Zechstein (Upper Permian)

No abstract

No abstract

The Up per Rotliegend/Weissliegend sand stones in the Zielona Góra Ba sin are char ac ter ized by poorer res er voir prop er ties than in the cen tral part of the Pol ish Rotliegend Ba sin. How ever, there have been no de tailed stud ies of the rea sons for these dif fer ences. The main aim of this pa per is to in ter pret the fac tors that played a ma jor role in the dis tri bu tion of res er voir proper ties in the Zielona Góra Ba sin. Anal y sis of vari abil ity in res er voir prop er ties was per formed us ing po ros ity-depth, per meabil ity-depth, and per me abil ity-po ros ity plots. The res er voir qual ity ra tio (RQ), cal cu lated by mul ti ply ing po ros ity and per me abil ity val ues, was also in tro duced. The RQ ra tio was found to be a use ful tool to dis tin guish six types of res er voir rocks. Anal y ses of the vari abil ity of res er voir prop er ties, cou pled with mi cro scopic ob ser va tions, were dis cussed in re la tion to the sed i men tary set ting of each type of rock. These sedimentological and pet ro graph i cal stud ies were in tended to de ter mine the vari abil ity of res er voir prop er ties with re spect to pri mary depositional or lithofacies ef fects and sec ond ary diagenetic effects. The re sults in di cate that ce men ta tion was a ma jor fac tor con trol ling the dis tri bu tion of res er voir prop er ties, mainly by af fect ing the amounts of car bon ate, sul phate, and illite. Com pac tion had only a mi nor in flu ence on the res er voir prop er ties stud ied here.

A gas and crashed rock burst in 2009 in the Rudna Copper Mine was the motivation to re-investigate the dolomite succession of the first Permian cyclothem (Werra), which covers the ceiling section of the excavations. Gas traps were recognized by previous research; however, the stability of gas traps during mining operations has not been studied yet. Mitigation of future gas bursts requires a complex analysis of these gas traps, involving petrological, petrophysical and mechanical analysis of the reservoir dolomite facies. The results indicate the significant influence of dolomite texture, porosity and extent of late diagenetic dolomite cement on the reservoir and geomechanical properties, and the induced failure pattern of the dolomite facies. The mechanism of dolomite failure allowed for interpreting the degree of dolomite degassing during and after mining operations.