Point Of Crude Oil Research Articles

The potential blockage during CO2 displacement in the high pour point oil reservoir

CO2 displacement is a common technique for the enhanced oil recovery and simultaneously alleviates the greenhouse effect. However, the recent applications of CO2 displacement focus on the formations where the fluid and reservoir properties could not reach absolute miscibility. The reactions between CO2 and high pour point crude oil during the near-miscible displacement process would be far more complex. In this study, slim-tube and one-dimensional core (sand-filling model, splicing long core) displacement experiments were carried out. Group component analysis and saturated hydrocarbon analysis were applied during the process and the possibility of organic solid deposition and blockage was deduced. The indicator of permeability reduction rate of long core was introduced and used to evaluate the impact of the deposition of each short core on the permeability. Through analysis and comparison, deposition and blockage occurred in the front and middle of the long core, and the maximum permeability reduction rate reached about 0.04%. The results showed that although near-miscible displacement could improve the oil recovery, there was still the possibility of potential blockage which should be carefully considered in the design of the gas injection scheme.

Effect of paraffin precipitation on core flow in porous media capacity during fracturing

Low-permeability sandstone reservoirs have become an important exploration and reserve increase target in China, but most low-permeability sandstone reservoirs with high wax content and high freezing point will reduce their production after fracturing injection, especially in winter. Therefore, it is necessary to analyze the field fracturing construction measures and reservoir characteristics. Generally, the fracturing fluid injected by fracturing operation is at room temperature, even lower than 5 °C in winter, and the viscosity and freezing point of crude oil in this block are high. Therefore, the research focuses on the properties of crude oil and the influence of temperature reduction on oil-bearing cores. In order to find out the mechanism of reservoir cold damage, this paper first observed the pore throat of rock sample slice after displacement experiment, and found that there were black paraffin particles in some pore throats; then the distribution of core pore size after displacement was analyzed by T2 spectrum of NMR, and it was found that the proportion of small pores increased gradually with the decrease of temperature. Finally, the displacement experiment is used to simulate the change of permeability in the process of formation cooling and heating after field fracturing. The permeability of crude oil is tested by changing the ambient temperature of displacement experiment. It is found that the permeability before cooling is larger than that after heating recovery, and the process is irreversible. Therefore, the cause of cold damage is that the injection temperature of fracturing fluid is far lower than the formation temperature and the precipitation of paraffin during the cooling process of crude oil. For reservoirs with high wax content and high freezing point, paraffin precipitation caused by cold damage has a great influence on formation permeability, and cold damage can be prevented by changing injection fracturing fluid temperature or adding paraffin inhibitor.

Development and Application of Efficient Oil Displacement System for Middle-Low Permeability and High Pour-Point Heavy Oil Reservoirs

In view of the problems of low permeability, high oil viscosity and freezing point, and low productivity of single well in Luo 321 and Luo 36 blocks of Luojia Oilfield, the chemical viscosity-reducing cold production technology was studied. By analyzing the properties of crude oil, it is concluded that the reason for high viscosity and high freezing point is the high content of asphaltene, pectin, and wax. The viscosity is mainly affected by asphaltene; the wax precipitation point and pour point are mainly affected by the wax; and the solidification point is affected by the wax and asphaltene. The treatment idea of reducing viscosity and inhibiting wax is determined. By compounding the synthetic pour point depressant POA-VA and the viscosity reducer DBD-DOPAMA, the effect of reducing the viscosity and freezing point of crude oil was evaluated. PD-7 (POA-VA 40%, DBD-DOPAMA 50%, and P-10C 10%) system was selected as the optimal formula. When the concentration of the system is 10%, the viscosity reduction rate reaches 95.2%; the freezing point can reduce by 10.2°C; it has good oil sample adaptability, salinity resistance, and temperature resistance; and the oil washing rate can reach more than 60%. The oil displacement system was injected into the formation by means of multiconcentration and multislug and was applied in the field of Luo 321-2 Well. A total of 500 t of the oil displacement system was injected, and the effect of measures lasted for 400 days, with a cumulative oil increase of 883 t. It has been applied in different blocks 30 times and achieved a good field application effect.

Study on structure control and pour point depression mechanism of comb-type copolymers

A series of poly (n-alkyl acrylate-maleic anhydride) with different molecular weights were prepared as pour point depressants (PPDs) for JENM waxy crude oil obtained from the China-Myanmar crude oil pipeline. The crystallization temperature, wax morphology, and rheological behavior of crude oil were analyzed by differential scanning calorimetry, polarizing microscope, and rotary rheometer, respectively. The results indicate that the molecular weight significantly affects the performance of the pour point depressant. When the weight-average molecular weight (Mw) of copolymers were ranging from 60,000 to 70,000, it has a better pour point depression effect for JENM crude oil. The added copolymer (MW = 68,300) has achieved optimal performance which decreased the pour point of crude oil from 30 to 19 °C and crystallization temperature from 39.5 to 36.1 °C with the smallest wax crystal size and the 96.7% reduction viscosity.

Method for Exploiting High-viscosity and High-pour-point Crude Oil

Because of its high viscosity and high freezing point, high viscosity and high pour point crude oil has always been a difficult problem in production. On the basis of fully studying the viscosity temperature characteristics of high viscosity and high pour point crude oil, this paper puts forward the idea of hydraulic cutting. This method accurately grasps the freezing point of high viscosity and high pour point crude oil. The high viscosity and high pour point crude oil is cut by high-speed cold water hydraulic cutting near the freezing point, which is cut into fine crude oil particles or crude oil flocs. These fine crude oil particles or flocculent crude oil float in continuous water phase, and are mined to the surface with solid or semi-solid water flow. Thus, the problem of low cost exploitation of high viscosity and high pour point crude oil is solved. This method not only provides an effective technical means for the exploitation of high viscosity and high pour point crude oil, but also greatly reduces the production cost. It has a high application prospect and good economic benefits.

Numerical method for interfacial heat transfer in an oil‐water displacement flow

AbstractA numerical study of interfacial heat transfer is performed in an oil‐water displacement flow. The process of oil‐water displacement is one of the key technologies for the underwater tank in offshore oil exploitation. There is a need to investigate the interfacial heat transfer between oil and water as the wax precipitation and solidification of high pour point crude oil at low temperature will particularly affect the flow of oil. Before the numerical simulation is performed, it is necessary to find out the optimal numerical method. For the volume of fluid method, the property parameters in the temperature equation are mixture ones weighted by each fluid. When the unsteady term, convective term, and diffusion term are considered, there are three property parameters that are the coefficient of each term. For each coefficient, whether an algebraic scheme or a harmonic scheme could be used. When the three coefficients are considered together, there would be eight combinations of weighting form. A numerical method is developed by exploring an optimal combination of the weighting form. The results are demonstrated with an analytical solution. It is found that the combination of three harmonic schemes will significantly improve the error. The maximum and total error from this combination are reduced by 62% and 79% compared to the second‐best one and by 86% and 93% compared to the worst one. Meanwhile, the clock time only increases by 1.6% and 0.4%. The combinations of three harmonic schemes will result in the largest order of accuracy which is as large as 1.60. The harmonic scheme should be used for the property parameter of all the three terms in the vertical oil‐water flow.

Discussion on Design of Flow Assurance for High Pour Point Crude Oil Transportation Pipeline

Flow assurance is very important for design and operation management of the high pour point crude oil transportation pipeline. This paper choose one oil pipeline of CNOOC as an analysis example. Research on two main design plan according to the thermal management mode. In the heating, hot water preheating and displacement plan, the best temperature of hot water is existed. Hot water 88°C will be adopted. The greater of the preheating water flowrate, benefits thepreheating. The design flowrate 6359m3/d will be used. In skin effect electric heat plan, the pipeline insulation layer thickness of 80 mm and skin heating power of 2534 kw will be used through technical economical comparison, and the advantage of skin effect electric heat plan is analyzed relative to heating, hot water preheating and the displacement plan. The above research results may provide technical reference for the future design of high pour point crude oil transportation pipeline.

Application of bayesian regularized artificial neural networks to predict pour point of crude oil treated by pour point depressant

ABSTRACTThe pour point of the crude oil treated with the pour point depressant (PPD) is easily affected by the shear history effect. Models for pour point of PPD-treatment crude oil affected by the shear history effect based on Bayesian regularized artificial neural network (BRANN) were established. The results showed that BRANN models not only had a good ability of fitting to the training data, but also had a good ability of predicting the testing data. By evaluating network performance with several statistical indicators, the three models have excellent performance, high accuracy, and strong generalization ability. The influence of each parameter on the pour point were also investigated through a sensitivity analysis, which shows that the entropy generation due to viscous flow is the most important parameter in predicting the pour point.

Reducing the pour point of crude oil by using of ultrasonic wave

With the global economical development, high pour point crude oil (HPPCO) is getting more and more attentions. Due to its higher pour point and worse fluidity when it is cold, more difficulties are faced for its extraction. Ultrasonic wave technology is investigated to reduce the pour point of Sudan HPPCO in this paper. First, an ultrasonic horn is proposed and made. Then, after processing for 3 min by the horn, a decrease of more than 3 of the pour point of Sudan HPPCO is obtained. Furthermore, compared with that without ultrasonic processing, the percentage of higher molecular weight constituents becomes more, while that of heavier molecular weight component is less. The mechanism that the pour point of HPPCO can be changed through ultrasonic processing is analyzed and investigated by an experiment that three types of paraffin wax whose molecular weights are different are processed by ultrasonic wave. The main advantage of the ultrasonic processing for HPPCO is economical and environmental and the decrease of pour point after ultrasonic processing is irreversible.

Research of Thermal Insulation Control for Underwater Storage of High Pour Point Crude Oil

Underwater oil storage is a new offshore oil drilling technique developed in recent years. Because of the high pour point, crude oil condensation will affect its storage and transportation. In order to solve this problem, a set of thermal insulation control system for underwater oil storage was designed in this paper. Flexible isolation cloth with low thermal conductivity and insulation coatings on the inwall of oil tanks are applied to reduce temperature loss, while mamdani fuzzy controller was used to control the heating of hot water and to solve nonlinear and large time delay and inertia of the object so as to maintain the stable oil temperature.

Idea of Pollution-Free Underwater Oil Storage Technology and Test of Crude Oil Underwater Thermal Insulation

Pollution-free underwater oil storage model is raised, realizing zero-pollution underwater oil storage with oil-water replacement through flexible separation method to prevent crude oil from directly contacting seawater. Experiment on thermal insulation of underwater crude oil with separate replacement of oil and water was made, proving that high pour point crude oil does not change significantly within a time and still possesses a good liquidity. Therefore, it is feasible to apply this underwater oil storage system to the storage of high pour point crude oil.

Pour Point Depressant(PPD) and Flow Improver Additives (FIA) of Crude Oil and its Study Method Progress

The situation of low temperature crude oil pipeline carrying is universal. The rapid developing of pipe line supposes higher asking on new carrying technology. The problem of long distance carrying at normal temperature of high waxy crude oil is impel to resolve and its potential social economic profit is obvious. As the pipeline is designed at high production period of field so there must have low carrying situation at beginning and ending time. At the situation the high waxy crude oil and high pour point crude oil will face on great resistance and blockage problem. Further more the pipeline has to make great energy expense on high temperature carrying. So take new carrying technology to realize atmosphere temperature carrying is crucial of resolving low temperature carrying. The method of adding chemical pour point depressant(PPD)/flow improver additives (FIA) into crude oil directly was widely used at present. The progress of the additives and its study methods was summarized in the paper and supply some reference for the technology of PPD/FIA.

The Variation of the Gel Point of Daqing Crude Oil with Pipelining History

Daqing crude oil is a typical waxy crude oil with a wax content of 26.6 wt% and a gel point of 32°C. In order to conduct the safety analysis of pipeline operation, the variation of gel point of Daqing crude oil with thermal and shear history was studied through pipelining simulation experiments. The experiments were performed under different annual throughputs and shear rates of pipeline flow. The results suggest that the change of shear action has little effect on the gel point of crude oil. As the final dynamic cooling temperature is increased, the change of gel point experiences two stages, staying constant at first and then decreasing. Through 13 groups of pipelining simulation experiments, the effects of heating temperature ranging from 45°C to 65°C on gel point of Daqing crude oil were studied. It has been indicated that the gel point increases as the heating temperature is increased under the same final dynamic cooling temperature. The relation equation was constructed to be used to predict the gel point under certain heating temperatures and final dynamic cooling temperature. The average absolute deviation of 52 predicted values of gel point is 0.58°C.

The static yield point of crude oil at −15°C decreased by ultrasonic shear oscillations

Experiments on a laboratory prototype setup showed that ultrasonic shear oscillations produce a statistically reliable decrease in the static yield point (normalized to the initial temperature) of crude oil in a near-wall layer at temperatures in the interval of −(13–17.5)°C. The observed effect amounted to about 19% at a specific power of ultrasonic oscillations on a level of 0.002 W/cm2.

Hybrid Petri Net Modeling and Schedulability Analysis of High Fusion Point Oil Transportation Under Tank Grouping Strategy for Crude Oil Operations in Refinery

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> There are varieties of constraints for a short-term scheduling problem of crude oil operations in a refinery. These constraints are difficult to model and complicate the short-term scheduling problem. Among them, oil residency time and high fusion point crude oil transportation constraints are the challenging ones. With high setup cost for high fusion point oil transportation, it is desired that the volume of high fusion point oil can be transported as much as possible by a single setup. This may result in late transportation of other types of crude oil, leading to the violation of crude oil residency time constraint. These constraints are ignored by existing methods in the literature. To solve this problem, this paper studies the problem in a control theory perspective by viewing an operation decision in the schedule as a control. With this idea, the system is modeled by a hybrid Petri net. With this model and tank grouping strategy, schedulability analysis is carried out and schedulability conditions are presented with tank charging and discharging costs being taken into consideration. These conditions are necessary for determining a refining schedule and can be used to check whether a target-refining schedule is realizable or not. If so, a feasible detailed schedule for the refining schedule can be easily obtained by creating the operation decisions one by one. </para>

The Phazaphot instrument for determination of the low-temperature properties of petroleum products

A new method of determining the solid point and flow point of crude oil and petroleum products, crystallization/melting of waxes in petroleum products, and the Phazaphot instrument for implementing the method are described. The method consists of recording the intensity of light mirror-reflected from the surface of the sample during structural transitions when the temperature changes. The new principle of measurements allowed significantly simplifying implementation of the method, making the determinations faster, and expanding the range of objects investigated and problems solved.

New Correlation for Estimating the Viscosity of Undersaturated Crude Oils

Abstract A new general correlation for estimating the viscosity of undersaturated crude oils has been developed using 253 experimentally obtained oil viscosities on 41 different oil samples collected from two different unpublished sources. The developed correlation is derived from plotting (P-Pb) vs. (µoa - µob) on log-log paper. The plot reveals a series of straight lines of a constant slope equal to 1.11. It is found that the intercepts of the resulting lines can be accurately represented as a function of API gravity and solution gas-oil ratio at bubble point pressure. The present correlation shows excellent results and clearly outperforms the existing correlations, when tested against the present data bank (253 points) and against available data from the literature (137 points). Introduction Viscosity in general can be defined as the internal resistance of fluid to flow. Like other physical properties of liquids, the viscosity is sensitive to changes in pressure and temperature. Increasing temperature always causes a decrease in viscosity. Increasing pressure always increases viscosity above the bubble point. However, below the bubble point, an increase in pressure causes an increase in solution gas which in turn decreases viscosity. Crude oil viscosity is essential for both petroleum reservoir engineering and production design operations. The present work deals with the correlations of viscosity of undersaturated crude oils (above bubble point pressure). The common empirical correlations available for predicting this property are those of Beal and Vasquez. In 1946, Beal presented a graphical method derived as the rate of change of the undersaturated oil viscosity per unit pressure increase above the bubble point pressure and the bubble point crude oil viscosity. The disadvantages of Beal's correlation are:it is based on only 26 data points covering limited ranges of flow conditions, andno analytical expression is given for the correlation. Using only 11 data points, obtained from Figure 11 of Beal's work, Standing found that Beal's correlation can be approximated by the following equation, which fit the 11 points with average error = 1% and standard deviation = 4.64%.

Biological markers in lacustrine Chinese oil shales

Summary A major objective in molecular organic geochemistry is the assessment and characterization of sedimentary depositional environments from the occurrence of specific biological marker compounds related to particular source organisms. The aliphatic hydrocarbon distributions of petroleums and/or sediments from Chinese freshwater and hypersaline lacustrine environments are described and contrasted in the search for diagnostic features among their biological marker distributions. The Eocene Maoming oil shale, which crops out in Guangdong Province, shows major differences in hydrocarbon composition through its stratigraphic succession. These variations reflect changes in lithology and in the origins of the sedimentary organic matter, as seen from petrographic examination. The lower lignite and vitrinite layers contain significant contributions of biological markers from bacterial sources, plus components derived from terrigenous higher plants, such as C 29 steroids. In contrast, the overlying shales show a dominance of dinoflagellate-derived 4-methylsteroids and culminate in an horizon with botryococcane homologues as their dominant alkanes. Thus, the geochemical profile suggests that a swampy environment, in which peats accumulated, deepened to support populations of dinoflagellate and, finally, blooms of Botryococcus green algae. The aliphatic hydrocarbons of a series of sediments and petroleums from the Eocene hypersaline sequence of the Jianghan Basin in southern Hubei Province shows various features that may be typical of such facies. These include a dominance of even-numbered n-alkanes, high amounts of phytane and gammacerane, and an abundance of C 35 -hopanes. Similar characteristics are observed in shales from the Eocene Green River Formation and in Rozel Point crude oil, a petroleum thought to originate from sediments deposited under hypersaline conditions. The same features also appear in a lower Tertiary evaporitic mudstone from south of the Renqui oil field in Hebei Province, together with 4-methylsteranes, β-carotane and 18α(H)-oleanane, a marker for terrigenous higher plants. These data illustrate the potential of biological markers in the differentiation of different lacustrine environments and suggest that such characteristics may provide signatures for environmentally similar, but geographically distant, deposits.

A Study on Solidified Oil and Heat Flux at Tank Bottom of a Tanker Carrying High Pour Point Crude Oil

The supplied quantity of heat energy for keeping in low viscosity of loading oil is necessary to be estimated with accuracy in a tanker carrying high pour point oil or high viscous oil. It is difficult to assume it exactly, because the heat transfer coefficient through tank bottom is various due to depending on the configulation of bottom structure and the physical properties of loading oil.In order to investigate the heat transfer through tank bottom, the measurement of heat flux is carried out using the tank in the shape of bottom structure on the scale of one-third in which the paraffin as one kind of high pour point oil and the high viscous lubrication oil are heating up with three heaters. The predicting formulae on variable thickness of solidified oil and heat flow at bottom as time proceeds are derived from the theory and the experimental values. These formulae are applied for estimating the heat transfer coefficient of actual ship. As the results, the heat transfer coefficients through tank bottom excepting the effect of ship oscillation are assumed to be 78 W/m2K for high viscous oil and 4.7 W/m2K for high pour point oil.

A Study on Solidified Oil and Heat Flux at Tank Bottom of a Tanker Carrying High Pour Point Crude Oil

A lage quantity of high pour point oil which tends to be solidified at a normal temperature is carried by the oil tankers that are equiped with oil heating system for purpose of keeping in low viscosity of crude oil. As cooling bottom plate by sea water, the crude oil near bottom is solidified in spite of heating up and the solidified layer is likely as insulation against heat flow through bottom. The solidified oil blocks up oil courses bored at bottom structural members and prevents from gathering oil at the final period of pumping up crude oil. Besides, the tank capacity is decreased since solid oil at bottom is just unpumpable.In this paper, the predicted method on thickness of solidified oil at bottom is proposed in comparison with the measured data on an actual tanker and the numerical analysis on Stefan-problem is carried out by using the enthalpy with delta-sequence function in order to investigate the solidifying process of high pour point oil. Furthermore, the experiment of melting solid paraffin by heating up in the tank in the shape of bottom structure on the scale of one-third is executed in addition to calculate by use of physical properties on Minas crude oil. By the results of measurement, it has been recognized to be practically difficult for melting the solidified oil between frame space without heating coil and some useful consequences for design of oil heating system are obtained.