3D Modeling of the CoalBed Methane (CBM) Resources in the Taldykuduk Block Karaganda Coal Basin, Kazakhstan

International audienceCoal Bed Methane (CBM) is gas stored in coal layers, generally extracted from wells after hydraulic fracturing and/or CO2 or solvent injections. The Karaganda Basin was selected to develop CBM production because of its huge gas potential (4 300 Bm3 equivalent to 2 billion tons of coal, with gas content about 15-25 m3/t of coal (for comparison San Juan basin, US, has < 20 m3/t)). This work aims at modeling the Taldykuduk block coal layers focusing on CBM production. The methane extracted during mining actually released in the atmosphere, will be collected. A 3D geological model was built on Gocad/Skua using all available datasets (about 1000 wells over 84 km2, cross-section and maps acquired during coal exploitation, and fractures network reported on geological cross sections). The resulting 3D model including hundreds of faults, is used to simulate the secondary recovery of methane by CO2 injection on a flow simulator, assuming a two phase dimensionless formulation in a double porosity model with the matrix (m) and the fracture (f) for which the initial and boundary conditions are different. The resulting 3D models had helped in better understanding the regional tectonic structures, faults relationships, the hydrogeology regime and the potential gas reserves

Aspergillus protein degradation pathways with different secreted protease sets at neutral and acidic pH.

Aspergillus fumigatus grows well at neutral and acidic pH in a medium containing protein as the sole nitrogen source by secreting two different sets of proteases. Neutral pH favors the secretion of neutral and alkaline endoproteases, leucine aminopeptidases (Laps) which are nonspecific monoaminopeptidases, and an X-prolyl dipeptidase (DppIV). Acidic pH environment promotes the secretion of an aspartic endoprotease of pepsin family (Pep1) and tripeptidyl-peptidases of the sedolisin family (SedB and SedD). A novel prolyl peptidase, AfuS28, was found to be secreted in both alkaline and acidic conditions. In previous studies, Laps were shown to degrade peptides from their N-terminus until an X-Pro sequence acts as a stop signal. X-Pro sequences can be then removed by DppIV, which allows Laps access to the following residues. We have shown that at acidic pH Seds degrade large peptides from their N-terminus into tripeptides until Pro in P1 or P'1 position acts as a stop for these exopeptidases. However, X-X-Pro and X-X-X-Pro sequences can be removed by AfuS28 thus allowing Seds further sequential proteolysis. In conclusion, both alkaline and acidic sets of proteases contain exoprotease activity capable of cleaving after proline residues that cannot be removed during sequential digestion by nonspecific exopeptidases