Online Journal for E&P Geoscientists

Caline, Bruno ^*1; Aurell, Marcos ²; San Miguel Sanchez, Galo ²; Bádenas, Beatriz ²; Martinez, Victor ²; Pabian-Goyheneche, Cécile ¹; Grasseau, Nicolas ³; Rolando, Jean Paul ¹
(1) E&P, TOTAL, S. A., Pau, France. (2) Ciencias de la Tierra, Zaragoza University, Zaragoza, Spain. (3) EGID, Universite Bordeaux, Bordeaux, France.

Reservoirs from the Middle East are some of the most important hydrocarbon sources worldwide. Arab Formation (Upper Jurassic), and specifically Arab-D, is one of the representative reservoirs which shows some facies complexities and heterogeneities to overcome. Thereby, this key aspect in exploration and production led us to study an Upper Kimmeridgian analogue exposed in NE Spain: a low-angle carbonate ramp that includes the development of reef buildups formed by colonial forms (corals, stromatoporoids), and microbial crusts with associated encrusting organisms.

The well-exposed outcrops around the Jabaloyas village (Eastern Spain) have been used for a precise facies and sequential reconstructions within a 16-22 m thick high-frequency sequence. These outcrops show strike and non-strike sections across a 12 km2 area (i.e., 4 x 3 km). The studied sequence is bounded by discontinuities that are traceable across a total of 17.5 km lineal distance and encompasses the coral-microbial buildups 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 reefs have been mapped across the different reconstructed 2D transects. Density calculation resulted in a minimum average distance of 50 m between the buildups, although there is a recognizable spatial distribution trend along the studied area. Seventeen stratigraphic profiles were carried out to control vertical and lateral facies distribution. The facies follows an overall retrogradational-progradational trend, with the development of low-energy peloidal-skeletal wackestones-packstones in the middle part of the sequence. Different types of grain-supported facies (ooidal, peloidal, intraclastic, skeletal) are found both in high-energy mid-ramp domains and inner ramp areas.

The field data were used for further 3D modelling. The overall distribution of the main facies were included in a full-field model (20 x 20 m grid increment) while the geometry, size and distribution of the reefs were better adjusted in sector models (1 x 1 m). These models assess the distribution of reservoir bodies and the connectivity. They will be used as a template for further diagenesis modelling and constitute the geological input for dynamic phenomenology using real field data set.