Initial production of hydrocarbons is accompanied by the use of natural energy and usually this is known as primary production. Oil and gas are shifted to producing wells on primary production through:
a) expansiónde fluid
b) displacement of fluids
c) gravity drainage
d) hair removal.
When there is no aquifer or injection of fluids, oil recovery should mainly to the expansion of fluid, however crude, this could occur by gravity drainage. The use of natural gas or water injection is called secondary production and its main purpose is to maintain la presión del yacimiento (adición de energía), de modo que el término mantenimiento de presión normalmente se usa para describir procesos de recobro secundario. Cuando el agua procede de un acuífero o es inyectada en los pozos, el recobro es acompañado por un mecanismo de desplazamiento, el cual puede ser ayudado por drenaje gravitacional o expulsión capilar. El gas se inyecta como fluido de desplazamiento para ayudar al recobro de crudo y también como gas cíclico para recuperar condensados. Dicha inyección normalmente modifica la presión de rocío y por lo tanto desplaza el diagrama de fases.
Other displacement processes called tertiary recovery, better referred to as enhanced recovery (Enhanced Oil Recovery, EOR) which is developed for when the child processes are ineffective. Adding additional energy to the reservoir, this process considers changes in rock properties (eg wettability) or fluid (such as viscosity or surface tension). However, the same process is considered for cases where the primary recovery was not used by low potential for recovery. In this case the term Tertiary being misused. In some fields it is advantageous to initiate a secondary or tertiary process before the end of primary production. In these cases the term enhanced oil recovery (Improved oil recovery, IOR) has become popular and some believe that the difference between EOR and IOR is that the latter involves a process re-engineering and reservoir characterization.
THEY MAY In many sites simultaneously operate several production mechanisms, but usually dominates one or two. During the life of the reservoir the dominance may change from one mechanism to another either naturally or artificially. For example, a reservoir volume expansion may cause fluid initially, when this is depleted enough production to wells could be due to gravity drainage assisted by a pumping mechanism. Later, a water injection process can be used to add further impetus to hydrocarbons. In this case the cycle-expansion mechanism is gravitational drainage displacement. In general the production of the deposits is due to the following mechanisms:
1. Water, when presented with water from an adjacent aquifer.
2. Solution gas (line BC in Figure 1.2.a). The gaseous help produce the
liquid phase when the gas tries to free breast oil.
3. Gas cap (no uniform distribution of fluids)
4. Fluid and rock expansion (until the bubble point) Line AB in Figure 1.2.a.
5. Gravity or gravitational segregation, which is common in thick deposits
considerable and have good communication vertical or sites that have high
dip they allow gas migration to the top of the structure .
6. Combined
7. In gas fields have gas depletion or expansion (line DEF in Fig
1.2.a).
Fig. 1.2.a. Classification of Deposits according to the bubble point
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