Abstract In recent years, the successful application of shale gas mining technology in the United States and other countries has brought about a diversified development of global energy strategy, which has gradually changed the industry's judgment on the future supply and demand pattern of oil and gas resources. The latest research results of the 2012 Oil and Gas Center of the Ministry of Land and Resources show that China's shale...
In recent years, the successful application of shale gas mining technology in the United States and other countries has brought about a diversified development of global energy strategy, which has gradually changed the industry's judgment on the future supply and demand pattern of oil and gas resources. According to the latest research results of the Oil and Gas Center of the Ministry of Land and Resources in 2012, the recoverable resources of shale gas in China is 25 trillion cubic meters. In China's shale gas “Twelfth Five-Year†development plan, shale gas production will reach 6.5 billion cubic meters in 2015. However, China's shale gas development has problems such as high cost, long drilling cycle, unsuitable drilling tools, imperfect fracturing technology system, and key technologies provided by foreign companies.
Drill bit "transformation" adapts to unconventional development
The burial and occurrence of unconventional natural gas resources have similarities and differences with conventional natural gas resources, mainly manifested by hidden gas reservoirs, unstable recovery factors, complex development techniques, and high requirements for mining technology.
The complexity of the formation conditions of unconventional oil and gas drilling in China, the multi-directionality of the force of the drill pipe, and the harshness of the bottom hole environment, drilling equipment (drill, mud pump), machine tools (drill pipe, drilling tools, drill bits, etc.) , drilling fluids, and drilling processes have put forward higher requirements. The development of new and more adaptable drill bits has become the focus of major domestic and foreign manufacturers of drill bits.
In view of the complexity of strata in different regions and the diversification of drilling technology, the bit manufacturing enterprises continue to optimize the bit design, accelerate the “transformation†of the drill bit, extend the service life of the drill bit, increase the drilling speed, and reduce the number and purity of the drill. Drill time and reduce the overall cost of drilling.
Drill development cannot copy foreign experience
The reservoir conditions of shale gas reservoirs in China are significantly different from those in the United States. The shale gas reservoirs in the United States are buried between 200 and 2,000 meters deep, while the shale gas layers in the Sichuan Basin of China are buried at depths of 1,500 to 4,000 meters. The shale layers in the Yunnan, Yunnan and Hunan provinces are thin and often multi-layered. Setting the state is difficult to develop.
The development of shale gas in China is not suitable for copying the theoretical and technical parameters of the United States. Combining the actual geological characteristics of China, the study of shale gas development theory, technology, and related equipment is a feasible way.
Expert Guo Zhongzhi believes that scientific research personnel in the field of petrochemical equipment in China should go deep into the shale gas drilling site to understand the current status and use requirements of the drill bit, determine the detailed content and decomposition indicators of the drill bit development; combine the site formation, the drilling tool combination and the drill bit usage. Optimize the bit structure; carry out the application research of diamond composite sheet and carcass material according to the decomposition index of the bit material, and independently develop the long horizontal section bit of shale gas horizontal well. "Only by doing so, can extend the life of the drill bit, speed up the drilling speed of the drill bit, reduce the number of times the drill bit is drilled, and meet the relevant maneuverability requirements," he said.
PDC drill bit is expected to become the main drill bit for shale gas development
At present, PDC bits are widely used in the field of conventional oil and gas exploration and development. Since the conventional natural gas burial depth in China is between 1,500 m and 3,000 m, the depth is not much different from the burial depth of shale gas. The use of PDC bit in shale gas exploration and development can improve the drilling speed, reduce the frequency of replacing the drill bit, and greatly improve the economic benefits of drilling. .
The shale layer belongs to the medium soft grade rock formation, while the PDC bit has a significant advantage in rock formation below the medium hard level. At present, the global consumption of PDC bit accounts for 65% of the total number of drill bits, while the domestic PDC bit market capacity is equivalent to the roller bit in 2011. Experts predict that the replacement of roller cone bits by PDC bits and gradually become the main bit of shale gas development is the trend of the times.
In October 2012, Schlumberger announced the successful development of a new generation of Spear shale optimized steel PDC bits tailored for unconventional shale gas production. Guy Arrington, Schlumberger Drill Bit and Senior Technology Chairman, said: "With the application of the Spear PDC drill bit to shale gas mining in 2011, the drilling performance of equipment bending and horizontal sections is improved."
“As of now, there are 6,000 Spear drills in use. We apply special design originals to the new generation of drills to increase the rate of penetration, significantly reducing the drilling costs of unconventional wells,†says Guy Arrington.
For a long time, the domestic core oil and gas PDC market has been occupied by overseas products. Compared with imported products, domestic oil and gas PDCs have gaps in impact resistance, wear resistance and thermal stability. In order to close the gap, domestic drill manufacturers have combined the actual development of drill bits.
Since 2012, Jiang Diamond Co., Ltd. has undertaken Sinopec's “Fuling High-efficiency PDC Bit Development†project. Based on the construction characteristics of the Fuling area, it has developed a personalized PDC bit by relying on the diamond bit production line. Through continuous improvement, testing and application, they will achieve the goal of significantly improving the comprehensive use of drill bits.
Shaanxi Hancheng Zhongsheng Company used to use roller cone bits mainly in the development of coalbed methane. After using the PDC drill bit in two wells, the total drill footage is 1333.53 meters, and the average mechanical drilling speed is 6.51 meters per hour. The use of the drill is better, the tool surface is stable, and the mechanical drilling speed is high.
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