Discussion on Threshold Value of Reservoir Protection in Xihu Sag

The skin factors of exploratory wells in Xihu Sag are 0～80. With the improvement of reservoir physical properties, the skin factor increases firstly and then decreases, which shows that the formation damage in low porosity and permeability oil fields is low, which in medium-high porosity and permeability oil fields is high, and recovery effect of formation damage in ultra-high porosity and permeability oil fields is good. Damage has a certain impact on gas well productivity, but the productivity is mainly related to the physical properties of the reservoir itself. For reservoirs with extremely poor physical properties, productivity can not be effectively released only through reservoir protection and it causes economic losses. In view of the above problems, combined with well testing data, the test method is used to determine the threshold value of reservoir production, which provides theoretical reference for the implementation of reservoir protection. The calculation shows that the lower limit of permeability is 1.19×10⁻³ µm², the lower limit of porosity is 9.81%, the upper limit of water saturation is 46.2%, and the verification coincidence rate is 86.36%. When the physical properties of the reservoir are within the threshold value, it indicates that the reservoir has productivity under natural conditions, necessary reservoir protection measures can be taken; when the reservoir physical properties are not within the threshold value range, it is necessary to consider the reconstruction measures to obtain productivity.