Sichuan ~ Kawaminami Transition Zone River Private Use Area Xujiahe Sec,, Sec Effective Reservoir

The reservoir with high quality could grow in the"the sweet dessert zone"cluster-block alike among the one with low porosity and permeability in horizontal plane in the Xujiahe formation,upper triassic system of Hebaochang area,central Sichuan-South Sichuan transitional belt.Under the guidance of new principles and methods of stratigraphic geology, sedimentology,reservoir geology,based on core anlysis and logging interpreation,through the analysis of propertity and fine comparison of effective reservior,the lower limit of effective reservior was studied and advantageous exploration development sub-area and section was indentified and selected.Based on predecessor' previous research results,formation comparison between external and internal stratum in the targer area and the sequnce in the Xujiahe formation of Sichuan basin were seperrated in to six members according to lithology and logging and then it was taken into detailed final sorting.After repeatedly rebuilded and reallocated by wave and lake -rive,the fragmentary material that had been carried to lake through alluvial fans and rivers,formed beach -dam face sandstone along seacoast and alongshore,swamp containing coal developed shallow-shore sub-enviroment.The reservoir space are mainly remainder intergranular and secondary dissolved pore and the type of reservoir space is small pore and thin throat,which is so sensitive to compacting stress and water blocking.By means of method for testing least pore throat radius,correlation method by mercury penetration analysis,activate pressure gradient allocation metod,binding water film mensuration,water saturation and porosity correlation and water saturation phase,permeability combined method and mercury saturation under sequece compacting,porosity lower limit of reservior was determined(T₃X₄6%,T₃X₂8%)which was applied to assort and appraise reservoir. lower limit of least throat radius using gas imbibition binding water film mensuration is gained(averaged 0.0245μm of T₃X₄,averaged 0.0233μm of T₃X₂)which has very good uniformity with the result(0.0278μm by nuclear magnetic resonance experiment,binding with the relationship of permeability and mean radius,the permeabilty of T₃X₄ and T₃X₂ was 0.15×10^-3μm²and 0.18×10^-3μm²respectively and the porosity of T₃X₄and T₃X₂was 5.62% and 8.13%respectively;the bound water saturation of T₃X₄ and T₃X₂ was 40.5%with experimental analysis of gas-waterreiative permeability and 36.5%respectively;lower limit of gas saturation is 30%and one of gas saturation which can have industrial producing is 60%.With study on stress sensitivity,the damage of permeability is lower than 50%in the process of crocking up development which is to say stress sensitivity weak or medium.The permeability damage relation of dry sample and wet sample showed that when the permeability is lower than 0.3×10^-3μm²,correspondingly loss ratio of stress sensitivity was descending gently,so the lower limit of permeability of reservior with much water contained was identified as 0.3×10^-3μm².Through the capacity simulating,under the differential producting pressure condition industrial volume of producing reserves could be achieved.Under the producing presurre is 5MPa and accumulative thickness is changing from 10m to 15m,it will be effective and avilable for 2^ndmember when the porosity is above 9.6%and the permeability above 0.1×10^-3μm²;also effective and avilable for 4^thmember when the porosity is above 4%and the permeability above 0.02×10^-3μm².Last is not least,the lower limit of effective reservior is restricted and defined by the elements of heterogeneity and available thickness altogether.According to the parameter of property and pore structure and analysing results on the effctive reservior,the reservoir were classified into 4 types under the comprehensive consideration.And theⅠ-Ⅱsecondary reservior developed in the 2^ndmember(T₃X₂)and theⅢ-Ⅱsecondary reservior developed in the 4^thmember(T₃X₄)where the advantageous bed well growed in the 4th sub member(T₃X_4¹)comparatively where the advantageous bed well grow in the 2^ndsub member(T₃X_2²)which is to say the advantageous reservior developed in the middle bottom of the 4^thmember(T₃X_4¹)and upper part of the 2^ndmember(T₃X₂).In a word,the degree of reservior development are different among the secondary structures and well segments in vertical section and it presents sandbody cluster- block alike in horizontal plane,which led to gas-water distribution so complex.And so,the further exploration and development should attach importance to "the sweet dessert zone "cluster- block alike in horizontal plane.