Oil Gathering Research Articles

Effect of doped emulsifiers on the morphology of precipitated wax crystals and the gel structure of water-in-model-oil emulsions

Waxy crude oils can easily form water-in-oil (W/O) emulsions in submarine gathering and transportation pipelines. When the temperature becomes lower than the wax appearance temperature (WAT), wax crystals will gradually precipitate and the emulsions will thus change to a gel state. This paper aims to uncover the effect of wax crystal morphology on the gel structure of W/O emulsions. Experiments were performed on the crystallization exothermic characteristics, viscoelasticity, and yield stress of the different emulsifier-doped model oils and their emulsions with different wax crystal microstructures. The structural strength of the emulsion gels was mainly correlated with the morphology of the precipitated wax crystals, and also related to the water cut. The needlelike wax crystals could easily overlap with each other and form a compact and solid network structure. In this case, the wax crystals played a leading role in forming the emulsion gels. Therefore, as the water cut decreased, more wax crystals were there to be precipitated, leading to a stronger structural strength of the emulsion gels. On the contrary, when the precipitated wax crystals aggregated into large flocs, it was hard to build a network on their own, so they could enhance the structure by adsorbing at the dispersed water droplets. In this case, the water droplets played a leading role in the formation of the network structure. Therefore, as the water cut increased, the structural strength of the emulsion gels became stronger, mainly due to the increase in the number of water droplets. These findings are of great significance to the safe operation of waxy crude oil gathering and transportation systems under low-temperature subsea environments.

Batch transportation of oil and water for reducing pipeline corrosion

Different from the conventional transportation of oil-water mixtures, we proposed a method to reduce pipeline corrosion based on a concept of flow management, where the mixed fluids were firstly separated into oil and water and then a batch transportation of oil and water was introduced to tune the water wetting state at pipeline bottom. In this way, the corrosion risk of pipe bottom can be properly reduced with a minor modification of the transportation procedure. In this paper, the idea was theoretically and experimentally verified, and the modified procedure was effective in corrosion mitigation compared with the conventional oil gathering system in a CO2-enhanced oil recovery (EOR) production system. It was found that the corrosion mitigation efficiency held a positive relationship with the dimensionless length of the oil phase, which was determined by the input length of oil and water batch and the evolution of flow pattern at the oil/water interface. This is of special benefits for the case where a large amount of free water is unable to be entrained into oil phase. Such a concept of corrosion mitigation can be applied in the transportation of corrosive oil-water mixtures in petroleum industry, such as in CO2-EOR and offshore oil production.

Numerical study for removing wax deposition by thermal washing for the waxy crude oil gathering pipeline.

Exploring the wax removal process by numerical simulation is beneficial for guiding field operations. In this paper, enthalpy-porosity and volume of fluid (VOF) methods were adopted to simulate the melting process of wax in the crude oil gathering pipeline. The melting patterns and liquid fraction of the wax were used to validate the mathematical model. The results show that the wax melts quickly before the liquid fraction reaches 80%, while the remaining 20% melts very slowly. Since the water with higher density sinks to the lower part of the pipeline, the wax in the lower part of the pipeline melts first, while the wax in the upper part of the pipeline melts slowly. The water temperature and flow rate disproportionately affect the melting process. Increasing the water temperature and flow rate can accelerate the melting process, but the effects on shortening the melting time of wax gradually decrease. Increasing the flow rate, the heat transfer rate and the melting rate are increasing progressively, the change of flow rate also affects the outlet temperature of the pipeline.

Failure Analysis and Solution to Bimetallic Lined Pipe

Owing to low cost, excellent pressure and corrosion resistance, bimetallic lined pipes were regarded as one of the most important methods to resolve corrosion of traditional steel pipes used for oilfield. Nowadays, the pipes are widely used in the projects of oil and gas gathering and transportation. However, there were some failure cases in succession in recent years. In this paper, the failure causes were excavated from multiple perspectives, and on this basis further countermeasures were put forward. Firstly, three typical failure accidents, including CRA layer collapse, CRA layer corrosion and weld joint failure, were listed throughout the whole life cycle from product ordering, construction technology to later operation. Secondly, failure analysis was carried out from five aspects: product quality, test technology, welding process, standard specification and application threshold, and a serial of comprehensive views were proposed. 1) Manufacturing period: Water seepage and tightness between CRA layer and backing pipe could not be effectively monitored. The ratio of collapse test was low so that proposed relevant risk could not be eliminated; 2) Welding period: the process has high risk failure in theory and lack of process assessment and construction acceptance standards. Potential danger could not be effectively assessed, and weld quality could not be guaranteed; 3) Application period: The CRA application range remained unclear, and bimetallic lined pipes were used in the environment beyond the threshold sometimes. The paper also summarized further improvement measures and research directions about these five aspects, including process quality, inspect technique, welding process, standard specification and application range. Finally, solution suggestions were proposed for the whole chain from manufacturers, testing institutions, construction units to oilfield users.

Test Analysis of Corrosion Perforation in a Crude Oil Gathering Pipeline

The reason for perforation leakage of gathering pipeline in an oilfield was investigated by size measurement, mechanical properties, metallographic structure, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrum (EDS). The results showed that the failure form of the spirally submerged arc welded pipe (SAW) was the corrosion perforation caused by local corrosion. The main cause of corrosion perforation was due to the existence of chlorine ion, H2O and O2 in the pipeline transportation medium. A large cathode and small anode electrode corrosion formed in the pipe marking area and the base metal, which eventually led to the perforation of the steel pipe.

Research on a Safety Assessment Method for Leakage in a Heavy Oil Gathering Pipeline

At present, the number of oil and gas gathering and transportation pipelines is numerous, and leakage accidents occur frequently. Each year, due to pipeline failure, there are immeasurable consequences for people and the environment around the affected pipelines. In order to reduce the risk of leakage accidents in heavy oil gathering pipelines and prevent the occurrence of major spills, it is of great significance to carry out safety assessments of them. However, failure data of these pipelines is seriously deficient and statistical methods used to evaluate pipeline safety are incompatible. Therefore, this paper proposes a risk assessment system for heavy oil gathering pipelines in the absence of failure data. Firstly, a Bayesian network (BN) for the leak safety evaluation of heavy oil gathering pipelines is established via mapping from a bow-tie (BT) model. Then, information diffusion theory is combined with fuzzy set theory to obtain the failure probability of each factor affecting the pipeline failure, and then the failure probability of the pipeline is obtained by the full probability formula. In addition, in order to assess the extent of consequences due to accidents, variable fuzzy set theory is used to comprehensively consider the consequences of the leakage of heavy oil gathering pipelines. Finally, the above two parts are combined to form a safety assessment system to realize risk management and control for pipelines, which is necessary to ensure the safety of heavy oil gathering pipelines.

Application of mineral fertilizers and bacterial preparations under sunflower on ordinary chernozem

The results of field experiments to study the effect of mineral fertilizers and bacterial preparations on the yield and quality of sunflower seeds are presented. The studies were carried out in 2011–2014 in the Rostov region on medium-power ordinary chernozem. The object of research was a hybrid of sunflower Patriot. The predecessor is winter wheat. Ammonium nitrate, ammophos and potassium chloride in various doses were used as mineral fertilizers, according to the experimental scheme. Fertilizers were introduced before sowing, before the main tillage and pre-sowing cultivation. Bacterial preparations were represented by associative nitrogen fixers of the strains Mizorin, Flavobacterin, PG-5 and 17-1 produced by the All-Russian Scientific Research Institute of Agricultural Medicine, Pushkin. In the field experiment, variants of the joint application of mineral fertilizers and presowing treatment of seeds with bacterial preparations were also studied. The control was the variant without the application of mineral fertilizers and bacterial preparations. The Patriot sunflower hybrid seed yield in the control variant on average for 3 years amounted to 1.61 t/ha. A significant increase in the yield of sunflower seeds and oil gathering was established in the variant with pre-sowing application of mineral fertilizers in a dose of N40P50. The increase compared to the control variant was 0.53 t/ha, or 34.2%, and in the oil gathering in the crop - 226 kg/ha, or 36.4%. The application of biologics of associative nitrogen fixers contributed to an increase in the yield of sunflower seeds. Inoculation of sunflower seeds with a strain of the biological preparation PG-5 was more effective. The increase in the yield of sunflower seeds amounted to 0.44 t/ha, or 28.6% compared to the variant without the application of fertilizers. The increase in the oil gathering in the crop was by 29.3%. The application of bacterial preparations under sunflower against a background of nitrogen-phosphorus fertilizers was ineffective.

Exergoeconomic pricing strategy of crude oil gathering and transportation system

Taking a typical oil transfer station in eastern China as an example in this paper, exergy economics theory in algebraic pattern is applied to the energy system of the oil transfer station on the b...

Exergy analysis of crude oil gathering and transportation system by 'three box' model

Exergy analysis of crude oil gathering and transportation system by 'three box' model

Коррозионно-механическое разрушение электросварных труб в нефтепромысловых средах высокой агрессивности

Pipes welded from specially prepared sheet steel, in comparison with the seamless drawn ones, are characterized by the low cost, higher corrosion resistance, and dimensional stability. When ensuring the properties of a welded joint at the base metal level, they can compete with seamless pipes. To start using welded pipes made of new steels, long-term field tests in fields with high aggressiveness of extracted fluids are required. It is necessary to have the comparative results on corrosion resistance of the base metal and welded joints. The paper aimed at obtaining information on the mechanisms and kinetics of stress-corrosion fracture and the operating ability of electric-welded pipes during continuous service. The authors carried out the field (bypass) tests of the electric-welded pipe spools made of 08HMFChA, 13HFA, 09GSF, and 20-KSH steels on the operating oil gathering main of Mamontovskoye oilfield of Western Siberia with the high content of H 2 S and CO 2 dissolved gases and bacterial contamination. The study identified the rates of general and local corrosions of base metal, welded joints, and the area of low generating lines of the pipe. The study showed the peculiarities of corrosion fracture initiation and development and change in the rate of general and pit corrosions depending on the chemical composition of steel and its running time. The authors identified the interrelation of the dependence of change in the rate of corrosion fracture with the increase in the running time on the composition and structure of the corrosion products. For the chromic steels (08HMFChA and 13HFA), chromium concentration in the corrosion products is the main factor of surface passivation. The authors proposed the passivation coefficient, in other words, the criterion for evaluation of change in the corrosion rate during running time.

Research and Application of Air Source Heat Pump Technology at Rd. 60-10 Oil Delivery Site

The heating methods currently used at oil delivery sites and transfer stations on North China Oilfield include electric bar heating, fuel oil heating, gas heating, etc. The traditional heating methods have adverse effect on energy conservation and environmental protection. They have low energy efficiency of heating and produces great pollution to the environment. The air source heat pump technology uses the heat in the air as the low-temperature heat source and transforms it to the high-temperature hot water, which will later serve as a heat tracing for crude oil gathering and transportation. No combustion effluent is produced in operation and the energy-saving effect is outstanding with high social-benefit.

Exergy analysis of crude oil gathering and transportation system by 'three box' model

'Three box' exergy analysis optimisation method is applied to oil field system in order to identify and improve the weak links of crude oil gathering and transportation system. The universal 'black box', 'white box', 'grey box' models and balance equations of oil field analysis are established according to different requirements of rough, fine and sub-fine analysis. The weak link of energy utilisation is determined. The heating furnace is identified as the lowest exergy efficiency equipment in crude oil gathering and transportation system, which can provide a theoretical basis and scientific method for improving system energy efficiency.

Exergoeconomic pricing strategy of crude oil gathering and transportation system

Exergoeconomic pricing strategy of crude oil gathering and transportation system

A mathematical model of the pulsator for cleaning paraffin deposits of pipelines and downhole equipment

An important task for the oil industry is considered the issue of cleaning paraffin deposits of downhole and surface equipment; Xmas tree, oil gathering pipelines, oil treatment plants. As a result of the paraffin blockage, there is a decrease in oil production, an increase in pressure drop in pipelines, disruption of the normal operation of oil collection and treatment devices, the field operation itself is still difficult, therefore preventing and removing paraffin deposits with various cleaning methods is a pressing problem in the oil industry.

АНАЛИЗ ОТЛОЖЕНИЙ НЕОРГАНИЧЕСКИХ СОЛЕЙ В СИСТЕМЕ СБОРА НСП «Б», ДНС-5 «А»

Актуальность. В настоящее время проблема образования отложения солей очень актуальна и важна. Добыча нефти затрудняется с появлением неорганических отложений, которые образуются в призабойной зоне скважин и в системах сбора и подготовки скважинной продукции. Последствием отложения солей является снижение коэффициента продуктивности скважин, из-за чего происходит значительная потеря нефти. Также по причине недостаточного притока возникает риск отказа глубинно-насосного оборудования, происходит снижение наработки на отказ этого оборудования из-за того, что возникают заклинивания электроприводного центробежного насоса и клапанов штангового глубинного насоса. По этим причинам нефтяные компании терпят значительные убытки, так как возникает необходимость больших затрат на мероприятия по предупреждению и борьбе с солевыми отложениями. Цель. Определить методы предупреждения отложений и методы борьбы с ними. Выяснить будет ли выпадать осадок в результате определения коэффициента пересыщения φ по методике Скилмена–Мак-Дональда–Стиффа. Провести анализ исследований по определению компонентного состава отложений. Методы. При проведении расчетов использовалась методика Скилмена–Мак-Дональда–Стиффа. Неорганическая часть отложений определялась методом рентгеновской дифрактометрии на порошковом дифрактометре Shimadzu ХRD-6000. Результаты. Анализ результатов определения макро- и микрокомпонентного состава вод показал, что в пробах попутно-добываемых вод, отобранных с добывающих скважин и автоматизированные групповые замерные установки месторождения Х, содержится существенное количество ионов кальция и сульфат-ионов, что может привести к образованию отложений нерастворимых солей, таких как кальцит и гипс. В скважинах под номерами 5 и 311 коэффициент пересыщения φ>1 (существует пересыщенность пластовой воды гипсом). В этих скважинах гипс имеет возможность выпадать и в объеме, и на самой поверхности теплообмена. В скважине под номером 158 коэффициент пересыщения φ<1. При ненасыщенности им пластовой воды выпадение осадка в объеме не будет. Однако на поверхности теплообмена, вследствие частичного выпаривания раствор особо насыщается гипсом. Из-за этого гипс способен откладываться и при некоторой недонасыщенности им пластовой воды – при понижение коэффициента φ до 0,9. Чтобы отложения гипса не осложняли добычу нефти, нужно заранее предупреждать образования отложений. Для предотвращения образования отложений необходимо подобрать эффективный ингибитор солеотложений для условий месторождений, осуществляющих сбор на НСП «Б». С целью защиты системы нефтесбора рекомендуется организовать подачу ингибитора солеотложений.

Exergoeconomic analysis for crude oil gathering and transportation system in matrix pattern

AbstractBased on exergoeconomic theory, the energy consumption situation for a typical oil transfer station in eastern China is evaluated. According to the analysis of the distribution for logistics and exergy flow, the crude oil gathering and transportation system is divided into two subsystems: pipe network and oil transfer station. The unit exergoeconomic costs for each component exergy flow are calculated by computing method in matrix pattern, of which the pressure exergy and thermal exergy at the end of the process are 812.58 yuan/GJ and 1575.24 yuan/GJ, respectively. Simultaneously, exergoeconomic evaluation indicators such as exergy cost growth coefficient, relative cost difference, and exergoeconomic coefficient are calculated, which can conclude the weak link of technical system is heating furnace equipment. The growth value of its exergy cost growth coefficient is 14.988, the relative cost difference is 94.503, and the exergoeconomic coefficient is 9.046, so it has great potential for energy saving. Exergoeconomic analysis method can provide a scientific and effective method or basis during the energy‐saving reconstruction for oil gathering and transportation system.

To the issue of the destruction of persistent oil emulsions in order to ensure high-quality oil treatment

The article raises a question about the qualitative preparation of separator oil under the conditions of the formation of stable emulsion, which is stabilized by the products of the production of hydraulic fracturing and acid treatments. We present relations that make it possible to determine the flow parameters of produced gas-liquid mixture in an oil gathering pipeline. As a result, we propose a technological scheme for oil treatment, which provides the required quality of oil treatment. The scheme is based on the developed and justified method of dynamic combined oil treatment.

QUANTITATIVE DIAGNOSTICS METHODS FOR ASPHALT-RESIN-PARAFFIN DEPOSITS IN WELLS AND OIL PIPELINES

Background The formation of asphalt-resin-paraffin deposits in oil-producing wells and oil collectors depends largely on the temperature and pressure conditions for transporting the gas-liquid mixture; therefore, monitoring the temperature and pressure at oil producing facilities along the entire length of the facilities becomes relevant. The appearance of organic deposits in the well leads to a change in the speed of movement of the well production, retains its thermal energy, increases the pressure in the pipes. The equilibrium in the «reservoir - well - pump» system changes due to the increase in pressure at the discharge of the submersible electric centrifugal pump. Temperature sensors, installed evenly along the length of the lifting pipe string, provide important information on the temperature distribution in the pipe string without deposits and with deposits. Thermometry during the well operation will show the effect of fluctuations in the dynamic level of the fluid on the formation of sediments, will increase the informational content of measures for the inhibition and removal of sediments from wells. Aims and Objectives: to justify different methods of using pressure and temperature sensors in wells and oil gathering pipelines for evaluating their internal state; show the possibility of thermometry on a stationary basis for the implementation of a quantitative diagnosis of deposits in the tubing string of an oil producing well. Methods The known dependences of the state of the gas-liquid mixture on the thermobaric conditions in the tubing string of the well pipes and the continuity equation of the pipeline products are used. Results A method has been developed to monitor the formation of asphalt-resin-paraffin deposits in a tubing string according to temperature sensors, which are uniformly distributed along the length of the tubing on a stationary basis.

Pitting Corrosion Failure Analysis of a Produced Oil/Water Fluid Pipeline

This paper presents corrosion failure analysis of an underground natural gas pipeline. The pipeline material grade is 20# steel. The pipeline transfers multiphase fluid (Crude oil and water) from an oil well to an oil gathering plant. A portion of the line failed due to pitting corrosion under unknown circumstances. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are employed to characterize the scales and/or corrosion products near the failed portion. Based on visual and microscopic analyses and reviewing the background information, the following pitting corrosion sequences were identified: When the water ratio was smaller than 50%, the oil slick could cover the surface of the 20# test samples. Some uncovered surface would be corroded. When the water ratio was more than 70%, the surface of 20# steel contacted with more water. The average corrosion rate increased, and the corrosion products also formed, which would behave as a good diffusion barrier to prevent the underlying steel from further dissolution. Meanwhile, because of the corrosion products, the penetration rate also increased, the trend of local corrosion became weak with the water ratio continued to increase. The pitting corrosion varied with the water ratio because of the protection conferred by the oil slick or the corrosion product layer. Under such conditions, pits emerged on the steel surface until one of them grew faster and failed the oil pipeline.

Influence of micro‐pore structure in tight sandstone reservoir on the seepage and water‐drive producing mechanism—a case study from Chang 6 reservoir in Huaqing area of Ordos basin

AbstractTo study the influence of pore structure on the seepage and water‐drive producing mechanisms, various methods were combined to describe the micro‐pore structure in the Chang 6 tight sandstone reservoir in the Huaqing area, Ordos Basin, China. Nuclear magnetic resonance (NMR) was combined with displacement experiments to determine the distribution of oil and water in pores of different scales before and after water flooding. There are few micro pores in the reservoir. As permeability increases, the distribution of nano pores decreases, while sub‐micro pores increase. Also, sub‐micro pores are the main pathway within the reservoir. There is a negative power function correlation between the minimum starting pressure gradient of the oil (Swc) and maximum throat radius. Also, with a decrease of permeability, smaller pore throats become more abundant and the nonlinear section of the flow velocity‐differential pressure curves increase. There is a large amount of crude oil gathering in the nano pores. As permeability increases, the main sources of movable oil are from the nano pores (kg < 0.4 × 10−3 μm2), sub‐micro pores (kg ≈ 0.4 × 10−3 μm2‐1.0 × 10−3 μm2), and micro pores (kg > 1.0 × 10−3 μm2). Displacement efficiency is always the highest in sub‐micro pores.