Use of the Interface Survey in Irregular Bore Holes
Authors: Peterson J.E. 
Published: December 2007

This paper was prepared for presentation at the 47th Annual Fall Meeting of the Society of Petroleum Engineers held in San Antonio, Tex., Oct. 8–11, 1972. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by who the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
Among the most frequently used techniques for surveying water injection wells is the radioactive tracer survey. However, in irregular bore holes, its application becomes limited because a bore hole diameter is required for each flow rate calculation. The actual selection of the bore hole diameters for the flow rate calculations can result in a large uncertainty in the injection profile.
The results of the interface survey are independent of the use of a bore hole diameter for the injection profile calculations. Therefore, the interface survey can be used with confidence in irregular boreholes. The interface survey does require a different well completion design from the radioactive tracer survey so that water can be injected down the annulus and tubing simultaneously. By ejecting water soluble radioactive material in the tubing stream, the interface created by the radioactive and non-radioactive waters can be located with a Gamma Ray detector. By changing the rates of annulus and tubing flow, the interface can be moved up hole or down hole. The distance the interface moves can be directly related to the changes made in the flow rates. After each change in the flow rates is made, sufficient time must be allowed for equilibrium to be reached. Due to the equilibrium conditions required for each interface, extensive logging time is required. Increased costs are also required for the preparation of the well and additional surface preparation of the well and additional surface metering equipment. The additional costs may well be justified for the accurate data obtained in irregular bore holes.

Introduction
A successful waterflood requires that the moveable oil be displaced with injection water. However, if injection well problems are not defined and corrected, they can lead to an economic failure of the project. For early definition of injection well problems, the project engineer has many surveillance tools and surveys available to determine the injection conditions. Among these are the radioactive tracer survey and the interface survey.

Radioactive Tracer Survey
The radioactive tracer survey requires that the movement of fluid over a fixed distance be timed. The fixed distance is a function of the tracer tool configuration and is either from the ejector to the detector or from detector to detector.