Abstract

Numerical simulation has been applied to study the water coning behavior in a well producing from a highly heterogeneous reservoir in an oil field located in the onshore part of the Potiguar Basin, Rio Grande do Norte, Brazil. In this reservoir, the scale of lateral heterogeneities is too small to be represented by layer average properties.

Small scale heterogeneities in the drainage area of the well were modeled by sequential stochastic simulation of categorical variables representing flow units of the reservoir. Variographic analysis was performed using logging and core data from the reservoir and also data from outcrops in the same depositional environment

The purpose of this work was to evaluate the effect of small lateral heterogeneity on the water coning behavior. This was accomplished by history matching production data and numerical results of flow simulation performed in geostatistic realizations of the reservoir.

Introduction

A well producing from a completed interval close to the oil-water contact may experience the water coning phenomenon. If viscous forces overwhelm gravitational forces, water will break through the oil zone, forming an elevated or cone shaped surface

At a critical production rate, the water coned surface will reach the bottom line of the production interval. Above this rate, the well will produce oil and water simultaneously. Because the water mobility is usually greater than the oil mobility and the flowing pressure gradient decreases as production goes on, the well will show a continuous increase in water-oil ratio.

Muskat and Wick of (1935) were the first authors to present the fundamental physical principles underlying the coning behavior and to establish an approximate analytical method to determine the critical production rate. Later, Sobocinski and Cornelius (1965) presented an empirical correlation to predict water-cone breakthrough time, obtained from an experimental model scaled to duplicate field behavior.

Many authors have applied numerical simulation to study the coning phenomenon.

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