The present invention relates to the technical field of petroleum drilling, specifically provides an encapsulating agent and preparing method thereof, and a drilling fluid, wherein the encapsulating agent comprises an acrylamide monomer structure unit represented by formula (I), an anti-temperature monomer structure unit represented by formula (II) and an cation monomer structure unit represented by formula (III); ##STR00001##
wherein R.sub.1 and R.sub.2 are each independently H, and linear or branched alkyl of C1-C15, and R.sub.3 is H or the linear or branched alkyl of C1-C5. The drilling fluid provided in the present invention has strong inhibition property and stable rheological property.

A method may include: circulating a drilling fluid in a wellbore, wherein the drilling fluid includes: an aqueous phase; and a reclaimed carbon black additive; and drilling into a subterranean formation to extend the wellbore while the drilling fluid is circulated therein.

A method may include: circulating a drilling fluid in a wellbore, wherein the drilling fluid includes: an aqueous phase; and a reclaimed carbon black additive; and drilling into a subterranean formation to extend the wellbore while the drilling fluid is circulated therein.

In accordance with one or more embodiments of the present disclosure, a method of inhibiting shale formation during water-based drilling of subterranean formations includes introducing a shale inhibitor to the subterranean formation during the water-based drilling, the shale inhibitor comprising a cationic polymer comprising repeating units of [A-B]. A is a substituted benzene or a substituted triazine of formula (2). B is a N-containing heterocycle. The cationic polymer and a method of making the cationic polymer are also described.

In accordance with one or more embodiments of the present disclosure, a method of inhibiting shale formation during water-based drilling of subterranean formations includes introducing a shale inhibitor to the subterranean formation during the water-based drilling, the shale inhibitor comprising a cationic polymer comprising repeating units of [A-B]. A is a substituted benzene or a substituted triazine of formula (2). B is a N-containing heterocycle. The cationic polymer and a method of making the cationic polymer are also described.

Well fluids and methods are provided that can be used for stabilizing a shale formation, especially during drilling of a well into or through a shale formation. The well fluids include: (i) a continuous water phase; (ii) a viscosity-increasing agent, wherein the viscosity-increasing agent comprises water-soluble hydrophilic polymer; (iii) a fluid loss control agent; and (iv) a cyclodextrin-based compound. The methods of drilling include the steps of: (A) introducing the well fluid into a zone of a subterranean formation; and (b) drilling the zone.

Well fluids and methods are provided that can be used for stabilizing a shale formation, especially during drilling of a well into or through a shale formation. The well fluids include: (i) a continuous water phase; (ii) a viscosity-increasing agent, wherein the viscosity-increasing agent comprises water-soluble hydrophilic polymer; (iii) a fluid loss control agent; and (iv) a cyclodextrin-based compound. The methods of drilling include the steps of: (A) introducing the well fluid into a zone of a subterranean formation; and (b) drilling the zone.

Pumpable process-fluid compositions comprise polyacrylamide, a non-metallic crosslinker and a pH-adjustment material. Such compositions have utility in the context of controlling lost circulation in subterranean wells. Upon entering at least one lost circulation zone, the compositions crosslink, thereby forming a barrier that minimizes or stops fluid flow from the wellbore into the lost circulation zone.

Pumpable process-fluid compositions comprise polyacrylamide, a non-metallic crosslinker and a pH-adjustment material. Such compositions have utility in the context of controlling lost circulation in subterranean wells. Upon entering at least one lost circulation zone, the compositions crosslink, thereby forming a barrier that minimizes or stops fluid flow from the wellbore into the lost circulation zone.

A polyoxalate copolymer that includes main ester units of oxalate linked together like a straight chain, and branched ester copolymer units derived from a trifunctional or more highly functional alcohol or an acid. The polyoxalate copolymer initially undergoes the hydrolysis in a suppressed manner.