Cleaning Oil-Based Drilling Cuttings with Synthetic Gemini Surfactants.

The chemical cleaning method is the simplest approach for degreasing oil-based drilling cuttings (ODCs), with the effectiveness of the treatment relying mainly on the selection of the surfactant and the cleaning conditions. However, achieving the standard treatment of ODCs directly using conventional surfactants proves challenging. In light of this, this study introduces a synthesized and purified Gemini surfactant named DCY-1. The structure of DCY-1 was confirmed through Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) analyses. The characterization in this article encompasses the use of an interface tension meter, nanoparticle size analysis, scanning electron microscopy, and infrared oil measurement. The critical micelle concentration (CMC) of DCY-1 was determined to be 3.37 × 10-3 mol/L, with a corresponding γcmc value of 37.97 mN/m. In comparison to conventional surfactants, DCY-1 exhibited a larger micelle size of 4.52 nm, approximately 24.52% larger than that of SDS. Moreover, the residual oil rate of 3.96% achieved by DCY-1 was the lowest among the chemical cleaning experimental results. Through a single-factor experiment, the optimal cleaning ability of DCY-1 for ODCs was determined as follows: a surfactant concentration of 3 mmol/L, a temperature of 60 °C, an ODC/liquid mass ratio of 1:4, a cleaning duration of 40 min, and a stirring speed of 1000 rad/min. Under these optimal conditions and after merely two cleaning procedures, the residual oil content of ODCs was reduced to 1.64%, accompanied by a smooth and loose surface structure.

Analytical Perspectives on Cement Sheath Integrity: A Comprehensive Review of Theoretical Research.

The cement sheath, serving as the primary element of well barriers, plays a crucial role in maintaining zonal isolation, protecting the casing from corrosion, and providing mechanical support. As the petroleum industry shifts from conventional to deep unconventional resources, the service environment for cement sheaths has become increasingly complex. High temperatures, high pressures, cyclic loading, and thermal stresses in downhole conditions have significantly increased the risk of cement sheath failure. A growing trend toward theoretical analysis of stress distribution, failure modes, and control mechanisms within the casing-cement sheath-formation system is evident. This paper comprehensively reviews theoretical research on cement sheath integrity from four key perspectives: (1) the concept of cement sheath integrity failure, (2) cement sheath constitutive models, (3) analytical models of the cement sheath-casing-formation system, and (4) numerical simulations of the cement sheath-casing-formation system. Through these discussions, this review provides profound insights into cement sheath integrity failure and offers valuable guidance for future research and practices.