We show that the morphology of a thin polymer film spin coated directly on to a topographically patterned substrate is strongly influenced by the wettability of the substrate, in addition to other well-known parameters such as concentration of the polymer solution (c(n)), spin speed (RPM), and spin duration. Similar to spin coating on a flat surface, (1, 2) on a topographically patterned substrate as well, a continuous film forms only above a critical polymer solution concentration (c(t)*), for a specific RPM and dispensed drop volume. It is believed that for c(n) > c(t)*, the resulting continuous film on a topographically patterned substrate has an undulating top surface, where the surface undulations are in phase with the underlying substrate patterns. (3) On the basis of experiments involving spin coating of polymer thin films on topographically patterned grating substrates, we show that the surface undulations on the film are in phase with the substrate patterns only when the substrate is completely wetted (CW) by the solvent. In contrast, when the substrate is partially wetted (PW) by the solvent, then the undulations are 180° out of phase with respect to the substrate patterns. We further show that for c(n)< c(t)*, a variety of ordered and disordered structures, like array of aligned droplets, isolated strips of polymers, etc., result on both CW and PW substrates, depending on c(n).

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAs reservoirs mature, understanding the source and reversibility of any formation damage is particularly critical for sustaining production. The 26R Reservoir at Elk Hills contains a substantial oil column. Gravity drainage is the primary recovery process of this remaining oil in place. Recently, two horizontal wells were successfully drilled through the bottom of the oil column to enhance gravity drainage. Subsequent testing revealed drilling fluids leak off will create a wellbore skin; reducing permeability and production potential by over 90%. This paper will review analytical calculations and assumptions used to determine well production potential and discusses extensive core description and core flow work completed. The core work has validated production potential assumptions. The extensive core description work and core flow tests has generated a better understanding of rock and mineralogical properties, at a pore level. Cores were exposed to various drilling and workover fluids and stimulation procedures. Treatment effects were then measured via return permeability tests and then further evaluated by preparing contaminated core thin sections and using a scanning electron microscope. Workover fluids are now more carefully applied during well remedial operations. In addition, the core work has modified acidizing and perforating procedures. Follow-up well treatments have shown promise by reducing observed skin, and increasing production