Abstract

Detecting flow behind pipe (tubing/casing) is a critical process for the success of reservoir management. Designing a proper water shut off technique is very dependent on having data of flow behind casing. Water injection profiles can be corrected by quantifying water down flow and/or up flow behind tubing for water injection wells completed with cup packer assemblies and perforated tubing for zone isolation.

Oxygen activation (OA) techniques have been applied to the measurement of flow behind pipe for several years. The basic principle involves the activation of oxygen atoms by using high energy neutrons (higher than 10 MeV) and measuring their decay by counting the emitted gamma rays (GR). The water movement is identified by an increased gamma ray count rate compared to the background count rate. The Water Flow Log (WFL^) is a new oxygen activation tool which applies improved techniques to identify and quantify the water movement.

This paper reports the application of WFL to several water injection wells and one oil producer in the Minas Field. In water injection wells, the WFL was run to quantify the water down flow and/or up flow in the annulus between the 7" casing and the 3-1/2" perforated tubing. The interpretation of the logs indicated obvious water flow in the annulus. The injection profiles determined using only the Spinner Flowmeter Survey (SFS) were incorrect. A correct injection profile is required to determine the re-completion technique to insure injection rate targets are reached. Running the WFL in a new oil producer enabled the identification and quantification of water flow in channels behind the 7" casing. Remedial cementing was successful in improving cement bond. Some of the tool limitations are also reviewed in this paper.