Effectiveness Log Evaluation of Low Porosity and Low Permeability Sand Reservoir in Xujiahe Group of Hechuan Gas Field

Xujiahe Stage Second Segment(Tx2) formation is a low porosity and permeability or extra low porosity and permeability sand reservoir in Hechuan gas field.Logging evaluation of the reservoir effectiveness is important and difficult.Analyses results about this reservoir show that: interstitial material of Xujiahe Stage Second Segment(Tx2) reservoir rock is complicated and lithology is fine;reservoir properties are not good;formation water is high salinity and there is thick water film;they have great impacts on the reservoir effectiveness.Combining test data with the conventional and special logging data provides four indicators,such as reservoir pore structure,reservoir characteristics,percolation and fracture development.Then they were comprehensively used to evaluate the reservoir effectiveness,and the evaluation indicators can be used to determine production capacity of gas wells in the studied area.Practical application in 38 wells of Hechuan area shows that reservoir effectiveness evaluation result has good consistency with different well capacity types,and it provides important decision-making basis for oil production.