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Australian Energy Producers Journal Australian Energy Producers Journal Society
Journal of Australian Energy Producers
RESEARCH ARTICLE

A laboratory set up for the measurement of wellbore instability due to erosion of unconsolidated formations

Ghazal Avijegon A and Joel Sarout B
+ Author Affiliations
- Author Affiliations

A Curtin University

B CSIRO Energy

The APPEA Journal 55(1) 329-336 https://doi.org/10.1071/AJ14025
Published: 2015

Abstract

Borehole instability is a recurring issue encountered during drilling operations in the oil and gas, and mining industries. In exploration drilling using coiled tubing technology, boreholes are slim and the annular space is usually tight. Similar situations are also encountered around the drill-collar section in standard drilling where the annular space can be tight; therefore, the drilling fluid has a high flow velocity and a turbulent flow regime is dominant.

The flow conditions are the governing conditions for borehole erosion, which can lead to borehole instability. Erosion of the borehole introduces more cuttings into the annulus space, which is detrimental to the efficiency of cuttings transport and brings contamination to samples being retrieved at the surface for geochemistry and mineral analyses.

In this peer-reviewed paper a new laboratory set-up aimed at estimating borehole erosion in pre-drilled rock samples is reported. A flow loop unit is used, which allows the injection of high flow-rates of any type of fluid composed of chemical additives and simulated cuttings.

Early results of an exploratory study are reported in terms of changes in the internal borehole diameter (ID) of the sample before and after the erosion experiment. These were recorded using X-ray CT scanning. This change in ID acts as a measure of the formation’s erodibility, from which shear stress is estimated.

Ghazal Avijegon is presently a PhD student at the Department of Petroleum Engineering at Curtin University. She received her BSc in chemistry from Persian Gulf University in 2001. In 2013 Ghazal received her Postgraduate Certificate in Environmental Assessment and Management from Murdoch University in Perth, WA.

She has also gained one year of laboratory work experience while performing research on water quality as part of a joint Curtin University CSIRO Water Corporation project from 2013–14.

Ghazal’s research activities now concentrate on borehole stability, erosion lab experiments and numerical simulation of borehole wall erosion.

Joel Sarout is a research scientist at CSIRO Energy.