涠洲油田低渗储层长岩心驱替实验研究

中海油在南海西部海域的涠西南凹陷发现低渗透油气田。目前,该油田开发面临的主要问题包括:特低渗(渗透率小于10×10-3μm2)油藏储量所占比例大,如何提高低渗透储层产能,如何有效动用储量,以及注水开发可能存在注入能力低等。由于地层原油黏度低,油质较轻,注气开发是提高低渗透油藏采收率的有效手段;此外,该油田开发过程中将产生大量伴生气,有足够的气源。因此,采用油田伴生气回注是值得探索的提高采收率的方法。为此,有必要通过长岩心驱替实验,对低渗透油气田的注入方式进行评价优选,为编制海上低渗透油田开发方案提供依据。选取涠洲某油田流沙港组低渗透储层,通过室内长岩心驱替实验研究,综合评价了衰竭、水驱、气驱、气/水交替驱替时的驱油效率和渗流特征,从而为注水、注气驱提高采收率开发方式的选择提供实验数据支持和参考。实验结果表明:衰竭式开采方式效果最差,注水比注气效果要好,注液化气前置段塞+外输气驱的方式,能够达到最好的驱替效果。

Long Core Displacement Test Study in Low-permeability Reservoirs of Weizhou Oilfield

CNOOC found low-permeability oil and gas field in southwest of Weizhou sag in the west water of South China Sea.At present,this oilfield is facing the issues of large-scale reserves in the extra-low-permeability oil reservoir（permeability is less than 10×10-3μm2）,trying to enhance productivity of the low-permeability reservoir and how to produce reserves effectively,and low injection capability in water flooding.Because of low viscosity and light weight of crude oil,gas injection is the effective tool for enhancing recovery efficiency in the low-permeability oil reservoir.Otherwise,a large amount of associated gas will be produced in the process of oilfield development,which will provide enough gas source.So,reinjection of the associated gas is a method of EOR worthy for exploring.In this paper,through the study of long core displacement test,we evaluated the injection ways in the low-permeability oil and gas field,which will provide foundation for development programming for offshore low-permeability oilfield.Low-permeability reservoirs in Liushagang formation,some oilfield of Weizhou were selected.Displacement efficiency and flow characteristics when depletion,water drive,gas drive and gas/water alternating displacement were evaluated comprehensively through long-core displacement test study.It will give the data support and reference to choose the development fashion such as water injection or gas injection for enhancing the recovery efficiency.The results show that： in Weizhou oilfield,it has the worst effects when the depletion exploitation and the effect of water injection is better than gas injection,but LPG injection pre-slug and external gas drive will achieve the best effect of displacement.