Weighted Inhibitors Solve Special Oil-Well Corrosion Problems
Authors: Havlena Z.G. , Wasmuth J.F. 
Published: March 2010

Abstract
The weighted liquid corrosion inhibitors provide an effective and economical means of mitigating corrosion in wells that heretofore were difficult, or impossible, to effectively treat with conventional corrosion inhibitors. The high-density liquid corrosion inhibitors have been very effective in treating the following types of wells: High-fluid-level pumping wells, even those with liquid columns so high that they occasionally flow out of the casing annulus. Low-pressure gas wells that will not flow against the hydrostatic head of a tubing full of oil, as used in a tubing displacement or formation inhibitor squeeze-type treatment. High-pressure flowing wells that are difficult to pump fluid into because of high formation pressure. The annular area of multiple completion wells. Typical field data are presented to show the effects of corrosion inhibitor treatments with the weighted inhibitor in several different fields.

INTRODUCTION
THE TERM ‘HIGH-DENSITY CORROSION INHIBITOR’ is used to designate those formulations that have been coupled with a weighting agent to make the product heavy enough to fall through well fluids. The connotation has generally been narrowed even further to include only those liquid products that will fall through an oil column and into or through a water column at the bottom of a well and will eventually be decoupled from the weighting agent. The decoupled inhibitor will then rise to the oil-water interface and enter the tubing through the tubing perforations if the, well is under production. The need for a high-density corrosion inhibitor has been recognized almost since the initiation of corrosion inhibitors into down-hole corrosion mitigation work. The stick inhibitor was probably the earliest form of a high-density corrosion inhibitor. It consisted essentially of a conventional inhibitor mixed and/or intermingled with a resinous, or wax, substance and barite. The entire mix was heated above the melting point of the wax and then cast into sticks., when cooled below the melting point of the wax, the stick attained a semi-rigid form. The barite provided the additional weight for the stick. Products made by crushing the inhibitor sticks were also used in treating down the casing annulus of pumping wells. Encapsulated inhibitors have also been used in an effort to facilitate the application of the inhibitor to the area needing protection, Development of a high-density liquid corrosion inhibitor has been a logical sequence of these earlier developments. In other words, it was the recognition of the need for such a product and the development of a product to meet that need. The high-density liquid corrosion inhibitor provided the industry with a product containing most of the more desirable characteristics of the stick and crushed inhibitors and without many of their undesirable features.

Widely Accepted by the Oil Industry
The use of high-density liquid corrosion inhibitors has been widely accepted by the oil production industry, The first well treatments with high-density inhibitors were made about five years ago.