Resource Utilisation of Solid Waste from Oil-Based Shale Drilling Cutting in Shale Gas Well Cementing

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), which are difficult to degrade and biologically toxic. The current treatment methods do not meet the requirements for oily sludge. This study begins with the pyrolysis of OBSDC and uses it as an external admixture for preparing cement slurry to realise its resource utilisation. The research results showed that when the OBSDC content was 35%, the mechanical properties of the cement were suitable, which increased the proportion of drill cuttings that were used as an external admixture. Evaluating the cement sheath integrity shows that the OBSDC cement meets the subsequent production requirements of a casing with an internal pressure of 50.01 MPa, and can be used for the cementing of surface casings and technical casings. The active SiO 2 and feldspar in OBSDC after pyrolysis can promote the hydration reaction of cement and accelerate the crystallization of C-S-H, which complements the mechanical properties of cement. When OBSDC is in the proper dosage, the particle gradation characteristics further optimizes the pore structure of the cement matrix and increases the strength of the cement