Studies On Distribution Regulation Of Sandbody Of He₈ And Shan₁ Section, Sulige Gas Field Of Ordos Basin

Basaed on predecessor's achievements,guided by the theory of sedimentology, sequence stratigraphy,sedimentology, geophysical, petroleum geology, for the purpose of offering service to the oil and gas exploration and development,based on outcrops,well logs and seismic data of Shan1 and He8 section in Ordos Basin,combined with lithostratigraphic division with existing programs and principles of sequence stratigraphy base-level cycles,the passage analyzed the sedimentary system,sequence stratigraphy,sequence litho-paleogeography comprehensivly.(1)The passage carded every identifications of stratigraphic units inShanxi group-Xiashihezi group,built division plan of small layer in Sulige area.divided the first section of Shanxi group intoShan₁³,Shan₁²,Shan₁¹.(2)Based on the information surrounding outcrops of study area,drilling cores in basin,logging data,seismic data and analysis of test data,the passage study the facies of Shan1-He8 in Suliga systermly.The results shows that the study area river facies and delta facies.(3)Based on the the information surrounding outcrops of study area,drilling cores in basin,logging data,seismic data,study on the base-level cycles of sequence stratigraphy in the Suliga area descriped styles of Interface causes,characters about base-level cycles of sequence,devidedclass of base level cycle sequences. Accordingly devided He8-Shan1 into 3 long-term cycles,7 middle-term cycles,and the characters and types every middle-term cycles in detail.The results identified 2 basic stytles :asymmetric "deep " upward A stytle and symmetrical C stytle ,and 3 sub-stytles: C₁ stytle,C₂ stytle,C₃ stytle.Middle-term cycle develop C₁ stytle, A stytle partly.Built up framework of base level cycle sequence stratigraphic .(4)On the base of study on detailed sedimentary facies and sequence stratigraphy,the passage draw up lithofacies paleogeography of sequence diagram from Shan1to He8 ,levely and systermly,revealed deposition pattern in different time from Shan1 to He8. Alluvial-delta depositional system widely distributed from north to south in LSC1. Alluvial plain,delta plan, delta front and the former Delta - shallow lake sediments appeared from north to south in LSC2. Continental basin is in LSC3.(5)Taking the long-term cycle as the drawing unit,the passage drawed every period from Shan1 to He8 in north of Erdos basin, depicted the layers of sand body morphology and distribution characteristics accurately, preparated He 8 - Shan 1 sand body thickness contour map. Among them, the Hill Section 1 was deposited, the gas field which is relatively low tectonic activity and source of climate and distance close to the combined effect of erosion area, resulting in the deposition of thin sand thickness, widely developed in the - Coarse-grained sandstone, small gravel, river sand distribution from north to south lanes, showing shallow meandering river delta sedimentary environment of the sand bodies Boot point. 8 segment with regional tectonic activity continued to strengthen, to uplift the northern source area, the seasonal water extremely active sediment supply full and rich clastic resulting in relatively rapid decline in lake level, making the rapid deposition of sediments, braided river Center channel sand continued to promote the lake, and often braided distributary channel diversion, continue to vertical stacking of sand bodies, the plane was blanket large areas, expressed as blanket shallow braided river delta sand body distribution characteristics.