Tight Gas Reservoir Capillary Pressure

Tight gas sands constitute a significant percentage of natural gas resource and offer tremendous potential for future reserve growth and production. PanTerra already recognized this and developed customized techniques and laboratory methods to obtain petrophysical parameters for such rocks.

PanTerra developed an inhouse the ultra-low permeameter (pulse decay technique) and made a publication at the Society of Core Analyst, held in Napa Valley, USA (paper SCA2013-010). With this tool we measure down to 0.1 nano-Darcy, and have successfully employed this over the subsequent years in shale gas, tight siliciclastics and caprock evaluations.

PanTerra can also experimentally determine the full capillary pressure curve on such low permeability rocks. For this we use a combination of methods.

Below is a Pc example of a recent study that PanTerra did, showing Centrifuge Pc, Vapor Pressure Pc, and converted mercury capillary pressure data. One can clearly see that Vapor Pressure Pc technique is suitable for the higher Pc and Centrifuge more for the lower Pc data. But the two methods actually are in line, describing the full capillary pressure curve, up to 10,000 psi Pc. The black line is mercury injection data (done on small trim-end) and converted from air-mercury to air-brine, in this case. Also here, the MICP is in line with the other two techniques. This builds confidence that the obtained laboratory measurements, are reliable and can be used to validate log Sw, reducing uncertainty in reservoir saturations.

Tight gas sand reservoir capillary pressure