致密油藏驱渗结合采油可行性研究

Investigation on Availability of Method Combining Water Flooding and Soaking for Tight Oil Reservoirs

致密油藏孔喉较小而渗吸作用显著,为提高致密油藏水驱效率,提出驱渗结合采油方法,同时利用驱替与渗吸作用。为验证该方法的可行性与主控因素,在水驱模型的基础上,考虑了渗吸作用,并基于实验数据特征建立了渗吸项模型,建立了驱渗结合采油数值模拟模型。结果表明,渗吸作用有效增加了注入水的波及面积,有效置换出基质中的原油,提升了采油效率;主控地质因素包括基质/裂缝孔隙度、渗透率和渗吸经验参数,主控工程因素包括注水压力、裂缝间距和半长;现场应用表明相较水驱方式,驱渗结合采油的日产油速度提高了约1倍,受效时间约为200 d,提高累产约为340 t,说明驱渗结合采油工艺可有效提高中国致密油藏的采收率,所建模型可用于驱渗结合采油的优化设计。

Tight oil reservoir has tiny pores so the imbibition effect is obvious.In order to enhance efficiency of waterflooding for tight oil reservoir,the method of combining water flooding and soaking was proposed.In order to clarify the mechanism of enhanced oil recovery of this new method and its main influencing factors,the impact of imbibition effect was considered and a model was proposed for imbibition.Combining this new model and the numerical simulation model for waterflooding,the numerical simulation for the water-flooding-soaking method was built.The results show that the effect of imbibition increases the swept volume of reservoir and displaces crude oil from the matrix,which improves the production efficiency.The main geology factors affecting oil recovery include matrix/fracture porosity,permeability and coefficient of imbibition.The main engineering factors affecting oil recovery include injection pressure,fracture interval and half-length.The field case also shows that this method can enhance production rate,its rate is twice time of the one by water flooding,the efficient period is about 200 d and the cumulative enhance oil is about 340 t.It indicates that this new method can enhance recovery rate of tight oil reservoirs in China and the built model can optimize parameters of this new method.