Abstract
This study evaluates the wellbore shear bond strength of oil-well cement pastes containing nano-SiO2 and nano-TiO2 particles with an average of 20 ± 5 nm particle sizes. The nanoparticles were selected by weight of cement at proportions equivalent to 1, 2, 3 and 4%. The findings demonstrated that nanoparticles significantly increased the shear bond strength, and the strength increase was dependent on the nanoparticle types, dosage and curing period of the specimens. Due to effective pozzolanic activity, nano-SiO2 provided higher shear bond strength compared to nano-TiO2. The specimens containing 3% nano-SiO2 cured for 28 days displayed the utmost shear bond strength results (0.553 MPa). The optimal replacement dosage was 3% for all nanoparticles. The particle type did not affect the optimum nanoparticles replacement content. To examine the influence of nanoparticles on cement-formation bonding, a Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), and thermogravimetric technique were used.
Highlights
Oil-well cementing is performed to provide zonal isolation, i.e. to restrict the movement of the fluid across different formations
The cement pastes were blended at a low-speed (4000 r/min for 15 s, at a high speed of 12 000 r/min for 35 s according to American Petroleum Institute (API) 10A standards) [38]
The results indicate that the interfacial shear bond strength was improved by the increasing dosages of NP indicating that these nano-scale materials are capable of boosting the interaction between cement and formation for improved zonal isolation
Summary
Oil-well cementing is performed to provide zonal isolation, i.e. to restrict the movement of the fluid across different formations. In Pang et al.’s work, it was reported that the use of nano-SiO2 powders containing 4–6 nm particle size would increase the compressive strength of oil-well cement by 30 and 136% within 2 and days respectively. The works of [30,31,32] confirmed the effect of nano-SiO2 on oil-well cement properties such as setting time, compressive strength and microstructure. These investigations acknowledged that the inclusion of nanoSiO2 to cement slurry reduced the thickening time, increased compressive strength, and modified the hardened cement microstructure by depressing porosity and permeability. In spite of the widespread research of NanoParticles (NP) on cement properties recently, studies on the effect of nanomaterials on strengthening wellbore shear bond strength for successful zonal isolation are rarely found. X-Ray Diffraction (XRD), ThermoGravimetric Analysis (TGA), and Scanning Electron Microscope (SEM) techniques were used to verify NS and NT pozzolanic behavior and the microstructure adjustment of the bonded cement-formation interface
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