姬塬地区长8超低渗油藏注水井欠注规律研究

Law of Under-injection of Water Injection Well in Chang 8 Ultra-low Permeability Reservoir in Jiyuan Area

注水开发作为超低渗油藏主要开发方式,而注水井欠注对油藏开发影响显著。姬塬地区长8油层组为典型超低渗油藏,针对其注水井欠注问题,在分析油藏注水井欠注现状的基础上,通过建立超低渗油藏有效驱动渗透率以及地层结垢量计算模型,系统地总结姬塬地区长8超低渗油藏的储层物性、地层结垢和注入水水质等因素对注水井欠注的影响,并提出对应的解决方案。研究结果表明:地层渗透率小于0.3×10^-3μm^2时注水井开始欠注,且表现为长期欠注、欠注程度高的特征;当地层结垢量大于2000 mg/L或注入水中悬浮物及含油量大于70 mg/L时,引起注水井欠注且表现为后期欠注特征。针对不同影响因素下欠注井的特征,提出5种增注工艺体系,在姬塬地区长8超低渗油藏实施后有效率高达88.2%,可有效治理该地区的注水井欠注问题,同时为同类型油藏的注水井欠注提供理论支持和治理依据。

Water injection has long been a principal development method for the ultra-low permeability reservoirs.Therefore,the under-injection issue involved in water injection well can exert a significant influence on the reservoir development.According to the under-injection problems existing in Chang 8 reservoir from Jiyuan area,a typical ultra-low permeability reservoir,the status quo of under-injection was first studied.Through the establishment of effective drive permeability and formation scaling calculation model of ultra-low permeability reservoir,the influence of reservoir physical properties,formation scaling and injection water quality on the under-injection were systematically analyzed.Further,the corresponding solutions were put forward.Results show that:the under-injection probably occurs in the formation with the permeability less than 0.3×10^-3μm^2,and it can be characterized as long under-injection duration and high under-injection degree.Meanwhile,when the formation scaling is greater than 2000 mg/L or the suspended solids and oil content in injection water is larger than 70 mg/L,the under-injection usually appears in the later period.According to the characteristics of under-injection wells caused by different factors,five injection stimulation process systems were proposed.When dealing with the under-injection problems in the Chang 8 ultra-low permeability reservoirs from Jiyuan area,the effective rate of these systems reaches 88.2%,which proves that it is a certify solution for the under-injection problem and can provide a theoretical and practical method for other similar reservoirs.