Publications

A geomechanical model was constructed to provide new information for a Coal Bed Methane (CBM) field, in South Sumatera Basin, using well and core data from the field. The aim was to perform a more detailed geomechanical model to identify the critical-stressed cleats, which are most likely to be hydraulically conductive/permeable. These cleats may enhance gas production and may respond to pressure changes during the dewatering phase. The geomechanical model was created by combining drilling events, pore pressure measurements, wireline log data, image log interpretation and triaxial compression tests. Results show that the field is associated with a strike-slip stress regime (SHmin < SV < SHmax). In this case, overburden profile was determined using exponential approximation of density from surface to TD based on density log, sonic density in the unlogged interval and actual bulk density log data. Leak Off Test (LOT) was used to constrain the SHmin profile. Breakouts were observed over the logged interval. Average breakout azimuths are oriented at ~138°N in well X-1 and ~125° in well X-2. The SHmax azimuth based on the breakouts analysed from the image log is consistent with the regional SHmax azimuth from the World Stress Map. The cleats are generally small in size, and cannot be recognized within seismic resolution. Therefore cleat premeability analyses were performed based on outcrop study, processed image log interpretation and cores from wells. The cleat analyses were used for well placement decisions. If the dewatering wells placement for gas production intersects the maximum population of these critical-stressed cleats, there may be a corresponding increase in permeability and gas production. Thus, the geomechanical model will be useful for the CBM field development direction and well-spacing optimization efforts. Keywords: Geomechanics, permeability, cleat, CBM