The distribution of σ_r and σ_θ at different revolving speeds for SSFVC and conventional cementing.

<p>The distribution of σ_r and σ_θ at different revolving speeds for SSFVC and conventional cementing.</p

Effect of pulse pressure on borehole stability during shear swirling flow vibration cementing

<div><p>The shear swirling flow vibration cementing (SSFVC) technique rotates the downhole eccentric cascade by circulating cementing fluid. It makes the casing eccentrically revolve at high speed around the borehole axis. It produces strong agitation action to the annulus fluid, makes it in the state of shear turbulent flow, and results in the formation of pulse pressure which affects the surrounding rock stress. This study was focused on 1) the calculation of the pulse pressure in an annular turbulent flow field based on the finite volume method, and 2) the analysis of the effect of pulse pressure on borehole stability. On the upside, the pulse pressure is conducive to enhancing the liquidity of the annulus fluid, reducing the fluid gel strength, and preventing the formation of fluid from channeling. But greater pulse pressure may cause lost circulation and even formation fracturing. Therefore, in order to ensure smooth cementing during SSFVC, the effect of pulse pressure should be considered when cementing design.</p></div

Relationship between pulse pressure and revolving speed with different eccentricity.

<p>Relationship between pulse pressure and revolving speed with different eccentricity.</p

Governing equations in moving bipolar coordinates.

<p>Governing equations in moving bipolar coordinates.</p

Basic parameters.

<p>Basic parameters.</p

Boundary conditions in moving bipolar coordinates.

<p>Boundary conditions in moving bipolar coordinates.</p

The pressure distribution at <i>δ</i> = 0.6 with <i>Ω</i> = 2000r/min.

<p>The pressure distribution at <i>δ</i> = 0.6 with <i>Ω</i> = 2000r/min.</p

Measurement for gel strength of cement slurry.

<p>Measurement for gel strength of cement slurry.</p

Measurement for gel strength of drilling fluid.

<p>Measurement for gel strength of drilling fluid.</p

The assembly of POM-induced inorganic–organic hybrids based on copper ions and mixed ligands

<div><p>Three inorganic–organic hybrid materials based on Keggin-type polyoxometalates (POMs), [Cu^II₂(phen)₂(4,4′-bipy)(H4,4′-bipy)₂(H₂O)₂][PMo₁₂O₄₀]₂·2H₂O (<b>1</b>), [Cu^II(phen)₂(H4,4′bipy)][PW₁₂O₄₀]·H₂O (<b>2</b>), and [Cu^II₂(phen)₂(4,4′-bipy)(BW₁₂O₄₀)(H₂O)₂](H₂4,4′-bipy)_0.5·3H₂O (<b>3</b>) (phen = 1,10-phenanthroline, 4,4′-bipy = 4,4′-bipyridine), were synthesized using different POMs in the hydrothermal conditions. Compounds <b>1–3</b> were characterized by single-crystal X-ray diffraction, IR spectra, elemental analyses, powder X-ray diffraction analyses, and thermogravimetric analyses. Compound <b>1</b> presents a two-dimensional (2-D) network containing the Keggin-type [PMo₁₂O₄₀]³⁻ anion and dinuclear metal–organic units [Cu^II₂(phen)₂(4,4′-bipy)(H4,4′-bipy)₂(H₂O)₂]³⁺. Compound <b>2</b> is a 2-D architecture constructed from a [PW₁₂O₄₀]³⁻ and mononuclear metal–organic units [Cu^II(phen)₂(H4,4′-bipy)]³⁺. In <b>3</b>, the [BW₁₂O₄₀]⁵⁻ anions link [Cu^II₂(phen)₂(4,4′-bipy)] units to form a one-dimensional (1-D) chain [Cu^II₂(phen)₂(4,4′-bipy)(BW₁₂O₄₀)(H₂O)₂]; the 1-D chain connects with protonated 4,4′-bipy ligands and lattice waters, yielding a 2-D layer. Fluorescence spectra, UV–vis spectra, and electrochemical properties of <b>1–3</b> have been investigated.</p></div