Impact of Wettability on Two-Phase Flow Characteristics of Sedimentary Rocks: A Quasi-Static Model
byAhmed Al-Futaisi, Tadeusz W. Patzek
Al-Futaisi, A. and Patzek, T. W., “Impact of Wettability on Two-Phase Flow Characteristics of Sedimentary Rocks: A Quasi-Static Model,” Water Resources Research J., 39 2 1042-1055, 2003.
We describe a twophase pore network simulator of drainage and imbibition, which integrates a realistic representation of pore connectivity and morphology, a quasistatic description of uid displacement mechanisms, and a sound representation of the wetting properties of a sedimentary rock and of their alteration. The simulator works with 3D disordered net works of cylindrical ducts with triangular, square and circular crosssections obtained directly from the analysis of microCT images of rock samples. All porelevel displacement mechanisms: pistontype, snapoff, and cooperative pore body lling are considered with arbitrary receding and advancing contact angles. Bond invasion percolation description is used in primary drainage, while bondsite invasion percolation with ordinary percolation on a dual net work and compact cluster growth are used in secondary imbibition. In the paper, we resolve how to calculate the relative permeability of NAPL in the quasistatic approximation of imbibition, and illustrate spatial distribution of the clusters of trapped NAPL using our generalization to disordered networks of the HoshenKopelman clusterlabelling algorithm. To understand the impact of wettability alteration on the capillary pressure and relative permeability functions, we perform a series of drainage and imbibition simulations by changing the range of advancing contact angles. Our study indicates that in imbibition, transport properties of a permeable solid are quite sensitive to the hysteresis between the receding and advancing contact angle. This sensitivity reects competition among the different displacement mechanisms, which shapes the relative permeabilities, capillary pressures, and the distribution of the trapped NAPL.