Skin evolution

The relative skin (5 - S0) evolution with respect to the cumulative acid volume is given in Figure 3 (solid line). Peaks at about 0.5 and 3.5 m3 are artifacts due to hammering effects following rapid variations of the injection rate. According to Equations 6 and 13, the skin evolution, if the formation were a primary porosity one, should be ... 

Figure 5 Actual skin evolution during treatment of Well B.

Because of the highly unstable nature of the acid attack in most of the carbonate reservoirs (propagation of wormholes), the development of a descriptive model of the skin evolution was not possible until the recent advent of the theory of fractals. In addition, the characteristics of the damaged zone greatly affect the behavior of the skin during acid injection in any type of reservoir, but particularly in carbonate ones. 

Although Mg is generally considered non-toxic, the inhalation of fumes of freshly sublimed Mg oxide may cause metal fume fever. There is no evidence that Mg produces, true systemic poisoning. Particles of metallic Mg or Mg alloy which perforate the skin of gain entry thru cuts and scratched rilay produce a severe local lesion characterized by the evolution of gas and acute inflammatory reaction, frequently with necrosis. The condition Has been called a chemical gas gangrene . Gaseous blebs may develop within 24 hrs of the injury. The lesion is very slow to heal (Ref 23)... 

Sytsma, K. J., Smith, J. F. and Berry, P. E. 1991. The use of chloroplast DNA to assess biogeography and evolution of morphology, breeding systems, and flavonoids in Fuchsia sect. Skin-nera (Onagraceae). Syst. Bot. 16 257-269. 

Dixson A.F. (1983). Observations on the evolution and behavioural significance of sexual skin in female primates. Adv Stud Behav 13, 63-106. 

The determination of the evolution of the permeability of these rocks during acidizing is necessary when attempting to predict the evolution of the skin (Equation 2). Previous studies (6) have tried to model the shift of the pore size distribution due to acid attack. Then, permeability profiles were computed by integrating the contributions to the overall flow of each of the rock pores, all over the considered volume of rock. The main limitation of this method lies in the disregarding of the spatial correlation between rock pores. 

Matrix acidizing treatments are more often performed, nowadays, with sensors and data acquisition systems continuously recording the surface pressure and rate histories. According to a recently proposed methodology (15), these records can be used to compute downhole rate and pressure evolutions. The bottomhole pressure history is then compared to the theoretical response of an equivalent reservoir wherein a non-reactive fluid would have been injected according to an identical rate schedule. Following this method, the difference between both theoretical and actual pressure responses originates from the evolution of the skin of the true reservoir under the influence of the acid attack. Equation 1 is then used to derive the skin decrease from this pressure difference. 

The present study should be seen as a step in the evolution of the colloidal morphology of phase inversion membranes, which conceptually began with dense polymer films and diverged into the two principal branches skinned and skinless membranes (Figure 1). 

Innate or nonspecific immunity has probably developed during evolution and includes anatomical barriers such as the skin, cilia in the lungs, and bronchial tubes, as well as the presence of specific components in specialized tissues that combat invasion. 

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