水驱砂岩油藏在不同水质下的渗透率时变特征

油田注水开发过程中，注入水中的悬浮固体颗粒物、油以及细菌等污染物会堵塞油层的孔隙，造成储层渗透率缓慢下降。因此，对于长期注水的油田，继续利用原来的地层渗透率选择水质是不合理的。考虑到油田长期的注水历史，利用不同渗透率的砂岩岩心进行大量的室内实验，研究油田水质标准（SY/T 5329-2012）中5种不同水质的注入水对地层渗透率的伤害规律，提出渗透率水质敏感性的概念；并通过理论推导建立渗透率衰减规律的数学表达式，描述了水驱砂岩油藏在不同水质下的渗透率时变特征。在此基础上确定水质与储层相适应的选取标准，研究了水质决策界限，建立高含水期注水水质决策方法，为长期注水开发的油田重新进行水质决策、提高注水开发效果提供了理论依据。

Time-varying permeability of sandstone reservoirs under waterflooding of different water quality

Water injection may lead to a chronical reduction of reservoir permeability due to the blockage of formation pores by suspended solid particles, oil, bacteria, and other impurities in the injected water.For fields under water flooding for quite a long time, it is not wise to continue sticking to the water quality determined on originally measured formation permeability.This study investigates possible formation damage caused by water injection through laboratory experiments on sandstone cores of different permeability from wells with long water injection history according to 5 different standards of water quality(SY/T 5329-2012), and put forward a concept of water quality-sensitive permeability.And through theoretical derivation, a mathematical expression describing the attenuation law of permeability is established to describe changing sandstone reservoir permeability with time during injection of water of different qualities.The criteria for water and reservoir selection are determined for better decision making on injection water quality for high water-cut wells.It provides a theoretical basis for achieving better performance of wells with long-time water flooding through water quality adjustment.