Volume 57

Exploration and application of CO2 huff-and-puff technology to individual wells and blocks with hard-to-recover reserves Kuifeng Dong, Zezong Zhao, Xiaoqi Li, Guinian Li, Jiaqi Jiang, Guangsheng Zhang, Changyun Liu, Shede Dai, Meng Wang, Sheng Zhang

Abstract

It is imperative to acknowledge the significance of the existing single well, single-block reservoirs within the Wenliu Oilfield, as their inherent limitations hinder the establishment of a comprehensive drilling network, the extent of their productivity, and the efficient development of their potential. The imminent necessity to enhance oil recovery (EOR) rate of “three-low” (low permeability, low productivity, low efficiency) reservoirs is underscored by the prevailing challenges. The implementation of CO2 huff-and-puff (CO2 HnP)in conjunction with wells possessing a certain degree of storage capacity can yield a substantial augmentation in the recovery rate of oil. This approach is characterized by its cost-effectiveness and expeditious outcomes. Through the utilization of numerical simulation techniques, the optimization of the slug injection methods and the design of injection parameters can be achieved. This facilitates the reduction of operational periods and the attainment of enhanced recovery rates. In order to optimize the ground injection process and tubular designs, as well as the supporting anti-corrosion process, it is essential to improve CO2 HnP monitoring technology in order to guide the field application. Furthermore, the application of quantitative characterization technology of CO2 displacement leading edge is required to guide the optimization of the implementation of the plan. Finally, the formation of the CO2 HnP process should be facilitated. From 2022 to 2025, 3 well-times of CO2 HnP were conducted in single well and individual block difficult-to-produce reserves, with cumulative injection of 3655.4 t CO2 and cumulative water injection of 8350 m3 by water injection slug. Up to now, the cumulative oil increment is 1462 t and the oil exchange ratio is 0.4 t/t, a excellent level of CO2 utilization is achieved.

Keywords single wells and individual blocks, enhanced oil recovery (EOR), optimization design, CO2 huff-and-puff technology