Abstract In 1993, Australia saw a surge in horizontal well drilling and completion. This surge was motivated by two main factors: the desire to produce oil from fewer wells per field at substantially higher production rates per well, and the necessity of draining the reservoirs with horizontal wells as dictated by local conditions of formation geometry and petrophysical characteristics.
One of the most efficient ways of evaluating the productivity of a horizontal drain is to run production logs in the recently completed well. The technique used is called CTL* Coiled Tubing Logging, which was first implemented in 1988 and has become routine since.
Applications of production logging in horizontal wells include:initial completion evaluation,
in-situ measurement of the productivity index,
flow profile determination,
multiphase flow regime characterization,
determination of unwanted water and gas entries,
dynamic reservoir characterization by pressure transient testing.
Through-tubing formation evaluation tools can also be run together with the production logs to complement openhole evaluation.
More than ten wells have been successfully logged in approximately one year, in different oil and gas provinces of Australia and in a variety of completion configurations. The paper describes the data acquisition programs, the downhole sensors which have been used and their application to horizontal flows. The data interpretation methodology is presented, and a number of interpreted examples are shown.
The paper concludes with the relevance of production logging to the optimization of production engineering, and reservoir drainage by horizontal wells.
1) Introduction. Production logs have been run in horizontal wells since 1988. Early experience was summarized in 1990 in Ref. 1 by Chauvel et al.