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Jorge E. Nieto1, Alejandro Salgado2
(1) Ecopetrol - Columbia, Bogata, Colombia
(2) Ecopetrol - Columbia

Abstract: Facies & petrophysical 3D modeling, upscale and numerical simulation, reserve implications and recommendations according to production maturity: Reservoir characterization of Apiay Field, Llanos Basin, Colombia

During the active development of the Apiay Field, many numerical simulations have been attempted to adjust and predict the future production behavior. Through time, it has been noticed that it is progressively more difficult to predict production in this field due to the initial conception of the geological model. As production advances, the presence of barriers tends to be notorious and create substantial implications in the general drainage patterns. Production forecasts from models without detailed perception of heterogeneities are optimistic because of different rock types being grouped into the same grid cell.

This first study attempting to subdivide the formerly considered homogenous reservoir started with the recognition of six distinctive lithotypes as a product of the differentiation of thirteen sedimentary facies. In this way, basal cemented and very fine-grained sandstones, and abandoned channel successions conform the main non-permeable facies to model in the fluvial "massive" reservoir. These lithotypes create vertical and lateral restrictions to flow that have been clearly noticed in the current state of production, sometimes restricting water entrance or producing water fingering.

The detailed rock type characterization, the effective determination of petrophysical properties along with a right calibration of capillary pressure and relative permeability curves, and the optimum simulation grid considering the internal heterogeneities within the reservoir, have produced a better understanding of production and a more reliable set of predictions in a more heterogeneous reservoir, with uneven saturation profiles through time, all of which has been reflected in different approaches to maximize reserves economically attractive.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana