Water Injectivity-What We Have Learned in the Past 30 Years

Abstract

Abstract This paper reviews the field-scale water-injection experiences from the early Barkman and Davidson's water quality study in the 1970s to one of the latest Gulf of Mexico offshore field studies. It summarizes what petroleum engineers have learned during the past 30 years and provides a concise compendium to the current understanding of the water injectivity issue. Both onshore and offshore projects have been included and various water injection cases are presented, showing both successes and failures. The main objective of this paper is to help operators to develop operation and design strategies for current and future waterflooding projects. Introduction Waterflooding has a lengthy history of application in the petroleum industry(1–2). In the early years of waterflooding, it was mainly applied as an improved oil recovery technique after the reservoir pressure had fallen below its bubble point pressure in mature onshore fields. However, with the development of offshore fields around the world, waterflooding has come to the forefront and has been applied from the outset in offshore fields. As more and more of the world's major oil fields mature, oil wells begin to produce more water because of aquifer encroachment and widely applied waterflooding. Currently, it has been reported that the oil industry has to handle more water than oil which makes it seem like a "water industry." How to wisely handle the tremendous amount of unwanted produced water therefore is a crucial task the industry has to face. Water injection in reservoirs and the disposal of produced water are becoming increasingly important issues in the reservoir management process. The re-injection of produced water into the subsurface is a potentially attractive option to lower environmental pollution, especially for offshore fields, although considerable uncertainty about the costs of implementation and the consequences still exists. During the past 30 years, many waterflooding projects, including many offshore deepwater projects, have been started and lots of valuable experiences have been gained on water injectivity. Therefore, the purpose of this paper is to present lessons learned and best practices on water injectivity from published literature, and to provide a compendium to the current understanding of water injectivity to help operators better manage their current and potential waterflooding projects. Water Injectivity Observation During the literature search, we found only a dozen or so papers on water injectivity studies among the thousands of technical papers on waterflooding. It seems that petroleum engineers paid less attention to water injectors than producers, although waterflooding has been practiced worldwide for about a century in the industry. One of the reasons that water injectors were not fully studied was that oilfield operators do not have time to conduct water injectivity studies, especially for mature onshore fields with large numbers of wells. Another reason is that the improvement of water injectors usually takes weeks or even months before the increased volumes of injected water show an effect on oil production.