—The first carbon dioxide dry fracturing well in Daqing Oilfield – Xing 5-2-28 well has a significant increase in oil production
Recently, the first carbon dioxide dry fracturing well in Daqing Oilfield – Xing5-2-28 well in the experimental area of the Saring Formation in Xingbei Development Zone, has been successfully fractured. The initial daily production of liquid is 4.5 tons, the daily production of oil is 2.2 tons, and the water content is 52%. Compared with conventional anti swelling fracturing measures, the daily production has been increased by 1 ton.
Carbon dioxide dry fracturing, also known as carbon dioxide anhydrous energy storage fracturing, uses liquid carbon dioxide instead of water-based fracturing fluid compared to conventional fracturing. It utilizes the super fluidity and rock breaking ability of carbon dioxide to create fractures and carry sand, which can achieve clean transformation of sensitive reservoirs and effectively increase the volume of reservoir transformation.
The Sa Ling Formation in the Xingbei Development Zone of Daqing Oilfield belongs to a water sensitive reservoir, with montmorillonite, illite, and kaolinite being the main clay minerals. Among them, montmorillonite has a high content and the rock is highly sensitive to water. If conventional hydraulic fracturing is used, it is easy to cause clay mineral hydration expansion, severe dispersion and migration, and block the fracture diversion channel, resulting in poor fracturing effect. Therefore, the carbon dioxide dry fracturing technology was first tested and applied in the fracturing transformation of this reservoir.To ensure the expected effect, in response to the complex stress conditions in the reservoir and the problem of turning and extending cracks, based on the analysis of adjacent well fracturing construction and the modeling simulation of this well, the design parameters are optimized to control risks from the source and ensure the effectiveness of fracturing transformation. In addition, for the low closure pressure of the reservoir and the problem of easy backflow of proppants, 20-40 mesh film coated ultra-low density proppants are preferred to ensure the support effect of cracks while also considering the sand consolidation effect.
Carbon dioxide has the characteristics of not containing water phase, improving formation energy, enhancing crude oil fluidity, and improving infiltration and absorption displacement. Combined with hydraulic fracturing, it can further increase the oil release area, strengthen infiltration and absorption displacement, and achieve the integrated effect of fracturing, energy enhancement, and infiltration and absorption. It has a wide range of application prospects in water sensitive reservoirs, various low-pressure reservoirs, and tight oil reservoirs.
