Geological Analysis On Shale Gas Accumulation Of Well Yuye1

Marine shale in the north China are characterized by wide distribution area, large thickness and high thermal evolution, but the shale gas resource potential need to be further confirmed as the complex geology and topography conditions and the large variation extent of gas bearing. The Well Yuye1 in the Southeast of Chongqing reveals the shale development and conservation conditions of Longmaxi formation, Lower Silurian in the uplift area. Theory research on shale gas based on core drilling has been conducted in this paper, and the large potential of shale gas in the study area has been demonstrated.The drilling of Well YY1(325.48m) shows the 220m-thickness black shale of Longmaxi formation, Lower Silurian. Concerned to this well, Core analysis indicates that the sediment system of the black shale is mainly the neritic shelf and the REE analysis indicates that the structure background of the black shale are mainly the continental island arc and the active continental margin, and the parent rock mainly sedimentary rock and the granite.A large number of experimental analysis shows that, quartz and the clay minerals are the main composition of the black shale of Well Yu Shale 1; the kerogen type is mainly the Type III, and the TOC and the maturity are respectively 3.23% and 2.13%; the black shale is rich of fractures and pores. reservoir space are mainly the micropores of inter grains and the structure fractures with the mesopore of 2-5nm. the porosity and permeability are respectively 2.5% and 0.01mD. The above conditions show that there exists shale gas accumulation conditions in YY1.The main factors controlling the gas bearing of YY1 has been analyzed in this paper. It can be shown that both the TOC and the mineral composition content of quartz and pyrite have the positive correlation with gas absorption quantity, and the clay mineral which is lack of montmorillonite with large specific surface has little affect on gas absorption quantity. The carbonate is mainly the cement form which results the declining gas absorption quantity, and the density has a negative correlation with gas absorption quantity. Free gas is mainly affected by the development degree of pores and fractures, and the pores and fractures development is controlled by mineral composition, structure activity and the hydrocarbon generation, which are also the main factors on gas absorption quantity of Well YY1.All the parameters can be filtered by standardized processing, then analyzed by cluster analysis and multiple regression analysis to obtain the quantitative relationship between the multiple parameters and the gas absorption quantity. According to the analysis results, TOC is the main factor on gas absorption quantity, and secondly are the content of quartzs, pyrite, clay minerals which are all affected by sediment environment. All the above results can be used to the shelf formations of Upper Yangtz area.Based on multiple methods and comprehensive analysis, the gas absorption content of Well YY1 can be speculated as 0.05~5m3/t with mean value 1.68m3/t. The gas absorption content of segment 240-275m (the 2-3 strata of the standard section) is more than 2.5m3/t, which is the favorable segment for the further research. The gas content / predicted reserves of Well YY 1 is estimated to 749.8×104m3.