fax 01-972-952-9435. AbstractThe ASP flooding Pilot tests in Daqing Oilfield commenced in 1982. And since 2005, APS flooding has entered commercial application in several main oil companies. Although the recovery rate can be improved by 20% over that with water flooding, severe scaling in downhole equipment turned out to be the biggest issue for artificial lift systems in ASP producers. Sucker rod failure rate was extremely high for beam pumping wells. As for PCP system, its running life was relatively the longest one among all lifting methods, but it was still not economic. Severe scaling on the surface of pump and string was the major factor causing drastic oscillation of operating load. Study indicated that surface energy of the material has great effect on scaling degree. Scale was easier to be formed on the materials with higher surface energy than that with lower surface energy. Using higher surface energy coating material was the main reason resulting in the severe scaling on traditional PCP rotors in ASP area. In that case, a novel ceramic coating technique was developed to decrease the coating material's surface energy to a much lower degree, and to prolong PCP wells' running lives effectively. Experiments showed that, elastomer's visco-elastic effect enhanced the periodic oscillation of PCPs' operating load leading to high rod fatigue failure rate. In addition, interference fit design between rotor and stator also has certain influence on PCPs' operation load. Based on the above studies, stator's surface modification technique and optimum interference fit design technique were developed to improve PCP's operation status. As an auxiliary treatment, a special chemical scale remover was developed to decrease the scaling degree of tubing and rod string. These novel techniques have been applied in 58 PCP wells, the average running life increased from several months to more than one year. PCP systems' operating status was improved effectively, and rod fatigue failure rate was decreased drastically.

The ASP flooding Pilot tests in Daqing Oilfield commenced in 1982. And since 2005, APS flooding has entered commercial application in several main oil companies. Although the recovery rate can be improved by 20% over that with water flooding, severe scaling in downhole equipment turned out to be the biggest issue for artificial lift systems in ASP producers. Sucker rod failure rate was extremely high for beam pumping wells. As for PCP system, its running life was relatively the longest one among all lifting methods, but it was still not economic. Severe scaling on the surface of pump and string was the major factor causing drastic oscillation of operating load. Study indicated that surface energy of the material has great effect on scaling degree. Scale was easier to be formed on the materials with higher surface energy than that with lower surface energy. Using higher surface energy coating material was the main reason resulting in the severe scaling on traditional PCP rotors in ASP area. In that case, a novel ceramic coating technique was developed to decrease the coating material's surface energy to a much lower degree, and to prolong PCP wells' running lives effectively. Experiments showed that, elastomer's visco-elastic effect enhanced the periodic oscillation of PCPs' operating load leading to high rod fatigue failure rate. In addition, interference fit design between rotor and stator also has certain influence on PCPs' operation load. Based on the above studies, stator's surface modification technique and optimum interference fit design technique were developed to improve PCP's operation status. As an auxiliary treatment, a special chemical scale remover was developed to decrease the scaling degree of tubing and rod string. These novel techniques have been applied in 58 PCP wells, the average running life increased from several months to more than one year. PCP systems' operating status was improved effectively, and rod fatigue failure rate was decreaseddrastically. Background From 1993, three ASP pilot tests were implemented in Daqing Oilfield: West Central Block, Xing V Block, and West Block. Another two ASP industrial tests were put into production in Bei I Block and Xing II Block. These ASP pilot tests commenced after water flooding. Application indicated that the recovery rate was improved by 20% on average with ASP flooding. Although ASP flooding has made great success in improving the recovery, another negative issue emerged at the same time: severe scaling was formed on the surface of production systems and resulted in producers' abnormal operation. See Figure 1. In beam pumping systems, when scaling particles dropped and accumulated in the space between pump barrel and piston, pump would be blocked in a short period. It was recorded that the minimum running life was less than one month. In ESP systems, the main problem was motor failures resulted from separators blocked by scaling. The shortest running life was half a month. Due to the special structure, PCPs' failure rate was much lower than the above two lifting methods. The averaged running life was around 3 months, but still limited. The main problems were pump abrasion (See Figure 2) and rod fatigue broken. The Mechanism of PCP Scaling Issue Abrasion Wear In the process of ASP flooding, alkali lye reacted with rock mineral and formation water, causing the increment of scaling ions concentration (Ca2+??CO32-??SiO2–3 etc.) in formation. When the production fluid was driven close or into the wells, due to the drastic change of temperature and pressure, the balance of scaling ions was broken, and scaling was formed near the wellbore, on the surface of downhole equipments and inner surface of transferring pipes.

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This paper introduces the performance history of the Daqing Oilfield and analyzes the potential for further development. The residual oil distribution characteristics are analyzed taking the advantage of the core data of Well La8-JP182 and Well Bei1–330-J49. Then the numerical simulation method is used to analyze the recovery ratio, production rate, and the variation of pressure gradient under different production conditions. Finally, the technology of potential tapping of the isolated untabulated reservoirs, tabulated reservoirs, the huge thick reservoirs, and multiple rhythm reservoirs are brought forward in this paper. Introduction Daqing Oilfield has undergone the water flooding stage, the artificial lift production stage, and the stage of polymer flooding since the oilfield was put into production in 1960. The pressure gradient between the producers and the injectors were raised after each conversion of the stages. As a result, the pressure gradient rose from 0.15MPa/60m in the flowing production stage to 0.62MPa/60m in the polymer flooding stage. The production rate and the recovery ratio were increased. There is little room left for increasing the pressure gradient further. Whereas, The analysis of the reserve potential in Daqing placanticline area indicated that the residual recorerable reserves in basic well pattern and the first round infilled wells pattern are still relatively reacher, which is 19,287×104tons and 14,871×104tons respectively. Therefore, the optimization and the combination of various development regimes, the production methods should be taken into consideration to tap the potential further. Moreover, the efficiency of the combinations should be forcasted either through numerical smulation method. The following pages analyze the residual oil potential in Daqing Oilfield, the simulation results, and the technologies to be taken for different layers. Residual Oil Potential Analysis The Daqing Oilfield has been developed for 44 years. And 36.81% of the total OOIP has been produced by water drive method, which accounts for 75.57% of the recoverable reserves. Current water cut of the oilfield is 88.9%. The annual output of polymer flooding is 1,134×104tons. The oilfield has entered the late stage of high water cut period. Therefore, It becomes harder and harder to continue producing as much as before. The potential distribution analysis is base for further develop the oilfield. Core data of Well La8-JP182 and Well Bei1–330-J49 were used to analyze the status and the distribution characteristic of the residual oil. Core data of Well La8-JP182 were got before polymer driven. The analysis of the data revealed watered out status of the core. The Well La8-JP182 encounted three sets of oil reservoirs vertically, which are S, P, and G reservoirs respectively. All the layers in these three groups add up to 73.9m, among which 15.4m are not watered out, 4.9m are watered out slightly, 36.1m are watered out medially, and 17.4m are watered out heavily. In terms of percentage, they are 20.9%, 6.7%, 48.9%, and 23.5% respectively. There is 26.3% of thickness of S reservoirs layers unwatered out. That of G reservoirs is 37.4%. As for the P group, on the other hand, there is 3.91% of thickness that is not watered out. Threfore, the residual oil potential in S and G reservoirs are much richer than that of P reservoirs after water drive. The total thickness of isolated untabulated reservoirs in this well is 26m, among which 22.7m are not watered out. The unwatered out thickness accounts for nearly 90% of the total isolated untabulated reservoirs thickness. The Well Bei1–330-J49 was drilled after polymer flooding. The core data of this well indicates that more than 74.3% of total thickickness are watered out. Whereas, watered out layers are mainly concentrated in the PI2 payzone, while the other layers are washed slightly. After polymer flooding, there are still some potential to be tapped in relative thinner layers.

This paper presented the development of Progressing Cavity Pump (PCP) technologies in Daqing Oilfield during the past 27 years, covering the successful experiences and lessons learned. The history of PCP lifting technology development was reviewed in the round. Several main PCP techniques were presented in detailed as well, including high efficiency and low profile PCP drivehead, hollow rotor PCP water flushing technique, PCP trouble-shooting technique, and PCP logging technique, etc. Daqing Oilfield was the largest continental oilfield in China developed from 1960. Beam pumping units was the main artificial lift method. To date, there are more than 40,000 beam pumping wells. PCP was applied in Daqing Oilfield from 1983. In the past 27 years, the scale of PCP increased at a higher rate. Till the end of 2010, 6,000 plus PCP wells were applied in Daqing Oilfield. PCP has become the second largest artificial lift method in Daqing Oilfield. To date, a series of PCP products have been developed covering the displacement and lift arrangement for different blocks in Daqing Oilfield. Based on the study and experiences for years, a set of completed PCP system design methodology was also created for water flooding, polymer flooding, ASP flooding and other complicated conditions. The fast improvement of PCP mainly resulted from two respects: Firstly, the quick development of PCP production techniques. The adaptability and reliability of elastomer was improved effectively and matching techniques were developed as well. Secondly, the requirement of low energy consumption and environmental protection in petroleum production policies enhanced the application of PCP technologies considerably. This paper applied a successful case study of a novel technology developed in the mature oilfield which could be a great reference for the industry.

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In recent years, a unique electrical submersible reciprocating pumping system (ESRP) was developed and has been applied in Daqing Oilfields. The main structure of ESRP is similar with ESP, consisting of an electrical submersible motor, pump, tubing and cable. The key equipments of ESRP are the reciprocating motor and the pump. The motor is a novel permanent magnetic line motor consisting of stator and mover. The pump is a special reciprocating pump. In operation, the mover slips in the stator from one end to the other periodically controlled by surface equipment, applying the power to the plunger of the reciprocating pump. Because of its small outerdiameter, the whole system could be run into the horizontal wellbore conveniently. This unique lifting system was designed mainly for the production of satellite oilfields in Daqing Oilfield. Unlike the properties of the main blocks of Daqing Oilfield with thick pay zones, high permeability and shallow imbedded reservoir, these satellite oilfields distributed discontinuously, the layers are thin and imbedded deeply with poor permeability. The producers’ averaged production is below 35 bpd. Beam pumping system showed poor benefit due to the high investment and operating cost. PCPs and Bailing lifting systems were applied later in a larger scale. But the management was relatively complicated and still limited in horizontal wells. As the result, ESRP showed great advantages both in technical and economic respects in the production. Till the end of 2010, ESRP has been applied in more than 30 wells in Daqing Oilfield. The longest running life has reached above 400 days. It showed remarkable advantages in the production of low displacement and deep reservoir, especially for horizontal wells. With the improvement of displacement and other specifications, this unique lifting system design has great potential in the development of unconventional reservoir as well as mature oilfields.

Daqing Oilfield is the largest continental oilfield in China. After 50 years development, the total quantity of drilling and artificial equipments of the oilfield has reached to a considerably large size and it is still increasing with a higher rate. Daqing Oilfield had to spend a lot in maintenance and renewal of the equipments. For example, only the replacement of artificial lifting equipments would cost 156.75 million USD each year. In the past tens years, Daqing Oilfield invested huge funding to improve the equipment management and recycling manufacturing techniques. After years of study, a set of management methodology was created and a series of rebuilding techniques were developed. This paper presented the practices both in drilling and production equipment management and rebuilding techniques. This paper also decribe the outlook of oilfield equipment management and rebuilding techniques in the future.