Formation Evaluation Parameters of the Rotliegendes Sandstone, North Sea Area

Abstract

Abstract Over the past few years the Permian Rotliegendes Sandstone in the North Sea area has been established as a profilic and fascinating gasbearing formation. Realistic evaluation of major gas deposits accumulated in this reservoir rock requires an engineered use of well logging data and core interpretation on a comparative basis. Permeability relationship, data on cementation factor and saturation exponent, matrix grain density, rock compressibility, etc. are discussed on several field cases. Introduction Over the past several years the shelf region of the North Sea has developed into Europe's most promising offshore area of exploration for gas and oil. In rapid succession substantial gas reserves have been delineated especially in the southern region of the North Sea area. This is illustrated by figure 1 showing a generalized map of offshore operation in the North Sea area (Hark et.al., 1971). A corresponding schematic geological profile through the southern part of the British North Sea shelf profile through the southern part of the British North Sea shelf area is given in figure 2 (Hornabrook, 1967). The so-called Rotliegendes sandstone, or Lower Permian age, has been established as a profilic gasbearing formation of major areal extent, covering large parts of both the North Sea and NW-Europe (Holland, Germany). A stratigraphic table of the North Sea area is given in figure 3 (Heybroek et.al., 1967). Despite the fact that several hundred wells have been drilled in the North Sea, only limited data have been published on formation properties of the Rotliegendes. Our present discussion attempts to shed some light on our many observations and the problems one may face in evaluating reservoir characteristics problems one may face in evaluating reservoir characteristics of the Rotliegendes using well logging, core analysis, and other laboratory data.