A Method for Prediction of High-Water-Production Areas in Coalbed Methane Blocks Based on γ Logging Data: A Case Study of the Taiyuan Formation in Liulin Area, Eastern Ordos Basin, China.

The roof aquifer of the Carboniferous Taiyuan Formation coal beds in the Liulin area severely restricts the development and utilization of coalbed methane (CBM). A method for quantitatively predicting high-water-production areas was established by analyzing the relationship between the geophysical logging data and water production. The results showed that the logging profile of the limestone aquifers in high-water-production wells was unique, with high acoustic velocity (AC), high γ-ray values (GR), and low resistivity (Rd). The developed pores and fractures in the roof limestone increase the interval transit time. The formation water in the pores and fractures of the roof limestone decreases the resistivity. The clay filling in the pores and fractures of the roof limestone originated from the dissolution product of limestone and hydrodynamic transportation, which resulted in increased GR values. Furthermore, the representative natural GR log data were used to calculate the clay content in limestone, which indicated that the clay content in limestone had a positive correlation with the water yield of the CBM wells. The water-bearing characteristics of roof limestone showed that the water content was higher in the northern area and decreased gradually toward the south. The method for predicting the high-water-production area was helpful for the CBM exploration and production.