Formation damage nature

In most air and gas drilling operations, open-hole well completions are common. This type of completion is consistent with low pore pressure and the desire to avoid formation damage. It is often used for gas wells where nitrogen foam fracturing stimulation is necessary to provide production. In oil wells drilled with natural gas as the drilling fluid, the well is often an open hole completed with a screen set on a liner hanger to control sand influx to the well. 

Mineral acids include hydrochloric acid and blends of hydrochloric and hydrofluoric acid (usually 12% HCl/3% HF). Hydrochloric acid is used to acidize carbonate formations. Its advantages are relatively low cost, high carbonate mineral dissolving power, and the formation of soluble reaction products (which minimizes formation damage). The primary disadvantage of hydrochloric acid is its corrosive nature. 

Piot B.M. Lietard O.M. In Reservoir Stimulation Economides M.J. and Nolte K.G. Ed. Schlumberger Educational Services, Houston, 1987 chapter 12, Nature of Formation Damage 1. 

Steels for WWER-type RPVs are of low-alloyed type, mostly with bainitic microstructure, and thus their radiation damage nature is, in principle, identical with all other RPV steels, with matrix damage, formation of copper-rich precipitates and solute segregation in grain boundaries. Additionally, in materials with a high nickel content, the existence of a late blooming phase is not excluded. 

The primary purpose of matrix acidizing in sandstones is to remove formation damage caused by clay and other siliceous fine particles plugging near-wellbore permeability. Particles may be naturally occurring or may have been introduced into... 

HF reaction is controlled by surface reaction kinetics. HF reacts preferentially with high surface-area particles. It usually spends within a short distance from the wellbore if such minerals are abundant, which they usually are. Treatment typically does not exceed the wellbore by more than 1-2 ft (except in naturally fractured formations), and it can be much less. Nevertheless, removal of very near-wellbore formation damage can result in severalfold increases in well productivity, as indicated by the substantial reduction in productivity resulting from severe, very near-wellbore damage, as shown in table 4-1. 

These treatments were conducted in naturally fractured Monterey shale. Based on DST results, formation damage was suspected. Evaluation of previously unsuccessful acid jobs in the same zones, drilling records, workover data, and laboratory testing suggested that formation damage was due to one or more of the following ... 

There are two basic types of acid treatments applicable to carbonates. They are characterized by injection rates and pressures. Acid treatment with injection rates below formation fracturing pressure is called matrix acidizing. Matrix acidizing is applicable only to formations exhibiting formation damage. There are exceptional cases— in particular, naturally fractured formations— in which acidizing at matrix rates in an undamaged carbonate formation may result in an acceptable stimulation response. 

The cavitation damage in this spacer was due to vibrations from operation of the engine. The localized nature of the damage in this case is an illustration of a common feature of cavitation. Pits formed by initial cavitation damage become preferred sites for the development of subsequent cavitation bubble formation due to the jagged, irregular contours of the pit. This tends to localize and intensify the cavitation process, especially in later stages of pit development. 

It is important to note that we assume the random fracture approximation (RPA) is applicable. This assumption has certain implications, the most important of which is that it bypasses the real evolutionary details of the highly complex process of the lattice bond stress distribution a) creating bond rupture events, which influence other bond rupture events, redistribution of 0(microvoid formation, propagation, coalescence, etc., and finally, macroscopic failure. We have made real lattice fracture calculations by computer simulations but typically, the lattice size is not large enough to be within percolation criteria before the calculations become excessive. However, the fractal nature of the distributed damage clusters is always evident and the RPA, while providing an easy solution to an extremely complex process, remains physically realistic. 

The treatment of an autoimmune disease very much depends on the nature of the clinical outcome it causes. Although the formation of autoantibodies causes the inactivation of the gastric intrinsic factor, the subsequent shortage of vitamin B12 can be easily overcome by supplying it via an parenteral route. Lifelong immunosuppression (with all its side effects) thus is inappropriate. When, however, as in sympathetic ophtalmia, after damage of the first eye the second eye is endangered, an even drastic immunosuppression is mandatory. 

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