Production Logging in Horizontal Wells: Applications and Experience to Date

Abstract

ABSTRACT Reservoir drainage by means of horizontal wells has become a new frontier in the oil industry, and all the divisions of this industry: drilling, cementing, logging, completion, stimulation and production are active in this endeavour, both at the research level and in the field. One of the most relevant reasons why horizontal wells are drilled and completed resides in the favourable productivity indices that are associated with horizontal well production. In order to evaluate the flow mechanisms leading to these gains in productivity, production logging is becoming a common practice, in spite of some operational’ difficulties many of which have been overcome by means that we shall review. Production logs are used in horizontal wells to diagnose unwanted-fluid entries, to obtain flow profiles, to locate producing fractures or for transient testing. In this paper we shall review the essential characteristics of production logging in horizontal wells. Some are due to the effect of the environment: flow regimes, well geometry. Some come from limitations of the current sensors, caused by the unorthodox position of the tool string as opposed to its traditional near-vertical position in standard wells. We shall also review the application of some measurements which have not been widely used, but which carry a high potential for diagnosis. We shall give examples of data acquisition and interpretation, showing that satisfactory answers of often excellent quality can be obtained in many types of flow regime and completion configuration, in spite of the hostility of the environment.