Research and Application of Key Technologies for Quality Improvement and Efficiency Enhancement in Ultra-Super Heavy Oil Fields

As the first large offshore oilfield to achieve large-scale thermal recovery development, the LD5-2 N Oilfield utilizes steam stimulation and was put into operation in April 2022. Throughout the first steam injection cycle, problems like inter-well steam breakthrough, elevated water cut, and a high water recovery ratio were detected; analysis results verify that low-quality reservoirs function as the main water-producing zones and steam channeling routes. To tackle these problems, a set of key technologies for improving efficiency were developed, which include: regional steam injection to inhibit channeling, classified water shutoff and control, as well as the optimization of production systems. Besides, dedicated materials were developed, including high-temperature-resistant nitrogen foam, high-temperature-soluble gel, and high-strength ultra-fine cement systems. Up to now, regional steam injection has been carried out on 10 well groups, water shutoff treatments have been applied to 12 wells, and production optimization adjustments have been implemented on 5 wells. After the application of these measures, no steam channeling has been found in the well groups, the steam sweep efficiency has increased by 15%, and the average water cut of each well has dropped by 10%. Consequently, the total cumulative incremental oil output has hit 15,000 tons, while the overall oil production has surpassed 800,000 tons. This research, therefore, offers vital technical support for promoting the large-scale and high-efficiency development of ultra-heavy oil reservoirs in the Bohai Oilfield.