The Chemical Squeeze Process Some New Information on Some Old Misconceptions

Abstract

There are a number of gaps in our knowledge of the principles and mechanisms involved in the squeezing process. Among the things learned through a series of tests was that adsorption isotherms, contrary to common theory, are not very important to the process. And some factors that have been largely ignored flow velocity, for example are very important indeed. Introduction The squeeze technique as a means of depositing chemicals in an oil-, gas-, or water-bearing formation finds extensive use in the petroleum industry. This trend was started after the first publications of Kerver et al. on squeezes utilizing publications of Kerver et al. on squeezes utilizing the adsorption-desorption characteristics of corrosion inhibitors. Later, Smith et al. and Kerver and Heilhecker applied the same ideas to the deposition of scale inhibitors in the rock matrix around the wellbore of a producing well. Here, again, the adsorption-desorption characteristics of chemicals provided the basis for the technique. Recently, a different type of squeeze technique has been suggested by Miles. In this "precipitation" method. a dissolved chemical is first injected into the matrix and precipitated some distance from the wellbore. The precipitate is then partially redissolved by the oilfield brine at a very low but still effective concentration and transported back to the wellbore. In a previous paper, we described our tests on the compatibility of inhibitors with constituents of common oilfield brines. From these earlier data, and from the results given here, we conclude that there is no clear-cut line between these two basic types of squeeze methods. Both mechanisms can occur concurrently, depending on the chemical nature of the inhibitor and on formation parameters. However, the first mechanism (deposition based solely on adsorption-desorption characteristics) is to be preferred because it completely avoids formation damage that occurs when pores are plugged with secondary deposits. A third mechanism of inhibitor squeeze has been proposed by Tinsley et al. The inhibitor solution proposed by Tinsley et al. The inhibitor solution enters small fractures and vugs during squeezing and later slowly bleeds back into the stream of produced water. This mechanism should not play any important role in formations consisting of a sand matrix where no fractures exist. Basic Concepts of the Study We think the literature shows a lack of information regarding the following: The basic mechanisms and principles involvedin the squeeze technique. The design and limitations of squeeze jobs asa function of formation parameters (rockmaterial, formation temperature, flow rates, etc.)and the chemical nature of the squeezedcompound. Methods of evaluating squeeze tests in thelaboratory and in the field. We also believe that inadequate tools and methods are often used to conduct and evaluate actual squeezes. The "results" of these squeezes cause considerable confusion in some instances and may lead to misconceptions about the method and its value. To develop some reliable information about the squeeze method, we conducted a series of laboratory and field tests. JPT P. 339