Zhihua Wang

Study of deposition behavior in small-diameter gathering pipelines for water-cut oil

Buildup of waxy paraffin deposits in pipes has been studied for the example of the intrafield oil gathering system at the Songfangtun oil field. We have developed a predictive model for calculating the deposition rate in small-diameter gathering pipelines for water-cut oil. The model takes into account the effect of the water cut of the oil, its temperature and flow velocity on the impurity deposition rate. We have studied the mechanism for the effect of the indicated factors. The applicability of the model and the reliability of the results obtained were assessed from the average relative deviations between the predicted and measured values. The results of this work can be used to improve oil gathering systems and for cleaning the interior of pipelines (pigging).

The effects and control of viscosity loss of polymer solution compounded by produced water in oilfield development

To avoid the environment pollution and remit the pressure of produced water stored up in water stations at high-water-cut stage, a special technology of enhanced oil recovery (EOR), in which produced water is used for compounding polymer solution, has been formed in Daqing Oilfield. However, the viscosity loss is difficult to be avoided only by modifying the polymer production. Then the effects of salinity, bacteria and reducing substances of produced water on viscosity loss are analysed respectively in this paper. The results proved that biodegradation and chemical degradation are as important as mechanical degradation in polymer solution. As more complicated processes and higher cost are needed for the desalination of produced water, a sterilisation-aeration treatment technique with simple process and low cost is proposed. The application of proposed procedures indicated that, viscosity loss of polymer solution with different molecular weights and different concentrations can be reduced by 10 mPa.s, and more than 100 mg/L polymer working concentration can be saved in compounding with the same viscosity.

An Environmentally-friendly Method for Removing Polymer Plugging in Well Boreholes

With the progresses of industrial scale of high concentration and high molecular weight polymer flooding in Daqing oilfield, there are severe polymer plug problems, which occur in the perforated zone and the interstices of the formation adjacent the perforated zone. In attempts to remove or at lease reduce these polymeric build-up plugs, the strong oxidants are widely used in oilfields. The use of oxidants is undesirable because of the high price and short efficient period. What is more, it cannot meet standards of safety and environmental protection. This article presents lab and field test results of this removing polymeric plug method based on microbial degrading polymer. Lab experiments results show that polymers with different molecular weights were efficiently degraded by screened bacteria under different reservoir temperatures. It can be seen in visualization model that polymer plugs in pore were removed obviously. The polymer injection pressure was decreased 25%. The pilot tests in Daqing oilfield showed that by applying the method, average injection pressure of each well was decreased 435 psia, the average effective period reached to 520 days, and more than 7,000 barrels (bbl) of oil were increased in the test field.

Dehydration of Aging Oil by an Electrochemical Method

In oilfield development, accumulation of large amounts of aging oil is inevitable. In this paper, we study the properties of aging oil and consider the reasons for its accumulation. It has been shown that dehydration of this oil by only a chemical or an electrostatic method is inefficient. Combining these two methods provides a degree of demulsification for which the water content in the oil and the oil content in the water meet the industrial standard. We consider the details of operation of an electrostatic dehydrator in processing aging oil having high solids and iron contents and high emulsion stability. We select the optimal conditions and design an industrial process for dehydration of aging oil.

Distribution of Sulfide in an Oil-water Treatment System and a Field Test of Treatment Technology in Daqing Oilfield

In recent years, the sulfide in oil-water treatment system of Daqing Oilfield has brought serious problems, to induce electric dehydrator trip and waste oil recycle difficultly and eventually so severe as to prevent further oil productions. The treatment difficulty of wastewater with sulfide will increase, the oily wastewater after treatment will be deteriorated and induce the formation plugging. Meanwhile, the equipments and pipelines will also be seriously corroded. The authors studied the generation and distribution of sulfide in oil water treatment system in Daqing Oilfield and the field test was conducted in the dewatering and wastewater treatment system based on microbiological method. The results showed that the dynamic microcontrol technology could effectively prevent the generation and accumulation of aging oil, avoid frequent electric dehydrator trip, and decrease the labor quantity to ensure the normal production and meet the dehydration standards. The application of this method would bring better profit and environmental benefits for Daqing Oilfield.

A Performance Evaluation of Glycolipid Biosurfactant Synthesized by the Enzyme-catalyzed Method

The practice of enhanced oil recovery (EOR) technique shows that the study and application of biosurfactant flooding system have a vast potential for future development. The authors challenge the traditional idea that the oil displacement surfactant must have ultra low interfacial tension. By changing the wettability of reservoir rock as main target, the glycolipid biosurfactant compounded system was developed by enzyme-catalyzed method in laboratory, and a series of experiments had been done combining with reservoir physical measurement. The properties of the active system were characterized by interfacial characters, disbonded, seepage characteristics, antibiotic property, and oil displacement efficiency.

Design and Practice of Multimedia Technology for Innovating Talents' Teaching Pattern in Oil & Gas Storage and Transportation Engineering

The application of multimedia technology on teaching has entered a new developmental and improvement stage. The multimedia technology describes knowledge point during class vividly and dynamically by images and animations, visualizes teaching contents easily understood by students, and improves learning efficiency and teaching effect comprehensively. It is beneficial to the cultivation of innovative thought and ability and the individual development of students. In this paper, combining the study on teaching reforms of engineering majors and regarding the establishment of teaching pattern for innovating talents in oil & gas storage and transportation engineering as the fundamental goal, the author introduces and illustrates the design and practice of multimedia technology in theoretical and practical teaching, and analyzes the effect of multimedia technology on the teaching quality security system of oil & gas storage and transportation engineering from the perspective of modernization, diversification and systematization. The study shows that the information organization mode of multimedia technology can enrich the infection and expression of teaching, stimulate students learning interest, and break difficulty to ensure the improvement of teaching quality. Based on this, strengthening enterprise-college-research cooperation and constructing teaching pattern for innovating talents can promote the construction and development of engineering majors.

Study of Corrosion Behavior of Oil Gathering Facilities with Co 2 Flooding In Low-Permeability Oilfields

Carbon dioxide (CO2) gas flooding for enhancement of oil recovery is known to face challenges such as corrosion and scaling of oil-gathering facilities and environmental pollution. The corrosion behavior of the gathering facilities must be studied to select the optimum measures for protecting them from the corrosive effect of CO2. Surface corrosion of the separator, a key problem with using CO2, is evaluated in the present work. The corrosion characteristics, corrosion rate, and corrosion products in different functional areas of the facility were determined by the weight-loss method, scanning electron microscopy (SEM), and x-ray diffraction (XRD) analysis. The results indicate that pitting corrosion is the main characteristic of Fe-360 A steel facilities and that the average corrosion rate in vulnerable areas can reach 0.1358 mm/yr with formation of Fe2O3 and FeS. The combined effects of contact time and CO2 volume in conjunction with the activity of sulfate-reducing bacteria influence the corrosion kinetics and mechanism of Fe-360 A steel. The results are of great significance for minimizing corrosion using chemical inhibition and proper selection of materials that come into contact with CO2.

Study on Technical Limits of Single-Pipe Concatenation Gathering Process during High Water-Cut Stage

In order to optimize the gathering system and reduce the energy consumption in the production, single-pipe concatenation process has been widely used after the tertiary oil recovery technique is applied and development enters into high water cut stage in the oilfield. Aiming at condensate oil in gathering pipeline and obvious increase of the high circle pressure wells in the operation of the process, the adaption relationship between oil gathering pipeline size and flow, as well as the temperature limit of the gathering system start are studied, through the hydraulic and thermodynamic calculations of oil-gas-water multiphase flow. It has directive function for making effective schemes to solve the production problems caused by the high back pressure of wells.

Design and Selection of the Project Scheme of Qing-Tie Oil Pipeline River-Crossing

Highway, railway, waterway and pipeline are ways to transport oil. The pipeline has irreplaceable superiority, such as high throughput, low energy consumption and low cost. So the pipeline is the artery of energy source of national economy and very important to the development of social economy. When the pipeline is constructed, crossing some rivers is inevitable. If the crossing method and engineering management were unreasonable, the environment will be damaged, especially the pipeline may be destroyed seriously by the third party damage. Recently, the techniques of design, construction and management of pipeline river-crossing have made a great progress in the world. But pipeline river-crossing is still a technical problem, it needs hydrological research and analysis, geological prospecting and scheme selection. Qing-Tie crude oil pipeline located in the Northeast of China and has been operated for 35 years. It crosses 121 rivers. In these rivers, most sections of the pipeline are attacked by water directly because of the covering soil was washed away. Some sections are baring and hanging tens of meters. It is hidden trouble of security of operation. Especially the pipeline crosses Chai River in Liaoning province, it is laid by culvert of stone, once had an accident and it cant be remedied. So remaking the crossing project scheme is essential. This paper has introduced the basic situation of Qing-Tie pipeline and Chai River. The stratum description, weather and hydrogeology, earthquake situation and the stability of bank are analyzed and evaluated. Heavy excavation, directional drilling, shield pushing and drilling blasting are compared by merits and drawbacks, construction period and engineering cost. Finally, the directional drilling is considered to be the best. The crossing horizon, embedded point, out point and laying parameters are worked out. The establishment and implementation of the project scheme is reference for the technique of pipeline river-crossing.