Abstract: To provide an additive for crude oil recovery, used in secondary/tertiary recovery of crude oil, which has high heat resistance and high mechanical shear resistance, of which the viscous property does not degrade even under high-temperature and high-shear conditions; has high pseudoplastic flowability and therefore has a light transfer workload; and is a naturally-derived one and is therefore highly biodegradable and has least adverse impact on environment. An additive for crude oil recovery, which contains cellulose fibers having a number-average fiber diameter of from 2 to 500 nm and a fiber aspect ratio of 50 or more and having a cellulose I-type crystal structure, and, in the cellulose fibers, a hydroxyl group on a surface of the cellulose fibers is preferably chemically modified.

Abstract: To provide an additive for drilling mud, used in drilling for petroleum, natural gas, civil engineering, mines, etc., which has high heat resistance and high mechanical shear resistance, of which the viscous property does not degrade even under high-temperature and high-shear conditions; has high pseudoplastic flowability and therefore secures high flowability during discharging; and is a naturally-derived one and is therefore highly biodegradable and has least adverse impact on environment. An additive for drilling mud, which contains cellulose fibers having a number-average fiber diameter of from 2 to 500 nm and a fiber aspect ratio of 50 or more and having a cellulose I-type crystal structure.

Abstract: A cellulose fiber nano-dispersion pressing-in device for pressing a liquid, in which a cellulose fiber of a conifer-derived pulp is nano-dispersed, into a stratum, includes a grinding means for grinding the conifer-derived pulp in water, a dilution means for diluting a cellulose fiber-containing liquid obtained in the grinding means and a pressing-in means for pressing a nano-dispersion of the cellulose fiber obtained in the dilution means into a well. Therefore, it is applicable to water-stopping operation in a civil engineering process or to a process of industrial production of hydrocarbons such as crude oil, gas and the like for improving the recovery rate thereof.

Abstract: To provide an additive for crude oil recovery, used in secondary/tertiary recovery of crude oil, which has high heat resistance and high mechanical shear resistance, of which the viscous property does not degrade even under high-temperature and high-shear conditions; has high pseudoplastic flowability and therefore has a light transfer workload; and is a naturally-derived one and is therefore highly biodegradable and has least adverse impact on environment. An additive for crude oil recovery, which contains cellulose fibers having a number-average fiber diameter of from 2 to 500 nm and a fiber aspect ratio of 50 or more and having a cellulose I-type crystal structure, and, in the cellulose fibers, a hydroxyl group on a surface of the cellulose fibers is preferably chemically modified.

Abstract: To provide an additive for drilling mud, used in drilling for petroleum, natural gas, civil engineering, mines, etc., which has high heat resistance and high mechanical shear resistance, of which the viscous property does not degrade even under high-temperature and high-shear conditions; has high pseudoplastic flowability and therefore secures high flowability during discharging; and is a naturally-derived one and is therefore highly biodegradable and has least adverse impact on environment. An additive for drilling mud, which contains cellulose fibers having a number-average fiber diameter of from 2 to 500 nm and a fiber aspect ratio of 50 or more and having a cellulose I-type crystal structure.

Abstract: The present invention provides new process for preparing inorganic fine particles, which suppresses agglomeration and adhesion of particles due to heat when preparing powder from a raw material liquid such as a slurry of zirconia hydrate fine particles in order to obtain inorganic raw material powder having sharp particle size distribution. Furthermore, the present invention provides a new process for preparing inorganic fine particles, which can make the chemical structure homogenous among the produced particles and inside the particles even in a multi-component system. The present invention provides a process for preparing inorganic fine particles, which comprises heating and applying impulse waves to a raw material liquid.

Abstract: A process for forming a gel by gelling an aqueous solution of a water-soluble polymer with a chromium compound as a gelling agent, in which a copolymer of acrylamide, 0.5 to 40% by mole of an unsaturated sulfonic acid or its salt, and optionally an unsaturated carboxylic acid or its salt having an intrinsic viscosity of at least 10 in 1N-NaNO.sub.3 at 30.degree. C., is used as the water-soluble polymer, and which is availably applied to improvement of water-oil ratio in oil production and to civil engineering for preventing leakage of underground water. The formed gel is very stable in a water system containing salts in high concentrations at high temperatures.