Utilization of water-based drilling cuttings from offshore oil development to manufacture lightweight aggregates: a case study in the Bohai oil field, China.

Offshore water-based drilling cuttings (OWDC) are by-products of offshore oil-well drilling, whose effective management has become an urgent environmental and engineering issue. This study investigated the feasibility of recycling OWDC from the Bohai oilfield in China as a raw material for manufacturing lightweight aggregates (LWA). The effects of OWDC content (0-50%), preheating temperature (300-500 °C), and sintering temperature (1050-1200 °C) on the physical-mechanical performance of the resulting LWA were investigated through single-factor experiments. The microstructural and expansion mechanism analyses were determined based on X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive X-ray spectrometric microanalysis. The results showed that under the optimum preparation conditions (mass ratio of OWDC and fly ash at 50:50, preheating at 400 °C for 30 min, and sintering at 1150 °C for 30 min), the OWDC-based LWA could meet the requirements of Chinese standard GB/T 17431.1-2010. The incorporation of OWDC lowered the aggregate melting points and promoted dense structure formation inside the aggregates due to the presence of flux agents (e.g., Na2O and K2O). Besides, OWDC additions promoted the formation of the liquid phase and gases inside the pellets, which was beneficial to the expansion behavior and lightweight performance of the aggregates. However, OWDC also had a negative effect on the compressive strength of the aggregates owing to the formation of enlarged pores. Furthermore, the results of the environmental performance tests indicated that the LWA were safe for the environment. This study provides a reference for recycling water-based drilling cuttings from offshore oilfields and contributes to the circular economy.

Comparative life cycle assessment of cement, sintered bricks and non-sintered bricks manufacturing using water-based drilling cuttings from shale gas production in the Sichuan Basin, China.

This study determined the environmental impacts of three recycling pathways for water-based drilling cuttings (WDC), namely cement, sintered bricks, and non-sintered bricks, based on the life cycle assessment (LCA) method. A life cycle inventory was developed with based on the resource utilization of 1t drilling cuttings as the functional unit, and a sensitivity analysis was conducted to identify the essential materials and energy consumption. The results showed that the sequence of the environmental impact index for the three recycling pathways was cement, non-sintered brick and sintered brick. Primary energy demand and direct emissions were the main reasons for this difference. Direct emissions, electricity, and binder were the largest contributors to the inventory of cement, sintered bricks, and non-sintered bricks, accounting for 54%, 33.4%, and 62.1% of the environmental impact burden, respectively. Furthermore, a 5% reduction in direct emissions, electricity, and binder decreased the integrated impact index by approximately 2.67%, 3.04%, and 3.38% for cement, sintered bricks, and non-sintered bricks, respectively. Based on the LCA results, strategies for reducing emissions and conserving energy were proposed. These results provide a useful reference for creating a sustainable system for recycling water-based drilling cuttings.