Mobil Oil Corporation

Randy D Hazlett

Alfred R Jennings, Jr

Paul Shu

Alvin S Cullick

E Thomas Strom

Duane C Uhri

Ibrahim S Abou-Sayed

James M Sanchez

A solvent stimulation process whereby a viscosity reducing agent is circulated through a horizontal well via a production string. Said agent exits the production string and enters an annulus formed by said string and a liner. Said agent diffuses into the reservoir at a pressure below the reservoir pressure. As said agent diffuses through the reservoir under the influence of a concentration gradient, it reduces the oil's viscosity and makes it mobile. Simultaneously, oil of reduced viscosity migrates into the well under a pressure drawdown influence. A pseudo steady state production rate is achieved when convective movement of the oil of reduced viscosity is exactly counterbalanced by the diffusional rate of the viscosity reducing agent in a stimulated radial zone along said well. This stimulates a large volume of oil through the extensive surface area of the wellbore thus producing increased volumes of hydrocarbonaceous fluids from the reservoir.

Single horizontal well process for solvent/solute stimulation

A process for recovering oil from fractured formations is provided which involves altering the wettability of the formation, particularly at the interface of the fracture and rock matrix. The process of the present invention improves the ability of injected fluids flowing in the fracture to enter the rock matrix to displace oil. When employed in conjunction with a water-wet fractured oil-bearing formation, the process comprises the steps of: injecting a wettability agent capable of transforming the water-wet fractured formation from water-wet to oil-wet; contacting the oil-wet fractured formation with the wettability agent so injected at a fracture/matrix interface; injecting an oil miscible solvent; and recovering oil. A process for use with an oil-wet fractured oil-bearing formation is also provided.

Oil recovery process for use in fractured reservoirs

A process is described to direct heat towards a productive interval of a reservoir during a thermal enhanced oil recovery (EOR) operation. A chemical composition suitable for producing a rigid polymer foam is injected above or below the productive interval. Once in place the temperature of the composition is increased and it reacts to produce a foamed polymer thermal barrier. The temperature can be increased by steam injection or in-situ combustion. After a rigid foam is formed, thermal efficiency is increased by reducing heat losses to non-producing zones during a thermal stimulation.

Thermal barriers for enhanced oil recovery

A process for killing and suspending mixtures of hydrocarbonaceous fluid production, particularly oil, in a formation containing same which minimizes formation damage. First, a 'spacer volume' of liquid containing a chemical blowing agent is directed into the formation's productive interval. Said blowing agent decomposes in the formation and generates gas sufficient to force hydrocarbonaceous fluids away from a wellbore in said formation. Thereafter, a solidifiable pumpable gel mixture is placed via a wellbore into the formation's productive interval and also within said wellbore. Said mixture solidifies in the formation and forms a gel plug within the wellbore. Thereafter, a light weight cement is placed over said gel plug effectively 'killing' and suspending the production of hydrocarbonaceous fluids.

Method for suspending wells

A process for killing and suspending mixtures of hydrocarbonaceous fluid production, particularly oil, in a formation containing same which minimizes formation damage. First, a 'Spacer volume' of liquid containing a chemical blowing agent is directed into the formation's productive interval. Said blowing agent decomposes in the formation and generates gas sufficient to force hydrocarbonaceous fluids away from a wellbore in said formation. Afterwards, a solidifiable pumpable gel mixture is placed via a wellbore into the formation's productive interval and also within said wellbore. Said mixture solidifies in the formation and forms a gel plug within the wellbore. Thereafter, a light weight cement is placed over said gel plug effectively 'killing' and suspending the production of hydrocarbonaceous fluids. The gel mixture comprises (1) water; (2) a cross linkable polymer having at least one functional group selected from a member of the group consisting of an amide, an amine, a hydroxyl, or a thiol group; and (3) a partially methylated aminoplast resin which cross links with said polymer.

A method for extending a vertical fracture formed in a formation having original in-situ stresses that favor the propagation of a horizontal fracture. In this method, a subsurface formation having original in-situ stresses that favor the propagation of a horizontal fracture is penetrated by a cased borehole which is perforated at a pair of spaced-apart intervals to form separate pairs of perforations. Fracturing fluid is initially pumped down said cased borehole and out one of said sets of perforations to form the originally favored horizontal fracture. The propagation of this horizontal fracture changes the in-situ stresses so as to favor the propagation of a vertical fracture. Said horizontal fracture is extended by placing a chemical blowing agent and surfactant into the fracturing fluid. Gas released by decomposition of said agent causes foam to be generated along with an increase in pressure thereby extending the horizontal fracture. Thereafter, while maintaining pressure on said horizontal fracture, fracturing fluid is pumped down said cased borehole and out of the other of said sets of perforations to form the newly favored vertical fracture.

Enhanced hydraulic fracturing of a shallow subsurface formation

A method for reducing the permeability in a desired area of a formation wherein a solid foam is formed in situ by injecting a one phase solution into the formation. Said solution comprises an alkali metal silicate, a chemical surfactant, and an alkali metal salt of azodicarboxylic acid in an amount sufficient to produce a foam. The azodicarboxylic acid salt decomposes when the pH is reduced to less than about 12 and generates gas in an amount sufficient to form a foam which subsequently hardens. When hardened the foam reduces the permeability in a desired area.

Use of alkali metal silicate foam with a chemical blowing agent

A chemical blowing agent is incorporated into a polymer formulation to provide delayed foaming in a subterranean reservoir when, via catalysis through reservoir temperature or minerals present, the reservoir itself initiates or accelerates decomposition of the chemical. The resultant gelled foam expands and stiffens thereby closing pores in a more permeable zone of said reservoir. Once foaming is completed, a carbon-dioxide or water-flooding oil recovery process can be used to recover hydrocarbonaceous fluids from a zone of lesser permeability.

In-situ foaming of polymer profile control gels

A method for increasing the efficiency by which fracture fluids are produced back from a hydrocarbonaceous fluid bearing formation. To remove said fracture fluid, a chemical blowing agent is placed into the formation. After placement of said blowing agent and fracturing the formation, the blowing agent decomposes thereby either causing the filter cake to become more porous or providing a driving force for fluid load removal from the matrix. Increased porosity enhances communication between the formation and the fracture, thus increasing the efficiency of fracture fluid production. Gas liberation within the matrix establishes communication pathways for subsequent removal of hydrocarbonaceous fluids by displacing fluid loads into the fracture and the well.

Removing fracture fluid via chemical blowing agents

A method for reducing the permeability in a desired area of a formation wherein a foamed gel is formed in-situ by injecting a solution into said formation. Said solution comprises a gellable composition including water; a cross linkable polysaccharide biopolymer; an aminoplast resin which reinforces said biopolymer; and sufficient transitional metal ions to form a gel of the desired size and strength. The gelled solution is foamed by including therein a chemical surfactant, and a chemical blowing agent. Once in the formation to the desired depth, the chemical blowing agent decomposes and generates a gas sufficient to foam the gelled solution. The gelled foam stiffens and reduces the permeability in a desired area.

Amino resin modified xanthan polymer foamed with a chemical blowing agent

A process for generating gas in-situ where a decomposable chemical blowing agent is utilized in combination with an aqueous medium. When a slug of the aqueous medium containing said blowing agent is injected into the formation, heat from the formation, coinjected activators, reservoir fluids, or formation mineralogy causes said blowing agent to decompose thereby generating a gas. This gas forms bubbles which close pores in a more permeable zone of a formation which causes a drive fluid to be diverted into a less permeable zone for removal of hydrocarbonaceous fluids therefrom. Bubbles can also be formed by incorporating a water thickening amount of a water soluble polymer or gel into an aqueous medium containing a decomposable chemical blowing agent. A foam can be made in-situ by placing into an aqueous medium, a surfactant and a decomposable chemical blowing agent. In-situ generated bubbles or foam can be used to divert a drive fluid into a formation's less permeable zone.

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Dallas, TX, United States of America

Randy D Hazlett