Shale gas EUR estimation based on a probability method: a case study of infill wells in Jiaoshiba shale gas field

Abstract

The characteristics of shale gas reservoirs and the engineering characteristics of "factory" operation lead to repeated production performance among wells, which is the theoretical basis of a probability method to calculate estimated ultimate recovery (EUR). Compared to the conventional deterministic method, the probability method can calculate a reserve probability distribution. The well spacing of the Jiaoshiba shale gas field in the Sichuan Basin is 600 m, leading to low production extent. Infill wells have been introduced in order to improve gas recovery. In this paper, a probability method was adopted to calculate the EUR for the infill adjustment. Suitable analogy wells were selected by taking geological characteristics, engineering conditions, testing data and well locations into consideration. Based on the EUR probability distribution of analogy wells, the EUR probability curves of infill wells were calculated with the Monte-Carlo method. Typical well curves were established by analyzing the decline parameters of analogy wells. Future production performance and EUR of new wells or undrilled wells can be estimated with this probability method, which is the basis for future strategic decisions.

Keywords

• shale gas
• probability method
• estimated ultimate reserve
• jiaoshiba shale gas field
• sichuan basin