This disclosure relates to a foamable resin composition containing a nitrogen gas-generating compound and methods of using the composition for loss circulation control.

The present disclosure may relate to a method of remediating a wellbore. The method may comprise pumping a resin treatment fluid from a surface location to an annular space bounded by an outer diameter of a production tubular, wherein the resin treatment fluid comprises a liquid hardenable resin, a hardening agent, and a particulate bridging agent. The resin treatment fluid may gravity settle in the annular space to contact production equipment in the annular space such that at least a portion of the particulate bridging agent bridges across one or more damaged sections of the production equipment, wherein at least a portion of the liquid hardenable resin sets to form a hardened mass to seal the one or more damaged sections.

A method of designing a cement blend for a wellbore isolation barrier based on the analysis of a stress state of the wellbore isolation barrier from the injection of CO.sub.2 into a porous formation. The analysis software may determine an optimized cement blend for a future CO.sub.2 injection schedule. The analysis software may determine a current near wellbore stress state for a current CO.sub.2 injection schedule. The analysis software may optimize a CO.sub.2 injection schedule based on the analysis of a future near wellbore stress state of the wellbore isolation barrier. The near wellbore stress state of the isolation barrier may be determined by at least one model accessed by the analysis software. The inputs into the model comprise periodic CO.sub.2 injection pressure and flowrate datasets, cement properties, and formation properties.

A method of designing a cement blend for a wellbore isolation barrier based on the analysis of a stress state of the wellbore isolation barrier from the injection of CO.sub.2 into a porous formation. The analysis software may determine an optimized cement blend for a future CO.sub.2 injection schedule. The analysis software may determine a current near wellbore stress state for a current CO.sub.2 injection schedule. The analysis software may optimize a CO.sub.2 injection schedule based on the analysis of a future near wellbore stress state of the wellbore isolation barrier. The near wellbore stress state of the isolation barrier may be determined by at least one model accessed by the analysis software. The inputs into the model comprise periodic CO.sub.2 injection pressure and flowrate datasets, cement properties, and formation properties.

A pH-sensitive temporary plugging agent and its preparation method, and the use thereof in exploitation of a low-permeability oil reservoir are disclosed. The temporary plugging agent is prepared by raw materials including, in percentages by mass, 3-8% of carboxymethyl chitosan, 0.2-0.7% of gelatin, 0.1-0.6% of an initiator, 5-15% of a toughener, and a balance of water, wherein the initiator is a solution of AgNO.sub.3 in ammonia water having a concentration of 0.1-0.3 mol/L, and the toughener is a carboxyl-terminated hyperbranched polyester.

A cement slurry in a downhole well has a composition that includes a cement in an amount of 60% to 80% by weight of the cement slurry, water in an amount of 20% to 40% by weight of the cement slurry, and a retarder in an amount of 0.1% to 2% by weight of the cement slurry. The cement includes 70% to 90% of at least one silicate by weight of the cement. The retarder includes sodium lignosulfonate with an alkali content of no more than 5.0 g Na.sub.2O equivalent/liter of admixture.

Embodiments relate to use of graphite nanoplatelets (GnP) to enhance the mechanical and durability characteristics of cement that may be used as cement sheaths in wellbores of oil and gas wells. Generally, undesired permeability of cement is caused by diffusion of trapped oil and/or natural gas through the cementitious matrix of the cement, leading to material degradation of the cement. Methods disclosed involve using modified GnPs (having physically modified surfaces or chemically modified surfaces energies) to generate a cementitious nanocomposite with uniformly dispersed GnPs, which can effectively arrest the undesired diffusion mechanism. Modified GnPs can also increase the strength of interfacial adhesion (e.g., interfacial bonds and interfacial energies) between the GnP and the cement matrix (e.g., hydrations of the cement). Physical modification of GnP can involve non-covalent treatment techniques. Chemical modification of GnP can involve covalent treatment techniques.

A method includes introducing an epoxy resin system to a wellbore defect in a wellbore. The epoxy resin system comprises a polyhedral oligomeric silsesquioxane (POSS) epoxy resin with at least one reactive group and a curing agent. The method includes maintaining the epoxy resin system in the wellbore such that a cured epoxy resin system product forms in the wellbore defect.

An improved oil or gas well cement for penetrating, sealing and plugging wells to be abandoned. The cement fill includes (a) a cement component including a calcium sulfoaluminate cement and a Portland cement having a ratio by weight of Portland cement to calcium sulfoaluminate cement ranging from 1/19 to ⅕ and (b) an aggregate component with gradation spanning 1,200 microns to 5 microns. Further an improved oil or gas well microcellular cement for penetrating sealing and completely filling wells to be abandoned that includes (a) a cement component including a calcium sulfoaluminate cement and a Portland cement having a ratio by weight of Portland cement to calcium sulfoaluminate cement ranging from 1/19 to ⅕ and (b) an aggregate component with gradation spanning 200 microns to 5 microns and (c) a foaming agent.

A wellbore is plugged using a bismuth alloy. The wellbore is arranged so that a liquid bismuth alloy sets with an excess pressure of the plug relative to the borehole fluid pressure along a desired seal height distance.