Enhanced Oil Recovery from Siliceous Shale Reservoir Cores by Aqueous Ketone Solution

This paper presents an experimental study on the wettability alteration in siliceous shale using an aqueous 3-pentanone solution for potential applications in well treatment and enhanced oil recovery (EOR). Several key uncertain details near fracture networks must be addressed before practical cyclic-injection (or huff-n-puff) applications in the field: (i) the effectiveness of 3-pentanone across different initial wettability conditions in shale reservoirs and (ii) the retention behavior of 3-pentanone within the shale matrix and its impact on the oil recovery rate and efficiency. The experiments covered two flow conditions: (i) forced oil displacement by aqueous 3-pentanone solution in three core floods with different initial wettability states and (ii) three huff-n-puff experiments with varying 3-pentanone concentrations and initial water saturation. The injection fluids used were sulfate-rich low-salinity injection brine (IB) and 3-pentanone solutions in IB (3pIB). Core flooding results showed that 3pIB injection was particularly effective under more oil-wet conditions, where preceding IB injection was inefficient in recovering oil. EOR by 3pIB injection indicated that 3-pentanone facilitated the extraction of additional oil from the matrix that had been bypassed during the earlier IB flood. Huff-n-puff results demonstrated that a greater concentration of 3-pentanone accelerated oil recovery. Phase behavior data and material balance analysis indicated that increasing the 3-pentanone concentration tends to increase the 3-pentanone K-value, causing 3-pentanone to imbibe into the oil-bearing shale matrix. The shale core with initial water saturation exhibited more rapid oil recovery, with most of the oil recovered during the early stages, than the core with no initial water saturation.