致密油体积压裂耦合渗吸产能预测模型

1)中国石油大学(华东)石油工程学院,山东青岛 266580; 2)中国石油勘探开发研究院廊坊分院,河北廊坊 065007

致密油; 渗吸; 压裂水平井; 产能计算; 窜流; 复合模型

Production capacity prediction model for multi-stage fractured horizontal well coupled with imbibition in tight oil reservoir
SU Yuliang1, HAN Xiuhong1, WANG Wendong1, SHENG Guanglong1, YANG Zhengming2, HE Ying2, and WANG Zhiyuan2

1)College of Petroleum Engineering, China University of Petroleum(East China), Qingdao 266580, Shandong Province, P.R.China2)PetroChina Research Institute of Petroleum Exploration and Development-Langfang, Langfang 065007, Hebei Province, P.R.China

tight oil; imbibition; fractured horizontal well; productivity calculation; cross flow; composite model

DOI: 10.3724/SP.J.1249.2018.04345

备注

致密/页岩油储层在进行大型水力压裂时,注入压裂液返排率平均仅为10%,压裂液滞留在地层中通过渗吸作用置换储层中的原油,从而达到提高单井产能的目的 .为了表征压裂液滞留与渗吸采油在压裂水平井中的复杂作用,从渗吸机理出发,建立了水平井体积压裂耦合渗吸产能预测模型,模型中通过引入基质与裂缝间的毛管力来修正窜流项,表征渗吸作用,同时考虑启动压力梯度来描述基质的低渗特性.通过Laplace变换和Stehfest数值反演方法对模型进行求解并完成模型验证,研究了致密油压裂过程中压裂液滞留量、储层岩石润湿性以及启动压力梯度对体积压裂水平井产能的影响机制.研究结果表明,较高的压裂液滞留量和较小的启动压力梯度有利于提高生产井产能; 油湿性储层应减弱毛管力作用,而水湿性储层应增强渗吸的作用,以提高油井生产能力.致密油压裂水平井渗吸产能计算模型为渗吸采油以及致密储层的开发提供了理论依据.

In the procedure of large-scale hydraulic fracturing in tight and shale oil formation, the flow-back efficiency is only up to 10%. Parts of oil could be replaced out by the fracturing fluid retained in formation through the imbibition process, leading to the increase of single well productivity. In order to characterize the effects of fracturing fluid retention and imbibition on the performance of fractured horizontal well in tight reservoir, a mathematical model considering fluid imbibition for well production prediction is developed by using Darcy's law, in which the imbibition is represented in terms of capillary pressure between matrix and fracture, and the fluid flow in low-permeability reservoir is modeled by incorporating the threshold pressure gradient. A semi-analytical solution is achieved by applying Laplace transform and Stehfest numerical inversion. The analytical solution is also verified by numerical solution using Eclipse software. The effects of fracturing fluid retention, formation wettability and threshold pressure gradient on the performance of fractured horizontal well in tight oil are then analyzed by using the novel model. The results show that the higher amounts of fracturing fluid retention and the lower value of threshold pressure gradient could be helpful to enhance well production. In order to increase well production, the capillary pressure should be weaken in oil-wet reservoir, while the imbibition effect should be enhanced in water-wet formation. The novel model for fractured horizontal well in tight oil provides a theoretical foundation for analysis of oil recovery using imbibition and the further development of tight oil formation.

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