Interwell Tracer Tests To Determine Residual Oil Saturation To Waterflood At Judy Creek Bhl'a'pool

Abstract

This paper describes the implementation and interpretation of two successful interwell tests conducted consecutively within five months at the same location in the R5 Zone of the Judy Creek Beaverhill Lake "A" Pool to determine the residual oil saturation to waterflood. An accurate knowledge of Sam was required for the evaluation of the miscible flood performance at Judy Creek. Upon exomining all the conventional methods for Sorw determination, the interwe11 test, though still largely an unproven technique at the time, was deemed to be tire most cost-effective and technically feasible. For the two interwell tests, tritiated water (THO), tritiated n-butonol (TNB) and C-I4 tagged i-amyl alcohol (CIA) were used as tire nonpartitioning and the two partitioning tracers. A "salt-out method was developed for separating and analyzing the tracers in produced water. A chromatographic transformation technique with forced normalization was formulated for direct calculation of Sorw by comparing the separation of the tracer profiles. Since an Sorw value was estimated independently from each of the two partitioning tracers, the reliability of the method was greatly improved. From the results of the first and second tests. Sorw values were determined to be 27 ±1% and 12 ±1% respectively. These two numbers, though vastly different, were self-consistent. Therefore, it is not likely that the discrepancy came from interpretation errors, Further examination of the core analysis data, also supported by the breakthrough times, suggested that 26% of the flow was conducted through a 0.12 m thick high permeability streak, resulting in a high water frontal velocity of 64 m/d and hence a high capillary number (1.2 × 10–6). Based on the published data(29) on the capillary desaturation curve of Caddo limestone this Nc was high enough to mobilize residual oil during the five months of prolonged water flood at high rate prior to the second test. Leaching of light/water soluble components and cooling of the reservoir by the injected water only accounted for 4% PV and 2% PV declines in Sorw in the second test. As well, the close agreement between the Sorw calculated from the TNB and CIA profiles indicated that there was no detectable mobile oil during the tests; the persistent 10% oil cut registered throughout the tests came from the bottom zones (R2-R4). This argument was indirectly proved in the second test by the immediate start-up produced tracer concentrations. The constant Sorw calculated over the whole production curves for each test proves against non-equilibrium tracer transfer during the tests. Based on the data published in the literature, tracer transfer between oil and water should be fast enough to be at near equilibrium conditions. As for the tracer transfer between flowing and dead-end pores, equilibrium can be achieved both at extremely fast and slow transfer rates. Since the contact time and hence the dimensionless mass transfer rate i. e. Damkohler number (equation available in full paper) is directly proporational to the system length L, it is likely that at reservoir-scale the transfer is a fast process.

Modeling of Pollutant Transport from a Stationary Phase into a Flowing Stream with Reversible Adsorption

“…Adsorption also gives rise to low phenol concentration and a broad peak with a long tail. This is consistent with the partitioning tracer profiles observed in interwell tracer tests for residual oil saturation measurement (Tang, 1992;Tang, 1995). A mass balance calculation was carried out to check the consistency between the model and the computer program.…”

“…(8) and (9) after replacing the velocity v, dispersion coefficients D w;x , D w;y , and D e with the corresponding reduced entities. This is the chromatographic transformation method which is analogous to Tang (1992) that interpreted the delayed production of partitioning tracers in an interwell tracer test for direct calculation of residual oil saturation.…”

Tracer tests for the investigation of heterogeneous porous media and stochastic modelling of flow and transport—a review of some recent developments

“…Partitioning tracer tests (PTTs) as employed in these experiments were initially developed in oil reservoir engineering using both single well tests (Tomich et al, 1973;Sheely, 1978) and interwell tests (Tang, 1992). Here, a typical single well test is carried out by injecting a certain tracer slug of a dissolved primary partitioning tracer (ethyl acetate) into a formation that is at residual oil saturation.…”

“…Additionally it should be mentioned that this method may suffer from the limitations (nonuniqueness of interpreted parameters) of single-well push -pull tests (Hall, 1993;Hall, 1996;Haggerty et al, 1998;Schroth et al, 2001;Novakowski et al, 1998;Kunstmann et al, 1997). The interwell PTTs conducted by Tang (1992) overcome these limitations by injecting tritiated water as non-partitioning tracer and tritiated n-butanol as well as 14 C labeled i-amyl alcohol as partitioning tracers in one well and extracting it at the other. The determination of residual crude oil saturation was again based on distribution coefficients and the relative separation of the two breakthrough curves.…”

Partitioning Gas Tracer Tests for Measurement of Water in Municipal Solid Waste

“…[11][12][13] More recently, the same principles were applied by hydrologists to determine the amount of water in the vadose zone. 6,7 In each case, investigators reasoned that the retardation factor (R f ) of a chemical tracer was related to tracer partitioning and the amount of immobile liquid (oil or water) present, where…”