An integrated approach to characterize naturally fractured reservoirs and quantify their properties in the Bugani field

Abstract

Naturally fractured reservoirs are the most important geological features that contain large amounts of hydrocarbon reserves. Therefore, the identification and evaluation of fractured zones are crucial in the oil production optimization and field development decisions. While different techniques have been introduced to detect and characterize fractured zones, using each method in isolation may not lead to a full detailed reservoir description and lower hydrocarbon recovery. The purpose of this paper is to provide a combined approach to characterize naturally fractured reservoirs. Conventional petrophysical logs were used in combination to identify the reservoir fractures. Pressure transient analysis was conducted for the same wells to evaluate the properties of the detected natural fractures. The integration process was applied to three wells belonging to one of the Libyan oilfields known as the Bugani Field, located in the country's southeast region. Three fractures were detected at different depths where most of the fractures were large, open, nonhorizontal, and filled with hydrocarbon. Well test analysis results showed different flow stages and models for the reservoir. Flow regimes for wells BU-02, BU-03, and BU-04 were 4, 5, and 9, respectively, where each flow regime was used to define specific fracture and reservoir properties. The skin factor was negative for all wells; thus, the fracture permeability was very high, varying between 2200-4500 md. Also, there was a variation in the two porosity system obtained from the well test.