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A Method for Measuring the Enhanced Oil Recovery Potential of Injection Waters using a Modified Steady‐State Coreflood Method

IP.com Disclosure Number: IPCOM000224471D
Publication Date: 2012-Dec-21
Document File: 7 page(s) / 208K

Publishing Venue

The IP.com Prior Art Database

Related People

Robin Gupta: INVENTOR [+2]

Abstract

This study describes a new method that can improve laboratory determination of enhanced oil recovery (EOR) potential for a test fluid relative to a base fluid. The new method measures the shift in oil saturation in a rock at an intermediate fractional flow with a test EOR brine(s) compared to a base brine using a modified steady-state fractional flow method. This study uses fractional flow analysis and simulations to illustrate the new method and compare with the conventional unsteady-state approach. The study also discusses how to determine optimal values of fraction flow and total flow rate, both of which are critical test parameters for the new method.

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A Method for Measuring the Enhanced Oil Recovery Potential of Injection Waters using a  Modified Steady‐State Coreflood Method 

Robin Gupta and Pengbo Lu 

ExxonMobil Upstream Research Company 

 

Abstract

This study describes a new method that can improve laboratory determination of enhanced oil recovery (EOR) potential for a test fluid relative to a base fluid. The new method measures the shift in oil saturation in a rock at an intermediate fractional flow with a test EOR brine(s) compared to a base brine using a modified steady-state fractional flow method. This study uses fractional flow analysis and simulations to illustrate the new method and compare with the conventional unsteady-state approach. The study also discusses how to determine optimal values of fraction flow and total flow rate, both of which are critical test parameters for the new method.

Problem Being Solved

The conventional coreflood test method for estimating the enhanced oil recovery (EOR) potential of a given injection water is as follows. A base brine (e.g., formation water, produced water, aquifer water, sea water, or mix of them) is injected first at 100% water fractional flow (Fw) into an oil saturated rock(s) at some initial water saturation until oil production is minimal or ceases. The base brine is then immediately followed by injection a second (test) water of interest at Fw=100%. The EOR potential of the second brine is gauged from the additional oil produced over the base brine oil recovery. Sometimes multiple injection waters are injected in sequence to evaluate their respective EOR potential in comparison to the previously injected waters. At every injection water step, the injection is continued until oil production is minimal or ceases before switching to the next injection water. This conventional coreflood technique poses several limitations to correctly estimate the EOR potential of injection brine(s):

1. In the case where the fractional flow curve of the second brine is significantly shifted in favor of incremental oil recovery at abandonment water saturations compared to a base brine, but the ultimate residual oil saturations are not significantly different between the brines, then the conventional coreflood method could significantly underestimate the EOR potential of the second brine. The point is illustrated in Figures 1(a) and 1(b). The fractional flow curves shown in Figure 1(a) are representative of a system in which the second brine alters rock wettability to more a water-wet state or lowers mobility ratio compared to the base brine - in both cases without changing endpoints. The curves show that if the base brine is injected at Fw=100% for many pore volumes, it will drive the oil saturation close to residual oil saturation. Hence, when the second brine is injected, the additional oil recovery will be small,


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and in many cases within experimental errors. In this example, the second brine re...