[en] Highlights: • 1The EC unit removed 98.3% turbidity, 78.5% TOC and 56.5% Ca²⁺, respectively. • The optimum operating conditions were recommended as 318 A/m², 20 min for reaction time, and 4.4 for initial pH. • The operating cost under the proposed conditions was 0.80 US$/m³. Shale gas drilling wastewater is a challenging waste stream generated in gas industries. It is a mixture of different organic and inorganic compounds. Treatment of this complex wastewater relies on a suitable technology for the removal of small suspended particles and dissolved elements. This study employed electrocoagulation (EC) as an efficient method for shale gas drilling wastewater pretreatment. The optimum operating conditions for turbidity, TOC, and Ca²⁺ removal were determined using a response surface methodology (RSM). The chloride (Cl⁻) removal and residual iron of effluent in the EC process were also tested and evaluated. Based on the analysis of variance (ANOVA), the coefficient of determination (R²) was calculated and found to be above 0.86 for all the responses. The maximum removal efficiencies were found to be around 98.3%, 78.5%, and 56.5% for turbidity, TOC, and Ca²⁺ removal under the optimum conditions, respectively. In order to treat drilling wastewater by EC process both efficiently and economically, the following operating parameters are recommended: 318 A/m² for current density, 20 min for reaction time and 4.4 for initial pH. A total operation cost of 0.80 US$/m³ was estimated under these conditions.

[en] This paper establishes a model that would allow China’s oil and gas enterprises to scientifically evaluate and measure their low-carbon level and status. It considers various characteristics of China’s oil and gas enterprises and the implications of low-carbon development, and is based on an overall analysis of factors that influence the reduction of carbon emissions. In view of low-carbon economic theories and the general principles of an evaluation index system, a comprehensive system for measuring the low-carbon status of China’s oil and gas enterprises has been developed. This measurement system is comprised of four main criteria (energy structure, energy utilization, carbon emissions and utilization, and low carbon management) as well as thirty indexes. By the Delphi method and the analytical hierarchy process (AHP), the weight of the rules hierarchy and indexes hierarchy were determined. The standardized indexes were then integrated using a linear weighted sum formula, and a comprehensive formula for index measurement was established. Taking into account the status of low-carbon development in the petroleum and petrochemical industry at home and abroad, an evaluation criterion is proposed comprising four levels: ideal low-carbon, economical low-carbon, medium-carbon and high-carbon, whose values were organized within the settings of [0,1].