Modeling injection well performance during deep-well injection of liquid wastes

Deep-well injection of municipal and industrial wastes, and liquid hazardou s wastes is an important waste disposal practice worldwide. Performance of injection wells during the deep-well injection of liquid wastes and waste w aters is critically dependent upon the physico-chemical properties of the w aste, the operational parameters such as injection rates and pressures, as well as the hydrogeologic and geochemical character of the host formation. Development of theories and models that can predict the injection well perf ormance as a function of these parameters is a vital research need. This pa per presents the development and application of a well injectivity decline (WID) simulator, that can be used to model injection well performance durin g deep-well injection. Injectivity decline due to particulates in the injec tion fluid is modeled for various types of well completions. Results from t he simulator are presented with an emphasis on the resulting well plugging and injectivity decline. The significant role played by injected wastewater quality, host formation properties, injection rate and pressure, well comp letion type, initial damage to the well/formation and the presence of grave l packs around the wellbore is discussed. The results quantitatively show t hat under typical injection conditions a high total suspended solids (TSS) concentration in the waste stream, low injection rate, low injection pressu res, formation heterogeneity (layering), low porosity and permeability of t he formation all contribute to a rapid decline in injection well performanc e. The simulator provides a tool for predicting well performance during was te injection as a function of the waste, formation and operational characte ristics. Such simulations can be valuable during planning and operating inj ection wells to achieve and sustain satisfactory well performance. (C) 2000 Elsevier Science B.V. All rights reserved.