The times create heroes. China's complex and diverse reservoirs provide soil for the advancement of fracturing technology. China's oil and gas production and engineering technology service enterprises are based on oil fields, and have carried out effective fracturing technology research, forming unique fracturing technologies for oil and gas. The storage provides technical support.

 

In Daqing Oilfield, the compact and interbedded horizontal well fracturing technology has promoted the stable production of 40 million tons of Daqing Oilfield; in the Changqing Oilfield, the large-scale application of multi-stage fracturing of vertical wells, staged fracturing of horizontal wells, etc. The "three low" oil and gas reservoirs with well oil and no mouth flow are no longer "silent", the output arrow continues upwards, and "Western Daqing" is ready to go; in Jilin Oilfield, the casing inner packer sliding sleeve segmental fracturing technology can be More than 400 wells have been applied in one time, and the wells of Heihe Ping 2 have been divided into 15 sections, which provides important technical support for the effective development and utilization of Fuyang oil layer in Jilin Oilfield; in Tarim Oilfield, it was born. The Kuqa Sag over 7000 meters ultra-deep high-pressure tight sandstone gas industrial fracturing technology; in the southwest oil and gas field, fracturing technology promoted the effective development of the "three high" oil and gas reservoirs.

 

From the first single well fracturing construction in Yumen Oilfield in 1955 to the current large-scale horizontal well segmentation and volume fracturing construction; from conventional small-scale sand fracturing to today's platform multi-well industrial fracturing; The single-well construction scale of “Hundred Square Sand and Qianfang Liquid” has been developed to “Qianfangsha and Wanfang Liquid”. Over 50 years, PetroChina’s fracturing technology has made great progress and revolutionary breakthroughs. Go steady and go fast.

 

Schematic diagram of packer sliding sleeve segmentation

 

Catch up: technology research and development test

 

Although China has made great progress in key technologies such as vertical well splitting and horizontal well segmental fracturing, there is still a certain gap compared with the international advanced level. This makes the road of research and development and application of China's reservoir transformation technology a long way to go.

 

At present, the ultra-deep well fracturing of low-permeability tight sandstone reservoirs in China has exceeded 7,000 meters, the acid pressure and hydraulic fracturing of carbonate reservoirs have exceeded 5,000 meters, the construction pressure has reached 130 MPa, and the formation temperature has been continuously increased. At the current 200 degrees Celsius, the effective reserve limit is also continuously extended, and the reservoir permeability is declining. Reservoir rebuilding objects are becoming more and more complex, and higher requirements are imposed on fracturing equipment, downhole tools, and fracturing acidified materials. All of this means that reservoir retrofit technology needs to constantly challenge the limits.

 

At the same time, China's tight sandstone oil and gas has obvious thin layer characteristics, and the research ideas and transformation modes of reservoir reform technology need to go from low permeability to compact. This presents a new challenge for how to implement subdivision of small fractures. Coiled tubing hydraulic jet splitting cracking technology has not yet become a mainstream technology in China, and multi-lateral wells and multi-branch horizontal wells have just started to be staged.

 

Since the waterless fracturing technology is still in the experimental stage in the world, the fracturing construction is mostly large-scale hydraulic fracturing. According to US production practices, the shale gas pressure splitting single well requires more than 10,000 cubic meters of water, especially as the length of the horizontal section and the number of staged fracturing stages increase, the water consumption increases significantly in a shorter period of time. . The massive consumption of water resources and the impact on local aquatic life, fishing, urban and industrial water use makes hydraulic fracturing a double-edged sword.

 

For this reason, some environmental organizations and government agencies have protested the use of large-scale hydraulic fracturing to develop shale gas. Some European countries represented by France even enacted laws prohibiting the use of large-scale fracturing shale gas and canceled it. Multiple shale gas projects.

 

In addition, compared with foreign countries, China still has a large space for development in low-cost and high-efficiency fracturing fluids and unrestricted selective fracturing tools. China has a small number of staged fracturing segments, and has more than 50 segments abroad.

 

Number of Fracturing Wells in Section 10 of China Petroleum

 

The future: technological development does not follow the conventional path

 

Where is the development direction of fracturing technology? What kind of reservoir is more suitable for volume transformation technology? To what extent does the reservoir reform have to be achieved? What liquid and tool fracturing effect is better? How to achieve a win-win situation between fracturing effect and environmental protection... The solution of one problem will promote the progress of reservoir reform technology and the effective development of difficult-to-use reservoirs and unconventional oil and gas resources.

 

Experience is worth learning and ideas need innovation. Zou Cai believes that: "China has many types of oil and gas reservoirs, different lithology, different thickness and different water content, and the fracturing technology is different. The development of fracturing technology cannot completely copy foreign models, and must have its own unconventional ideas and unconventional technologies. Unconventional management as a support."

 

The innovation of theory and process and the improvement of comprehensive system research and development capabilities are the primary issues that need to be solved in China's fracturing technology. While drawing on foreign advanced technology, we should systematically summarize the characteristics of domestic reservoir reform technology and study the fracturing technology system that is really suitable for China's actual situation. "This requires major oil and gas production enterprises to further strengthen the integration with engineering technology research units to achieve joint planning, joint research, and joint design. Strengthen exchanges and cooperation between enterprises to achieve resource sharing, share of results, and benefit sharing." Engineering Technology Zhao Yerong, deputy general manager of the branch, pointed out.

 

High-efficiency, low-cost, and environmentally friendly fracturing technology is an important development direction in the future. For example, high-speed channel fracturing, volume modification, waterless fracturing, and platform multi-well factory fracturing techniques have been tested. At the same time, existing fracturing technologies such as coiled tubing fracturing and small wellbore fracturing need to be continuously developed and integrated, and fracturing fluid systems and supporting technologies for different rock properties should be developed. Fracturing equipment should be developed in the direction of high power, modularization, miniaturization, etc., which not only can reduce the number of equipment used, but also greatly reduce the land occupation area, and facilitate the fracturing construction under complex surface conditions. Fracturing tools should be developed in the direction of ultra-long horizontal segmental fracturing tools and selective staged fracturing tools. Fracturing fluids can be developed in the direction of low cost, harmlessness, and recyclability, while minimizing the effects of fracturing while minimizing environmental impact.