Jin Dui Li The Second oil Production Plant Sinopec Northwest Oilfield CompanyUrumqi830011China Yingmaili oil and Gas Production Management Area PetroChina Tarim Oilfield CompanyKorla841001China College of Petroleum Engineering Xi’an Shiyou UniversityXi’an710065China

A hard problem that hinders the movement of Waxy crude oil is wax deposition in oil pipelines.To ensure the safe operation of crude oil pipelines,an accurate model must be developed to predict the rate of wax deposition in crude oil pipelines.Aiming at the shortcomings of the ENN prediction model,which easily falls into the local minimum value and weak generalization ability in the implementation process,an optimized ENN prediction model based on the IRSA is proposed.The validity of the new model was confirmed by the accurate prediction of two sets of experimental data on wax deposition in crude oil pipelines.The two groups of crude oil wax deposition rate case prediction results showed that the average absolute percentage errors of IRSA-ENN prediction models is 0.5476% and 0.7831%,respectively.Additionally,it shows a higher prediction accuracy compared to the ENN prediction model.In fact,the new model established by using the IRSA to optimize ENN can optimize the initial weights and thresholds in the prediction process,which can overcome the shortcomings of the ENN prediction model,such as weak generalization ability and tendency to fall into the local minimum value,so that it has the advantages of strong implementation and high prediction accuracy.

关键词： Waxy crude oil wax deposition rate chaotic map improved reptile search algorithm Elman neural network prediction accuracy

Study of linseed oil,its biodiesel and xylene as flow improver for Nigerian Waxy crude oils

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Petroleum Research 2022年第1期7卷 138-143页

作者： Ogunkunle Temitope Fred Abraham Victoria Damilola Adebisi Abimbola Ashonibare Rukayat Adenike Tega-oboh Elohor Sylvia Petroleum Engineering Department Covenant UniversityOtaOgun StateNigeria Chemistry Department Covenant UniversityOtaOgun StateNigeria Nigerian Stored Products Research Institute Asa Dam RoadIlorinKwara StateNigeria

In this study,the physicochemical properties of linseed and linseed biofuel were studied and their effect on the flow properties of Nigerian Waxy crude oil at different volume fractions was investigated.The Nigerian wax crude oil was characterized for its specific gravity,API gravity,wax content,pour point and cloud point.The properties of the linseed oil and linseed biodiesel investigated include:density,specific gravity,viscosity,pour point,cloud point and flash point.Upon esterification of the free fatty acid(FFA)contained in the linseed oil reduced from 3.5 to 0.75 and the viscosity of the seed oil reduces from 2169 to 362 mm^(2)/s.The linseed oil and its biodiesel exhibited similar trend of reduced viscosity at higher shear rate,however,linseed biodiesel demonstrated the lowest viscosities,cloud points and pour points owing to reduced fatty contents.The effect of the linseed oil and its biodiesel on the pour point and cloud point of the Waxy crude oil was determined;and the performance compared to that of xylene.A rapid drop in the pour point and cloud point was observed with the wax crude pre-heated with 0.1 v/v linseed oil,its biodiesel and xylene.

关键词： Seed oils Cloud point Rheological properties Pour point Viscosity Waxy crude oil

Simulation of pipelining pours point depressant beneficiated Waxy crude oil through China West crude oil Pipeline

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Simulation of pipelining pours point depressant beneficiated...

Non-Newtonian steady shear flow characteristics of Waxy crude oil

The 9th National Conference on Rheology

作者：李鸿英张劲军凌霄黄启玉林小飞贾邦龙李宇光 Beijing Key Laboratory of Urban oil and Gas Distribution Technology China University of Petroleum

＜正＞Flow properties of Waxy crude oils,particularly the beneficiated Waxy crude oils,are sensitive to shear history that the crude oil experienced,called the shear history effect.To simulate this shear history effect accurately is vital to pipeline design and operation.It has been demonstrated by our previous that the energy dissipation or entropy generation due to viscous flow in the shear process is a suitable parameter for simulating the shear history effect.In order to further verify the reliability of this approach, experimental simulations were conducted for three PPD-beneficiated Waxy crude oils transported through the China West crude oil Pipeline,a most complicated long-distance-crude-oil-pipeline technically and operationally so far in China.The simulations were made by using a stirred vessel and with the energy dissipation of viscous flow as the shear simulation parameter.Comparison between the flow properties of crude oils obtained from field test and experimental simulations,it is found that the gel points and viscosities from experimental simulations are in good agreement with the field data.

关键词： Waxy crude oil flow properties shear history effect experimental simulation

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Non-Newtonian steady shear flow characteristics of waxy crud...

Performance improvement of Ethylene-Vinyl Acetate Copolymer Pour Point Depressant(EVA PPD)by adding small dosages of Laurylamine(LA)

The 9th National Conference on Rheology

作者：黄树新陈鑫鲁传敬侯磊范毓润 Department of Engineering Mechanics Shanghai Jiaotong University Department of Petroleum Storage and Transportation China University of Petroleum State Key Laboratory of Fluid Power Transmission and Control Zhejiang University

The experimental research on the non-Newtonian flow characteristic of a Waxy crude oil was conducted through a rotational parallel-plates rbeometer system.The test temperature is about 6.5℃ higher than its gel point.The shear stress and viscosity of the Waxy crude oil show sophisticate non-Newtonian characteristics in the shear rate of 10-10 s,in which the shear stress can be divided into three parts qualitatively,i.***.stress-up region,leveling-off region,and stress-up region.This indicates that there is a yielding process in shearing for the Waxy crude oil at the experimental temperature,which is similar to the yield phenomenon in thixotropy-loop test discussed by CHANG and BOGER.Furthermore,the steady shear experiment alter the pre- shear process shows that the stress leveling-off region at low shear rate disappears for the Waxy crude oil and the stress curve becomes a monotonic climbing one,which demonstrates that the internal structure property presenting through yielding stress at low shear rate can be changed by shearing.The experimental results also show that the internal structure of Waxy crude oil presenting at low shear rate has no influence on the shear viscosity obtained at the shear rate higher than 0.1s.The generalized Newtonian model is adopted to describe the shear-thinning viscosity property of the Waxy crude oil at high shear rate.

关键词： Waxy crude oil shear flow non-Newtonian flow generalized Newtonian model

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Petroleum Science 2022年第5期19卷 2472-2482页

作者： Xue Xia Chuan-Xian Li Guang-Yu Sun Ke-Ke Zhao Jie Zhang Bo Yao Fei Yang College of Pipeline and Civil Engineering China University of PetroleumQingdaoShandong266580PR China Shandong Provincial Key Laboratory of oil&Gas Storage and Transportation Safety QingdaoShandong266580PR China China Petroleum Engineering&Construction Corp.Beijing Company PR China

Lauramine is widely considered to be an asphaltene flocculant,but its effect on the modification of crude oil by PPDs has been little studied.In this paper,the effect of LA dosage on the rheology improvement of EVA PPDs(100 ppm)on Qinghai Waxy crude oil was investigated through rheological measurement,wax precipitating analysis,granularity test and resins/asphaltenes FTIR analysis.Compared with pure EVA,the compounding of LA and EVA obviously enhances the agglomeration degree and reduces the number of fine wax crystals,thus further enhancing the rheology of the oil samples,and the best performance is at the LA dosage of 200 ppm.At relatively small LA dosages,the LA facilitates the adsorption of EVA molecules on the asphaltene surfaces,which favors the becoming of EVA/asphaltenes composite particles;but at relatively high LA dosages,the LA makes the asphaltenes more aggregated and disturbs the EVA adsorption on the asphaltenes,which is adverse for the formation of EVA/asphaltenes compound particles.The compound particles can serve as wax precipitating templates and significantly influence its morphology,thus further improving the crude oil rheology.In consequence,the rheology improvement of EVA PPDs on Qinghai Waxy crude oil first increases and then decreases with increasing the LA dosage.

关键词： Waxy crude oil EVA PPD Laurylamine Asphaltenes Synergistic effect

A nonlinear creep damage model for gelled waxy crude

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Petroleum Science 2022年第4期19卷 1803-1811页

作者： Hong-Ying Li Qing-Bo Xie Hao Sun Wei Guo Feng Yan Qing Miao Chao-Fei Nie Yu Zhuang Qian Huang Jin-Jun Zhang National Engineering Laboratory for Pipeline Safety/MOE Key Laboratory of Petroleum Engineering/Bejing Key Laboratory of Urban oil&Gas Distribution Technology/China Universityof Petroleum Beijing102249China PipeChina Pipeline R&DCenter Langfang065000China Jinan Urban Planning and Design Institute Jinan250101China

Yielding behaviors of Waxy crude oil is one of the key issues of flow assurance challenges. The yielding of waxy crude under constant stress is actually a creep process of strain accumulation to structural failure,to describe the process completely and accurately is the basis of numerical simulation of restart process of the pipeline. The creep and yield behaviors of two gelled waxy crudes were investigated experimentally under different constant applied stresses. The results clearly show that the creep process of waxy crude is related to the applied stress and time. The greater the applied stress, and the longer the loaded time, the more obvious the nonlinear features. Based on the fractional calculus theory, a fractional viscous element was developed to describe the decelerated and steady creep process of gelled waxy crude. On the basis of the damage theory, an elastic damage element was proposed to describe the accelerated creep after the yielding. According to the idea of mechanical analogy, a nonlinear creep model was established by a fractional viscous element, an elastic damaged element, and an elastic element in series, which can accurately describe the whole creep and yielding process of gelled waxy crude.

关键词： Waxy crude oil Rheology Yield Creep Constitutive model Mechanical analogy

Pre-heating temperature induced flowability and wax deposition characteristics of crude oil adding wax inhibitors

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Petroleum Science 2023年第4期20卷 2468-2478页

作者： Bo Yao Hao-Ran Zhu Bao-Dong Yan Chuan-Xian Li Fei Yang Guang-Yu Sun Hong-Bo Zeng College of Pipeline and Civil Engineering China University of PetroleumQingdaoShandong266580People's Republic of China Department of Chemical and Materials Engineering University of AlbertaEdmontonABT6G 1H9Canada School of Petroleum Engineering Changzhou UniversityChangzhouJiangsu213164People's Republic of China China oil&Gas Pipeline Network Corporation Beijing100020China

This paper investigated the effects of pre-heating treatment temperatures(T_(pre))on the flowability and wax deposition characteristics of a typical Waxy crude oil after adding wax inhibitors.It is found that there is little difference in wax precipitation exothermic characteristics of crude oils at different T_(pre),as well as the wax crystal solubility coefficient in the temperature range of 25-30℃.For the undoped crude oil,the flowability after wax precipitation gets much improved and the wax deposition is alleviated as T_(pre)increasing.At T_(pre)=50℃,the viscosity and wax deposition rate of crude oil adding wax inhibitors are higher than those of the undoped crude oil.When the T_(pre)increases to 60,70,and 80℃,the flowability of the doped crude oil are largely improved and the wax deposition is suppressed with the T_(pre)increase,but the wax content of wax deposit increases gradually.It is speculated that,on the one hand,the T_(pre)increase helps the dispersion of asphaltenes into smaller sizes,which facilitates the co-crystallization with paraffin waxes and generates more aggregated wax crystal flocs.This weakens the low-temperature gel structure and increases the solid concentration required for the crosslink to form the wax deposit.On the other hand,the decrease in viscosity increases the diffusion rate of wax molecules and accelerates the aging of wax deposits.The experimental results have important guiding significance for the pipeline transportation of doped crude oils.

关键词： Pre-heating treatment Wax inhibitor Flowability Wax deposition Waxy crude oil