Identification Of Low-Permeability Gas-bearing Formation Using Conventional Logging Data

The conventional hydrocarbon reservoirs are very limited in China, and the prospecting is becoming more and more difficult for the conventional reservoirs. So people begin to regard the exploration and production of compact and deep hydrocarbon reservoirs. About 50% of total reservoirs are compact and deep hydrocarbon reservoirs in China. The Tabamiao region in north Ordos basin and Shiwu depression of southern Songliao basin are all of compact sandstone gas reservoir. For compact sandstone gas reservoir of upper Palaeozoic, we develop some applied researches. The point of these researches is using manifold conventional logging data and methods to distinguish the gas reservoir, and to evaluate the reservoir's parameter of compact sandstone gas reservoirs correctly. Through analysis the data of log and core sample, it was indicated that the physical property of reservoir bed is one of main factors for gas control. Sonic logging, density logging and compensated neutron logging has different character of response in reflecting the porosity. In processing, we used the core sample analysis porosity to standardize the curve of sonic differential time and curve of density logging. Through regression analysis build the logging interpret model of region porosity and prove its prominent feature. Using the method process and interpret logging data of Tabamiao region in north Ordos basin, finding the conclusion of interpret is inosculated with testing result.As the logging interpret model of grouping don't consider the relation between logging curve and reservoirs, so in the third chapter we used principal factor analysis method discussed the relativity between principal factors and logging curve, and research the relation between principal factor and lithology. The theory of principal factors analysis method is get new synthetically variable from many old variables with complicated logging character parameters. And the information quantum of principal factors is descending with factors' arrange sequence; therefore we can neglect subordinated information, and only pick the main factors. Using this method processed logging data of Tabamiao region in north Ordos basin, we find all logging curve can reflect different geology information in every principal factor. Nowadays, the applications of logging data not only calculate porosity, permeability and saturation, but also using synthetically all logging data develop elaborately interprets for reservoir. As every logging response comprises many information of differ substance from formation. So, it is chief question how build a fit model and get diversified logging response for interpret and estimate the reservoir. In addition, reservoir is a nonuniform body, it is controlled by many complex geology factors, it has many character parameters, and there are some complex relations among these character parameters. So it is very important that qualitative describe and synthesized estimate the reservoir for compact sandstone gas reservoir. In this paper we put forward the distinguish index method, it can get information of gas reservoir in all kind of logging data, and synthesize these information, so we can obtain a synthetically gas reservoir index. The application of this method is very good in south Songliao basin.