Non-wetting fluid

Interpretation for irreducible water saturation assumes that the rock is water-wet or mixed-wet (water-wet during drainage but the pore surfaces contacted by oil becomes oil-wet upon imbibition). If a porous medium is water-wet and a nonwetting fluid displaces the water (drainage), then the non-wetting fluid will first occupy the larger pores and will enter the smaller pores only as the capillary pressure is increased. This process is similar to the accumulation of oil or gas in the pore space of a reservoir. Thus it is of interest to estimate the irreducible water saturation that is retained by capillarity after the hydrocarbon accumulates in an oil or gas reservoir. The FFI is an estimate of the amount of potential hydrocarbon in... 

In order to visualize the process of non-wetting fluid injection Wood s metal Porosimetry was used [11-16], Wood s metal Impregnation technique is based on the same principles as Mercury Porosimetry, i.e., an immiscible,... 

The first one is the Katz and Thompson s model (1986) which interprets transports within pore solids in terms of these percolation ideas [2]. From that, the authors introduced a fractal percolation model to predict the permeability of a disordered porous media. In invasion percolation, a non-wetting fluid can have access to the first connection from one face of the sample to the other only when the driving pressure is sufficient to penetrate the smallest pore-throat of radius rc in the most efficient conducting pathway. So, the permeability of rocks saturated with a single liquid phase is given from the following relationship ... 

Drainage (i.e., displacement of a wetting fluid by a non-wetting fluid) was modelled by an invasion-percolation process (Wilkinson and Willemsen, 1983). This implies that viscous forces may be ignored (i.e., pressure drops in both fluids may be ignored) and that capillary forces (pressure difference AF between the two fluids) control the process ... 

Mercury is a non-wetting fluid for most materials. Because the contact angle (0) is 180°, cos = -1, and pressure is required to force mercury into the pores-see equation (1). We speak of mercury "intrusion pressures" these are quite high due to the high surface tension of mercury (476 dynes/cm). Thus, for a given pore size, the pressure required to force mercury into the pores is almost seven times greater than the pressure required to expel water from the pores. 

At room temperature, mercury is a non-wetting fluid for most porous materials. As a consequence, higher pressures are needed to force intrusion into small pores (e.g. 400 MPa for 4-nm diameter pores) while lower pressures are used for large pores and interparticular spacing (e.g. vacuum). Vacuum degassing of the sample is utilized to remove moisture from the pores prior to the analysis. Isotherms of the volume of mercury adsorbed versus pressure exhibit a hysteresis between the intrusion and extrusion process the overall shape of the isotherm affords information about the pore sizes and the size distribution. 

FIGURE 4 Capillary tube schematics of wetting versus non-wetting fluids. NAPL, Nonaqueous-phase liquid. [Adapted from Shackelford and Jefferis (2000).]... 

The above equation shows that by application of a pressure on the non-wetting fluid side higher than the capillary pressure, pores will be filled by the incoming fluid phase. 

Before commencing two-phase flow operations, single-phase permeability determinations were made at several flow rates, using brine in the water-wet sample, and Soltrol-oil in the samples that had been treated with Dri-Film. In every case, first the drainage relative permeability curves were determined. The first steady-state point was obtained typically at a wetting fluid/non-wetting fluid flow rate ratio of about 10. The filter velocities used... 

Knowledge of the mechanisms of the entrapment of non-wetting fluids within porous media is important in a number of fields of study. The mercury extrusion curve in porosimetry potentially contains useful information on the nature of a porous structure. However, in order to extract that information it is necessary to have an understanding of how the entrapment of mercury arises. Mercury porosimetry is also often used in the oil industry to evaluate reservoir rook cores. This is because the mercury recovery efficiency is expected to provide an indication of the oil recovery efficiency in a strongly water-wet system. 

Looyestijn (2007) defined a new index from NMR logs (see Chapter 3) based on the different relaxation characteristic of wetting and non-wetting fluid ... 

Water zone the rock is 100% water saturated. Note that the 100% water level is above the free water level as a result of the capillary forces. This position correlates with the displacement pressure (also called threshold or entry pressure). Displacement pressure is the capillary pressure at the top of the water-saturated zone. It is the minimum pressure required for the non-wetting fluid to displace the wetting fluid (water) and enter the largest pores (Jorden and Campbell, 1984). 

Ap is the density difference between wetting and non-wetting fluid, h is the height above the free water level. 

The drainage curve (Flue line in Fig. 2.40) starts with the 100% water-saturated situation at the displacement pressure Displacement pressure is the minimum pressure required for the non-wetting fluid (for example... 

For the first imbibition curve after drainage (red curve in Fig. 2.40), the process starts at and the wetting fluid (water) displaces the non-wetting fluid. Also in this process there is a remaining part of the displaced fluid— the residual (non-movable) oil saturation Sro in a reservoir. During the water-drive to produce the oil, a part of the oil eventually remains trapped as disconnected drops/blobs in the pore space. 

Lb, poo is the bulk volume occupied by the non-wetting fluid (mercury) at infinite pressure. 

A central problem in petroleum reservoir simulation is to model the displacement of one fluid by another within a porous medium. A typical problem is characterized by the injection of a wetting fluid (e.g. water) into the reservoir at a particular location displacing the non-wetting fluid (e.g. oil), which is extracted or produced at another location. The nature of the front between the water and the oil is of primary importance and the goal is to withdraw as much oil as possible before water reaches the production location. 

One very specific characteristic of the interfaces created by diffusion is their instability [1]. They fluctuate at a frequency much higher than the inverse of the average jump time of the particles. A very similar behavior is found during very slow drainage of a non wetting fluid displacing a wetting one [2]. 

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