The Study On Well Logging Evaluation Methods For Low Permeability Reservoir On Lower Karamay Formation In530Well Block Of8th Zone

The reservoir on lower Karamay formation in530well block of8th zone in Junggarbasin is typical low porosity and low permeability reservoir. Because of poor physicalproperty, heterogeneity of lithology and pore structure, it is difficult to identify the lower limitof petrophysical properties, recognize the reservoir type, evaluate the static reservoirparameters quantitatively and identify the fluid properties qualitatively. No efficient methodsare found until now. Based on the study of evaluation methods in low permeability reservoir,geological data, core analysis data, test data and well logging data collected, and according tothe study of petrophysical property lower limit, four characteristics of the reservoir on lowerKaramay formation in530well block are studied. Reservoir is classified by productivityindex and well logging method of identify reservoir types is developed. According to theprinciples of core calibrating logging and dynamic state calibrating static state, well loggingevaluation methods on static reservoir parameters and fluid property are established.Firstly, four methods including oil-bearing occurrence, statistics experience, minimumflow pore throat radius and cross plot of porosity vs permeability are used to study onpetrophysical property lower limit of the reservoir on lower Karamay formation in530wellblock of8th zone in Junggar basin. The lower limit of porosity and permeability of thereservoirs are7%and1.0×10-3um2(See section2in chapter2). Secondly, to identify theheterogeneity of lithology and pore structure in reservoir, the reservoir is classified as twotypes by cross plot of fluid production index per meter vs physical parameter (See section1in chapter3). Reservoir Ⅰ is bold skewness glutenite reservoir (fluid production index permeter PI>0.2m3/(d·m·MPa), and comprehensive physical parameter Z <0.028). Reservoir Ⅱ is fine skewness sandy conglomerate reservoir.(fluid production index per meter PI>0.2m3/(d m MPa), and Z <0.028). Well logging identification criterion is established by themethod of principal component analysis (See section2in chapter3), which lays a foundationfor well logging model and evaluation of reservoir. Thirdly, porosity models, permeabilitymodels and saturation models are established according to the principle of core calibratinglogging (See chapter4). The model precision is studied and result shows that the porosityabsolute error is lower than10%and the permeability error is lower than one order ofmagnitude. Finally, based on the principle of dynamic state calibrating static state, the methodon identification of fluid property by well logging and criterion using physical property,oiliness and electrical property to recognize oil-water layers are established (See chapter5).And effect of identification of fluid property is studied by3examples of oil-water layer.Application effect shows that, based on reservoir characters of geology, exploitation andelectronicity on lower Karamay formation in530well block of8th zone, the methodsdeveloped in this study which include petrophysical property lower bound identification,classification of reservoir types, recognition of reservoir types by well logging, quantitativeevaluation of static reservoir parameters and qualitative identification of fluid property canmeet the requirement of evaluation precision for low porosity and low permeability reservoir.This can provide technical support to efficient exploration and development of the reservoir inthis zone.