ESCHARD, REMI, Institut Francais du Petrole, Rueil Malmaison, France, CLAUDE BACCHIANA, Esso Rep., GUY DESAUBLIAUX, Institut Francais du Petrole, Rueil Malmaison, France, JEAN MARC CHAUTRU, Beicip, PIERRE EEMOUZY, Institut Francais du Petrole, Rueil Malmaison, France, and JAQUES PARPANT, Esso Rep.

ABSTRACT: Geostatistical Simulations of Alluvial Sandbodies in the Triassic Series of the Chaunoy Field, France

Chaunoy field, the largest oil field of the Paris basin, is exploiting heterogeneous reservoirs deposited during the Triassic in a large alluvial fan/lacustrine complex. The construction of a realistic reservoir model is difficult in such a setting because of the highly complex architecture of single reservoir units. Geostatistical simulations therefore have been performed to take into account the reservoir heterogeneities in the fluid flow modeling. A first layering has been determined from sedimentological and sequence stratigraphic analysis. The series was deposited in an alluvial outer fan environment. A lower siliciclastic member shows four heterogeneous sand sheets (7 m thick), which have been correlated across the field. Each of them is made up of stacked single channel sequenc s. The sand sheets are separated by extensive lacustrine and flood plain mudstone layers acting as permeability barriers. An upper siliciclastic/ dolomitic member has been divided into two units with porous conglomeratic channels interfingered with cemented lagoonal dolomites. Proportional curves in lithofacies have confirmed this layering, showing the continuity of the permeability barriers, and the variogram analysis has shown that the well spacing is larger than the channel width. Simulations in lithofacies have been performed with the Heresim software using three different variogram ranges (small, medium, and large values). Because a good correlation exists between the lithofacies and the petrophysical attributes, a transcription of the lithofacies simulations into petrophysical attr butes therefore was easy and realistic. Scaling-up techniques have given fluid-flow models corresponding to the three correlation ranges. Comparison of the global results of the fluid flow simulations with the observed production history enabled us to choose the more relevant case. Then the model using the selected correlation range helped determine optimum well spacing.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.