A method includes introducing into a drilling fluid a plurality of tags having a first clay nanoparticle and a first polymer embedded into the clay nanoparticle and circulating the drilling fluid and tags through a well during a drilling operation that creates formation cuttings such that the tags interact with the formation cuttings, creating tagged cuttings. The returned cuttings are collected from the circulating drilling fluid at a surface of the well, and the tags on the returned cuttings are detected to identify the tagged cuttings. The method also includes correlating the tagged cuttings with a drill depth in the well from the drilling operation.

A method includes introducing into a drilling fluid a plurality of tags having a first clay nanoparticle and a first polymer embedded into the clay nanoparticle and circulating the drilling fluid and tags through a well during a drilling operation that creates formation cuttings such that the tags interact with the formation cuttings, creating tagged cuttings. The returned cuttings are collected from the circulating drilling fluid at a surface of the well, and the tags on the returned cuttings are detected to identify the tagged cuttings. The method also includes correlating the tagged cuttings with a drill depth in the well from the drilling operation.

A wellbore fluid may include a base fluid and at least one cationic heterocyclic polymer in an amount effective to increase a viscosity of the base fluid, the cationic heterocyclic polymer includes at least two distinct cyclic monomers, at least one of which has at least two heteroatoms in the cyclic structure. A method of drilling a wellbore may introduce such wellbore fluid into the wellbore. A method of producing a cationic heterocyclic polymer may include reacting, in a solvent selected from the group that includes tetrahydrofuran, dioxane, dichloromethane, alcoholic solvents, chlorinated solvents, aromatic hydrocarbon solvents, or mixture thereof, at least two distinct cyclic monomers, at least one of which has at least two heteroatoms in the cyclic structure.

Various embodiments disclosed relate to crosslinked polymers including sulfonic acid groups or salts or esters thereof as viscosifiers and fluid loss additives for subterranean treatment. In various embodiments, the present invention provides a method of treating a subterranean formation. The method includes placing in a subterranean formation a composition including a crosslinked viscosifier polymer including an ethylene repeating unit including an —S(O).sub.2OR.sup.1 group wherein at each occurrence R.sup.1 is independently chosen from —H, substituted or unsubstituted (C.sub.1-C.sub.20)hydrocarbyl, and a counterion.

Various embodiments disclosed relate to crosslinked polymers including sulfonic acid groups or salts or esters thereof as viscosifiers and fluid loss additives for subterranean treatment. In various embodiments, the present invention provides a method of treating a subterranean formation. The method includes placing in a subterranean formation a composition including a crosslinked viscosifier polymer including an ethylene repeating unit including an —S(O).sub.2OR.sup.1 group wherein at each occurrence R.sup.1 is independently chosen from —H, substituted or unsubstituted (C.sub.1-C.sub.20)hydrocarbyl, and a counterion.

Wellbore fluids and methods of use thereof are disclosed. Wellbore fluids may include an aqueous base fluid, a rate of penetration enhancer, and a shale dispersion inhibitor, wherein the volume ratio of the rate of penetration enhancer to the shale dispersion inhibitor is greater than 1:1. Methods may include circulating the wellbore fluid into a wellbore.

A water-based drilling fluid containing high molecular weight crosslinked polyacrylic acid as viscosifying agent exhibits stability at well temperatures in excess of 150° C. The drilling fluid may further contain a lubricant, weighting agent and/or a wetting agent as well as laponite clay. The aqueous based drilling fluid exhibits a coefficient of friction which is substantially close to the coefficient of friction of oil based drilling muds.

A water-based drilling fluid containing high molecular weight crosslinked polyacrylic acid as viscosifying agent exhibits stability at well temperatures in excess of 150° C. The drilling fluid may further contain a lubricant, weighting agent and/or a wetting agent as well as laponite clay. The aqueous based drilling fluid exhibits a coefficient of friction which is substantially close to the coefficient of friction of oil based drilling muds.

The present invention relates to the petroleum drilling fluid field, and discloses a modified silicon dioxide nano-particle comprising a modifying polymer chain composed of structural units provided by one or more of monomers represented by the following formula (1) and one or more of monomers represented by the following formula (2). The present invention provides a method for preparing modified silicon dioxide nano-particles and a drilling fluid suitable for shale gas wells containing the modified silicon dioxide nano-particles as a plugging agent. When the modified silicon dioxide nano-particles provided in the present invention are used as a plugging agent in a drilling fluid, they will not agglomerate into large-size particles, and can achieve a good plugging effect. ##STR00001##

The present invention relates to the petroleum drilling fluid field, and discloses a modified silicon dioxide nano-particle comprising a modifying polymer chain composed of structural units provided by one or more of monomers represented by the following formula (1) and one or more of monomers represented by the following formula (2). The present invention provides a method for preparing modified silicon dioxide nano-particles and a drilling fluid suitable for shale gas wells containing the modified silicon dioxide nano-particles as a plugging agent. When the modified silicon dioxide nano-particles provided in the present invention are used as a plugging agent in a drilling fluid, they will not agglomerate into large-size particles, and can achieve a good plugging effect. ##STR00001##