Quantitative Evaluation Method Study Of Medium-deep Gas Reservoir And Source Rock

As the need of national economy development, the medium-deep coal-formed gas reservoir becomes gradually the main trend for exploration in most oil fields. Therefore, it is important to evaluate the medium-deep gas reservoirs quantitatively based on the research in gas source rocks.This paper begins with the evaluation of coal beds, generalizes the statistics characteristics for logging responses of coal beds in key wells and realizes the automatic identification of coal beds by crossplot method; then presents the quantitative computing methods for parameters such as coal components, porosity, permeability, gas content and so on. It's suggested that coal rank is classified by carbon content and the gas content also depends on carbon content, so the Langmuir equation is modified, the methods verified by geochemical analyses, experimental analysis and well test data, etc. Based on this, a suit of quantitative evaluation methods for coal beds is developed, which has good identification results and believable computations.On the basis of above studies, this paper evaluates the medium-deep gas reservoirs. The statistics characteristics of logging responses are compared between the medium-deep and shallow gas reservoirs, and the conventional well logging identification methods are generalized. Then, the porosity of gas formation has been fine evaluated using hydrocarbon correction or crossplot method according to the lithology distribution. In order to calculate the gas saturation more accurately, the Kukal method is tested by four wells' experimental data, the comparison between porosity recalculated by Kukal and core porosity shows that they have good correlation and approves the accuracy of Kukal saturation indirectly. Finally, the quantitative evaluation program is developed and shows effective in practical applications.