Method to determine drift and residual oil saturation
AssigneeShell Oil Company
InventorsEdwin A. Richardson, Scott L. Wellington
Life of this patent
Estimating the term…
Abstract
Drift or residual oil saturation within a reservoir around a wellbore is determined by injection of a water-soluble tracer and then producing from the well. This injection is performed twice. The first injection is immediately followed by production in order to create a baseline. The second injection is followed by a soak period, and then production. Production of the tracers is compared to determine drift or residual oil saturation within the reservoir.
Claims16
A process to determine residual oil saturation of a subterranean formation in the vicinity of a wellbore comprising the steps of:
- performing a no-soak test comprising (a) injecting into the formation through the wellbore a no-soak test aqueous solution comprising a tracer which is at least partially water soluble, (b) producing produced fluids from the wellbore without a soak period, and (c) determining the concentration of the tracer in the produced fluids as a function of the accumulated produced fluids;
- performing a soak test comprising (a) injecting into the formation through the wellbore, a soak test aqueous solution comprising a precursor capable of forming, within the formation, a partitionable tracer which is partitionable between water and oil and a water-soluble tracer which has greater water solubility and less oil solubility than the partitionable tracer, (b) neither injecting nor producing from the wellbore for a soak period, the soak period being of a duration at least long enough for a measurable amount of the partitionable tracer and the water-soluble tracer to form within the formation, (c) producing from the wellbore, and (d) determining the concentration of the partitionable tracer and of the water-soluble tracer as a function of the accumulated produced fluids;
- and
- selecting a residual oil saturation which best accounts for the concentration of tracers as a function of the accumulated produced fluids from both the no-soak test and the soak test.
A process to determine drift of reservoir fluids within a subterranean formation in the vicinity of a wellbore comprising the steps of:
- performing a no-soak test comprising.
- a) injecting into the formation through the wellbore a first aqueous solution comprising a tracer which is at least partially water soluble,
- b) producing from the wellbore without a soak period, and
- c) determining the concentration of the tracer in the no-soak test produced fluids as a function of the accumulated produced fluids,
- performing a soak test comprising.
- a) injecting into the formation through the wellbore a soak test aqueous solution comprising a tracer which is at least partially water soluble,
- b) neither injecting nor producing from the wellbore for a soak period,
- c) producing from the wellbore, and
- d) determining the concentration of the tracer as a function of the accumulated soak test produced fluids;
- determining dispersion from the concentration of the tracer in the no-soak test produced fluids as a function of accumulated produced fluids;
- and
- determining the drift of fluids within the formation by estimating the drift which would best account for the concentration of tracers in the soak test produced fluids as a function of accumulated produced fluids, at the dispersion determined from the no-soak test.
Dependencies are inferred from the claim text.