Modelling of continuous surfactant flooding application for marginal oilfelds: a case study of Bentiu reservoir

提高石油采收率（EOR）是增加老油田石油产量的成熟方法之一。其中一种高效的EOR方法是注入表面活性剂以释放被困石油。然而，在现场和实验室实践中都观察到了一些未固结的行为。本研究采用新框架评估Bentiu油田的连续表面活性剂驱（CSF）。研究旨在量化预期的石油产量范围、采收因子和残余油饱和度（Sor）。研究动机来自苏丹对石油的需求以及岩心样本的不足。研究采用的框架包括数值模拟建模和代理建模。从现场获取的36个岩心被修订并分为五个主要组。通过实验获得界面张力（IFT）数据。通过结合不同的实验设计集生成代理模型，开发了CSF敏感性研究。CSF数值模拟结果显示，与水驱相比，额外的石油采收率约为30%，石油产量在（20-30）cm³之间。生成的代理模型在关注输入的较低范围时外推结果，并显示出石油产量和采收的平均P50分别为74%和17 cm³。总体而言，CSF在广泛的输入范围内表现良好。此外，生成的代理模型提供了输入因素与观测值之间复杂相互关系的定性前瞻性因素。然而，结果证实CSF在岩心尺度上的适用性，并为现场尺度应用提供了见解。

CMG软件的应用情况

在本文中，使用了CMG-STARS软件进行CSF的数值模拟。STARS软件在模拟实验室规模和岩心结果方面表现出色。研究中假设岩心为立方体形状而非圆柱体形状，以简化初始流动困难。使用CMG的BUILDER界面构建模型，模型采用笛卡尔坐标系，分为15个块。模型的初始输入数据包括初始压力、温度、油API度、初始水饱和度、残余油饱和度、生产约束井底压力和注入约束表面水注入量。模型初始化在环境条件下进行，以避免不同位置油藏的压力和温度变化的影响。由于每个组的孔隙度和渗透率不同，计算了平均值并用作输入。相对渗透率曲线是根据可用的实验室报告生成的。为了进行比较研究，水驱场景与CSF进行了对比。时间步长为5分钟，从起点开始计数。CSF中使用的表面活性剂摩尔分数是通过软件计算得出的，使用临界胶束浓度和实验得出的IFT。生产注入约束在所有模型中保持不变。

中文作者单位

  1. 马来西亚技术大学工程学院石油工程系
  2. 亚太大学工程学院
  3. 阿费巴博拉大学化学与石油工程系
  4. 纳扎尔巴耶夫大学矿业与地球科学学院
  5. 阿曼技术和应用科学大学
  6. 赛伯贾亚大学

Abstract
Enhanced oil recovery (EOR) is a proven method to increase oil production from the brown fields. One of the efficient EOR methods is injecting surfactants to release the trapped oil. However, few unconsolidated behaviours were observed in both field and laboratory practice. In this study, a new framework was adapted to evaluate the continuous surfactant flooding (CSF) in Bentiu reservoir. The study aims to quantify the expected range of the oil production, recovery factor and residual oil saturation (Sor). The motivation came from the oil demand in Sudan and the insufficient cores. The framework adopted in the study includes numerical simulation modelling and proxy modelling. Thirty-six cores obtained from the field were revised and grouped into five main groups. The interfacial tension (IFT) data were obtained experimentally. The CSF sensitivity study was developed by combining diferent experimental design sets to generate the proxy model. The CSF numerical simulation results showed around 30% additional oil recovery compared to waterfooding and approximately oil production between (20–30) cm3 . The generated proxy model extrapolated the results with concerning lower ranges of the input and showed an average P50 of oil production and recovery of 74% and 17 cm3 , respectively. Overall, the performance of CSF remained benefcial in vast range of input. Moreover, the generated proxy model gave an insight on the complexity of the interrelationship between the input factors and the observants with a qualitative prospective factors. Yet, the results confrmed the applicability of CSF in core scale with an insight for feld scale application.

Keywords: Continuous surfactant fooding · Response surface method · Proxy models · Permeability · Porosity · Bentiu reservoir

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