Factor analysis is a variable quantitative simplification technique, whose purpose is to decompose the original variables and summarize the potential "categories". The indicators with strong correlation are classified into one category, and the correlation of variables between different categories is low. Each kind of variable represents a "common factor", that is, an internal structure, and factor analysis is to find this structure. There are many kinds of analysis methods, the most commonly used are two: one is principal component analysis; The other is general factor analysis. The so-called factor analysis refers to the general factor analysis, which constructs factors through the variance of original variables. Generally speaking, the number of factors is always less than the number of variables. Therefore, for general factor analysis, how to correctly explain the factors will be more difficult than principal component analysis.

Factor analysis can generally be divided into four steps:

Investigate the correlation between variables and judge whether to carry out factor analysis;

After analysis, the number of extraction factors is determined according to certain standards, and the eigenvalue is generally required to be greater than1;

Investigate the interpretability of factors, rotate if necessary, and find the best explanation;

Calculate intermediate indicators, such as factor scores, for further analysis.

Using factor analysis, we can compress the messy original data collected, find out the most important factors, and sort them out according to their causes, find out several main lines, and help analyze the main control factors of fullness.

In this study, 354 lithologic traps were counted, and 249 traps participated in statistical analysis and calculation. Because the failed traps can't participate in factor analysis and the establishment of fullness prediction model, there are 222 lithologic oil and gas reservoirs that actually participate in analysis and prediction. After preliminary geological analysis, the average porosity is selected as%; Average permeability,10-3 μ m2; Hydrocarbon expulsion intensity,104t/km2; Plane distance from hydrocarbon expulsion center, km; Vertical distance from hydrocarbon expulsion center, m; Formation pressure coefficient; Sand body thickness, m; Sand body area, km2；; Abundance of organic matter,%; Thickness of surrounding rock, m; Average buried depth, m; A total of 1 1 geological parameters were analyzed by factor analysis.

In this study, different reservoir-forming systems are developed, and their fullness prediction models are established, which are verified by back generation. The reservoir-forming conditions of lithologic oil and gas reservoirs in the same reservoir-forming system, such as source, reservoir, cap, circle, migration and preservation, influence, restrict and are closely related. Lithologic reservoirs in the same reservoir-forming system are divided into structural-lithologic reservoirs and lenticular reservoirs for prediction.