DIAGENESIS OF THE SANDSTONES OF A TIGHT-GAS RESERVOIR: THE LAJAS FORMATION IN THE HUINCUL HIGH, NEUQUÉN BASIN

ANA LAURA RAINOLDI; DANIEL BEAUFORT; MARTA FRANCHINI; DANIEL MINISINI; PATRICIA PATRIER

Puerto Madryn

Congreso; XXI Congreso Geológico Argentino; 2022

UNPSJB, CONICET-MEF, UNRN, YPF

The analyses indicate that, during early diagenesis, framboidal pyrite (Py1) precipitated as a result of bacterial sulfate reduction of aqueous sulfate. Framboidal pyrite occurs in fi ne-grained sandstones and siltstones in bioturbation traces and in phytoclasts, as well as disseminated in coarse-grained sandstones. Cubic pyrite crystals are commonly associated with framboidal pyrite suggesting recrystallization of earlier framboids. Kaolinite and berthierine were formed during eodiagenesis. Crystal size, blocky habit and composition of kaolinite close to ideal stoichiometry (Si2Al2O5 (OH4)) support a diagenetic origin. It is inferred that, with increasing burial, berthierine was progressively converted to Fe-rich chlorite (according to the intensity of d001