人工气顶形成评价理论方法与参数界限研究

Evaluation theory method and parameter boundary for the formation of artificial gas cap

刘维霞

LIU Weixia

中国石化胜利油田分公司勘探开发研究院

Exploration and Development Research Institute, SINOPEC Shengli Oilfield Company, Dongying 257015, Shandong, China

高角度构造油藏可采用人工气顶驱的方式开采局部富集剩余油，气顶的形成界限是影响人工气顶驱可行性的重要因素。为明确人工气顶形成的理论界限，依据多孔介质中气泡的受力特征，建立气泡微观控制模型，开展了模型主控因素敏感性分析，明确了室内模拟和油藏条件下氮气驱水和氮气驱油时人工气顶形成所需最小气柱高度。研究结果表明：人工气顶生成所需最小气柱高度随界面张力、油藏压力和毛管力与质量力反方向的夹角增大而增大，随渗透率、密度差和地层倾角增大而减小，降低界面张力是人工气顶形成的关键。室内实验条件下，氮气驱油最小气柱高度为65.4 cm，氮气驱水最小气柱高度为86.9 cm；油藏条件下，氮气驱油最小气柱高度为42.9 cm，氮气驱水最小气柱高度为93.5 cm，气泡启动所需的临界气柱高度远大于长岩心尺度。研究结果为相关油气田的开发和生产提供技术支持和理论指导。

Artificial gas cap flooding can be used to exploit the locally enriched remaining oil in high-angle structural oil reservoirs, and the formation boundary of gas cap is an important factor influencing the feasibility of artificial gas cap flooding. In order to define the theoretical formation boundary of artificial gas cap, this paper established a microscopic control model of gas bubble according to the mechanical characteristics of gas bubbles in porous medium. Then, sensitivity analysis was carried out on the main control factors of the model. Finally, the minimum gas column height needed for the formation of artificial gas cap during nitrogen displacing water and nitrogen displacing oil under the conditions of laboratory simulation and oil reservoirs was determined. It is indicated that the minimum gas column height needed for the formation of artificial gas cap increases with the increase of interfacial tension, oil reservoir pressure and reverse included angle between capillary force and mass force, and decreases with the increase of permeability, density difference and stratigraphic dip. The key to the formation of artificial gas cap is to reduce the interfacial tension. Under the condition of laboratory experiment, the minimum gas column height for nitrogen displacing oil is 65.4 cm and that for nitrogen displaceing water is 86.9 cm. And under the condition of oil reservoir, they are 42.9 cm and 93.5 cm, respectively, and the critical gas column height for the initiation of gas bubble is much larger than the size of long core. The research results provide the technical support and theoretical guidance for the development and production of similar oil and gas fields.

10.13639/j.odpt.2020.02.014