Water blocking and wettability

Water blocking and wettability alteration are related acidizing damage mechanisms, especially useful in sandstones. In tight formations, water that is introduced to the formation may be retained by capillary forces. Gas or oil production rates may be severely impaired. Proper selection of surfactant additives is necessary to avoid water blocking. This is quite often difficult to assess without the benefit of core flow testing with a representative formation core. 

Concrete dampproofers are integral admixtures that alter the concrete surface so that it becomes water repellent, or less wettable . This is illustrated in Fig. 4.1, which shows a close up of a water drop on a surface of a concrete that has had a dampproofer incorporated into it. This water repellency conferred on the concrete is only effective in preventing water from entering the surface when the applied pressure is small, e.g. rainfall in windy conditions, or capillary rise. The latter effect is shown in Fig. 4.2. In view of this, these materials are used normally for improving the quality of concrete pavers, tiles, bricks, blocks and cladding panels where the additional benefits of reduced efflorescence, the maintenance of clean surfaces and the more even drying out of adjacent bricks and panels are also obtained. 

A problem in the WAG process is that injected water blocks contact between the injected gas phase and resident oil. This reduces displacement efficiency at the pore scale i.e., it results in a larger ROS. This effect has been found to be a strong function of rock wettability and more detrimental in water-wet rocks. 8... 

Lin, E.C. and Huang, E.T.S. The Effect of Rock Wettability on Water Blocking During Miscible Displacement, SPERE (May 1990) 205-12,... 

Here, fa is dimensionless time, f is time, is porosity, k is permeability, Oo/w is interfacial tension, IFT, fi , is viscosity of water, and L is block dimension (length). They assumed that gravity effects are negligible, and that the shape of the matrix blocks, wettability, initial fluid distributions, relative permeabilities, and capillary pressures are the same. From equation 4 it is seen that the imbibition rate decreases if interfacial tension decreases. 

Several methods are available to determine the physical parameters of polymer surfaces. Biomaterials penetrate liquids like blood or water present in soft tissue. It is known that the free surface energy at the biomaterial/water interface is the driving force for the reorientation processes of the polar groups of the uppermost molecular layers of the polymer surface towards the aqueous phase. The chemical composition of the surface of the biomaterial is different depending on its contact with an aqueous medium or with air. Hydrophilic domains of polymer systems like those found in block copolymers, for example, are mostly located at the aqueous interface, while the hydrophobic ones tend to remain at the air interface. The investigation of surface wettability by means of contact angle determination and the measurement of the streaming potential ( -potential) is of special interest in the characterization of the polymer surface. 

H2S reacting with nickel can block electrochemically active sites for the hydrogen oxidation, can change the wettability of the anode toward carbonates, can modify the anode surface and its porous structure, can alter the anode conductivity, can change the carbonate conversion to sulfate and can poison catalytic sites for the water gas shift reaction. 

The modification of the surface properties of polypropylene and block copolymer is carried out by ozone treatment. Thus, the wettability of the polymers is improved - the contact angle of water becomes < The... 

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