Fluid Identification in Complex Carbonate Reservoir: An Example from Mexico’s Poza Rica Field

Frass, Manfred¹, Efrain Mendez², Alfredo Marhx³, Sean Boerner⁴ (1) Veritas VES, Villahermosa, Mexico (2) PEMEX E&P, Villahermosa, Mexico (3) PEMEX Exploración y Producción, Poza Rica, Veracruz, Mexico (4) Veritas VES, Houston, TX

The Poza Rica field is one of the oldest in Mexico, producing from complex carbonate limestone dolomite lithology mixtures. Described as dolomitic lime packstone matrix, with significant skeletal moldic porosity and/or development of vuggy porosities .

Three major carbonate facies are present. 1- consists of non-reservoir suspension deposits composed of peloidal/skeletal lime mudstones to wackestones that are variably dolomitic. 2- facies consists of transported, shallow shelf peloidal/bioclastic packstones with thin interbeds of chaotic breccias. 3- This facies consists of transported, detrital breccias.

Based on the petrophysical analysis and fluid substitutions, a combination of Lambda-Rho and Mu-Rho could be used to predict fluid types within the reservoir. While lithology variations were more evident within the intervals of interest than fluid changes, it was clear that seismic data could be used to predict fluid content within the reservoir, at the time the seismic survey was acquired.

The well to seismic tie process provided the wavelet that was used for the inversion and also the time/depth relationship, for relating the rock properties from the wells to the seismic.

The time horizons were the boundaries of the 3D models that were used for the deter­ministic and stochastic inversions. These results were the input as a covariate in the joint stochastic inversion. Simultaneously were modeled Vp, Vs, and density, which were then converted to Lambda-Rho and Mu-Rho. These horizons were also converted to depth along with the Lambda-Rho and Mu-Rho attributes.These results were then combined using the fluid substitution results from seven wells in the field, to predict fluids.