Abstract: Regional Controls on Diagenesis of Rotliegendes Formation in Dutch Sector of North Sea

William R. Almon, Roland Schwab

The sandstone of the Rotliegendes Formation in the Dutch North Sea has undergone varied diagenesis depending on the depth of burial and paleogeographic location. The major diagenetic features are illite pore linings, kaolinite pore fills, kaolinized feldspar grains, quartz overgrowths, and dolomite cement. Minor diagenetic features are iron-oxide grain coats, anhydrite cement, and siderite cement.

The earliest diagenetic features (iron-oxide grain coats, dolomite cement, and illite pore linings) were developed under the influence of the surface or near-surface waters and thus the near-surface drainage pattern. The development of the later diagenetic features (kaolinite growth, feldspar alteration, quartz overgrowth, anhydrite cementation, and siderite cementation) is interpreted to be related to the introduction of Zechstein-derived waters into the underlying sandstones. Thus, the intensity of diagenesis in the Rotliegendes reflects the facies distribution of the overlying Zechstein. Diagenesis is most severe where the Zechstein is a thick evaporite sequence. Diagenesis is least severe where the Zechstein is a thin evaporite, carbonate, and clastic sequence.

The extent of diagenesis in this area should pose no problem in the completion of gas wells. The Rotliegendes should be amenable to stimulation by acid systems, if care is taken to prevent the precipitation of cements such as iron oxides and fluorite from the spent acid.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma