Study On Environmental Risk And Countermeasures Of Shale Gas Exploration Project

In this paper,the environmental risk of shale gas exploration process was taken as the research object.Taking the Jiaoshiba area of Fuling District of Chongqing as an example,the shale gas exploration process was analyzed from three stages: pre drilling,drilling and test gas engineering,so the environmental risk factors were identified at each stage.Based on the analysis of risk factors,the environmental risk assessment index system of shale gas exploration was constructed.The index system included three first-level indicators,namely,pre-drilling failure,drilling failure and test gas failure.The ten secondary indexes were wellsite selection,wellsite layout,drilling design,drilling fluid system,cementing process,well control technology,logging and logging,fracturing,bridge plugging and testing discharge;and 22 tertiary indicators.The weight matrix A of the index system was determined by inviting 10 experts to participate in the combination of scoring and analytic hierarchy process.According to the established evaluation index system,fuzzy comprehensive evaluation method model was established by the method of fuzzy comprehensive evaluation.Based on the fuzzy comprehensive evaluation model,a shale gas exploration project in Jiao Shibao area of Fuling District of Chongqing City wais analyzed as an example.The fuzzy language "very great,great,medium,small and very small" was used to analyze the environmental risk of shale gas exploration.By using the expert survey method and the fuzzy language,the index system was evaluated with the single factor evaluation to get the membership degree of the bottom of the index system,so as to get the evaluation rating matrix R..The index system was evaluated step by step through the fuzzy evaluation formula B = A·R from the bottom.The evaluation result of the target layer was B= 0698.02850.03925.02193.00333.0.According to the maximum membership principle,the final results showed that the rating of environmental risk was "medium",that meant attention was needed to attract and preventive measures should be taken.At the same time,according to the results of fuzzy evaluation,the risk level of the well field selection,drilling design,drilling fluid system,cementing process,well control technology and test discharge were recognized as higher risk level.Finally,according to the regional key risk factors identified in the fuzzy evaluation,the environmental risk control measures were put forward for the shale gas exploration project.As for blowout,well leakage and waste pool leakage,the corresponding risk contingency plans were provided as a theoretical basis for the safe operation of shale gas exploration..