Acceptable data quality for formation evaluation forms the foundation for understanding the petrophysical & reservoir properties, coal quality and properties and pay zones identification. The petrophysical logs are used in both subsurface modelling and to optimise the well completion strategy, ensuring effective coal dewatering and desorption for gas production. At the moment, the industry common practice for data acquisition is to use open-hole wireline logging tools, which were developed primarily for the oil and gas industry. These tools are designed for higher pressure and temperature specifications compared to the reservoir conditions normally seen in CSG operations. This results in heavier tools, bigger logging trucks and increased manpower requirements than seen in mining logging operations.
Arrow's CBM development projects in Queensland, Australia, are designed with a large volume of wells (more than ~1000 wells) that will need to be drilled and evaluated over the next ten years. At present, the cost of logging (direct wireline contractors and associated rig time cost) is forcing Arrow to choose between early data coverage (eroding project economics value) versus restricted logging (increasing project risk). In order to resolve this issue, Arrow has embarked on a series of technology trials to investigate various cost effective formation evaluation solutions, while still ensuring data quality and operational safety.
This paper will present the results of a comparison (logoff) of state-of-the-art mining logging technology and conventional oil and gas logging technology. Also, the paper will focus on the mining-style logging technology data quality, equipment footprint, tool handling, calibration procedures, limitations and general operational efficiency.