Investigating Low-Salinity Waterflooding Recovery Mechanisms in Sandstone Reservoirs

Abstract

Numerous core-flooding experiments have shown that Low-Salinity Water Flooding (LSWF) could improve oil recovery in sandstone reservoirs. However, LSWF recovery mechanisms remain highly contentious primarily because of the absence of crucial boundary conditions. The objective of this paper is to conduct a parametric study using statistical analysis and simulation to measure the sensitivities of LSWF recovery mechanisms in sandstone reservoirs. The summary of 411 coreflooding experiments discussed in this paper highlights the extent and consistency in reporting boundary conditions, which has two implications for statistical analysis: (1) Even though statistical correlations of the residual oil saturation to chlorite (0.7891) and kaolinite (0.4399) contents, as well as the wettability index (0.3890), are comparably strong, the majority of dataset entries are missing, and a prediction model cannot be generated; (2) If a prediction model is generated without clay content values and a wettability index, even though LSWF emphasizes wettability modification by virtue of oil aging time and the strong influence of brine cation and divalent ion concentrations on S or, the prediction model's regression curve and confidence level are poor. Reservoir simulations conducted to examine LSWF recovery sensitivities conclude that LSWF recovery mechanisms are governed based on the initial and final wetting states. In strong water-wet conditions, the increase in oil relative permeability is the underlying recovery mechanism. In weak water-wet conditions, the incremental recovery of LSWF is driven by low capillary pressures. In weak oil-wet conditions, the primary LSWF recovery mechanism is the increase in oil relative permeability, and the secondary mechanism is the change of the non-wetting phase to oil. In strong oil-wet conditions, the underlining LSWF recovery mechanism is the increase in oil relative permeability. In all cases, an appreciable decrease in interfacial tension (IFT) is realized at the breakthrough recovery however that is rapidly overshadowed by the increase in oil relative permeability and decrease in contact angle.

Meeting Name

18th SPE Improved Oil Recovery Symposium (2012: Apr. 14-18, Tulsa, OK)

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Analysis And Simulation; Clay Content; Confidence Levels; Data Sets; Improve Oil Recovery; Ion Concentrations; Low-Salinity Water; Non-Wetting; Oil Aging; Oil Relative Permeability; Parametric Study; Prediction Model; Recovery Mechanisms; Regression Curve; Reservoir Simulation; Residual Oil Saturation; Sandstone Reservoirs; Secondary Mechanisms; Statistical Correlation; Wettability Index; Boundary Conditions; Contact Angle; Experiments; Kaolinite; Mathematical Models; Oil Well Flooding; Petroleum Reservoirs; Salinity Measurement; Statistical Methods; Well Flooding; Wetting

International Standard Book Number (ISBN)

978-1618399625

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2012 Society of Petroleum Engineers (SPE), All rights reserved.

Publication Date

01 Apr 2012

Link to Full Text

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