Print this pageWALZEBUCK, JOHANNES, Nederlandse Aardolie Maatschappij, Velsen, Netherlands
ABSTRACT: Ranking of Geological Factors Controlling the Well Productivity in Rotliegende Gas Fields of the Dutch Offshore Area
Deeply buried Rotliegende sandstones deposited in the desert 
environment
of the Southern Permian Basin form a primary target for hydrocarbon exploration and production in northwest Europe. In the Dutch offshore sector, some highly profitable Rotliegende fields are known. However, the success rate for exploration and field development is adversely affected by the variable Rotliegende reservoir quality, with tight gas sands and productive reservoir units adjoining each other within fields. To improve the accuracy of reservoir performance forecasts, several case histories were analyzed and the observed well productivities correlated with key mineralogical and sedimentological parameters.
The overriding influence of facies is evident: the textural characteristics of the Rotliegende sand determined not only the initial porosity after deposition, but influenced also the response of the rock to burial diagenesis. The mature, better sorted sandstone facies suffered least from diagenesis, whereas the immature lithologies lost much of their porosity and permeability by pervasive diagenetic cementation and clay mineral growth.
The relative influence
of burial/temperature history and mineralogical and sedimentological factors on well productivity was evaluated with multivariate statistics. Three field studies from the Dutch offshore area demonstrated that the well productivity can be modeled as a function of a limited number of geological factors. Testing the statistical formula with additional wells showed that the multivariate method improves the accuracy of reservoir quality predictions.
AAPG Search and
Discovery Article #90990©1993 AAPG International Conference and Exhibition, The
Hague, Netherlands, October 17-20, 1993.