In the comprehensive workflow of oil and gas field exploration and development, the interfacial interactions between reservoir rock and fluids (oil, water, gas) are ever-present. Wettability, serving as the fundamental physical property characterizing this interaction, directly governs the distribution, flow resistance, and ultimate recovery of hydrocarbons within pore spaces. Wettability refers to the ability of one fluid to spontaneously displace another at a solid surface. Typical reservoir wettability classifications include water-wet (rock surface preferentially coated by water), oil-wet (preferentially coated by oil), and neutral-wet (balanced affinity for both).
The innate wettability of a reservoir is influenced by inherent factors such as rock mineralogy, crude oil composition, and formation water properties. Many sandstone reservoirs are originally water-wet, while carbonate reservoirs often exhibit oil-wet or mixed-wet characteristics. However, during prolonged development operations, subsequent factors can lead to unfavorable and often irreversible alterations in reservoir wettability. These include drilling fluid invasion, retained acids or fracturing fluids, adsorption of crude oil’s heavy components (asphaltenes and resins), and water flooding processes. For instance, a water-wet sandstone reservoir may shift towards oil-wet due to asphaltene adsorption, significantly increasing hydrocarbon flow resistance. Conversely, improper management of wettability in an oil-wet carbonate reservoir can result in substantial oil entrapment within pores, markedly reducing recovery. Industry assessments indicate that suboptimal wettability can contribute to hydrocarbon recovery losses in the range of 10% to 35%, with this figure potentially exceeding 40% in complex reservoirs such as low-permeability or tight formations.
Reservoir wettability agents are a category of surface-active substances engineered with specific amphiphilic structures. They are designed to precisely modify reservoir wettability or enhance the interfacial compatibility of operational fluids with the rock matrix through mechanisms like targeted adsorption and interfacial activity. This functionality aids in reducing hydrocarbon flow resistance, mitigating formation damage, and improving displacement efficiency. Today, these agents have become essential chemical components in critical operational stages, including drilling, acidizing, fracturing, enhanced oil recovery (EOR), and fluid transport. They provide vital technological support for maintaining and increasing production in conventional fields, as well as enabling efficient development of unconventional resources.
Post time: Dec-22-2025