低渗透油藏启动压力梯度实验研究

The experimental study of start-up pressure gradient of low permeability oil reservoirs

随着油气资源的利用,越来越多的低渗透油藏投入开发,低渗透油藏由于渗透率低,孔隙结构复杂,在实际生产中的启动压力不可忽略。针对低渗透油藏的特点,分析了启动压力的产生是由于边界层的存在,并在实验室通过稳态法测定了岩心在纯油相,含水饱和度和束缚水下的启动压力梯度。结果表明,束缚水下的启动压力梯度大于含水饱和度下的启动压力梯度,它们都小于纯油相下的启动压力梯度。在粘度相同的情况下,这三种情况下的启动压力梯度都随着渗透率的增大而减小;当渗透率相同时,它们的启动压力梯度都是随着粘度的增大而增大。由于启动压力梯度的存在,在设计生产压差时必须将这一因素考虑进去才能保证油藏生产过程中原油的流动,因此该实验结果对油田的实际生产具有重要的指导意义。

With the use of oil and gas resources, more and more oil reservoirs with low per- meability are put into production. For the reservoirs characteristics of low permeability and the complex pore structure,the start-up pressure can not be neglected in actual production. According to the characteristics of low permeability reservoirs,this paper illustrate that the start-up pressure is a result of the boundary layer,and we measure the start-up pressure gradient under certain conditions by steady state method in laboratory,such as pure oil phase,water saturation and bound water. Results show that start-up pressure gradient of wa- ter saturation is greater than the bound water conditions,also,they are both smaller than start-up pressure gradient of the pure oil phase.Moreover, the start-up pressure gradient of the three cases decreases with the increase of the permeability when the viscosity is con- stant.And,at the same permeability,their start-up pressure gradient increase with the increase of viscosity.Because of the existence of start-up pressure,we must consider the factor during the designing of the product pressure to make sure that the oil can flow during production.So the experiment result plays an important role in the actual production of oilfield.