A PERMIAN BEACH IN THE ZECHSTEIN DOLOMITES FO WESTERN POLAND: INFLUENCE ON RESERVOIRS

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Abstract
Zechstein ooid grainstones, which have formed a narrow belt (several hundered meters in width) along the basin‐facing platform margin, have been greatly affected by fresh‐water diagenesis, resulting in contrasting resrvoir characteristics. fresh‐water diagenesis, which was related to a beach environment, was closely accompanied by dolomitization; there was competition between the dissolution of aragonitic ooids and their dolomitiztion. Dissolution of aragonitic ooids can produce an excellent intragranular porosity when early diagenetic dolomite cements form prior to dissolution (Kaldi and Gidman, 1982), or it can produce a non‐porous fabric of overcompacted deformed “spastoliths”. Although burial diagenesis significantly modified the reservoir characteristics of the Zechstein ooid grainstones, a very irregular pattern of early meteoric‐related diagenesis is the main reason why discoveries are so unpredictable in the Zechstein.