American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.

Abstract

Shut-in temperature profiles are in wide use to determine tops and bottoms of flooded zones and relative volumes in place in water injection wells.

This is a case history report that demonstrates the advantages of the shut-in temperature profile with its greater depth of investigation.

Vertical fracturing problems, common in West Texas, have been determined by extensive use of the Frac Evaluation Log. This data plus other investigative techniques prove the reliability of shut-in temperature profiles in water injection wells.

Introduction

This paper is written to reveal knowledge gained by running several hundred shut-in temperature profiles. This is a study of shut-in temperature profiles run in over 500 water injection wells with depths ranging from, 1,200 ft to 8,500 ft and accumulative volumes varying from 1,800 bbl to over 3 million bbl of water. The interpretation techniques were partially developed from the data contained in over 2,000 Frac Evaluation Logs that have been run, which indicate that wells often fracture out of zone and usually fracture up the hole from 20 ft to over 300 ft on most primary completions.

The shut-in temperature profiles on water injection wells are run at varying shut-in times according to the depth, accumulative volumes, injection rates and temperature differences between injected fluid and bottom-hole temperature.

All the shut-in temperature profiles were run with surface recording equipment on a single conductor wireline. Depth control and accurate temperature measurements are considered necessary for dependable data.

Pressure control is an absolute necessity. The fluid cannot be allowed to move up-hole while the well is being logged.

Discussion

Several logging techniques are in use to determine where and in what quantity a water injection well is receptive to fluid. Shut-in temperature profiles are employed to a great extent in West Texas. The data gained from this log, coupled with known fracture problems due to primary treatments, enable the operator to determine best how much net zone is being flooded.

It is believed that the case histories presented in this paper will confirm that one can determine, with certainty, the top of the flooded zone with shut-in temperature profiles. It is also possible to determine the relative volume of fluid in place opposite the borehole as well as the bottom of the flooded zone, if no fluid is going below total depth.

As water is pumped into a well, it will cool the immediate wellbore area by convection. The water, as it enters the formation, will cool by conduction. When a temperature profile is run while a well is on injection, the gradient will be abnormally cool and will not change from a linear slope until the sensing element passes below the point of major water losses from the borehole. If it is possible to log below the flooded zone the temperature will abruptly increase to normal bottom-hole temperature. The top of a flooded zone cannot be reliably determined under these conditions because of the constant flow of fluid past the temperature sensing element.

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