Mitigation of Lost Circulation in Oil-Based Drilling Fluids Using Oil Absorbent Polymers

In order to mitigate the loss circulation of oil-based drilling fluids (OBDFs), an oil-absorbent polymer (OAP) composed by methylmethacrylate (MMA), butyl acrylate (BA), and hexadecyl methacrylate (HMA) was synthesized by suspension polymerization and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electronic microscopy (SEM). The oil-absorptive capacity of OAP under different solvents was measured as the function of temperature and time. The effect of the OAP on the rheological and filtration properties of OBDFs was initially evaluated, and then the sealing property of OAP particles as lost circulation materials (LCMs) was examined by a high-temperature and high-pressure (HTHP) filtration test, a sand bed filtration test, a permeable plugging test, and a fracture sealing testing. The test results indicated that the addition of OAP had relatively little influence on the rheological properties of OBDF at content lower than 1.5 w/v % but increased the fluid viscosity remarkably at content higher than 3 w/v %. It could reduce the HTHP filtration and improve the sealing capacity of OBDF significantly. In the sealing treatment, after addition into the OBDF, the OAP particles could absorb oil accompanied with volume enlargement, which led to the increase of the fluid viscosity and slowing down of the fluid loss speed. The swelled and deformable OAP particles could be squeezed into the micro-fractures with self-adoption and seal the loss channel. More important, fluid loss was dramatically reduced when OAP particles were combined with other conventional LCMs by a synergistic effect

Wellbore Stability through Novel Catechol-Chitosan Biopolymer Encapsulator-Based Drilling Mud

The problem of wellbore stability has a marked impact on oil and gas exploration and development in the process of drilling. Marine mussel proteins can adhere and encapsulate firmly on deep-water rocks, providing inspiration for solving borehole stability problem and this ability comes from catechol groups. In this paper, a novel biopolymer was synthesized with chitosan and catechol (named “SDGB”) by Schiff base-reduction reaction, was developed as an encapsulator in water-based drilling fluids (WBDF). In addition, the chemical enhancing wellbore stability performance of different encapsulators were investigated and compared. The results showed that there were aromatic ring structure, amines, and catechol groups in catechol-chitosan biopolymer molecule. The high shale recovery rate demonstrated its strong shale inhibition performance. The rock treated by catechol-chitosan biopolymer had higher tension shear strength and uniaxial compression strength than others, which indicates that it can effectively strengthen the rock and bind loose minerals in micro-pore and micro-fracture of rock samples. The rheological and filtration property of the WBDF containing catechol-chitosan biopolymer is stable before and after 130 °C/16 h hot rolling, demonstrating its good compatibility with other WBDF agents. Moreover, SDGB could chelate with metal ions, forming a stable covalent bond, which plays an important role in adhesiveness, inhibition, and blockage

Novel Acrylamide/2-Acrylamide-2-3 Methylpropanesulfonic Acid/Styrene/Maleic Anhydride Polymer-Based CaCO3 Nanoparticles to Improve the Filtration of Water-Based Drilling Fluids at High Temperature

Filtration loss control under high-temperature conditions is a worldwide issue among water-based drilling fluids (WBDFs). A core–shell high-temperature filter reducer (PAASM-CaCO3) that combines organic macromolecules with inorganic nanomaterials was developed by combining acrylamide (AM), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), styrene (St), and maleic anhydride (MA) as monomers and nano-calcium carbonate (NCC). The molecular structure of PAASM-CaCO3 was characterized. The average molecular weight of the organic part was 6.98 × 105 and the thermal decomposition temperature was about 300 °C. PAASM-CaCO3 had a better high-temperature resistance. The rheological properties and filtration performance of drilling fluids treated with PAASM-CaCO3 were stable before and after aging at 200 °C/16 h, and the effect of filtration control was better than that of commonly used filter reducers. PAASM-CaCO3 improved colloidal stability and mud cake quality at high temperatures

Novel hydrophobic associated polymer based nano-silica composite with core–shell structure for intelligent drilling fluid under ultra-high temperature and ultra-high pressure

Micro-nano-based drilling fluid has attracted a strong interest due to its attractive properties, and micro-nano composite materials have great potential for developing intelligent drilling fluid. In this study a novel hydrophobic associated polymer based nano-silica composite with core–shell structure was prepared and characterized by PSD, SEM, TEM and ESEM. The results showed that the composite, as a micro-nano drilling fluid additive, possessed excellent properties such as thermal stability, rheology, fluid loss and lubricity. Especially, it could plug the formation effectively and improve the pressure bearing capability of formation significantly

Effect of Amphiphilic Polymer/Nano-Silica Composite on Shale Stability for Water-Based Muds

Research on using nanotechnology to solve shale instability problems in drilling engineering has been increasing. The combination of amphiphilic polymer and silica nanoparticles may be a new way to improve shale stability. Herein, an amphiphilic polymer/nano-silica composite (poly(styrene-methyl methacrylate-acrylamide)/nano-SiO2) was introduced as a novel shale stabilizer SMA/SiO2 for water-based muds, which possessed the advantages of both physical plugging and chemical inhibition during the drilling operations. The SMA/SiO2 was prepared and characterized by Fourier transform infrared spectra (FT-IR), nuclear magnetic resonance (1H-NMR), transmission electron microscope (TEM), particle size distribution (PSD) and thermogravimetric analysis (TGA) experiments, which confirmed that SMA/SiO2 was regularly spherical with nano-scale and showed good high-temperature resistance. To evaluate the plugging capacity of SMA/SiO2, the pressure transmission test and BET analysis were applied. The results indicated SMA/SiO2 was capable of effectively plugging the pores and fractures in shale. To evaluate the hydration inhibition capacity of SMA/SiO2, the rolling dispersion experiment and contact angle test were adopted. The results demonstrated that SMA/SiO2 could reduce the tendency of shale hydration, which was better than potassium chloride (KCl) and polymeric alcohol (JHC). In addition, SMA/SiO2 only created slight variations on the rheological parameters of the water-based muds (WBMs) and showed a significant filtration control performance. Due to the outstanding performance of physical plugging and chemical inhibition, SMA/SiO2 was expected to be a novel shale stabilizer to solve shale instability problems

Effect of Environmental Factors on Nitrite Nitrogen Absorption in Microalgae–Bacteria Consortia of <i>Oocystis borgei</i> and <i>Rhodopseudomonas palustris</i>

The effects of temperature, salinity, and illumination on the nitrite uptake rate of the microalgae–bacteria consortia of Oocystis borgei and Rhodopseudomonas palustris were investigated. The absorption rates of nitrite and the contribution rate of each component in the consortia under different temperatures (15, 20, 25, 30, 35 °C), illuminations (0, 15, 25, 35, 45 μmol·m−2·s−1), and salinities (0, 5, 15, 25, 35‰) were determined by stable isotope labeling technique. The single and combined effects of three environmental factors on nitrite uptake by the microalgae–bacteria consortia were analyzed using single-factor and orthogonal experiments. The single-factor experiment showed that the microalgae–bacteria consortia could absorb nitrite efficiently when the temperature, salinity, and illumination were 20~30 °C, 0~15‰, and 25~45 μmol·m−2·s−1, respectively, with the highest absorption rates were 2.086, 3.058, and 2.319 μg∙g−1∙h−1, respectively. The orthogonal experiment showed that the most efficient environmental conditions for nitrite uptake were 30 °C, 5‰ salinity, 35 μmol·m−2·s−1 illumination, and the rate of nitrite uptake by the microalgae–bacteria consortia was 3.204 μg∙g−1∙h−1. The results showed that the nitrite uptake rate of the O. borgei–R. palustris consortia was most affected by temperature, followed by salinity, and least by illumination. Under the same conditions, the nitrite absorption capacity of the microalgae–bacteria consortia was greater than that of single bacteria or algae, and R. palustris played a major role in the nitrite absorption of the consortia. The O. borgei and R. palustris consortia still maintain high nitrite absorption efficiency when the environment changes greatly, which has broad application prospects in the regulation and improvement of water quality in shrimp culture