低渗透挥发油藏回注溶解气开发注采参数界限

低渗透挥发油藏回注溶解气在开发初期地层压力较高,存在“采油易,注气难”,随着地层压力的降低,开发中后期又会出现“采油难,注气易”的情况。因此,明确注采参数的界限是制定开发技术政策的前提。本文通过建立注采参数界限模型,推导得到已知地层压力下的最大采油速度、最大回注比以及临界压力的表达式,结合实例油藏绘制注采界限图版,研究了多因素对注采参数界限的影响规律并提出开发技术政策建议。结果表明,注采参数界限及图版准确可靠,能够反映实际生产情况；注采参数界限受注采能力、地层压力、采油速度、井网类型、井网密度等因素的影响,并且存在相应规律；溶解气应尽量全部回注,适当增大井网密度,在开发初期提高注气井比例,并根据回注比确定采油速度,在开发中后期降低注气井比例,提高采油速度,从而保障高质高效开发。

Limits of injection production parameters for the development of low permeability and volatile oil reservoir with solution gas reinjection

In the early stage of the development of low permeability and volatile oil reservoir with solution gas reinjection, the gas injection is more difficult than oil production due to the high formation pressure. However, in the middle and late stage of development, the gas injection gets easier than oil production with the decrease of formation pressure. Therefore, it is the premise of making development technology policy to define the limits of injection production parameters. This paper deduced expressions of maximum production rate, maximum reinjection ratio and critical pressure based on the limit model of injection and production parameters, made the chart to show the limits of injection and production parameters for a real case, studied the influence law of multi factors on the limit of injection production parameters, and proposed the development technical policy. The results show that the limits of injection production parameters and the charts are accurate and reliable, which can reflect the actual production situation. The parameter limits are affected by injectivity productivity index, formation pressure, production rate, well pattern type, well pattern density and other factors with corresponding laws. In the development period, it is advised to re-injected all solution gas produced as far as possible, increase the proportion of injectors and determine the production rate according to the reinjection ratio in the early stage of development, and reduce the proportion of producers to improve the production rate in the middle and late stage of development, so as to ensure high-quality and efficient development.