科研之友
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摘要
An important aspect of preliminary core preparation for SCAL experiments is the restoration of the core sample to its original wettability. The prevalent method for restoration of core samples, to either strongly oil-wet or weakly oil-wet, is largely dictated by increasing or decreasing the time of aging at reservoir temperature. There is no consistent or reliable method ascribed for a specific sedimentary core sample to restore to its original state, which is obtained from preserved core samples. In this study, we have identified three important parameters-brine salinity, restoration temperature, and restoration time (age in number of days)-as contributing to wettability. The objective of this study was to determine the optimum level of these independent variables (brine salinity, temperature, and age) for restoring wettability. We extend the Box-Behnken model of surface response methodology to analyze wettability determined via three methods: contact angle, USBM, and a new method using scanning electron microscopy-mineral liberation analysis (SEM-MLA) over extended ranges of brine salinity (10,000, 100,000 and 200,000 ppm total dissolved salts), temperature (60 degrees, 90 degrees, and 120 degrees C), and age of conditioning (2, 4, and 8 weeks). The samples for this study included 15 Berea Sandstone samples aged in crude oil and brine of varying salinity. The wettability was experimentally validated using contact-angle measurements, USBM tests, and a novel SEM-MLA imaging (at low vacuum conditions). A seminal effort in applying SEM-MLA image analysis for wettability determination was also explored. Linear regression models were developed and the adequacy of predicting the output variables (wettability) to nearly all conditions were verified. The study showed a comprehensive influence of brine salinity, aging time, and temperature towards wettability restoration. Further 2D and 3D surface plots were generated to show the interaction between the three independent variables in establishing a wettability value.
- 出版日期2018-2
