INVESTIGATION OF DISPERSION AND ITS EFFECT ON THE SURFACTANT-POLYMER FLOODING PROCESS
Open Access
- Author:
- Galimberti, Evan Barsness
- Graduate Program:
- Energy and Mineral Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 30, 2018
- Committee Members:
- Russell Taylor Johns, Thesis Advisor/Co-Advisor
Gregory R King, Committee Member
Hamid Emami-Meybodi, Committee Member - Keywords:
- Dispersion
Surfactant-polymer
Upscaling
Enhanced Oil Recovery
Incremental Efficiency - Abstract:
- Surfactant-polymer (SP) flooding holds significant promise for enhanced oil recovery, but the procedure for determining the best choice of chemical slug sizes does not consider reservoir mixing. Reservoir mixing at pattern scale can affect optimal slug sizes, but to date there is a lack of understanding of its impact. This thesis examines the impacts of mixing on SP flooding, and to show how grid-block sizes can be optimized through characterizing dispersion. Through these contributions SP flooding can become closer to becoming an economically viable production technique in the field. In this thesis, design selection relies on showing incremental efficiency (STB oil/chemical mass) as a function of both SP slug and polymer buffer sizes. Thousands of UTCHEM simulations give tertiary recovery results across a range of tested designs and key input parameters. Important dimensionless groups are tested for their effects, as well as optimum salinity. Permeability upscaling into effective grid-blocks isolates the dispersion contribution from heterogeneity, and extrapolation to a block size of zero gives an estimate of physical mixing in the reservoir by matching concentration histories to the convection dispersion equation. Grid selection allows the largest block size to represent physical mixing. Optimized grid selection is shown to decrease computational time and uncertainty in project design. Economic analysis multiplies oil and chemical costs by the incremental efficiency and is optimized for profitability. Mixing is shown to affect the strength and sweep of the SP slug, polymer buffer and salinity slug in the reservoir. Similar to miscible gas flooding’s minimum miscibility pressure and enrichment, surfactant’s critical micelle concentration (CMC) and concentration are greatly impacted, specifically when injection conditions are close to the CMC and optimum salinity. Unlike gas flooding, the effects of mixing on recovery depend on mixing of several components injected in different slugs and key reservoir parameters. Dependent on the process design, mixing can be beneficial or detrimental to efficiency; beneficial when increased sweep effects dominate, and detrimental when concentration effects dominate. The design of maximum process efficiency is described while varying key values, including heterogeneity and an effective chemical cost ratio on a per mass basis. Economic analysis indicates a larger slug design than incremental analysis. An increasing trend is found between each component’s endpoint mobility ratio and measured dispersivity. A new parameter is defined in the fluid dispersivity factor, which characterizes the nature of each injected component’s impact to mixing, where the dispersivity of the component is divided by the dispersivity of a single-phase tracer. Favorable mobility ratios decrease mixing with a fluid dispersivity factor below unity, while adverse mobility ratios associated with components such as surfactant and gas in miscible gas flooding, increase the effective mixing with a dispersivity factor greater than unity.