Phase Characteristics of Fluids in Offshore Buried Hill Condensate Gas Reservoirs and Their Influence on Formation Permeability
BZ气田是中国渤海的第一个大型气田,储量达到1000亿立方米。其正式投入运营将极大促进当地的绿色低碳发展。然而,凝析气藏具有埋藏深度大、温度和压力梯度陡峭、凝析含量高、微裂缝发育及地面与露点之间的压力差小等特点。这导致在气田开发的早期阶段会出现反凝析现象,导致更多的凝析液留在储层孔隙中,无法通过降压生产方式开采。
为了提高该储层的采收率,本文通过实验研究了不同比例的干气注入对形成流体相态的影响。然后,在高温高压条件下,对来自BZ凝析气藏的实际潜山变质岩核心进行了反凝析渗透率伤害实验,测量了不同压力下的气体有效渗透率。结果表明,气体注入可以采出反凝析油,降低其饱和度,提高凝析气藏的回采收率。早期注入和更高的注入压力更有利于提高采收率。反凝析伤害实验显示,低渗透岩心的渗透率伤害更为严重,裂缝的存在加剧了这种损伤。该研究为长岩心气体注入的物理和数值模拟实验提供了基础参数,并对全球深水油气开发具有积极的启示意义。
CMG软件应用情况:
在本研究中,使用了CMG软件进行流体相态的计算和模拟。具体而言,利用PVT仪器进行高压相态测试,并通过CMG软件生成相图,分析了不同气体注入比例对凝析气藏流体相态的影响。这些模拟为理解气体注入对凝析气藏采收率的影响提供了重要的数值支持。
Abstract
The BZ gas field is the first large gas field in the Bohai Sea of China, with reserves of 100 billion cubic meters. Its formal operation can greatly promote local green and low-carbon development. However, the condensate gas reservoir has characteristics such as a large burial depth, a steep temperature and pressure gradient, high condensate content, developed microfractures, and a small pressure difference between the surface and dew point. As a result, the retrograde condensate phenomenon will occur in the early stage of gas field development, which will lead to more condensate remaining in the reservoir pores and cannot be recovered if depletion production is adopted. In order to improve the recovery of this reservoir, the influence of dry gas injection in different proportions on the phase behavior of formation fluid is studied by compounding original formation fluid through laboratory experiments. Then, under the conditions of high temperature and high pressure, a retrograde condensate permeability damage experiment was carried out on the actual buried hill metamorphic rock core from the BZ condensate gas reservoirs, with the gas effective permeability measured at different pressures. The results show that gas injection can extract retrograde condensate oil, reduce its saturation, and improve the recovery of condensate gas reservoir. Early injection and higher pressure injection are more conducive to enhancing recovery. The retrograde condensation damage experiment shows that permeability damage is more severe in lower permeability cores, and the presence of fractures aggravate this damage. The study can provide basic parameters for physical and numerical simulation experiments of gas injection in long cores and can also have positive enlightenment significance for global deepwater oil and gas development.
作者单位
胜利油田公司勘探开发研究院