Facies Heterogeneity in a Kimmeridgian Carbonate Ramp System (Jabaloyas, Eastern Spain) - Outcrop Analogue for the Arab D Reservoir

Martínez, Victor ¹; San Miguel, Galo ¹; Aurell, Marc ¹; Bádenas, Beatriz ¹; Caline, Bruno ²; Pabian-Goyheneche, Cecile ²; Rolando, Jean-Paul ²; Grasseau, Nicolas ³
(1)university of Zaragoza, Zaragoza, Spain. (2) Total E&P, Technology Centre, Pau, France. (3) EGID, Univ. Bordeaux 3, Bordeaux, France.

The well-exposed Upper Kimmeridgian carbonate ramp of the Sierra de Albarracín area (Eastern Spain), allow precise facies and sequential reconstructions. The obtained results have provided excellent analogs to stratigraphically equivalent subsurface reservoirs, such as the carbonate ramps of the Arab-D of the Middle East. Critical questions regarding the facies heterogeneities in low-angle carbonate ramp systems reservoirs can be addressed using these continuous exposures, which encompass a full range of shallow carbonate facies.

The studied outcrops around Jabaloyas village provide a continuous and extensive exposure of the Upper Kimmeridgian ramp succession in both depositional dip and strike directions across a 12 km² area (i.e., 4 x 3 km). A 16-22 m thick high-frequency sequence has been mapped and analyzed in detail. The studied sequence is bounded by discontinuities that are traceable across the study area. The sequence includes coral-microbial patch reefs 5 to 15 m high (many of them with pinnacle morphology), developed in mid-ramp setting during the stages of maximum accommodation gain. A total of 274 coral-microbial reefs have been mapped across the different reconstructed 2D transects. These transects cover a total of 17.5 km lineal distance, resulting in a minimum average distance of 50 m between the coral-microbial reefs. There is also a wide range inter-reef and post-reef facies, which are dominated by different type of carbonate grains (i.e., ooids, peloids, intraclasts, skeletal grains). The characterized set of facies follows an overall retrogradational-progradational trend, with the development of low-energy peloidal-skeletal wackestones-packstones in the middle part of the sequence. Grain-supported facies (grainstones, packstones, rudstones) are found in the lower and in the upper part of the sequence and are graded in down-dip direction.

The field reconstructed 2D transects were used for further 3D modeling. The overall distribution of the main facies as well as the geometry and size of the pinnacle reefs were included in a 3D reservoir model. Results of this model will contribute to reduce the geological uncertainties associated with facies heterogeneity in carbonate ramps systems such as in the Arab D reservoir of the Middle East. Indeed, a better understanding of the fine scale reservoir heterogeneity is now required for enhancing hydrocarbon recovery of many mature oil fields in Arab D carbonates.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.