Spatial Distribution of Diagenetic Geobodies in Carboniferous Host Rock, Picos de Europa, Northern Spain

Abstract

Reservoir heterogeneity may have a significant impact on hydrocarbon production. Therefore, it is crucial to document such heterogeneities, which may have a sedimentologic, diagenetic or structural character. Reservoir heterogeneities are typically challenging to map in the subsurface, but can be characterized using information derived from outcrop analogues. In this study, we focus on diagenetic heterogeneities in outcrops in Picos de Europa (northern Spain). Specifically, we look at dolomite geobodies and concentrate on their dimensions and spatial distribution at inter-well length scales. The study applied field mapping using GPS to document in detail all dolomite occurrences in a delineated plan-view area of more than 1 km² in the Picos de Europa Formation and on a cliff face with cross-sectional area of about 0.25 km² in the Barcaliente Formation. The dolomite bodies have irregular shapes that can be simplified to elliptical cross-sections in both datasets. The ellipses show lognormal distributions in their lengths and widths. We applied two spatial statistical methods, lacunarity and Ripley's K function, to evaluate the distribution of the mapped dolomite bodies in both datasets. The analyses indicate that the dolomite bodies are randomly distributed at horizontal length scales of less than 200 m and at vertical length scales of less than 600 m. At larger length scales (up to the maximum dimensions of the studied datasets), the statistical analysis suggests the bodies have a regular distribution. The same spatial statistical patterns characterize the distribution of the observed, irregular cross-sectional shapes of the dolomite bodies and their approximation as ellipses, implying that ellipsoidal bodies may reasonably be used in object-based models. The results of this outcrop work help in better defining diagenetic geobody parameters for analogue subsurface characterization and modeling. This study is funded jointly by Qatar Petroleum, Shell and the Qatar Science & Technology Park.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016