Fundamental Studies of Carbon Dioxide Enhanced Oil Recovery (CO2-EOR) in Tight Oil Formations

致密油地层二氧化碳提高采收率 (CO2-EOR) 的基础研究

• 批准号: RGPIN-2014-06265
• 负责人: Gu, Yongan
• 金额: $ 1.46万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=638309
• 关键词: Fundamental; Studies; Carbon; Dioxide; Enhanced

The Bakken formation has recently become a vital oil resource in Western Canada and the adjacent US states as it has approximately 271 to 503 billion barrels of light oil in place. This oil formation is extremely tight with permeabilities of 0.01 to 1 mD, about 100 times lower than those of typical light oil reservoirs. Most oil reservoirs in this formation are currently under the primary oil recovery process, and the oil production rates are being reduced drastically due to quick pressure depletion. The Bakken’s oil recovery factors are estimated to be as low as 1 to 3%. As a secondary oil recovery process, waterflooding is usually adopted and normally proven to be effective but water is very difficult to inject in large volumes into tight formations. The large water source requirement and high water treatment costs are two major concerns. Alternatively, carbon dioxide-enhanced oil recovery (CO2-EOR) methods can be used as tertiary oil recovery processes because CO2 is much less viscous and, thus, much easier to inject than water. It remains unknown, nevertheless, whether CO2-EOR can be successfully applied as CO2 may breakthrough a tight oil formation much more readily than water. In addition, it needs to be determined when and how water and/or CO2 should be injected so that the light oil recovery in the Bakken formation can be optimized.The primary research objective of the proposed NSERC DG research program is to pursue a comprehensive fundamental understanding and generate new technical knowledge of CO2-EOR in tight oil formations. The following four key research topics will be studied in depth:1. The mutual and complex interactions between the injected CO2 and the reservoir oil, brine, and tight formation and quantification of their respective effects on CO2-EOR, CO2-induced brine scaling, and reservoir integrity;2. The light oil-CO2 miscibility development and the major CO2-EOR mechanisms, such as CO2-induced oil-swelling effect, interfacial tension reduction, light-hydrocarbons extraction, and asphaltene precipitation;3. Application and comparison of the following five water- and CO2-based oil recovery processes in a tight oil formation: continuous waterflooding or miscible CO2 flooding, water-alternating-CO2 (WAG) injection, CO2-alternating-water (GAW) injection, and carbonated water injection. Each process involves one-phase (water/CO2) injection at a time. In this way, the best timing, the optimum slug size and ratio for water and CO2 injections will be identified; and4. Exploration of a new water- and CO2-based EOR process in a tight and fractured oil formation by co-injecting water and CO2, which is a two-phase (water-CO2) injection. The major purpose is to determine the most appropriate water-gas ratio (WGR) and total injection rate, both of which help to simultaneously control the mobilities of the injected water and CO2 and significantly enhance the light oil recovery in the tight and fractured oil formation.The ultimate goal of this research program is to find the optimum water- and CO2-based EOR technique for applying CO2-EOR projects in tight oil formations in terms of the overall oil recovery rate and factor and the economic and environmental benefits. At present, almost all the oil companies in the Bakken formation are planning to apply various water- and CO2-based flooding processes after the primary oil recovery process. This new NSERC DG research program will provide direct, timely, and strong technical support for conducting more efficient CO2-EOR projects and recovering more light crude oil from the vast oil-rich tight formations. In the long term, the optimum water- and CO2-based EOR technique will also help to preserve Canada’s abundant fresh water and clean air.

巴肯地层最近已成为加拿大西部和邻近美国各州的重要石油资源，因为它拥有约2710亿至5030亿桶轻质油。该油层非常致密，渗透率为0.01至1 mD，比典型的轻质油藏低约100倍。目前，该地层中的大多数油藏处于一次采油过程中，由于压力快速耗尽，石油产量急剧下降。巴肯油田的采油系数估计低至1%至3%。作为二次采油工艺，注水通常被采用并且通常被证明是有效的，但是水很难大量注入致密地层。大量的水源需求和高的水处理成本是两个主要问题。或者，二氧化碳强化采油（CO2-EOR）方法可用作三次采油工艺，因为CO2的粘性小得多，因此比水更容易注入。然而，由于CO2比水更容易突破致密油层，因此CO2-EOR能否成功应用仍是未知数。此外，还需要确定何时以及如何注入水和/或CO2，以便优化Bakken地层中的轻质油采收率。拟议的NSERC DG研究计划的主要研究目标是对致密油层中的CO2-EOR进行全面的基本了解，并产生新的技术知识。将深入研究以下四个重点研究课题：1.注入的CO2与储层油、盐水和致密地层之间的相互和复杂的相互作用以及它们各自对CO2-EOR、CO2诱导的盐水结垢和储层完整性的影响的量化;2.轻质油-CO2混溶性的发展及CO2驱油的主要机理，如CO2驱油膨胀效应、界面张力降低、轻质烃抽提、沥青质沉淀等;以下五种水基和CO2基采油工艺在致密油层中的应用和比较：连续水驱或混相CO2驱、水-交替-CO2（WAG）注入、CO2-交替-水（GAW）注入和碳酸水注入。每个过程每次都涉及单相（水/CO2）注入。通过这种方式，将确定水和CO2注入的最佳时机、最佳段塞尺寸和比例;通过共注入水和CO2（这是两相（水-CO2）注入）在致密和裂缝性油层中探索新的水基和CO2基提高采收率工艺。主要目的是确定最佳的水气比和总注入量，本研究的最终目标是找到最佳的水基和CO2基提高采收率技术，以应用CO2-从总体采收率、采收率、经济效益和环境效益等方面对致密油层提高采收率项目进行了评价。目前，巴肯地层中几乎所有的石油公司都计划在一次采油工艺之后应用各种水基和CO2基驱油工艺。这项新的NSERC DG研究计划将为开展更有效的CO2-EOR项目和从大量富含石油的致密地层中回收更多轻质原油提供直接，及时和强有力的技术支持。从长远来看，最佳的基于水和二氧化碳的EOR技术也将有助于保护加拿大丰富的淡水和清洁的空气。