Shenjia Hydraulics

Release Date:

2022-04-13

Reservoir sensitivity refers to the degree to which a reservoir is susceptible to various types of formation damage. Oil and gas reservoirs commonly contain clays, carbonate minerals, and iron-bearing minerals. During oil and gas exploration and development, at every stage—drilling, cementing, well completion, perforation, production, water injection, workover, and stimulation—the reservoir comes into contact with external fluids and their solid particulates.

Reservoir sensitivity refers to the degree to which a reservoir is susceptible to various types of formation damage. Oil and gas reservoirs commonly contain clays, carbonate minerals, and iron-bearing minerals. During oil and gas exploration and production, at every stage—drilling, cementing, well completion, perforation, production, water injection, workover, and stimulation—the reservoir comes into contact with external fluids and their solid particulates.

Five types of reservoir sensitivity:

1. Velocity sensitivity: This refers to a phenomenon in which changes in fluid flow velocity induce the migration of fine particles within the formation, leading to throat blockage and a subsequent reduction in permeability. Research on velocity sensitivity primarily aims to determine the critical flow velocity of the reservoir and to elucidate the relationship between permeability variations and the fluid flow rate within the reservoir.

2. Water sensitivity: Under the original formation conditions, clay minerals and certain authigenic minerals in the reservoir are immersed in a brine environment of a specific salinity. When fresh water or low‑salinity water enters the formation, the alteration of external environmental conditions can induce these minerals to swell, disperse, detach, and migrate, thereby narrowing or blocking the reservoir’s pore throats and reducing its permeability.

3. Acid Sensitivity: Treating formations with various acid solutions has become a common practice in oil and gas field development and stimulation. This approach can remove acid‑soluble blockages near the wellbore, dissolve rock minerals, enlarge flow pathways for hydrocarbons, and enhance reservoir permeability. However, when acid solutions penetrate the formation, they may react with acid‑sensitive minerals, leading to precipitation or the release of fine particles, thereby reducing formation permeability.

4. Alkali sensitivity: This refers to the phenomenon whereby, upon contact between an alkaline working fluid and reservoir rocks or reservoir fluids, the reservoir’s permeability is reduced.

5. Stress sensitivity: Stress sensitivity refers to the phenomenon whereby a rock’s permeability decreases as effective stress (also known as net confining pressure) increases.

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