An integrated approach to Zechstein Ca2 carbonate reservoir facies prediction in the south Oldenburg area, Upper Permian, northwest Germany
- BEB Erdgas und Erdol GmbH, Hannover (Germany)
- Exxon Production Research Co., Houston, TX (United States)
Integrating seismic, well log, and core data from the Zechstein Ca2 makes it possible to predict reservoir facies distribution, increasing likelihood of drilling successful wells. Well logs and cores show that Ca2 thickness and facies distribution are related to thickness of underlying Werra Anhydrite (A1) and overlying Basal Anhydrite (A2). Thin (30-80 m), dolomitized, porous Ca2 platform facies occur where the A1 sulfate platform is thick (about 300 m). Thick upper and middle slope facies (100-250 m) lie basinward of an abrupt decrease of A1 thickness from 300 to 40 m, but platformward of an abrupt thinning of the A2 from 80 to 2 m. Slope facies are porous where not calcitized. Platform-influenced carbonates overlying the slope facies lie basinward of the A1 thickness change. Nonporous lower slope facies (40-100 m) occur farther basinward, overlying thin A1 (about 40 m). Syndepositional structuring causes anomalies in Ca2 thickness and facies distribution. Intra-Ca2 mineralogical variation makes mapping intra-Basal Zechstein with thicknesses from three-dimensional (3-D) surveys difficult. However, the total thickness of the Basal Zechstein can confidently be mapped from 3-D seismic. Abrupt changes in Basal anhydrite [open quotes]cliffs,[close quotes] providing control on Ca2 facies limits. Integrating total Basal Zechstein thickness maps made from seismic interpretations with maps made from well log interpretations yields maps that honor all data. Potential reservoir zones are low-impedance layers in seismic models and appear as anomalies on seismic attribute maps. Lithologic variation hinders direct interpretation of anomalies as porosity. Improved prediction of calcitization trends will enhance recognition of porous zones.
- OSTI ID:
- 6849529
- Report Number(s):
- CONF-9310237-; CODEN: AABUD2
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 77:9; Conference: American Association of Petroleum Geologists (AAPG) mid-continent section meeting, Amarillo, TX (United States), 10-12 Oct 1993; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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