Osvaldo C. Carbone¹, Carlos D. Arregui², Mark W. Longman³

(1) Petrolera Perez Companc S. A, Neuquen, Argentina
(2) Perez Companc S. A, Neuquen, Argentina
(3) Consulting Geologist, Denver, CO

ABSTRACT: Stratigraphic Analysis of the Lower Member of the Quintuco Formation in Entre Lomas Field, Neuquen Basin, Argentina

Entre Lomas field, on the east flank of the Neuquen basin, Argentina, produces hydrocarbons mainly from the lower part of the Berriasian (lowermost Cretaceous) Quintuco Formation. The main reservoir rocks are shallow marine to nearshore carbonates deposited as part of a generally shallowing-upward sequence ranging from deep-water shaly source rocks in the Tithonian (uppermost Jurassic) Vaca Muerta Formation up into sabkha deposits of the Valanginian upper Quintuco Formation. Four depositional sequences occur in this package. The lower three are dominated by fine-grained siliciclastic sediments; the fourth, including the reservoir interval, contains high-energy carbonate-clastic deposits representing a prograding highstand parasequence.

Four main facies occur in this high-energy environment. These include storm deposits (Facies A, skeletal floatstones), upper shoreface and offshore bar deposits (Facies B, pebbly skeletal grainstones with rounded acid volcanic rock fragments and abraded bivalves), carbonate beach deposits (Facies C, dolomitic skeletal grainstones), and a capping sabkha facies (Facies D) with anhydrite and dolomite mudstones. The pebbly skeletal grainstones of Facies B and the dolomitic grainstones of Facies C both form excellent reservoir rocks with an average of 18% porosity and 100 mD permeability. Porosity occurs as moldic and intergranular pores. The diagenetic sequence began with micritization of skeletal fragments followed by precipitation of equant calcite, dissolution of some fossil fragments, and partial dolomitization. The reservoir interval is capped by the tight sabkha anhydrites and dolomite mudstones. This stratigraphic framework will be used to further develop the field during a waterflood program.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado