Techno-Economic-Environmental Analysis of CO2 Storage and EOR in an Underdeveloped Field
先前的研究表明,成功的CO2提高石油采收率(CO2-EOR)通常能有效作为CO2封存方法,因为在热力学条件下,大密度的CO2(例如,作为超临界CO2的15 mol/L)可以与储层油发生多次接触混溶。与以往研究不同,本研究调查了在欠开发的油田中CO2封存和CO2-EOR的实际机会,这些油田尚未完全枯竭,井数有限。构建了一个实际的组分模拟模型,代表墨西哥湾盆地的一个碳酸盐油藏。基于历史拟合的模拟模型,研究了一系列CO2气水交替(WAG)注入方案,通过改变操作条件(即CO2和水注入速度、产油速度和WAG循环周期)来分析油气开采和碳储存。
开发了一个全面的经济模型来评估净现值(NPV),并用于不同情景的评估,例如45Q税收抵免和油价。结果表明,油气开采 与CO2储存之间存在反向关系。即,高于最小混相压力(MMP)的置换压力产生了最大的CO2储存,但油气开采水平次优。这与在已开发油田中CO2-EOR/封存的广泛观察结果不同,在已开发油田中,高于MMP的操作可以最大化油气开采和CO2储存。
分析表明,在欠开发油田中,使用少量井进行压力管理可以在优化CO2-EOR/储存中发挥重要作用,因为油气开采不仅来自CO2-EOR机理,还来自有限数量井引起的油流潜力。在当前经济条件下,即使不考虑45Q税收抵免,NPV也为正。然而,与最大NPV相关的CO2-WAG方案与最小的CO2储存量相关,这从环境角度来看并不理想。通过根据油价适当调整碳税抵免,有可能同时增加CO2储存和NPV的协同方案。
CMG软件应用情况:
在本文中,使用了CMG-GEM(计算机模拟软件集团公司,Computer Modelling Group)的组分油藏模拟器进行历史拟合和优化模拟。该模拟器用于拟合包括井的气体生产数据和Well A的单次井底压力在内的历史数据。通过调整正在进行的水注入操作条件,在MMP以上进行油藏重新加压的模拟优化。
Abstract
Geological sequestration of carbon dioxide (CO2) is considered an important technology for mitigating the increasing level of atmospheric CO2. One of the most common methods for CO2 geological sequestration is to inject CO2 into depleted oil reservoirs, which recovers part of the remaining oil that has been unrecovered by simpler methods of oil recovery (e.g., water injection). Previous studies have shown that such CO2- enhanced oil recovery (CO2-EOR) effectively serves as a CO2 sequestration method because a successful CO2-EOR typically results from efficient displacement of resident fluids (water and oil) at thermodynamic conditions such that CO2 of a large density (e.g., 15 mol/L as supercritical CO2) can develop multi contact miscibility with the reservoir oil. Unlike previous studies, this research investigates practical opportunities of CO2 sequestration and CO2-EOR in underdeveloped oil fields, which are not fully depleted with only a few wells. A realistic compositional simulation model was constructed to represent a carbonate oil reservoir in the Gulf of Mexico Basin. Based on the history-matched simulation model, a series of CO2 water-alternating gas (WAG) injection strategies was studied by varying operational conditions (i.e., CO2 and water injection rates, production rate, and WAG cycle) and analyzed for oil recovery and carbon storage. A comprehensive economic model was developed to evaluate the net present value (NPV) and used for varying scenarios with, for example, 45Q tax credit and oil price. Results indicated an inverse relationship between oil recovery and CO2 storage. That is, a displacement pressure above the minimum miscibility pressure (MMP) yielded maximal CO2 storage, but a suboptimal level of oil recovery. This contrasts with the widely known observations for CO2-EOR/sequestration in developed oil fields, where operating above MMP maximizes both oil recovery and CO2 storage. Analysis showed that pressure management using a small number of wells in an underdeveloped oil field can play an important role in optimizing CO2-EOR/storage because oil recovery comes not only from CO2-EOR mechanisms, but also from oil flow potentials induced by the limited number of wells. Under the current economic conditions, NPVs were positive even without factoring in the 45Q tax credit accrual for the case studied. However, the CO2-WAG scenarios with the greatest NPVs were associated with the smallest amounts of CO2 storage, which was not desirable from the environmental viewpoint. A synergistic scenario was possible to increase CO2 storage and NPV together by proper adjustments in carbon tax credit according to oil price.
作者单位:
德克萨斯州奥斯汀的德克萨斯大学
台塑石化公司。