Lost circulation in fractured formations remains a persistent challenge in drilling operations, causing substantial economic losses and increased operational risk. Conventional granular bridging packs are mechanically fragile and can be destabilized by pressure fluctuations, limiting one-trip plugging efficiency. This study incorporates a thermosensitive adhesive resin into bridging assemblies to enhance plug integrity by promoting interparticle adhesion and particle-wall coupling after thermal activation. Oscillatory temperature-sweep rheometry is used to quantify the temperature-dependent viscoelastic response of resin-particle composites. A wedge-shaped fracture analogue with photoelastic visualization is used to monitor force chain development and uniformity during progressive loading. Discrete element method simulations in Particle Flow Code, using a linear parallel-bond contact model, resolve mesoscale load-transfer pathways and isolate the contribution of adhesive interactions. Results indicate that thermosensitive adhesive resin increases assembly coherence, promotes a stable load-bearing skeleton, and suppresses stress localization that typically precedes plugging failure. The strengthening trend is governed by particle rigidity and surface characteristics, yielding consistent load-transfer patterns across experiments and simulations. These findings demonstrate that thermally activated adhesion can transform unconsolidated granular packs into mechanically stable plugging zones, providing a mechanistic basis for designing high-stability lost circulation control systems in fractured formations.

In China, 83% of deep oil and gas remains to be developed, and it is a major strategic task to secure national energy security to enter deep oil and gas resources. However, lost circulation in fractured formation is the key “stuck neck” problem restricting ultra-deep oil and gas drilling. The research and development of special plugging materials to form efficient plugging technology and improve the success rate of plugging in deep fractured formations is one of the focuses of current research and practice in drilling engineering field. Bridge plugging is one of the most commonly used plugging techniques in fractured leakage formation. Therefore, this paper gives a detailed review on the bridging plugging technology of fractured formation, summarizes the classification of bridging plugging materials, the mechanism of action, the design method and composition of bridging plugging formula, expounds the mechanism of improving the stability of the bridging plugging layer of fractured formation and pressure plugging mechanism, and clarifies the formation, failure and structural evolution mechanism of the bridging plugging layer. Meanwhile, the development prospect of fracture formation bridging plugging technology is prospected, which is of great significance for realizing efficient and safe drilling, speeding up the process of ultra-deep oil and gas development, and ensuring national energy security.

As the global exploration and development of oil and gas resources advances into deep formations, the harsh conditions of high temperature and high salinity present significant challenges for drilling fluids. In order to address the technical difficulties associated with the failure of filtrate loss reducers under high-temperature and high-salinity conditions. In this study, a hydrophobic zwitterionic filtrate loss reducer (PDA) was synthesized based on N,N-dimethylacrylamide (DMAA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), diallyl dimethyl ammonium chloride (DMDAAC), styrene (ST) and a specialty vinyl monomer (A₁). When the concentration of PDA was 3%, the FL_API of PDA-WBDF was 9.8 mL and the FL_HTHP (180 °C, 3.5 MPa) was 37.8 mL after aging at 240 °C for 16 h. In the saturated NaCl environment, the FL_API of PDA-SWBDF was 4.0 mL and the FL_HTHP (180 °C, 3.5 MPa) was 32.0 mL after aging at 220 °C for 16 h. Under high-temperature and high-salinity conditions, the combined effect of anti-polyelectrolyte and hydrophobic association allowed PDA to adsorb on the bentonite surface tightly. The sulfonic acid groups of PDA increased the negative electronegativity and the hydration film thickness on bentonite surface, which enhanced the colloidal stability, maintained the flattened lamellar structure of bentonite and formed an appropriate particle size distribution, resulting in the formation of dense mud cakes and reducing the filtration loss effectively.

Unconventional oil and gas reservoirs have become a new focus of energy development due to their wide distribution and abundant reserves. However, the exploitation of these reservoirs is often accompanied by varying temperatures, which impose higher requirements for novel material, equipment, and technology. Recently, phase change microcapsules have been attracting increasing attention in oilfield applications, because they can absorb or release considerable latent heat during the phase change process, enabling stable temperature control. Herein, the current status and future development trend of phase change microcapsules in oilfield applications are reviewed. The classification of phase change materials, including solid-solid, solid-liquid, solid-gas, and liquid-gas phase change materials, is introduced, with an emphasis on their advantages and disadvantages. Then, the microencapsulation methods for phase change materials are presented. Next, the critical thermophysical properties of phase change microcapsules relevant to oilfield applications, including melting and freezing points, latent heat capacity, thermal conductivity, and cycling stability, are discussed. Subsequently, the specific applications of phase change microcapsules in oilfields, including temperature regulation of drilling fluid, thermal management of cement paste, thermal protection of drilling equipment, and thermal insulation of submarine oil and gas pipelines, are thoroughly overviewed. Finally, the critical challenges and future perspectives are outlined. This review highlights the critical role of phase change microcapsules in advancing thermal management solutions for the efficient development of oil and gas from high- and low-temperature reservoirs, guiding future research and development efforts.

Antarctica contains numerous scientific mysteries, and the Antarctic ice sheet and its underlying bedrock contain important information about the geological structure of Antarctica and the evolutionary history of the ice sheet. In order to obtain the focus of these scientific explorations, the Antarctic drilling engineering is constantly developing. The drilling fluid performance directly determines the success or failure of drilling engineering. In order to enhance the poor performance for drilling fluids due to poor dispersion stability and easy settling of organoclay at ultra-low temperatures, the small-molecule wetting agent (HSR) for drilling fluid suitable for Antarctica was prepared by oleic acid, diethanolamine and benzoic acid as raw materials. Its chemical structure, properties and action mechanism were investigated by various experimental methods. The experimental results showed that 2% HSR could improve the colloidal rate for drilling fluid from 6.4% to 84.8%, and the increase rate of yield point was up to 167%. Meanwhile, it also made the drilling fluid excellent in shear dilution and thixotropy. In addition, 2% HSR could increase the density from 0.872 to 0.884 g/cm³ at −55 °C. And the drilling fluid with 2% HSR had a good thermal conductivity of 0.1458 W/(m·K) at −55 °C. This study gives a new direction for the research of drilling fluid treatment agents suitable for the Antarctic region, which will provide strong support for the scientific exploration of the Antarctic region.

In order to settle the issues of poor rheology for drilling fluids in Antarctica, it is important to develop an agent that can availably address these challenges. For this reason, a rheological regulator (HSCN) of drilling fluid was synthesized by modifying montmorillonite with composite modifiers (DODMAC and CPL). The structure of HSCN was characterized by X-ray diffraction, contact angle, infrared spectroscopy and scanning electron microscopy. And HSCN properties were also evaluated by experiments such as colloidal rate, rheology, viscosity-temperature characteristics and corrosion test. Finally, the mechanism of HSCN was investigated. 2% HSCN can enhance the improvement rate of yield point for drilling fluid at −55 °C by 167%, and the colloidal rate of drilling fluid is 90.4% after 24 h. The corrosion of the three rubbers is weak, with a maximum mass increase of only 0.014 g and a maximum outside diameter increase of 0.04 cm. The mechanism study shows that the staggered lapping between HSCN lamellar units forms an infinitely extended reticular structure. The structure is mainly formed by the electrostatic attraction between HSCN particles, hydrogen bonding, physical adsorption and entanglement between the long carbon chains in HSCN. The formation of this structure can effectively enhance the rheology properties of drilling fluids. This research gives a direction for the investigation of drilling fluids suitable for Antarctic conditions, which is greatly sense for accelerating the efficient exploitation of oil and gas in Antarctica.

As drilling wells continue to move into deep ultra-deep layers, the requirements for temperature resistance of drilling fluid treatments are getting higher and higher. Among them, blocking agent, as one of the key treatment agents, has also become a hot spot of research. In this study, a high temperature resistant strong adsorption rigid blocking agent (QW-1) was prepared using KH570 modified silica, acrylamide (AM) and allyltrimethylammonium chloride (TMAAC). QW-1 has good thermal stability, average particle size of 1.46 μm, water contact angle of 10.5°, has a strong hydrophilicity, can be well dispersed in water. The experimental results showed that when 2 wt% QW-1 was added to recipe A (4 wt% bentonite slurry+0.5 wt% DSP-1 (filtration loss depressant)), the API filtration loss decreased from 7.8 to 6.4 mL. After aging at 240 ℃, the API loss of filtration was reduced from 21 to 14 mL, which has certain performance of high temperature loss of filtration. At the same time, it is effective in sealing 80–100 mesh and 100–120 mesh sand beds as well as 3 and 5 μm ceramic sand discs. Under the same conditions, the blocking performance was superior to silica (5 μm) and calcium carbonate (2.6 μm). In addition, the mechanism of action of QW-1 was further investigated. The results show that QW-1 with amide and quaternary ammonium groups on the molecular chain can be adsorbed onto the surface of clay particles through hydrogen bonding and electrostatic interaction to form a dense blocking layer, thus preventing further intrusion of drilling fluid into the formation.

During ultradeep oil and gas drilling, fluid loss reducers are highly important for water-based drilling fluids, while preparing high temperature- and salt-resistance fluid loss reducers with excellent rheology and filtration performance remains a challenge. Herein, a micro-crosslinked amphoteric hydrophobic association copolymer (i.e., DADC) was synthesized using N,N-dimethyl acrylamide, diallyl dimethyl ammonium chloride, 2-acrylamido-2-methylpropane sulfonic acid, hydrophobic monomer, and pentaerythritol triallyl ether crosslinker. Due to the synergistic effects of hydrogen bonds, electrostatic interaction, hydrophobic association, and micro-crosslinking, the DADC copolymer exhibited outstanding temperature- and salt-resistance. The rheological experiments have shown that the DADC copolymer had excellent shear dilution performance and a certain degree of salt-responsive viscosity-increasing performance. The DADC copolymer could effectively adsorb on the surface of bentonite particles through electrostatic interaction and hydrogen bonds, which bring more negative charge to the bentonite, thus improving the hydration and dispersion of bentonite particles as well as the colloidal stability of the drilling fluids. Moreover, the drilling fluids constructed based on the DADC copolymer exhibited satisfactory rheological and filtration properties (FL_HTHP = 12 mL) after aging at high temperatures (up to 200 ℃) and high salinity (saturated salt) environments. Therefore, this work provided new insights into designing and fabricating high-performance drilling fluid treatment agents, demonstrating good potential applications in deep and ultradeep drilling engineering.

Ocean gas hydrate is a potentially efficient and clean oil and gas alternative energy resource. Wells with complex structure, such as horizontal wells, can improve the extraction efficiency; however, drilling operations face challenges such as wellbore instability and reservoir damage due to the complex interaction between drilling fluids and hydrate reservoirs. This work presents a ceramsite temporary plugging microcapsule that uses ceramsite modified by 3-aminopropyltriethoxysilane as the core material and chitosan and sodium alginate as shell materials. It exhibits high strength during drilling and excellent plugging effects. After the action of bioenzymes, it can easily be dissolved, leading to high permeability post-drilling. The analysis and performance evaluation of ceramsite microcapsules show that their particle size is generally 40 μm, which can match the pore size of the hydrate reservoir depending on the number of encapsulation layers. Bioenzyme optimization at 15 ℃ yields the best permeability recovery of 74.5% for the low-temperature composite enzyme. As the temperature rises, the permeability recovery rate of ceramic microcapsules gradually increases and the difference in permeability recovery rate between 5 and 25 ℃ becomes more significant. With a longer degradation time, the permeability recovery rate of ceramsite microcapsules gradually enhances and the difference in permeability recovery rate becomes smaller after 12 h. The microcapsules exhibit a specific inhibitory effect on the decomposition of hydrates. Utilizing bioenzyme-responsive ceramsite microcapsules as temporary plugging materials can establish an “isolation barrier” around the wellbore, effectively sealing off the interaction between the wellbore and the gas hydrate reservoir during the drilling process. Re-opening the flow path around the well by bio-enzymatic unblocking at the end of drilling proves to be effective in solving the problem of balancing the stability of the well wall and protecting the reservoir.

Natural gas hydrate reservoirs in the northern South China Sea primarily comprise clayey silt, making exploitation more challenging relative to sandy reservoirs in other countries and regions. This paper provides an overview of the latest research developments in the exploitation mechanism covering the past five years, focusing on hydrate phase transition, multiphase flow in the decomposition zone, the seepage regulation of reservoir stimulation zone, and production capacity simulation, all of which are relevant to the previously conducted two rounds of hydrate trial production in offshore areas of China. The results indicate that the phase transition of clayey-silt hydrate remains in a dynamic equilibrium, with the decomposition efficiency mainly controlled by the coupling of heat and flow and high heat consumption during decomposition. The decomposition zone exhibits strong hydrophilicity, easy adsorption, and sudden permeability changes. A temperature drop is present that is concentrated near the wellbore, and once a water lock has formed, the gas-phase flow capacity significantly decreases, leading to potential secondary hydrate formation. To enhance permeability and increase production, it is imperative to implement reservoir and temperature field reconstruction based on initial formation alterations, which will further optimize and improve the transport capacity of the reservoir.