Experimental Study on Logging Response of Flushed Zones in the Orinoco Heavy Oil Belt, Venezuela

Abstract

The Orinoco heavy oil belt in Venezuela is the largest heavy oil enrichment belt in the world. There are flushed zones in some oilfields in the heavy oil belt, leading to serious water production of some horizontal wells in the oilfields. Aiming at the problems such as unclear formation mechanisms of flushed zones, unclear response of special logging such as nuclear magnetic logging etc., and high requirements for the core experiment scheme, an experimental scheme based on the nuclear magnetic experiment for measuring the porosity and saturation of cores without damaging them has been designed, so as to successfully solve the problem of measuring the porosity and saturation of cores containing extra-heavy oil without damaging them. The relative error between the experimental results of porosity and saturation in the reservoir is less than 1%. The measured porosity is significantly decreased in the formations of the flushed zones. Based on the response of conventional logging and special logging such as nuclear magnetic logging in this area, it has been confirmed that the viscosity of the crude oil in the formations of the flushed zones is higher than that in ordinary heavy oil reservoirs, which belongs to immovable crude oil under reservoir conditions. Based on the basic theories of cores, nuclear magnetic logging and foam oil, the NMR spectrum characteristics of the formations of the flushed zones have been summarized. The results of this study provide important evidence for the related research on the formation mechanisms and formation process of flushed zones, as well as great support for the classification and recalculation of the reserves of reservoirs with flushed zones.

Copyright 2022, IFEDC Organizing Committee

This paper was prepared for presentation at the 2022 International Field Exploration and Development Conference in Xi’an, China, 16–18 November 2022.

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