The Novel Technology of Shale Gas Play Evaluation——Sweetness Calculation Method

The evaluation results of a shale gas play based on geologic and engineering sweet spots can only show the probability of gas production after shale gas fracturing, while the production capacity after fracturing has no significant positive correlation with the sweet spot indicator. For this reason, the concept of geologic and engineering sweetness is proposed and corresponding calculation method is also provided in order to develop a "sweetness index". It is necessary to set the benchmark for the highest geologic sweetness and engineering sweetness of the area to be evaluated, namely the collection of a series of optimum geological parameter combinations and engineering parameters, then to calculate the Euclid approach degree to indicate the similarity between the parameter combinations and the benchmark. Taking it as the geologic sweetness and engineering sweetness, we need to determine weighted distribution of geologic sweetness and engineering sweetness by means of grey correlation in order to obtain the aggregative sweetness indicator, or a "sweetness index". The concept was applied to seven wells in Jiaoshiba Block of Fuling Shale Gas Field and results showed that gas production of clusters from each segment has significant positive correlation with geologic sweetness and engineering sweetness. According to results of the study and applications, geologic sweetness and engineering sweetness can be used in the quantitative evaluation of the gas production capacity of a shale gas play, which improves rationality and reliability of segment cluster selection in staged fracturing of horizontal shale gas wells and results in significant cost reduction and effectiveness of shale gas fracturing.