Abstract:

There are huge coalbed methane reserves existing in our country. These CBM reservoirs have the characteristics of low pressure, low saturation, low permeability, high heterogeneity and complex reservoir structure, with the easily broken coal rocks. The technology of the pore-creating by the hydraulic jet can avoid the collapse of the coal bed, eliminate the compaction effect caused by the conventional perforation and break the coal petrography to promote the permeability of the reservoir. By the study of the large physical models, the conclusion was that the bore diameter increases by the increasing of the nozzle diameter. The abrasive concentration and the pore diameter increases but the bore depth decreases after the increasing and the pumping pressure and the bole depth increase. Finally, the operation parameters were optimized, that is, the pumping pressure is 25 MPa, the nozzle diameter is 4 mm and the abrasive concentration is 6.6 %. These parameters are helpful for the parameter design of the site construction.

Key words: coalbed methane(CBM), horizontal well, hydraulic jet drill experiment, hole volume