Publications

There are eleven coal basins in Indonesia, estimated to contain 453 Tcf of CBM(5). The big four reserves are South Sumatra (183 Tcf), Barito (101.6 Tcf), Kutai (80.4 Tcf) and Central Sumatra (52.5 Tcf). It could be stated that CBM resources in South Sumatra are equal to the total (conventional) gas reserves in Indonesia.A conventional CBM production method can only be economical in coal seams with good porosity, permeability and natural fracture. Developments in directional drilling technology can however make drilling operation more easily controlled. In-seam horizontal drilling operations can also be carried out to increase the volume of gas through one wellbore. The next technology is multi-lateral wells to optimize the rate of production. There are many variations of horizontal and multi-lateral wells and their potential benefits and these will be compared with conventional vertical drilling before any method is applied.When drilling CBM wells, horizontal drilling is always preferred to vertical. This is because the formation will have greater productivity than that of vertical wells. However, choosing the right drilling design involves considerations of cost, formation type, coal seam location and trajectory parameters. During the drilling process, the fluid used must also be considered. Using underbalanced drilling fluids will prevent formation damage to the coal seam, resulting in higher productivity.Keywords: CBM, vertical drilling, horizontal multilateral drilling.