Micro-particle gel transport performance through unconsolidated sandstone and its blocking to water flow during conformance control treatments

摘要

High-permeability streaks, fractures, conduits, and fracture-like features can expedite an undesirable water channeling and early water breakthrough during water flooding. Micro-preformed particle gel (PPG) is one of the commercial gels invented exclusively to plug such features to reduce excess water production and increase oil production. This paper reports the results of laboratory experiments that studied the PPG's injection and placement mechanism through unconsolidated sandstone cores. Extensive experiments were conducted to examine the effect of the sand permeability, PPG size, concentration, and water salinity on the PPG injection process, passing criteria, and plugging efficiency to water flow. A two foot sand pack model with four pressure taps was designed to monitor PPG transport and plugging performance. The results showed that the PPG propagated deep into the unconsolidated sandstone. Fully swollen gel particles had better injectivity than partially swollen particles with a larger diameter size; particle strength was more dominant in influencing particle movement than was particle size. The injection pressure increased as the PPG concentration, water salinity, and gel particle size increased. High gel particle injection pressure was measured in the front part of the unconsolidated sandstone as a result of gel particle retention. The retention was controllable by selecting proper gel particle strength, concentration, and size. PPG transport through unconsolidated sand exhibited four patterns of injection processes: low gel particle retention and pass; high gel particle retention and pass; high gel particle retention, breaking, and pass; and gel particle accumulation and plug. The micro-gel particle's blocking efficiency to water flow increased as the PPG strength, size, and concentration increased. The PPG placement mechanism, such as washout, was also found to considerably affect the water injection flow processes. The results of this laboratory experiment will aid in the selection of future conformance control candidates and also optimize the particle gel treatment design for large-scale field projects.