An Integrated Approach to Selecting and Optimizing Demulsifier Chemical Injection Points using Shearing Energy Analysis: A Justification for Downhole Injection in High Pressured Well

摘要

Chemical demulsifiers are routinely injected into the petroleum production system at several points to effectively resolve water-in-oil emulsion issues. Point of injection varies from downhole through wellhead and manifolds to stocktanks (Batch treatment). Selection of the best injection points during oilfield practices still remains a very challenging task for both operators and chemical vendors. Many researches have not been done on this subject matter, and hence remains the focus of this study. In this paper , models to carefully analyze and study the relationship between shearing energy and pressure drops at various points in a production system is developed. It analyses the Shearing action as the reservoir fluid flows through formation pores, perforations, tubing, wellhead chokes and the surface flowline. This program determines the best injection points for demulsifier chemicals to ensure their adequate mixing, mobility and strong partitioning at the water-oil interfaces where their actions are needed. This novel approach applies to several well geometry and completions, ranging from open to cased wells. Developed models were tested and validated with real data from a known oilfield in Nigeria. Wellhead and downhole injection (through gas lift valves) appear to be one of the best practicable injection points selected by the program. This selection already considered the current conditions of the field and produced fluid and also the nature of demulsifier chemical in use, in terms of its residence time of action. Results obtained vary with changes in these factors as the reservoir becomes depleted and workover operations are performed. This paper emphasises the impact of shearing energy and pressure drops on the effectiveness of demulsifier chemicals. Determination of appropriate injection points combats lots of operational and economical problems such as over-treating and re-emulsification. It reduces unnecessary high budgets for demulsifier chemicals as injection rates will be optimized. This paper also discusses the benefits that can be realized by breaking emulsions downhole, and contributes to the existing literature in the design and construction of production chemical injection program for a green field development. The authors anticipate that the new concept of shearing energy analysis presented in this paper would contribute more to improving the technology of chemical-demulsification.