The Method and Expert System for Risk Assessment of Drilling In High-Sulfur Gas Field

Abstract

Abstract The drilling operations had posed great potential threats to the surroundings and the safety of personnel, due to geological complications, lithological complexity, overpressure and acidic gas corrosion in high-sulfur gas fields. In order to accurately identify, evaluate and control the risks of drilling, the comprehensive evaluation index system (CEIS) and model for safe drilling based on fuzzy theory are constructed, and an expert system for drilling risk management is developed based on historical accident cases in high-sulfur gas fields. The main structure of the expert system built in a framework way is introduced, and the operation principles of risk management by case reasoning for the expert system are discussed. Taking a drilling exploration area in the Northeast of Sichuan Basin as an example, the expert system is developed and then evaluates the drilling risk of Yuanba block. The results show that the comprehensive score of drilling security in YB-1 well is 0.559, which means very high drilling risks. In addition, the geological conditions and natural environment are identified as the two main potential factors that impact drilling security. All these evaluation results align well with the actual drilling practices, and this method of comprehensive evaluation for drilling risks is practical. The evaluation method and expert system could provide a prime and valuable reference and conduction in rapidly locating the risk sources, accurately assessing drilling risks and improving the overall safety level of drilling.