Reservoir damage and types, principles for preventing reservoir damage

The damage mechanism of oil reservoir is mainly divided into chemical damage mechanism and mechanical damage mechanism, and the principle of how to prevent these two types of damage is proposed: according to the characteristics of three types of reservoirs (sandstone reservoir, carbonate reservoir and metamorphic rock reservoir) in China, for sandstone reservoirs, chemical damage mechanism and mechanical damage mechanism generally exist at the same time, and the chemical damage mechanism is the main one. For carbonate and metamorphic reservoirs, mechanical damage is often the main thing, supplemented by chemical damage.

1.Prevents damage from water sensitivity.

According to the laboratory test and theoretical analysis of the three types of reservoirs in China's oilfield, it can be seen that the hydration and expansion of clay, as well as the dispersion and migration of particles, are all related to the chargeability of particles. At a pH of 6 9, montmorillonite, kaolinite, quartz, and hole walls are all negatively charged, and the following suggestions are made to control the repulsion caused by them

1) Improve the salinity of foreign liquid: prevent the hydration and expansion of the clay layer, compress the electric double layer on the surface of the particles, increase the Fan's force, reduce the electric double layer force, and help the particles to stabilize on the pore wall.

2) Use cationic stabilizers: neutralize the electronegativity of particles and pore walls, reduce repulsion, and prevent swelling, dispersion and migration.

3) Use of oil-phase foreign liquids: Stabilize the water-wetted particles in the bound water film.

4) Use temporary plugging completion fluid: try to reduce the filtration loss of foreign fluid.

2.Prevents acid-sensitive damage.

Try to avoid acidification measures, and if forced to do so, use a series of chelating agents to prevent the precipitation of CaF2 and Fe(OH)3.

3.Prevent damage from fouling of oil wells during production.

It is also a chemical damage, and the measures taken: one is to use antiscalants, the other is to supplement the formation pressure, reduce the production pressure difference, and prevent the precipitation and precipitation of CaCO3, Baso4, SRSO4, etc.

4.Principles for the prevention of mechanical damage.

Mechanical damage includes the insention of foreign solids and the transport of particles inside the formation. For high-pore sandstone reservoirs with high and medium permeability and mesoporous fine throat, as well as carbonate reservoirs of fracture-pore type and metamorphic rock (buried hill) reservoirs of fracture-pore type, it is necessary to focus on protecting the pores and fractures to avoid the intrusion of foreign solid particles.

The best approach is to use a temporary plugging type of completion fluid or perforating fluid (oil-soluble, acid-soluble) to reduce the ingress of solids. For the migration of particles inside the formation, the method of particle stabilizer pretreatment can be used. For loose skeleton particles caused by acidification, particulate release can be slowed down by using corrosion inhibitors in combination with particulate stabilizers.