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

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

SARABAND computer analysis using the gamma-ray and induction logs in open hole with the compensated neutron log (CNL) and the formation density log (FDC) in cased hole provides an alternate method for evaluating provides an alternate method for evaluating highly deviated offshore wells in the Gulf of Mexico.

Introduction

The number of highly deviated holes being drilled in the Gulf of Mexico is increasing rapidly. Often the hole conditions can become so severe that unorthodox logging methods, consuming large amounts of expensive rig time, are required to complete a minimum logging program. The use of open-hole gamma program. The use of open-hole gamma ray-induction resistivity log (GR-ISF) and the compensated neutron-formation density logs (CNL-FDC) made in casing as input to a SARABAND analysis is proposed in this paper as an effective solution to some of these problems. problems. Often in development drilling, enough geologic data is available to justify setting pipe after running only an electric log in open pipe after running only an electric log in open hole. This practice, however, usually leaves hydrocarbon type and volume undetermined in many zones. In order to define the accuracy with which these quantities can be determined in casing with a combination density-neutron (CNL-FDC) tool, 17 zones in a well with good open-hole data were logged in casing and systematically analyzed. The results show that in many cases this method of well evaluation will be a workable alternative to using conventional or even some newly developed open-hole techniques.

A full suite of open-hole log data, if available, remains superior to this approach. However, often conventional porosity and sidewall core tools simply will not reach the objective section in very high angle holes. Also, the advantages of obtaining open-hole porosity data are partially or completely offset porosity data are partially or completely offset by the additional rig time costs and increased risk of losing the hole.

OPEN VS CASED-HOLE DENSITY LOG

Attempts have been made to estimate formation density from cased-hole density logs. In the subject zones, the bit size was 9-7/8 in. and 39 lb — 7-5/8-in. casing was set.

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