A Study of Gel-Based Conformance Control Within Fractured Carbonate Cores Using Low-Field Nuclear-Magnetic-Resonance Techniques

Author:

Alshehri Amar J.1,Wang Jinxun1,Kwak Hyung Tae1,AlSofi Abdulkareem M.1,Gao Jun1

Affiliation:

1. Saudi Aramco

Abstract

Summary The extreme heterogeneity of carbonate in the form of fracture corridors and superpermeability zones challenges the efficient sweep of oil in both secondary- and tertiary-recovery operations. In such reservoirs, conformance control is crucial to ensure injected water and any enhanced-oil-recovery (EOR) chemicals optimally contact the remaining oil with minimal throughput. Gel-based conformance control has been successfully applied on both sandstone and carbonate reservoirs. Achieving effective deep conformance control in high-temperature reservoirs, however, remains a challenge because of severe gel syneresis and significant reduction in gelation time. The first step to improve the performance of gel in these challenging environments is the accurate understanding of the gel-conformance-control mechanism inside reservoir rocks. In this work, a laboratory study was conducted to evaluate a polyacrylamide/chromium gel system for application in a high-temperature/high-salinity carbonate reservoir. Oil-displacement experiments on carbonate-core samples, combined with nuclear-magnetic-resonance (NMR) measurements, were performed to demonstrate oil-recovery improvement using gel treatment and to illustrate the mechanisms of the improvement. In these tests, the gel solution was injected into specially prepared heterogeneous carbonate-composite-core samples, in which different configurations of high-permeability channels were created. Gel treatment was conducted after waterflooding and was followed by chase waterflooding. Oil-recovery improvement by gel treatment was 18% of original oil in core (OOIC) in the composite core with high-permeability channels extending midway through the composite, whereas the improvement was 38% of OOIC in the composite core with channels extending all the way through the composite. Detailed spatial fluid variations inside the core samples before and after gel treatment were closely monitored using low-field NMR techniques. Heavy water (D2O) was used in place of water to enhance the contrast between oil and brine for NMR by eliminating the protons in the aqueous phase. NMR measurements indicated that the bypassed oil during waterflooding was effectively recovered after gel treatment. Results in this study demonstrate the potential of the studied gel system and its favorable effect on the sweep-efficiency-improvement application in high-temperature/high-salinity carbonate reservoirs. The NMR study enhances our understanding of how gel helps improve the sweep efficiency of subsequent floods through blocking/reducing the permeability of highly conductive zones.

Publisher

Society of Petroleum Engineers (SPE)

Subject

Geology,Energy Engineering and Power Technology,Fuel Technology

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3