CO2辅助重力驱油开发效果影响因素分析

针对各类地质参数对CO₂辅助重力驱油技术开发效果影响规律尚不明确的问题,以某中低渗油藏为研究对象,建立多个一注一采机理模型研究地层沉积韵律、倾角、渗透率、孔隙度、垂直渗透率与水平渗透率比值、渗透率级差对CO₂辅助重力驱油效果的影响。结果表明:正韵律沉积地层相较于反韵律地层更适用于CO₂辅助重力驱油;地层倾角有利于重力分异和形成气顶;中低渗低孔油藏开展CO₂辅助重力驱油,对抑制气窜突破具有一定作用;垂直渗透率与水平渗透率比值越小,越有利于抑制气体的纵向快速扩散;渗透率级差对CO₂辅助重力驱油影响不大;不同地质因素对采出程度影响由大到小依次为垂直渗透率与水平渗透率的比值、地层倾角、地层渗透率、地层孔隙度、地层渗透率级差。A油藏矿场实践表明,CO₂辅助重力驱油能够使其阶段累计产油量提高3倍以上,可取得明显的增产效果。研究成果可为同类油田的CO₂驱开发提供理论指导。

Analysis of Influencing Factors on the Development Effect of CO2 Assisted Gravity Flooding

To address the problem that the effect of various geological parameters on the development of CO₂-assisted gravity flooding technology is still unclear, taking a medium and low permeability oil reservoir as the research object, a number of theoretical models of one-injection and one-recovery mechanism were established to study the influence of the formation sedimentary rhythm, dip angle, permeability, porosity, ratio of vertical permeability to horizontal permeability, and permeability max-min ratio on the effect of the CO₂-assisted gravity flooding. The result shows: The CO₂-assisted gravity flooding is more suitable for positive rhythm sedimentary strata than negative rhythm strata; there is a certain formation dip, which is conducive to gravitational differentiation and formation of gas caps; the CO₂-assisted gravity flooding is carried out in medium-low permeability and low-porosity oil reservoirs, which has a certain effect on the inhibition of gas channeling breakthrough. The smaller the ratio of vertical permeability to horizontal permeability, the more conducive to inhibiting the rapid vertical diffusion of gas. The permeability max-min ratio has little effect on CO₂-assisted gravity flooding. The influence of different geological factors on the recovery degree is the ratio of vertical permeability to horizontal permeability, formation dip angle, formation permeability, formation porosity, formation permeability max-min ratio in descending order. The field test of the A Reservoir shows that CO₂-assisted gravity flooding can increase the stage cumulative oil production by more than 3 times, and can achieve a significant increase in production. The research results can provide theoretical guidance for the development of CO₂ flooding in similar oilfields.