| The paper is guided by the theory of petroleum geology and geochemistry,and through the data collection,X-ray diffraction,rock pyrolysis test,microscopic sheet observation and other.technical means,the 44 wild profiles of the Bole Basin and the samples of the BoYe-1 well are carried out.Test analysis,comprehensive study of shale gas accumulation conditions and mechanisms in the Bole Basin,establishment of research area accumulation model and preliminary delineation of favorable areas for shale gas exploration.On the basis of previous studies,comprehensive field exploration and other means to analyze the development law of the Lower Carboniferous shale in the basin,and it is believed that the Lower Carboniferous shale in the basin is widely developed,The cumulative thickness of the shale in the lower subgroup of the BoCan 1-Bole city area where is in the deep water shelf phase can reach 400m.The organic matter characteristics of the Lower Carboniferous shale in the basin are comprehensively analyzed by means of organic carbon test and rock pyrolysis test.The results show that the Lower Carboniferous mud shale The organic matter abundance is high,the TOC content is 1.1%-9.82%,the average is 3.6%,the TOC content of most samples is more than 2.0%,the organic matter type is mainly type II2 and type III,and the organic matter thermal evolution maturity is high,The shale vitrinite reflectance of Akeshake is 1.14%-4.01%,with an average of 2.4%.The span is large,and the whole has reached the mature stage.It is mainly in the early stage of high maturity-over-maturation,and the gas conditions are superior.The field samples and cores were analyzed by X-ray diffraction,porosity and permeability test.The results show that the content of quartz and clay minerals in the lower shale mineral shale is relatively high,which is a high-brittle mineral content.Rock;porosity is 0.36%-4.72%,with an average of 1.7%,compared with the shale porosity of the US shale gas field?4.22%-6.51%?and the shale porosity of the Sichuan Basin?0.47%-14.90%?.The shale porosity of the Akeshake formation in the study area is low;the permeability distribution range is between 0.00086×10-3?m2-0.0241×10-3?m2,with an average of 0.0057×10-3?m2,and the permeability of all samples is less than 1×10-3?m2,compared with the United States(average 0.049×10-3?m2)and the Sichuan Basin(average 0.0323×10-3?m2),the permeability of the shale in the study area is much smaller than the two.The reservoir space types are mainly composed of dissolution pores,micro-fractures,intergranular pores and organic pores,and the reservoir performance is good.Combined with pore permeability parameters and fracture pore development characteristics,it is believed that the Akeshake formation shale reservoir belongs to low porosity-extra-low pore and ultra-low permeability reservoirs,but due to the high content of brittle minerals in rock mineral components,pressure The cracking stage is easy to form cracks,so the reservoir still has certain development potential.The Lower Carboniferous organic-rich shale in the Bole Basin is dominated by gas at the beginning of the low-maturation stage.The gas is adsorbed in the source rock formation.The limestone and tuff developed from the upper and lower shale layers have shale gas.The vertical plugging effect,combined with the extensive development of the reverse fault zone in the zone,is highly closed and prevents the lateral escape of the gas,thereby forming shale gas accumulation in the Bole Basin.The area of BoCan1-Bole City in deep water continental shelf is characterized by large single-layer thickness of mud shale,good geochemical index of source rock,and the development of reverse faults with good sealing performance?limestone-tuff?roof and floor as well as the prevention of lateral gas escape.Therefore,it is considered that this area is an advantageous area for shale gas exploration in Bole basin. |
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