Evaluation of Water Production in Coalbed Methane Wells Based on Logging Data

In the process of coalbed methane (CBM) development, gas production is often affected by water production, and the productivity of most wells with high water production is low. The amount of water production determines the range of pressure drop and methane desorption area, which determines the level of gas production and the length of stable production period of a single well. Therefore, accurate prediction of water production is crucial. According to the change of water production in the drainage process and the analysis of curve morphology, the daily water production curve in the study area is divided into single peak attenuation type, stable production type, and multi-peak type. Coal seams with different water production types have different logging response characteristics and top-bottom sealing properties. Coal seams with different water production types have different logging response characteristics and sealing properties of roof and floor. Based on the key logging parameters which can reflect the water production type and the shale content of the top and bottom sealing property, Fisher discriminant equation is established to determine the water production type. Based on the comprehensive study of logging data and dynamic water production data, the calculation method of water production for different water production types is established. The coincidence rate between the calculated water production of coal seam and the actual water production is more than 80%, which provides a certain technical and theoretical basis for the exploration and development of coal seam in the future.