Gas Field Goldenstedt, Germany: Development Geology of a Deep Zechstein (Upper Permian) Gas Field

Franz X. Fuehrer

In Goldenstedt (northwest Germany) gas is produced from Zechstein carbonates at a depth of more than 3,600 m (12,000 ft). The reservoir is very heterogeneous with net thickness ranging from 5 and 100 m, porosity between 5 and 16%, and permeability ranging up to 320 md. Locally, fractures contribute to production. The gas contains 7-26% H₂S. Total reserves are currently estimated at about 0.5 tcf. A new appraisal drilling campaign, made possible by improved geophysical and geological techniques and their integration, has resulted in significant reserve additions.

Seismic resolution at reservoir level is severely influenced by the complex overburden. A 3,000-m Mesozoic section, characterized by inversion structures, is decoupled from the Paleozoic by thick salt layers. Pronounced seismic velocity contrasts complicate processing, interpretation, and time-depth conversion. Prediction of reservoir parameters was almost impossible in the past due to the complex sedimentological and diagenetic characteristics of the reservoir.

A three-dimensional seismic survey has improved structural definition. New log evaluation techniques, together with core analysis, allowed the identification of a tidal-flat depositional environment controlled by syndepositional faulting. Multistage diagenesis has overprinted and now partly controls reservoir characteristics. Attempts have been made to predict reservoir quality from seismic data.

Drilling and production operations in this densely populated area are severely restricted by safety considerations in view of the high H₂S content.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.