The Influence of Micro-Heterogeneity on Water Injection Development in Low-Permeability Sandstone Oil Reservoirs
Abstract: Micro-heterogeneity in low-permeability sandstone oil reservoirs significantly influences the uniformity of water injection during development. This leads to the formation of preferred channels for water injection, causing premature water breakthroughs in oil wells. Not only does this reduce oil displacement efficiency, but it also enriches residual oil in the formation, which ultimately impacts the overall recovery rate. This study employed various methods, including thin-section casting, qualitative analysis… Show more
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Cited by 5 publications
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Experimental simulation study on influencing factors of liquid production capacity in heterogeneous water drive reservoirs
Oilfield development involves a complex, dynamic flow process of oil and water, with reservoir characteristics and environmental conditions continually evolving as the field evolves. Particularly when a waterflooding reservoir reaches a stage of ultra-high water cut, prolonged waterflooding intensifies challenges in reservoir development: the exacerbation of reservoir heterogeneity and development behaviors disrupts the initial understanding of the reservoir's liquid production capacity from current development conditions. Thus, it becomes imperative to adjust the productivity prediction methods for oil wells in heterogeneous waterflooding reservoirs. Leveraging the flow simulation of reservoir micro channel networks, and integrating features such as the geometric characteristics of the reservoir percolation field, micro channel characteristics, interlayer differences of mixed layers, degree of plane heterogeneity, production pressure differentials, and fluid properties, a visual sand filling experimental model is established that adheres to specific similarity criteria. Using this sand filling experimental model, we simulate the percolation characteristics of oil–water two-phase flow during the waterflooding process, and uncover the diverse influencing factors and their varying degrees of impact on the oil-phase flow during this waterflooding phase. Qualitative and semi-quantitative percolation simulation experiments are employed to intuitively demonstrate the interlayer interference, degree of plane heterogeneity, and oil–water distribution in heterogeneous reservoirs, which influence the change in oil well productivity during waterflooding. This lays bare the microscopic percolation mechanisms behind the productivity changes in heterogeneous waterflooding reservoirs. The simulation experiment results show that the higher the permeability, the stronger the micro-heterogeneity, and the smaller the overall mobility increase after flooding, the smaller the JLDmax obtained by testing or calculation. At the same permeability, the greater the driving pressure difference, the greater the microscopic sweep coefficient within the pore network, and the greater the mobility increase after flooding, the greater the JLDmax. There is interlayer interference in commingled mining, and the higher the permeability of the high-permeability layer (the greater the interlayer difference), the higher the initial productivity of the commingled well. However, due to the high permeability layer being prone to flooding, resulting in ineffective water circulation, the low-permeability tube is difficult to completely flood, resulting in a small increase in overall mobility, and therefore, JLDmax is small. Water drive preferentially breaks through the high permeability zone on the plane, and the shape of the water drive sweep zone is controlled by the planar permeability gradient, the width of the high permeability zone, and the displacement pressure difference.
Experimental simulation study on influencing factors of liquid production capacity in heterogeneous water drive reservoirs
Oilfield development involves a complex, dynamic flow process of oil and water, with reservoir characteristics and environmental conditions continually evolving as the field evolves. Particularly when a waterflooding reservoir reaches a stage of ultra-high water cut, prolonged waterflooding intensifies challenges in reservoir development: the exacerbation of reservoir heterogeneity and development behaviors disrupts the initial understanding of the reservoir's liquid production capacity from current development conditions. Thus, it becomes imperative to adjust the productivity prediction methods for oil wells in heterogeneous waterflooding reservoirs. Leveraging the flow simulation of reservoir micro channel networks, and integrating features such as the geometric characteristics of the reservoir percolation field, micro channel characteristics, interlayer differences of mixed layers, degree of plane heterogeneity, production pressure differentials, and fluid properties, a visual sand filling experimental model is established that adheres to specific similarity criteria. Using this sand filling experimental model, we simulate the percolation characteristics of oil–water two-phase flow during the waterflooding process, and uncover the diverse influencing factors and their varying degrees of impact on the oil-phase flow during this waterflooding phase. Qualitative and semi-quantitative percolation simulation experiments are employed to intuitively demonstrate the interlayer interference, degree of plane heterogeneity, and oil–water distribution in heterogeneous reservoirs, which influence the change in oil well productivity during waterflooding. This lays bare the microscopic percolation mechanisms behind the productivity changes in heterogeneous waterflooding reservoirs. The simulation experiment results show that the higher the permeability, the stronger the micro-heterogeneity, and the smaller the overall mobility increase after flooding, the smaller the JLDmax obtained by testing or calculation. At the same permeability, the greater the driving pressure difference, the greater the microscopic sweep coefficient within the pore network, and the greater the mobility increase after flooding, the greater the JLDmax. There is interlayer interference in commingled mining, and the higher the permeability of the high-permeability layer (the greater the interlayer difference), the higher the initial productivity of the commingled well. However, due to the high permeability layer being prone to flooding, resulting in ineffective water circulation, the low-permeability tube is difficult to completely flood, resulting in a small increase in overall mobility, and therefore, JLDmax is small. Water drive preferentially breaks through the high permeability zone on the plane, and the shape of the water drive sweep zone is controlled by the planar permeability gradient, the width of the high permeability zone, and the displacement pressure difference.
Exploration and Understanding of Intermittent Water-Flooding in Low-Permeability Reservoirs Supported by New Energy Supply
The expansion of new energy construction, characterized by its scalability and cost-effectiveness, is increasingly integrated into the oil and gas industry, albeit still in the exploratory phase. Chinese oil fields predominantly employ continuous water injection methods, which incur substantial electricity consumption and costs. Embracing new energy sources for supply promises substantial reductions in electricity costs. However, the intermittent and unpredictable nature of wind and solar power generation does not align with the consistent and stable electricity demand required for continuous water injection, necessitating the exploration of novel water injection models compatible with new energy supplies. In pursuit of minimizing water injection electricity costs, this study proposes an intermittent water injection model grounded in the distinctive characteristics of new energy supply. During peaks of green electricity output surpassing production demand, "increased injection" is implemented, while during troughs of green electricity output falling below production demand, "reduced or halted injection" strategies are adopted. Insights derived from well test interpretations using shut-in pressure drop data guide the fine-tuning of water injection parameters. This transition shifts the water injection regime from the conventional "24-hour stable flow continuous water injection" to an "X hours injection/ 24-X hours shut-in intermittent water injection" approach. The feasibility of this model is comprehensively evaluated through real-time monitoring, engineering tests, and well test interpretations, assessing injection capacity, water absorption efficiency, reservoir characteristics, and productivity across the project lifecycle. A 5-month intermittent water injection trial was conducted across two injection-production well pairs in the low-permeability reservoirs of the Jilin oilfield. Three distinct intermittent water injection protocols were designed: "15 hours injection/ 9 hours shut-in", "13.3 hours injection/ 10.7 hours shut-in", and "12 hours injection/ 12 hours shut-in". The injection rates, set at 1.6 times, 1.8 times, and 2.0 times the rate of continuous water injection, respectively, were determined by these protocols. Trial outcomes demonstrate reasonable high-speed injection pressures, satisfactory injection volumes, intact reservoir conditions, a 2.5 % reduction in water cut, and a delay of over 1.5 % in natural decline. Calculations based on new energy generation costs reveal a reduction of over 60% in daily electricity expenses compared to continuous water injection methods. The successful field trial validates the feasibility of intermittent technology in low-permeability reservoirs, showcasing substantial savings in electricity costs and offering robust technical underpinning for the efficient development of such reservoirs.
Experimental Study on the Acid-Etched Fracture Conductivity of Novel Nano Retarded Acid System
The expansion of new energy construction, characterized by its scalability and cost-effectiveness, is increasingly integrated into the oil and gas industry, albeit still in the exploratory phase. Chinese oil fields predominantly employ continuous water injection methods, which incur substantial electricity consumption and costs. Embracing new energy sources for supply promises substantial reductions in electricity costs. However, the intermittent and unpredictable nature of wind and solar power generation does not align with the consistent and stable electricity demand required for continuous water injection, necessitating the exploration of novel water injection models compatible with new energy supplies. In pursuit of minimizing water injection electricity costs, this study proposes an intermittent water injection model grounded in the distinctive characteristics of new energy supply. During peaks of green electricity output surpassing production demand, "increased injection" is implemented, while during troughs of green electricity output falling below production demand, "reduced or halted injection" strategies are adopted. Insights derived from well test interpretations using shut-in pressure drop data guide the fine-tuning of water injection parameters. This transition shifts the water injection regime from the conventional "24-hour stable flow continuous water injection" to an "X hours injection/ 24-X hours shut-in intermittent water injection" approach. The feasibility of this model is comprehensively evaluated through real-time monitoring, engineering tests, and well test interpretations, assessing injection capacity, water absorption efficiency, reservoir characteristics, and productivity across the project lifecycle. A 5-month intermittent water injection trial was conducted across two injection-production well pairs in the low-permeability reservoirs of the Jilin oilfield. Three distinct intermittent water injection protocols were designed: "15 hours injection/ 9 hours shut-in", "13.3 hours injection/ 10.7 hours shut-in", and "12 hours injection/ 12 hours shut-in". The injection rates, set at 1.6 times, 1.8 times, and 2.0 times the rate of continuous water injection, respectively, were determined by these protocols. Trial outcomes demonstrate reasonable high-speed injection pressures, satisfactory injection volumes, intact reservoir conditions, a 2.5 % reduction in water cut, and a delay of over 1.5 % in natural decline. Calculations based on new energy generation costs reveal a reduction of over 60% in daily electricity expenses compared to continuous water injection methods. The successful field trial validates the feasibility of intermittent technology in low-permeability reservoirs, showcasing substantial savings in electricity costs and offering robust technical underpinning for the efficient development of such reservoirs.
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