Nitto Chemical Industry Co., Ltd.

Mitsubishi Rayon Company, Limited

Lion Corporation

Japan Petroleum Exploration Co., Ltd.

Nitto Kagaku Kogyo Kabushiki Kaisha

Diafloc Co., Ltd.

Kawaguchi Kagaku Kogyo Kabushiki Kaisha

Shoichi Kanda

Yukihiko Sekimoto

Makoto Yanagita

Masaharu Nagahama

Takeshi Narita

Masahiro Ushigome

Zengiro Kawamura

Makoto Yanagida

Gengiro Kawamura

Jun Hosoda

Yoshiyuki Yamaguchi

Shogo Suzuki

Masami Murakami

Keietsu Kato

Teruzo Otsuka

Takamasa Ohno

Hitoshi Tamura

Yasunosuke Tanabe

Takeshi Arai

Tsuyoshi Nakagawa

Toshikazu Oda

A process for preparing a water-in-oil emulsion of a water-soluble polymer is disclosed, comprising polymerizing at least one water-soluble vinyl monomer in a water-in-oil emulsion, wherein the dissolved oxygen concentration of the emulsion under polymerization is about 100 ppb or less. The desired emulsion can be obtained without being accompanied by the formation of agglomerates.

Process for preparing a water-in-oil emulsion

The present invention provides a composition for recovery of petroleum and gas, which comprises (a) a copolymer having a molecular weight of 100,000 or more, composed of 30-75 mole % of N-vinylpyrrolidone unit, 5-70 mole % of (meth)acrylamide unit and 0-20 mole % of (meth)acrylic acid unit or a salt thereof, (b) a water-soluble aldehyde, (c) a phenol compound, and (d) water. This composition can form a gel in a required gelling time even at high temperatures and even in the presence of bivalent metal ions and accordingly can be used for efficient recovery of petroleum and gas.

Composition and method for recovery of petroleum and gas

There is disclosed a process for producing an acrylamide polymer which comprises polymerizing acrylamide monomer alone or a monomer mixture composed of 50 mole % or more of acrylamide monomer and a monomer capable of copolymerizing with acrylamide monomer in the presence of an azo series polymerization initiator and 0.1% by weight or more of 2-mercaptobenzothiazole or a salt thereof based on the weight of the monomer in an aqueous medium having a pH of 6 or higher at a temperature range of 5 to 100.degree. C., and then drying the resulting material.

Process for producing acrylamide polymer

A water-in-oil emulsion of a cationic polymer suitable for inversion, comprising a continuous phase comprising a hydrophobic liquid, a discontinuous phase comprising a water-soluble cationic polymer, and a surface active agent system for inventing the emulsion in water, the system comprising a mixture of at least one alkyl phosphate represented by formula (I) or (II) and at least one other surface active agent compatible with the at least one alkyl phosphate: ##STR1## wherein R.sub.1 represents a saturated or unsaturated hydrocarbon group having from 8 to 18 carbon atoms; X and Y, which may be the same or different, each represents a hydrogen atom, an alkali metal, an ammonium group, or an alkanolamino group; and n1 represents 0 or an integer of from 1 to 4; ##STR2## wherein R.sub.2 and R.sub.3, which may be the same or different, each represents a saturated or unsaturated hydrocarbon group having from 8 to 18 carbon atoms; X represents a hydrogen atom, an alkali metal, an ammonium group, or an alkanolamino group; and n2 and n3 each represents 0 or an integer of from 1 to 4.

Water-in-oil emulsion of cationic polymer

A method of stabilizing an aqueous solution of xanthan gum is disclosed, comprising incorporating at least one stabilizing agent selected from thiol derivatives of heterocyclic compounds in an aqueous solution of xanthan gum.

Stabilization of xanthan gum in aqueous solution

A stabilized fracturing fluid and a method of stabilizing a fracturing fluid containing at least one of guar gum and its derivatives is disclosed, wherein at least one stabilizing compound selected from the thiol derivatives of heterocyclic compounds is added to the fracturing fluid. This method of stabilization prevents degradation of the fracturing fluid, i.e., reduction in its rheological properties at high temperatures and permits smooth practice of the fracturing operation.

Stabilized fracturing fluid and method of stabilizing fracturing fluid

A process for producing a modified hydroxyethyl cellulose comprising the steps of:

Process for production of modified hydroxyethyl cellulose

A stabilized fracturing fluid and a method of stabilizing a fracturing fluid containing at least one of guar gum and a derivative thereof is disclosed, comprising adding at least one stabilizing compound selected from 2-mercaptobenzimidazole and 2-mercaptobenzothiazole compounds to the fracturing fluid. This stabilization prevents degradation of the fracturing fluid, i.e., reduction in its rheological properties at high temperatures and permits smoothly carrying out the fracturing operation.

A completion and workover fluid which comprises an aqueous liquid medium containing hydroxyethyl cellulose, an inorganic salt selected from the group consisting of calcium chloride, calcium bromide and zinc bromide, and a component selected from the group consisting of the following components:

Completion and workover fluids

A completion and workover fluid is described, containing a soluble salt, a hydroxyethyl cellulose and at least one compound selected from 2-mercaptobenzimidazole compounds, 2-mercaptobenzothiazole compounds, 2-mercaptothiazoline and 2-thioimidazolidone.

A method of stabilizing an aqueous solution of xanthan gum is described, comprising incorporating at least one stabilizing agent selected from the group consisting of 2-mercaptobenzimidazole and derivatives thereof in an aqueous solution of xanthan gum.

A drilling fluid is described, consisting essentially of sodium carboxymethyl cellulose, bentonite, water, and at least one compound selected from 2-mercaptobenzimidazole compounds, 2-mercaptobenzothiazole compounds, 2-mercaptothiazoline and 2-thioimidazolidone.

Drilling fluids

2-Mercaptobenzoimidazole or its water-soluble salt is added to a water-soluble acrylamide polymer containing a predominant amount of acrylamide in the molecule to inhibit degradation, especially at high temperatures, in a petroleum recovery process.

Method for inhibiting the degradation of an aqueous solution of an

Method for stabilizing an acrylamide polymer in a petroleum recovery

An aqueous acrylamide polymer solution is stabilized by causing it to contain in combination a 2-mercaptobenzimidazole compound and a phenolic antioxidant compound.

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Kanagawa, Japan

Shoichi Kanda