Method development of laboratory bench and rig tests for assessing the suitability for application of chemicals via down-hole pressure tube systems is presented. Areas of interest include precipitation or viscosity changes due to solvent loss both in bulk samples and samples in capillaries, and long term product stability in capillaries using new flow rigs designed to more fully replicate pressure tube injection phenomena (particularly chemical stability under extreme T and P conditions). Indeed fluid stability and other challenges relating to down-hole continuous injection have led to a number of failures being recorded in recent years indicating that the physical properties rather than the absolute performance of the chemicals is often key to their successful deployment.

Continuous chemical injection systems for down-hole application are being included in more well completions as their usefulness is recognised. While the initial capital costs are increased, such systems provide a number of benefits over reliance on squeeze treatments for down-hole application. These may include the opportunity to use chemicals unsuitable for squeeze treatment due to the risk of formation damage, the ability to maintain higher doses, and avoiding the need to interrupt production to apply chemicals in complex subsea wells.

Using the developed methods we have identified a number of ways in which formulated scale inhibitors may produce problems within continual injection systems. These include particulate formation and line plugging in capillaries, and solid formation or viscosity increases in response to solvent loss within a tube (as opposed to bulk samples).

These methods will form the basis for future qualification procedures for chemicals intended for down-hole chemical injection with the aim of avoiding application issues in the field. They have been developed both to better understand chemical / fluid stability under down-hole continuous injection conditions following a number of recorded field deployment problems, and then to provide improved qualification for new chemicals and systems.

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