Data Analysis of Low-Salinity Waterflooding to Enhance the Oil Recovery in Sandstone Reservoirs

摘要

The lack of a single reasonable general mechanism to describe how low-salinity waterflooding can improve oil recovery in both laboratory and field pilot projects has increased the interests of many researchers and stakeholders. There has not been observed the relationship of formation brine salinity and injected brine salinity to see how much conventional waterflooding salinity is reduced to produce the maximum enhanced oil recovery by LSWF. There is no guidance in what EOR stage the LSWF is best implemented. This work collects data from various published literature to develop a comprehensive data set regarding low-salinity waterflooding in sandstone reservoirs. The LSWF mechanisms are discussed to gain better understanding of the LSWF effect on oil recovery in sandstone reservoirs. The data set consists of parameters from coreflooding experiments that involved core samples, crude oil, and brines from different places. Histograms and box plots are used to visualize various kinds of data, and cross plots and charts are used to analyze the relationship between the important parameters and oil recovery. This study revealed the complexity of LSWF mechanisms and the corresponding parameters in the COBR system that associate with this process. The effects of rock porosity and permeability, total clay content, core aging temperature, COBR wettability, initial water saturation, oil base/acid ratio, asphaltenes content, formation and injected brine salinity and composition on the enhanced oil recovery are discussed in both secondary and tertiary LSWF modes. The applicability of parameters affecting the LSWF process are summarized. It is also observed the relationship between formation brine salinity and how much injected brine salinity was reduced or diluted to produce the maximum incremental secondary and additional tertiary recovery. Finally, in comparison to the conventional waterflooding, the final recovery from all of the LSWF stages are higher than the one of the conventional waterflooding, and the secondary+tertiary EOR stage produces the highest final recovery.