US 5,415,231 AGranted

Method for producing low permeability reservoirs using steam

AssigneeMobil Oil Corporation

InventorsPaul S. Northrop, Robert S. Timmer

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Abstract

A method for recovering hydrocarbons (e.g. oil) from a low permeability subterranean reservoir of the type comprised primarily of diatomite. A first slug or volume of a heated fluid (e.g. 60% quality steam) is injected into the reservoir at a pressure greater than the fracturing pressure of the reservoir. The well is then shut in and the reservoir is allowed to soak for a prescribed period (e.g. 10 days or more) to allow the oil to displaced by the steam into the fractures by imbibition. The well is then produced until the production rate drops below an economical level. A second slug of steam is then injected and the cycles are repeated with the volume of each subsequent slug of steam being progressively smaller that the one before it (i.e. about 80%) and the respective soak period being increased by about 20% over that of the previous cycle.

Claims13

Dependent claims

A method for recovering hydrocarbons from a low permeability, subterranean reservoir, said method comprising:

providing a wellbore into said reservoir;
injecting a first volume of heated fluid through said wellbore and into said reservoir at a pressure above the fracture pressure of said reservoir;
shutting in said wellbore and allowing said reservoir to soak for a first period of time;
opening said wellbore and producing said reservoir therethrough until the production of hydrocarbons declines below a desired limit;
injecting a second volume of heated fluid through said wellbore and into said reservoir, said second volume of heated fluid is equal to about 80% of said first volume of heated fluid;
shutting in said wellbore and allowing said reservoir to soak for a second period of time wherein said second period of time is equal to at least about 120% of said first period of time;
and
opening said wellbore and producing said reservoir therethrough until the production of hydrocarbons again declines below a desired limit.

5 more elements

Dependencies are inferred from the claim text.