The first horizontal well wellbore in Changqing Oilfield was successfully tested for CO2 energy enhancement and repeated volume fracturing!

Recently, good news came from the site of the Changqing Oilfield Yuan 284 to change the development mode to enhance oil recovery, and the first horizontal well wellbore reconstituted carbon dioxide energy enhancement repeated volume fracturing test in China was successful. This indicates that with the maturity of the bridge-shot combined cropping process of wellbore reconstruction, the fracturing efficiency of horizontal wells has been greatly improved. More importantly, this technology can also carry out geological sequestration of carbon dioxide and realize the green and low-carbon development of unconventional oil and gas resources.

With the increase of production time, the oil recovery rate and recovery rate of some ultra-low permeability reservoirs in the Ordos Basin have decreased year by year. In particular, the horizontal wells put into production in the early stage have few construction sections and small transformation scale, and the water injection effect is very little due to the poor physical properties of the reservoir and the development of natural fractures. In view of this development dilemma, Changqing Oilfield actively explores new development methods for ultra-low permeability reservoirs, and has formed a horizontal well repetitive volume fracturing technology with "pre-pressure energy supplement, in-pressure energy enhancement, and post-pressure expansion" as the core, and carbon dioxide energy enhancement volume fracturing is the exploration and breakthrough of its new technology.

In 2021, the oil and gas equivalent of Changqing Oilfield will sprint to 62 million tons, and the old area of Yuan 284, as the first demonstration area for the transformation and development of ultra-low permeability reservoirs in China, has increased its annual oil production capacity from 23,000 tons to 100,000 tons under the continuous research of scientific researchers. "At present, the producing reserves of ultra-low permeability reservoirs account for more than 40% of the produced reserves of Changqing Oilfield, and the stable production of old oilfields is a key part of high-quality development, and it is particularly important to transform the development mode through volume fracturing." Yang Haien, vice president of the Oil and Gas Technology Research Institute, said.

Compared with ordinary burial, the injection of liquid carbon dioxide in the fracturing process of oil wells can make carbon dioxide more quickly and intensively injected into the formation. Through the miscible and extraction effect of carbon dioxide on reservoir crude oil, it not only leverages the new technical increment of enhanced oil recovery in ultra-low permeability reservoirs, but also makes beneficial explorations for the realization of green environmental protection, energy conservation and emission reduction in the development process of old oilfields. "The Chuanping 50-15 well in the Yuan 284 area adopts the wellbore reconstruction bridge-shot continuous cropping process, and the wellhead does not blow out under the condition of continuous pressure operation, which gives sufficient diffusion time for carbon dioxide," Xue Xiaojia of Changqing Oilfield Oil and Gas Technology Research Institute told reporters, "We are equipped with two carbon dioxide high pressure at the construction site."Pump trucks, the injection displacement is up to 2.2 cubic meters per minute, and the single-stage carbon dioxide injection is up to 100 cubic meters. In addition, there are 20 horizontal CO2 storage tanks on site to ensure the timely supply of liquid CO2. ”

According to reports, the Chuanping 50-15 well has carried out a total of 10 stages of carbon dioxide injection construction, and a total of more than 1,000 cubic meters of liquid carbon dioxide have been injected, which is equivalent to the energy enhancement effect of injecting 10,000 square meters of clean water. In order to further improve the efficiency of repeated fracturing operations in horizontal wells, solve the problems of precise segmented fracturing and external channeling of old well pipes, the fracturing efficiency was increased from 1 section in 2 days to 3 sections in 1 day by using the wellbore reconstruction bridge-injection combined cropping process, and a total of 77 clusters of fracturing in 26 sections were completed, 39 levels of temporary plugging were realized, and the amount of liquid entering the ground was 42,000 cubic meters, and the technical parameters were greatly improved compared with the previous stage.