It is well known that horizontal wells provide maximum reservoir contact to optimize production rates and recovery. This holds true for Coalbed Methane (CBM) drilling as well. The direction and position of a horizontal CBM well can be controlled to intersect face cleats and take advantage of directional permeability. In this manner one can stay in zone in CBM drilling just as in other horizontal applications.

The use of at-bit gamma ray and inclination measurements in a Logging-While-Drilling (LWD) tool string greatly enhances the geosteering capabilities of the Bottom Hole Assembly (BHA). The measurements are made in a short sub positioned immediately above the drill bit. At-bit measurements improve directional control in geosteering complex sections. These tools are routinely used in CBM drilling, and other horizontal applictions, to extend the horizontal section within a particular coal seam.

Geosteering requires a software package capable of pre-well modeling, displaying the measured information and interactively adapting the model to the real-time data. Offset well data are used with the well plan for a horizontal well to predict the log response of the different logging tools. Different models can be generated to predict what the log response will be when drilling out of zone either at the top or the bottom, or when dramatic facies changes occur. While drilling, the models are continuously updated and compared to the real-time data to improve the formation model and structure. This allows real-time decisions to modify the well path and stay in the intended zone.

This paper describes the results of drilling horizontal CBM wells. The horizontal drilling includes combining at-bit measurements, LWD resistivity, and forward-modeling software.

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