Quantitative evaluation of fault lateral sealing

摘要

Fault sealing mechanism mainly has two types including capillary seal and hydraulic seal. Capillary seal is the most common type, relying on the capillary pressure difference between fault and reservoir. Fault lateral seal types are divided into juxtaposition seal, fault rock seal and cementation seal according to the internal characteristics of fault zone. Fault rocks seal are classified into three categories depending on the content of shale or phyllosilicates of the faulted horizons, including cataclastic rock seal when it is less than 15%, phylloslicate-frame rock seal when it is between 15 to 40% and clay smear seal when it is greater than 40%. However, different seal types have different evaluation methods. Allan diagram and Knipe diagram provide methods to assess juxtaposition seal. But we use SGR algorithm to calculate the fault zone shale content to quantitatively evaluate fault rocks seal. Across fault pressure difference is increasing with increasing SGR, and the fault forms effectively seal, when the SGR reaches a certain number.