| Due to the relatively limited drilling and other relevant data during the exploration stage, the resource and
favorable area evaluation of shale gas have certain specificity. Suitable evaluation ideas and methods should be sorted out
based on the characteristics of the stage. According to the practice of marine shale gas exploration, the content and ideas
of shale gas resource and favorable area evaluation in the exploration stage are systematically sorted out, and the
corresponding resource and favorable area evaluation methods for this stage are clarified. The shale gas exploration stage
is divided into three secondary evaluation stages: play evaluation, target evaluation, and gas reservoir evaluation. It is
believed that the main methods for resource evaluation in the play evaluation stage are gas content analogy, resource
abundance analogy, genesis method, and comprehensive method. The main methods for target evaluation stage are gas
content volume method, gas content analogy method, resource abundance analogy method, and comprehensive method.
The main methods for gas reservoir evaluation stage are gas content volume method, gas content volume method+gas
saturation volume method and comprehensive method. Taking the Wufeng Formation-Longmaxi Formation in the
Jiaoshiba area as an example, a system of analogy parameters for the total gas content and resource abundance of marine
shale gas is established. This system can further improve the important aspects of analogy that still have shortcomings.
The methods for shale gas favorable area in the exploration stage can be summarized into two main methods:
comprehensive parameter superposition analysis method (stacking map method) and parameter normalization quantitative
evaluation method. The two favorable area evaluation methods are applicable for both play evaluation and target
evaluation, with the main difference of the differences in parameter types and quantities in the evaluation parameter
system. In view of the emphasis on the evaluation of shale gas formation and enrichment conditions (geological
conditions) and fracturing high production conditions (engineering conditions) in the play evaluation stage, a dual factor
play evaluation parameter system of “geological conditions-engineering conditions” has been established. In the stage of
target evaluation, it is necessary to consider the evaluation of economic benefits and further enrich the parameters. A three
factor target evaluation parameter system of “geological conditions-engineering conditions-economic conditions” has
been established. At the same time, the evaluation parameters in terms of hydrocarbon generation, preservation, resources,
and geostress have also been further deepened. The established play evaluation and target evaluation parameter system can
better reflect the characteristics of the evaluation stage and meet the corresponding evaluation needs. |
