--> Rock Microcharacterisation — A New Petrographic Approach to Reservoir Quality Prediction: Methodology and Case Study, Ortenzi, Andrea; Arduini, Monica; Golfetto, Francesca, #90100 (2009)

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Rock Microcharacterisation — A New Petrographic Approach to Reservoir Quality Prediction: Methodology and Case Study

Ortenzi, Andrea1
 Arduini, Monica2
 Golfetto, Francesca2

1Geolab, ENI E&P Division, San Donato Milanese, Italy.
2
SPES, ENI E&P Division, San
Donato Milanese, Italy.

Reservoir quality prediction in sandstone may be achieved through forward modelling. It is however evident that any model has to somewhat simplify the inherent complexity of the petrographic data and of the diagenetic evolution undergone by sediments.

The Rock Microcharacterisation is the Eni petrographic approach aimed to provide an objective classification of siliciclastic reservoirs based on the Reservoir Efficiency Index (R.E.I.) that takes into account all the compositional and pore network aspects crucial for the quality of the system. The input data are the result of a modal point-counting at the optical microscope and of a quantitative pore network characterisation at the scanning electron microscope, carried out on the same polished thin section. After these quantitative analyses a rock micro-characterisation spreadsheet is obtained, comprising more than 50 variables for each sample. The variables are than lumped into discrete indexes that are further lumped into the final R.E.I. The indexes are relevant to the pore dimension, to the amount of grain-authigenesis-matrix and to the texture of authigeneses in the pore space. It also contains corrections for the basic depositional parameters such as grain-size and sorting. The R.E.I. is a number that goes from 0 to 1, 0 meaning no (< 0.00001 mD) efficiency and 1 a maximum (>1000 mD) efficiency. The R.E.I. is always related to a specific sedimentary facies.

The rock micro-characterisation is a comprehensive approach and results to be extremely useful during the whole exploration activity as it reduces significantly the risk related to the quality of the reservoir. The R.E.I may be used for the prediction on a regional scale. This approach is applicable from the early phases of the activity since it could provide important information also with few and scattered data, even from outcrop samples. In the reservoir studies, it provides a tool for the extension of the observed quality into adjacent area, lying outside the range of the well itself.

This methodology is used in all type of reservoirs, from very fine to very coarse grained and from conventional to low permeability.

We acknowledge ENI E&P for the permission of submitting this abstract.

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil