Lower Cretaceous Sanjiang Basin Shale Gas Reservoir Geology Conditions In Eastern Heilongjiang Province

With the rise of "green energy revolution",governments and energy companies have increased the exploration and development of shale gas,China's shale gas followed the rapid development and rise of North America,all kind of study has confirmed that China's shale gas is rich in resources,Shale gas resources have great potential.As a Mesozoic typical superimposed basin,the study of the potential successor shale gas is of great significance to the economic development of the Sanjiang basin,and can guide the development of other Mesozoic continental basins.In this paper,the source rock characteristics,reservoir characteristics and main influencing factors of shale gas are studied by summarizing the successful experiences of previous research and conventional oil and gas resources development.Based on the relevant parameters obtained from the successful exploitation of the shale gas basins in North America,the relevant parameters of the shale gas accumulation in the Sichuan Basin were evaluated and evaluated.The organic matter characteristics of the Lower Cretaceous Chengzihe Formation and Muling Formation in the Sanjiang Basin were studied by means of geochemical method,organic carbon test,rock pyrolysis test and fluorescence microscope observation.The results show that the overall organic matter abundance of shale is high,with the type III and II2 organic matter,the hydrocarbon generation potential is good and the thermal evolution maturity of organic matter is high.The organic matter abundance TOC of the shale of Chengzihe Formation is between 10.6 and 12.96%.The average TOC of muddyshale in Muling Formation is between 0.20% and 3.83%.The Tmax parameter of Chengzihe Formation is higher than that of Mullin group with higher organic matter thermal evolution maturity.The sedimentary environment is used to study the sedimentary environment,which indicates that the shale gas source rocks in the Sanjiang basin are mainly distributed in the subfacies of the shallow lake and partly in the marsh facies and semi-deep lake subfacies.The distribution of dark shale shale is wide and the depth is thick,because the basin is relatively larger during the Chengzihe Formation,so the Chengzihe Formation has a wider range of shale distribution in the depth.The characteristics of source rock reservoirs in Chengzihe and Muling groups were studied by means of X-ray diffraction,low-temperature nitrogen adsorption experiment,porosity,permeability test and field emission scanning electron microscopy(SEM).The results show that there are four kinds of lithofacies in the reservoir,four kinds of pore types(organic matter pore,clay mineral pore,rock skeleton mineral pore,microcrack),two kinds of minerals(brittle mineral content of 49 ~ 54,clay mineral content 24 ~ 30%)and the four sides open the crack-shaped hole and the narrow end of the larger open degree of wedge V-shaped hole.The porosity of Chengzihe Formation and Muling Formation is between 1.23 and 18.65%,the permeability distribution is less than 0.01 ×10-3?m2,and the average permeability of Chengzihe Formation is higher than that of Mulian Formation.Based on the comparison of the characteristics and reservoir capacity of Chengzihe Formation and Muling Formation,combined with the characteristics of shale gas self-generated storage,it is preferable that Chengzihe Formation is a favorable evaluation interval.The slag TOC of Chengzihe Formation is relatively high,the seepage capacity is better,the content of quartz is higher,the mineral content of carbonate rocks is lower,and it is easier to form fracturing and later transformation.At the same time,the sedimentary thickness of the Chengzihe Formation is wide,the deposition thickness is large and the organic matter maturity is high.According to the completion report of the Bincan1# well,the dark mud shale in the Chengzihe Formation has a gas containing layer with a methane content of more than 80%.Comprehensive optimization of Chengzihe Formation is afavorable stratigraphy for shale gas accumulation.Based on the relevant test data of conventional oil and gas exploration in the Sanjiang basin,the relevant parameters of shale gas source rocks and reservoirs can be compared with the successful exploitation of shale gas in North America.The preferred Chengzihe Formation in Suibin depression of Sanjiang basin is Shale gas accumulation is favorable target area.