Abstract: A cationic copolymer represented by the following formula (I) has a viscosity average molecular weight in a range from 2 million to 10 million. In the cationic copolymer, the mole fractions of three structural units corresponding to three monomers are as follows: x being in a range from 0.01 to 20%, y being in a range from 0 to 15%, and z=1?x?y. When used in the construction of leaking stoppage in an oil well, a cationic chemical lost circulation additive prepared with the cationic copolymer is mixed with an anionic drilling fluid in a section of the wellbore where lost circulation occurs. Then neutral reaction and cross linking reaction occur, so that the viscosity of the resulting mixture rapidly increases to form a space grid structure. This blocks off the leakage path, and thus effects on efficient leaking stoppage in a short time period.

Abstract: A method of sampling ingredients of an oil-bearing inclusion includes a) providing a first container and a second container, an external diameter of the first container being smaller than an internal diameter of the second container, and the first and second containers both being transparent; b) adding a solvent into the first container and sealing said first container; c) adding an oil-bearing inclusion sample into the second container, and putting the first container that contains the solvent and is sealed in step b) into the second container; and d) using a laser to ablate the oil-bearing inclusion sample contained in the second container that is sealed in step c), and using the laser to break an end portion of the first container close to the sample on condition that the second container is maintained complete, so as to allow the solvent in the first container to enter the second container.

Abstract: A cationic copolymer represented by the following formula (I) has a viscosity average molecular weight in a range from 2 million to 10 million. In the cationic copolymer, the mole fractions of three structural units corresponding to three monomers are as follows: x being in a range from 0.01 to 20%, y being in a range from 0 to 15%, and z=1?x?y. When used in the construction of leaking stoppage in an oil well, a cationic chemical lost circulation additive prepared with the cationic copolymer is mixed with an anionic drilling fluid in a section of the wellbore where lost circulation occurs. Then neutral reaction and cross linking reaction occur, so that the viscosity of the resulting mixture rapidly increases to form a space grid structure. This blocks off the leakage path, and thus effects on efficient leaking stoppage in a short time period.