WanFu, Zhou (Daqing Oilfield Co. Ltd) | ZhongLian, Han (Daqing Oilfield Co. Ltd) | Gang, Cao (Daqing Oilfield Co. Ltd) | Xin, Wang (Daqing Oilfield Co. Ltd) | QingGuo, Wang (Daqing Oilfield Co. Ltd) | WenJiang, Chen (Daqing Oilfield Co. Ltd) | QingSong, Li (Daqing Oilfield Co. Ltd) | JingMei, Wang (Daqing Oilfield Co. Ltd) | Yang, Han (Daqing Oilfield Co. Ltd) | HaiRong, Fu (Daqing Oilfield Co. Ltd)
In the later stage of development, most oilfields faced high water cut issue after treatments. Meanwhile, how to effectively control oil wells water breakthrough after fracturing so as to increase oil production has become a big challenge for production engineers. This paper introduced a novel selective proppant which can effectively block water from entering well bore after fracturing.
Based on "eggshell principle" and interfacial tension theory, this novel proppant was developed with a new monolayer strong hydrophobic interface treatment technique. This special processing technique could not only reduce the proppant's flow resistance of oil, but also increase its flow resistance of water. As the result, this novel proppant showed the characteristics of excellent lipophilicity and hydrophobicity as well. Experiments indicated that oil water diversion ratio of selective proppant was greater than 1.2, while the ordinary proppant was less than 0.7. The oil wettability index of selective proppant was greater than 0.8, while the ordinary proppant was less than 0.3. The main characteristics of this supporting agent was small apparent density, low broken rate, and high flow capacity. The proppant surface is oil wet, which has the characteristics of oil increasing precipitation. Experiments showed that the seepage velocity of water in selective proppant was obviously lower than in quartz sand, selective proppant with water resistance.
Field test was carried out in 11 wells with selective proppant fracturing. A group of conventional fracturing wells were selected as contrasted wells with similar reservoir and operating conditions. After fracturing with novel proppant, the average water cut of producers was decreased by 7.2% per well, the average oil production was increased by 6.3 tons per well, and the average valid fracturing a period was 14.1 months. As for contrasted wells with conventional fracturing proppant, the average single well water cut decline was only 0.4%, the average single well daily oil 3.1 tons, an average period of only 5.8 months.
The novel proppant showed remarkable advantages in improving oil production and decreasing water cut. This technique has a great future for mature oilfield development.
Zhongxian, Hao (RIPED, Petrochina) | Gang, Cao (Daqing Oilfield, PetroChina) | Lianyu, Wang (Daqing Oilfield, PetroChina) | Mingzhan, Chen (Daqing Oilfield, PetroChina) | Yuan, Fu (Daqing Oilfield, PetroChina) | He, Liu (RIPED, PetroChina)
Suffering from serious rod-tubing eccentric wear, polymer-flooding wells usually have an average maintenance cycle of only 2-3 months. Analysis indicates that since the wellbore fluid causes a relatively large friction to the pump and rod in polymer-flooding production wells, rod-string buckling is likely to occur during the downstroke. In addition, the normal force difference will make collision between rod and tubing more frequently, which in turn aggravate the rod fatigue and rod-tubing wear. A special downhole pump newly developed and rod-string optimization for polymer-flooding production wells together work well in reducing the system load, rod-tubing contact and wear. The rod-tubing wear of PCP wells is reduced through structure parameter optimization, application of equal-wall thickness PCP, pump-type optimization, etc. After a series of remedial measures and scale application, the failure rate of artificial lift systems in polymer-flooding has been significantly reduced, and the meantime-betweenfailure (MTBF) increased to more than a year and a half in the study area. This technology is of great significance for the wide application of polymer-flooding and further improvement of tertiary oil recovery profit.
Wanfu, Zhou (Daqing Oilfield Co. Ltd.) | Guochen, Shi (Daqing Oilfield Co. Ltd.) | Gang, Cao (Daqing Oilfield Co. Ltd.) | Mingyan, Lu (Daqing Oilfield Co. Ltd.) | Mingzhan, Chen (Daqing Oilfield Co. Ltd.) | Yu, Hou (Daqing Oilfield Co. Ltd.) | Yongxin, Liu (Daqing Oilfield Co. Ltd.) | Mingyi, Zhang (Daqing Oilfield Co. Ltd.)
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.
Daqing Oilfield was discovered in 1959. It is the largest continental oilfield and the petroleum industry base in China. In the beginning of the development, natural flowing was the main producing method of the oilfield. From 1982, artificial lift method was widely used in the oilfield manily including beam pumping system and ESP. Till the end of last century, nearly 30,000 beam pumping systems and over 2,000 ESP pumping systems were in operation in Daqing Oilfield. See Figure 1.
In 2000, the average water cut for the whole oilfield reached nearly 90%. High cost on investment and operating of beam pumping system has become a bottleneck problem influencing the economy of oilfield development. In 2002, the total power consumption of artificial lifting systems was nearly 10 billion kW•h, which was over one third of the whole oil field's power consumption.
From 1990s, polymer flooding, APS flooding were applied in Daqing oilfield. The recovery of the oilfield improved
considerably. On the other hand, the failure rate for the artificial lift system increased dramatically due to the changing
properties of production fluid. For example, the average running life of beam pumping systems in polymer flooding areas from more than 600d down to 270d. Cost for overtime also increased by ten million RMB per year.
As for ASP flooding area, the results were even more serious. Due to high scaling in pumps and strings, the average running life of the beam pumping system was less than 60d, while the shortest running life was within a month. Artificial lifting technology has become a "bottleneck?? problem for Daqing Oilfield in EOR period.
PCP system was chosen to be the first alternative. It has lower investment and operation cost, higher efficiency, and a high viscosity and sandy liquid production.
Gang, Cao (Daqing Oilfield Co. Ltd.) | Youquan, Huang (Daqing Oilfield Co. Ltd.) | Dongyuan, Ge (NO.eight oil production plant daqing oil field campany CNPC) | Wensheng, Zhang (Daqing Oilfield Co. Ltd.) | Weiping, Zhang (Daqing Oilfield Co. Ltd.) | Huaifeng, Ren (Daqing Oilfield Co. Ltd.) | Junwen, Ge (Daqing Oilfield Co. Ltd.) | Lin, Wang (Daqing Oilfield Co. Ltd.) | Fengwu, Zhang (Daqing Oilfield Co. Ltd.) | Weitao, Ge | Guoxing, Zheng
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
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.
Beam pumping system is the most popular artificial lift method in oilfields due to its maturity and high reliability after more than 100 years application around the world. Take Daqing Oilfield for example, in this largest oilfield of China, there are more than 40 thousand producers in the oilfield while 80% equipped with beam pumping systems. After 50 years development, the annual production rate of Daqing Oilfield has decreased by 20% compared with its peak rate. A group of satellite oilfields around the main blocks had to been developed in recent years in order to release the huge production pressure of the oilfield.
These satellite oilfields distributed discontinuously, the pay zones are thin and imbedded deeply with poor permeability. In most cases, the averaged production is below 35 bpd per well. As the result, beam pumping system showed poor benefit due
to the high investment and operating cost. PCPs and Bailing lifting systems were tried in some areas, showed obvious limits in management and operating conditions. In order meet the requirement in the development of these , From 2004, a novel
Electric Submersible Reciprocating Pumping (ESRP) system was developed and in some oilfields, showing remarkable advantages in technical and economic respects as well.
Yang, Yonghua (China University of Petroleum, Beijing) | Zhou, Wanfu (Daqing Oilfield Co., Ltd) | Shi, Guochen (Inst of Daqing Oil Prod Tech) | Gang, Cao (Daqing Oilfield Co. Ltd.) | Wang, Guoqing (Daqing Oilfield Co. Ltd.) | Sun, Chunlong (Daqing Oilfield Co. Ltd.) | Qiang, Li (Daqing Oilfield Co. Ltd.) | Zhao, Yunlong (Daqing Oilfield Co. Ltd.) | Zhao, Changming (PetroChina Daqing Tamtsag, LLC) | Bai, Wenguang (Daqing Oilfield Co. Ltd.) | Wu, Miao (Daqing Oilfield Co. Ltd.) | Li, Yanfei | Zhang, Ming | Li, Jinling | Ma, Zhiquan | Xu, Wenlin
To date, ASP flooding has been applied in commercial test in Daqing Oilfield for 17 years. From the beginning of the test, scaling issue in downhole artificial lift equipments had been realized as one of the most difficult problems in ASP flooding which resulted in high pump failure rate and operation cost. Therefore, the scaling principle in producers was studied in order to create a scaling risk analysis and risk prediction mechanism. In addition, Based on numerous laboratory study and field trial, a series of anti-scaling artificial lift techniques were developed as well, including surface material modification technique, special pump design, chemical scaling remover, etc.
Due to the considerable diversity of scaling phenomena in different blocks, different period and different wells, the antiscaling artificial lift strategy was required to be adjusted respectively. Consequently, an innovative anti-scaling artificial lift methodology was created for different ASP flooding areas in Daqing Oilfield. This methodology was applied in 102 wells, both in beam pumping wells and PCP wells. The averaged running lives of artificial lift systems were improved from less
than 30 days to over 300 days.
This paper detailed the developments of innovative artificial lift technology in ASP flooding in Daqing Oilfield. These new developments will effectively propel the commercial application of ASP flooding in petroleum industry.
Alkaline Surfactant Polymer (ASP) is a novel EOR technique developed from the end of last century. It combines the advantages of surfactant flooding and polymer flooding which could improve the recovery rate and sweeping volume. Moreover, ASP flooding can reduce the developing cost considerably due to much less quantity of surfactant. From 1990s, Daqing Oilfield began to study the mechanism of ASP flooding. Both several hundred of surfactant formulas and different
molecule quantity polymer were tested in order to get proper ASP system formulas matching for different blocks. Based on numerous theoretic study and experiments, 6 ASP flooding pilot tests commenced from 1994 to 2004. Based on water flooding development, the recovery rate was 19.4 to 25 per cent by ASP flooding. Till 2010, 6 another ASP flooding pilot tests had been carried out in Daqing Oilfield. The recovery rate was 18.1 to 25 per cent higher than water flooding.
However, scaling issue in artificial lift equipments was a bottleneck problem for ASP flooding. In the process of producing in ASP flooding, ASP fluid reacted with rocks in the reservoir resulting to a small part of rocks solute. When the producing fluid enters the well bore, large quantity of scaling deposited on the surface of production equipments, including casing, tubing, pump, and sucker rods. See Figure 1, 2. Severe scaling issue resulted to high failing rate of artificial lift system as
well as fast increment of developing cost. In the scaling stage of ASP flooding, the averaged running life of PCP is only 47 days. As for beam pumping wells, it was less than a month. Scaling issue of artificial lift systems limited the development of ASP flooding considerably. In that case, Daqing Oilfield began to develop anti-scaling PCP technique, scale control beam pump and chemical scale removing techniques.
Gang, Cao (Daqing Oilfield Co. Ltd.) | He, Liu (Daqing Oilfield Co. Ltd.) | Guochen, Shi (Daqing Oilfield Co. Ltd.) | Mingyan, Lu (Daqing Oilfield Co. Ltd.) | Mingzhen, Liu (Daqing Oilfield Co. Ltd.) | Wang, Honghai (Daqing Oilfield Co. Ltd.) | Yunlong, Zhao (Daqing Oilfield Co. Ltd.) | Bo, Yu (Daqing Oilfield Co. Ltd.)
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.
Wang, Fengshan (Daqing Oilfield Co. Ltd.) | He, Liu (Daqing Oilfield Co. Ltd.) | Wanfu, Zhou (Daqing Oilfield Co. Ltd.) | Guochen, Shi (Daqing Oilfield Co. Ltd.) | Gang, Cao (Daqing Oilfield Co. Ltd.) | Ruiqing, Chang (Daqing Oilfield Co. Ltd.) | Deshi, Zhang (Daqing Oilfield Co. Ltd.) | Dingming, Lin (Trans-Asia Gas Pipeline Co., Ltd.)
Daqing Oilfield is the largest continental oilfield of China. And beam pumping system was the main artificial lift method of the oilfield. Till the end of 2008, the number of producers has reached more than 48,000 in the whole oilfield, in which 80% wells applied beam pumping system. Statistics indicated that, the averaged efficiency of beam pumping systems was only about 25% for the whole oilfield resulted in large quantity of power waste. Moreover, the power consumption of beam pumping wells was about one third of the total power consumption of the oilfield development which was the largest part of operation cost.
In the past tens years, Daqing Oilfield invested huge funding to improve beam pumping equipments' energy-saving techniques. And a series of energy saving rebuilding techniques were developed including two innovative beam pump units, three energy-saving motors, and two new control designs. This paper presented these energy saving techniques in details. Application in more than 2,000 producers indicated that the efficiency of beam pumping systems was improved considerably after using these innovative energy-saving rebuilding techniques.
Gang, Cao (Oil Prod. Research Institute) | Linghui, He (University of Science and Technology of China) | Zhaomei, Chen (Daqing Oilfield Co. Ltd.) | Xuecheng, Zheng (Daqing Oilfield Co. Ltd.) | Qingbo, Wang (Oil Prod. Research Institute) | Mingzhan, Chen (Daqing Oilfield Co. Ltd.)
Hailar Oilfield is a new block of Daqing Oilfield developed from the end of last century. In the beginning of the development, beam pumping unit was the only lifting method of the Oilfield. Due to the low pump efficiency and higher rod failure rate as well as the 2000m lift, beam pumping system was not as economic as other in blocks of Daqing Oilfield. As the result, PCP was put into production from 2005. Though all the four wells had a good performance with high pumping efficiency in the beginning, after several months' operation, rod strings suffered from severe oscillation and resulted in fatigue failures in a short period. Theoretical and experimental study indicated that, high working temperature (85 centigrade) and special oil characteristics caused much higher swelling degree of elastomer than in other blocks, which led to the increment of interference fit and friction force between rotor and stator.
In the initial application, although pump parameter and elastomer formula were adjusted before treatment to reduce the swelling effect, these adjustments didn't take into effect as predicted. In that case, a personalized PCP design was brought forward which gave an integrated methodology for PCP application in Hailar Oilfield. In this design, all the lifting parts from surface to downhole equipments were considered as a whole system. FEM analysis was applied to make a detailed description of the pump for different operating temperature. Based on deeper adjustment of elastomer and pump's structure parameters, the optimum design of rod and other equipments were take into consideration as well. In the end of 2006, 4 new personalized design pumps were put into production. In the following year, despite of small oscillation in the first few days due to the influence of treatment water, all PCP systems performed stably with high efficiency.
Hailar Oilfield located in the northeast of Inner Mongolia Autonomous Region, near the frontier of China and Mongolia. It was a continental facies deposit basin which was developed from 1980s. See Fig. 1. Till the mid of 2007, the oil production rate has reached 250,000 tons. In the beginning, the lifting methods of the oilfield were beam pumping system and bailing lift system. The production rate per well was around 10 m3/day, and many of them were under 5 m3/day. The lift of producers ranged from 1600m to 2500m, and temperature was from 70 to 90?. Due to the low displacement and higher lift on the average, beam pump system and bailing lift system wasn't so economic. In the beginning of 2005, one PCP well (Well#0) was put into production with 1400m lift. The system operated stably and was pulled out till the mid of 2006 due to the new development requirement of the block. According to the good performance of this case, PCP lifting technology was recommended to be applied in higher lift wells (above 1800m) in Hailar basin.
Pilot Test of PCP Lifting System
In 2006, a pilot test was implemented including 4 PCP wells in Hailar Oilfield from August to November. The pump efficiency was very high up to 90% in the beginning of the operation. But several weeks later, high flunctuate of operating loads were found in all the wells. See Fig. 2. Obvious oscillation could be observed from the surface polished rod and abnormal sound could be heard clearly, which indicated the pumps weren't operated in the constant speed. Under this abnormal operating condition, rod and pump failures were frequent in the following several months. Up to April, 2007, Well#1 has a rod failure after one month operation. Well#2 has three rod failures in five months. Well#3 has two rod failures in two months. Except that Well#3 operated normally, all the other three wells' average running life was around two months.
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.
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 werepump abrasion (See Figure 2) and rod fatigue broken.
The Mechanism of PCP Scaling Issue
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.
With years of study and experiments, a complete series of Progressive Cavity Pump (PCP) products has been developed. Sets of down-hole pumps for various rates and lifting capacities were developed for water-flooding, polymer-flooding and ASP flooding areas according to the specifics. One of the newest techniques, a hollow rotor PC Pump, has been applied in more than 800 wells. It has proved to be an effective way in removing the wax build-up and reducing operation cost. Another specially designed product was the sucker rod. By strengthening and redesigning the area susceptible to failure, the new sucker rod prolonged the running life of the lifting systems considerably. Also, a new type of drive head with compact structure has been proved to be more convenient in maintenance and more economic than the traditional products. By means of completed monitoring techniques including PC Pump testing equipment and diagnosing software, PC Pump systems can be monitored in real time. This decreased the frequency of failures and improved the benefits effectively.
With more than 2000 PCP wells in Daqing Oilfield, the capital and operating costs have reduced dramatically. The PCP system, the most effective lifting method, has great potential for Daqingâ€™s Oilfield.
Daqing Oilfield lies in the center of Songliang basin in North east China. In the beginning stages, commingle water injection and separate zone water injection technologies were used which allowed the reservoir pressure to remain at a high level. Therefore, by natural power the oil field produced for nearly twenty years. To maintain the output, artificial lift technologies were used from 1980s. Beam pumping system was the most popular one. Up to the end of last century, the number of beam pumping systems in Daqing reached over 20,000 wells. There were also about 2,000 ESP wells in operation.
In 2000, the average water cut for the whole oilfield reached nearly 90%. Huge operation cost was the most serious problem for beam pumping system. In 2002, the total power consumption of artificial lifting systems was nearly 10 billion kWÂ·h, which was over one third of the whole oil fieldâ€™s power consumption.