Degree of Water Lock Damage and Influencing Factors in Tight Carbonate Reservoirs

Tight carbonate reservoirs are widely distributed and contain enormous hydrocarbon potential. However, issues such as insufficient hydrocarbon charging and water blocking damage in tight carbonate reservoirs severely restrict efficient development of these reservoirs. Taking the carbonate reservoirs in the northwest Qaidam Basin as an example, this study addresses water blocking damage in local reservoirs through natural core flow experiments. By analyzing changes in oil-phase permeability before and after water-phase invasion, calculating the water blocking damage coefficient, and evaluating the degree of water blocking damage, the influencing factors of water blocking damage were systematically analyzed. Experimental results show that the average permeability damage caused by water blocking in the study area reaches 62.20%, belonging to the medium damage. The degree of water blocking damage is closely correlated with capillary force: when water invades the reservoir, increased capillary force during continuous oil flow through pore throats enhances seepage resistance, directly affecting oil-phase seepage and charging processes. This research not only provides critical guidance for developing carbonate reservoirs in the study area but also offers new insights into studying and preventing water blocking damage in unconventional reservoirs.