Doctoral Dissertations


Yang Zhao

Keywords and Phrases

Conformance treatment; Enhanced oil recovery; Gel treatment; Heavy oil; Microgel; Polymer flood; Petroleum geology


“Heavy oil resources account for a large portion of the total oil reserves around the world. The target heavy oil reservoir is located on Alaska’s North Slope (ANS). Advantages of low-salinity HPAM polymer (LSP) over high-salinity polymer (HSP) were demonstrated. LSP could recover more oil with 40% less polymer consumption. No additional oil was recovered by HSP after LSP flood. The first-ever polymer flood pilot on ANS showed remarkable success regarding water cut reduction, oil production increase, delayed breakthrough, and projected oil recovery improvement. Polymer alone was insufficient to achieve satisfactory recovery as the reservoirs were highly heterogeneous. Microgels could improve the effectiveness of polymer flood by reducing water cut and increasing oil recovery. Favorable working conditions were identified. Microgel transport behavior was studied using superpermeable sandpacks (27-221 darcies) with multiple pressure sensors. The particle-to-pore matching size ratio significantly impacted the effectiveness of the gels. A threshold differential pressure (ΔPth) and critical pressure gradient (∇Pcr) were required to push the gels to penetrate and propagate through the channels. The ΔPth and ∇Pcr revealed the underlying mechanisms of selective penetration/placement behavior of microgels in heterogeneous reservoirs. Diagrams were developed to estimate the maximum propagation distance of the gels in channels in conceptual field applications. Sandwich-like channel models and methodologies were developed to comprehensively evaluate the effectiveness of gel materials. Gel retention in the channels was quantified. Results also indicated that the retained gels were dehydrated. Fluid diversion and sweep improvement after gel treatments were evaluated by tracer tests”--Abstract, page iv.


Bai, Baojun
Wei, Mingzhen

Committee Member(s)

Seright, Randall S.
Flori, Ralph E.
Dunn-Norman, Shari
Neogi, P. (Partho), 1951-


Geosciences and Geological and Petroleum Engineering

Degree Name

Ph. D. in Petroleum Engineering


The funding support (DE-FE0031606) from the Department of Energy and Hilcorp is acknowledged.

"This material is based upon work supported by the Department of Energy under Award Number DE-FE0031606."


Missouri University of Science and Technology

Publication Date

Summer 2021

Journal article titles appearing in thesis/dissertation

  • Enhancing Heavy Oil Recovery Efficiency by Combining Low Salinity Water and Polymer Flooding
  • Experimental Study of Transport Behavior of Microgel Particles in Superpermeable Channels for Conformance Control
  • Selective Penetration of Microgels in Superpermeable Channels and Reservoir Matrices
  • Critical Pressure Gradients During Microgel Propagation
  • A Comprehensive Laboratory Method to Evaluate Microgel Conformance Control Performance Using Sandwich-like Channel Models
  • Transport, Placement, Fluid Diversion and Matrix Damage Behavior of Microgels for Conformance Control in Reservoirs Containing Superpermeable Channels
  • Experimental Study of Microgel Conformance-Control Treatment for A Polymer-Flooding Reservoir Containing Superpermeable Channels


xxi, 274 pages

Note about bibliography

Includes bibliographic references.


© 2021 Yang Zhao, All rights reserved.

Document Type

Dissertation - Open Access

File Type




Thesis Number

T 11932

Electronic OCLC #