# US 5,343,948 A · Sand control agent and process

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- Number: US 5,343,948 A
- Document ID: US5343948A
- Status: Granted
- Kind: A
- Application number: 08/063,200
- Filed: 1993-08-16
- Granted: 1994-09-06
- Earliest claimed: 1991-12-19
- Assignees: Mobil Oil Corporation
- Inventors: Paul Shu
- Web page: https://patentgrep.com/patent/US5343948A

## CPC

- E21B 43/025: {Consolidation of loose sand or the like round the wells without excessively decreasing the permeability thereof}
- C09K 8/5045: {containing inorganic compounds}
- C09K 8/572: {containing inorganic compounds}
- E21B 43/04: Gravelling of wells
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE

## Abstract

A method for forming a consolidated gravel pack in a washed-out interval is provided where a borehole penetrates an unconsolidated or loosely consolidated oil or gas reservoir which is likely to introduce substantial amounts of sand into the borehole. After perforating the borehole's casing at a washed-out interval of the formation, sand is introduced into the interval. Afterwards, an aqueous hydroxide solution is injected into said interval. Next, a spacer volume of a water-immiscible hydrocarbonaceous liquid slug is injected into the interval. Thereafter, a water-miscible organic solvent slug containing alkylpolysilicate is injected into the interval. A permeability retentive silica cement is formed in the interval thereby making a consolidated gravel pack. Injection of the aqueous hydroxide and alkylpolysilicate slugs is continued until silica cement has been deposited to an extent sufficient to exclude formation fines and sand.

## Claims

### Claim 1

A method for forming a cement for controlling sand production through a consolidated gravel pack in an unconsolidated or loosely consolidated formation penetrated by a cased borehole where sand is placed within a washed-out area adjacent said borehole, comprising the steps of:
a) injecting into said zone an aqueous hydroxide solution where the hydroxide is a member selected from the group consisting of an alkali metal hydroxide, ammonium hydroxide, or organoammonium hydroxide;
b) injecting next into said zone a spacer volume of a water-immiscible hydrocarbonaceous liquid; and
c) injecting thereafter a water-miscible organic solvent containing an alkylpolysilicate in an amount sufficient to react with said aqueous hydroxide solution so as to form a permeability retentive silica cement within said sand in a washed-out area which cement is of a strength sufficient to bind sand containing particles within the washed-out area and formation adjacent thereto while producing hydrocarbonaceous fluids and excluding formation fines or sand.

### Claim 2 (depends on 1)

The cement as recited in claim 1 where the aqueous hydroxide solution comprises ions of sodium, potassium, or lithium, and mixtures thereof.

### Claim 3 (depends on 1)

The cement as recited in claim 1 where in step c) the solvent is a member selected from the group consisting of methanol, ethanol, higher alcohols, glycols, ketones, tetrahydrofuran, and dimethyl sulfoxide.

### Claim 4 (depends on 1)

The cement as recited in claim 1 where in step c) the hydroxide is contained in the aqueous solution in an amount of from about 20 to about 60 weight percent.

### Claim 5 (depends on 1)

The cement as recited in claim 1 where alkylpolysilicate is contained in said solvent in an amount of about 10 to about 90 weight percent.

### Claim 6 (depends on 1)

The cement as recited in claim 1 where said silica cement withstands temperatures in excess of about 1,000.degree. C. (1,832.degree. F.).

### Claim 7 (depends on 1)

The cement as recited in claim 1 where the silica cement withstands pH's of 7 or lower.

### Claim 8 (depends on 1)

The cement as recited in claim 1 where in step c) said alkylpolysilicate is the hydrolysis condensation product of alkylorthosilicate according to the equation: ##STR2## where n.ltoreq.2 and R=C.sub.1 -C.sub.10

### Claim 9 (depends on 1)

The cement as recited in claim 1 where in step b) the spacer volume of fluid is a member selected from the group consisting of mineral oils, naphthas, C.sub.5 -C.sub.40 alkanes, and mixtures thereof.

### Claim 10 (depends on 1)

The cement as recited in claim 1 where in step a) said organoammonium hydroxide is selected from a member of the group consisting of C.sub.1 through C.sub.10 alkyl or aryl groups and hetero atoms.

### Claim 11 (depends on 1)

The cement as recited in claim 1 where in step a) said organoammonium hydroxide is tetramethylammonium hydroxide.