Abstract

Hot water flooding is a mature technology that dates back to the 1960's. Although a technical success, heating injected water by burning a fuel proved to be uneconomic in those days. However, using hot water from geothermal sources eliminates the need to burn oil and results in a true increase in ultimate recovery with attractive development costs.

This technique is particularly useful in fields with shallow, high viscosity waxy oil formations and deeper water bearing formations with relatively low salt concentrations. Many oil fields in the Sumatra basin fit this category. Costs to drill geothermal source wells in Sumatra are economic because of the high geothermal gradient observed in the central Sumatra basin (0.03 to 0.04 °F/ft).

This paper shows a novel approach of combining typical waterflood operations with geothermal hotwater sources is not only cost effective for new enhanced oil recovery projects but is also an effective optimization technique for existing waterfloods. A case study of the Balam South Telisa reservoir is presented. Results from two other fields in Sumatra are also shown to illustrate the application of this concept to other fields.

Introduction

The basic concept for a "Geothermal Hot Water Flood" is to implement a standard pattern waterflood that uses hot water from geothermal sources for the injection fluid. Fig. 1 illustrates this process.

An excellent description of the Hot Waterflood Process is provided by Martin et. al.4 The primary displacement mechanism is the same for both hot and cold waterfloods.

The oil is displaced in a near-piston like manner. After the initial water breakthrough, the hot water improves recovery by reducing the mobility ratio because of the decrease in oil viscosity. Increased rates also result.

Hot waterflooding as an enhanced oil recovery application has not occurred on a large scale. Early fieldwork in Pennsylvania used this technique to increase water injection in a tight formation with low injectivity and not to increase ultimate oil recovery. Work in the 1960's proved that hot water flooding increases ultimate recovery.1–4 Subsequent field trials were disappointing, with projects often technically successful but not economic.5–7

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