After three years of technological breakthrough and field practices, a complete set of patented waterless fracturing operation technology and supporting equipment with independent intellectual property rights have been invented. Obvious oil production increase effect has been observed in multiple field tests on tight sandstone oil reservoir. In this paper, the latest development of Chinese liquid CO2 fracturing technique is introduced through a case study of typical well.
The target depth of operating well is 1730.8m-1757m, with a daily fluid production of 1.6t and oil production of 0.5t, indicating that the displacement relationship has not been effectively established. The fracturing treatment was carried out using the independently developed equipment system, which has treatment capability of available pump rates up to 12 m3/min, sand transportation of 27 m3 and CO2 injection of 1000 m3. During this operation, 860m3 liquid CO2 was injected at a displacement of 5-6m3/min. and 23m3 proppant was preloaded and totally pumped into reservoirs with maximum instantaneous proppant concentration of 12%.
After the fracturing, the daily fluid production increased from 1.9t to 3.9t, the daily oil production increased from 0.7t to 2.3t and the water cut decreased from 63.2% to 41.0%, achieving a significant increase in production. In addition, the oil pressure of one adjacent well increased from 0.5Mpa to 12.4Mpa and the daily oil production of four adjacent wells increased by 0.7-1.1t through the energy enhancement and miscibility of CO2.
The field test shows that liquid CO2 fracturing technology has a significant effects of energy storage and stimulation, adjusts the injection-production relationship effectively, and greatly enhances the single well production. It is expected to become the key technology of the development of tight sandstone oil resources.
Ming, Eryang (PetroChina Research Inst Petr Expl & Dev) | Li, Tao (PetroChina Research Inst Petr Expl & Dev) | Li, Yiliang (PetroChina Research Inst Petr Expl & Dev) | Pei, Xiaohan (PetroChina Research Inst Petr Expl & Dev) | Hao, Zhongxian (PetroChina Research Inst Petr Expl & Dev) | Guo, Tong (PetroChina Research Inst Petr Expl & Dev)
In recent years, the flexible coiled composite pipe (FCCP) has developed rapidly in China. Because of its merit about chemical inertness, it has been introduced to onshore oilfields to endurance some severe situations, such as serving as tubing in corrosive and waxy oil wells, as tubing in scaling water injection wells or as surface gathering pipelines, especially suitable for mountainous areas. This paper will introduce the development status of FCCP in different applications.
According to our research and development, for FCCP structure manufacture, there are two main technical routes in China, non-adhesive pipe and adhesive pipe. These two kinds of pipe meet the merits of FCCP, however, there are some differences in technical parameters. Obviously, non-adhesive pipe has smaller bending radius, but the integrity of adhesive pipe is better which is good for fitting installation. In this technical stage, the FCCP has been applied in surface gathering system, general water injection system and rodless artificial lift system.
For surface gathering system, this is the most mature application of this technology. It has been laid over 30,000 kilometers. Compared with steel pipe, the equipment of FCCP is simple and high laying efficiency. For general water injection system, the FCCP replaces steel pipe by high working efficiency and long endurance. It has been applied more than 80 wells. For rodless artificial lift system, there are almost 60 wells applied FCCP. It is the severest running condition for FCCP with high temperature, high wellbore pressure and high varies suspension force. This application reveals the advancement of FCCP by twining cables inside the pipe body and adding functions of real-time monitoring and heating. Two typical applications are serving as tubing in cold heavy oil production and acid gas corrosion oil well. The application of FCCP has made great progress. But there are several key issues that need to be resolved in the future research. First, there is lack of post evaluation of performance. Second, the limit of material working temperature shrinks the application scope. Third, the external pressure resistance is limited.
This paper shows the applications of flexible coiled composite pipe in onshore oilfields of China in the past 5 years, including a summary of technical experience, and proposing the goal of further research.
Ming, Eryang (PetroChina Research Inst Petr Expl & Dev) | Li, Yiliang (PetroChina Research Inst Petr Expl & Dev) | Li, Tao (PetroChina Research Inst Petr Expl & Dev) | Huang, Shouzhi (PetroChina Research Inst Petr Expl & Dev)
The ultrashort radius lateral drilling technique has applied more than 20 wells in China, and it was reported that this technique increased the production of mature oil wells by 3 to 5 times in average. However, when the casing grade was relatively high, the flexible drilling tool was cut off by the sharp edge of open window. This paper will introduce a method to improve this technique.
By studying the failure case, there were two obvious defects for this drilling tool. First, the shell material was too soft. It was radially stripped of 2 to 3 mm. Second, the design of transmission fork was unreasonable. The cylindrical pins of transmission fork were placed from the outside of shell and were covered by welded discs. When the shell was stripped, pin was easy to drop off and causes disconnection. To find the essential cause, we deduce kinematics and dynamics analyzes, and redesign the structure of transmission fork. Test shows the performance of new tool is much better.
This paper introduces kinematics and dynamic to redesign the ultrashort radius lateral drilling tool, which improves the performance by principle. Though kinematics analyze, we found the rotational speed inhomogeneity might cause inefficient drilling depth, even sticking of tool in some extreme cases. Tough dynamic analyze, we found the additional torque caused by rotational speed inhomogeneity might cause the vibration of drilling tool, which may cause more serious problem. To solve these problems, the universal joint was design into constant velocity universal joint and the mounting position of transmission part was placed from inside to give enough margin for shell stripping off. After these work, the ultrashort radius lateral drilling tool has less vibration and provides continuous and stable torque. This method improves the efficiency and success rate of this technique.
This paper updates the design method of ultrashort radius lateral drilling technique, makes it much reliable and efficient. It will give the promise for the next generation technique, the ultrashort radius lateral coring technique.