Enhancing the Oil Recovery from Naturally Fractured Reservoirs Using Viscoelastic Surfactant (VES) Flooding: A Field-Scale Simulation

粘弹性表面活性剂(VES)具有表面活性剂和聚合物的双重特性。将VES流体注入自然裂缝储层(NFR)可以控制注入流体的流动性,并提高总的石油回收率。本文通过现场规模模拟评估了一种新型VES流体在提高自然裂缝储层石油回收率方面的性能。研究中,使用了核磁共振成像(CT)扫描、流变学、界面张力(IFT)和吸附测量的结果来构建和校准实验室规模模型。随后,使用计算机模拟集团(CMG-STARS)开发的化学增强采油(EOR)模型模拟器构建了现场规模模拟。利用实际地震数据、渗透率和孔隙度分布以及运行条件来开发和评估模拟模型。结果显示,VES在NFR中的性能优于表面活性剂-聚合物(SP)水驱和传统水驱;VES提高了10%的石油回收率,并减少了47%的水切割率,在相同条件下。VES比水驱降低了两个数量级(100倍)的IFT。此外,VES还改变了岩石的润湿性,使其更加亲水,平均降低了10倍的水相对渗透率(Krw)。最后,模拟研究表明,在VES水驱后应用水驱可以略微提高石油回收率。总体而言,本研究提供了VES水驱、SP水驱和传统水驱在NFR中的详细比较。通过敏感性分析研究了处理参数对自然裂缝储层石油回收率的影响,并使用实际的NFR数据确定了最佳的VES水驱条件,这将有助于实际的VES水驱作业。

CMG软件的应用情况

在本研究中,CMG-STARS软件被用于构建非热化学水驱实验的历程匹配。通过水驱和化学水驱(碱性/离子液体/聚合物)实现了历程匹配,选择了累积油回收量、油切、水切、生产率和压差作为历程匹配的指标。在成功实现历程匹配后,研究了实验室中无法研究的各种条件对提高残余油饱和度的影响。

ABSTRACT

A viscoelastic surfactant (VES) has the combined properties of a surfactant and a polymer. Injection of VES fluids into naturally fractured reservoirs (NFRs) can control the mobility of the injected fluid and enhance the total oil recovery. This paper presents a field-scale simulation to evaluate the performance of a noble VES fluid in enhancing the oil recovery from a naturally fractured reservoir. In this work, the results of coreflooding, computerized tomography (CT)-scan, rheology, interfacial tension (IFT), and adsorption measurements were used to build and calibrate a lab-scale model. Thereafter, a chemical enhanced oil recovery (EOR) modeling simulator developed by a computer modeling group (CMG-STARS) was used to build a field-scale simulation. Real seismic data, permeability and porosity distributions, and operating conditions were utilized to develop and evaluate the simulation model. The results show that VES can outperform the surfactant-polymer (SP) flooding and waterflooding in NFRs; VES improved the oil recovery by 10% and reduced the water cut by 47%, at the same conditions. VES reduced the IFT by two orders of magnitude (100 times) compared to waterflooding. Also, VES altered the rock wettability to a more water-wet status, leading to reduce the relative permeability to water (Krw) by a factor of 10, on average. Finally, the simulation study indicated that applying waterflooding after VES flooding leads to a minor increase in the oil recovery. Overall, this study provides a detailed comparison between VES flooding, SP flooding, and conventional waterflooding in NFRs. Sensitivity analysis was performed to study the impact of treatment parameters on the oil recovery from naturally fractured reservoirs. Using actual NFR data, the optimum VES flooding was determined, which will help in conducting VES flooding for real EOR operations.

作者单位

作者单位为沙特阿拉伯石油与矿产大学石油工程系(Petroleum Engineering Department, College of Petroleum Engineering & Geosciences, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia)。

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