Resource utilization from solid waste originated from oil-based shale drilling cutting during shale gas development

Abstract

With the large-scale development of shale gas, oil-based drilling fluids are widely used, generating significant amounts of solid wastes from oil-based shale drilling cutting (OBSDC). These solid wastes are biologically toxic and are difficult to degrade. The current treatment methods do not meet the requirements for oily sludge. This study begins with pyrolysis of OBSDC in order to use it as an external admixture for preparing cement slurry for resource utilization. The research results showed that when the OBSDC content was increased to 35%, the mechanical properties of developed cement were favourable. Evaluating the cement sheath integrity showed that the OBSDC cement met the subsequent production requirements for a casing with an internal pressure of 50.01 MPa, applicable for cementing surface casings as well as technical casings. The active SiO2 and feldspar in OBSDC after pyrolysis promoted the hydration reaction of cement and accelerated the crystallization of C-S-H, which in turn complemented the cement mechanical properties. When OBSDC was in the proper dosage range, the particle gradation characteristics further optimized the pore structure of the cement matrix and increased the cement strength.