Identification of Mechanisms and Parameters of Formation Damage Associated with Chemical Flooding

摘要

This paper presents a practical methodology and itsverification for determination of the mechanisms andparameters of chemically induced formation damage. It isbased on interpretation of laboratory core flood tests bydiagnostic straight-line plotting schemes. Laboratory testswere conducted to measure the permeability impairment andeffluent conditions as a function of time by flooding sandstoneand limestone outcrop rock samples with various alkalinesolutions (NaOH, KOH, NaSiO4) and alcohol (ethanol) asmight be used for improved oil recovery. The single-phasepermeability variation data were plotted according toprescribed diagnostic straight-line plotting schemes proposedby Wojtanowicz et al. and Civan. Plots that result insatisfactory straight-line trends reveal the predominatemechanisms of the formation damage. Further, the values ofthe parameters of the governing formation damage processesare determined from the intercept and slope of the straightlines.Higher pH solutions were observed to have causedgreater reductions in rock permeability. Civan's model betterdescribed the permeability variation due to scale dissolutionand precipitation processes. The Wojtanowicz et al. modelidentified the formation damage mechanisms as pore surfacedeposition and sweeping. Different rock damage conditionswere observed for the initial and the later test periods,indicating that more than one formation damage mechanismwas involved. The analysis of the same experimental datareveals that a numerical model such as UTCHEM will requiresignificantly more information to perform a similar analysis ofthe laboratory flood results. However, the diagnosticequations provide a practical and rapid means for thedetermination of the formation damage mechanisms. The methodology developed in this paper can be used forrapid detection and quantification of the formation damagemechanisms from core tests. The technique can be useful inthe design of alkaline-surfactant-polymer (ASP) and/ormicellar flooding chemical systems for field applications.