Mechanical Alteration of Near-Wellbore Mineralogy for Improved Squeeze Performance

Abstract

Summary Squeezing of clean, high-permeability reservoirs frequently results in relatively short treatment lifetimes because of the low inhibitoradsorption rates achieved. One of the main controls on inhibitor retention is near-wellbore mineralogy. Clay-rich reservoirs that contain abundant kaolinite, for example, often have long squeeze lifetimes because enhanced inhibitor adsorption can occur on the clay surface. The occurrence of calcium carbonate (CaCO3) cement in the near-wellbore region can also enhance inhibitor retention by forming a Ca2+/inhibitor complex. Previously published research (Fleming et al. 2009a) demonstrated the potential to mechanically alter the near-wellbore region through incorporation of low concentrations of kaolinite and organosilane. The data presented in the present work show that the additional incorporation of calcium carbonate provides a step change in the potential squeeze lifetimes achieved. This paper will present the results of using low, nondamaging concentrations of kaolinite and calcium carbonate particles in the preflush followed by scale inhibitor and organosilane in the main treatment. The kaolinite particles are retained in the near-wellbore region by the organosilane and enhance the number of potential sites for inhibitor adorption. At the same time, dissolution of the calcium carbonate particles by the acidic scale inhibitor forms a Ca2+/inhibitor complex that further enhances inhibitor retention. A review of the technology performance envelope has been made through coreflooding that includes optimizing the concentration of injection particles vs. permeability, the ratio of injected kaolinite to carbonate particles, and performance at elevated temperature (175°C) along with an assessment of how often a well would require retreatment with particles. The latter has involved successive coreflooding of the same plug with the full treatment package followed by brine flowback and retreatment with scale inhibitor alone or with organosilane. This information can be used by the assets in their evaluation on potential use of the technology.