The Sedimentary Facies And Sand Body Distribution Law Of Upper Tenggeer Formation In Wengte Area

Baiyinchagan depression,located in the north of Chuanjing depression on the west margin of Erlian basin,is a Mesozoic sedimentary basin.The western sag is the key oil and gas exploration object in the whole Baiyinchagan sag,which is rich in oil and gas resources.At present,it has been found that there are several oil blocks,such as Sanghe and Wengte.In view of such problems as unclear provenance direction,uncertain sedimentary facies and sedimentary system type,complex lithology and unclear characteristics of petroelectric response in Tenggeer formation,the main target member of Wengte formation,Baiyinchagan sag,we study on the stratigraphic division and correlation,sedimentary system and facies,paleogeomorphology and provenance direction,sand body distribution and other contents of the upper member of Tenggeer formation in Wengte area this time.Under the control of typical sequence interface,the methods of marker layer,skeleton section and cycle control are used to carry out stratigraphic correlation.The isochronal stratigraphic correlation framework of the whole area is established by using the method of well seismic combination to calibrate the stratigraphic correlation results,and the upper section of Tenggeer formation is divided into three sand formations.Using the methods of heavy mineral data,geophysics and sedimentology,the provenance of the upper member of tengger formation is determined to come from the southeast direction.Through core observation and description and petrological study,it is realized that the sedimentary system of the target member includes alluvial fan,fan delta and braided river delta.But the sedimentary systems in this area are mainly braided river delta sedimentary systems and the subfacies is the delta front.The characteristics of stratigraphic electrical response in the target interval are unclear.According to the characteristics of rock electrical response,natural gamma ray,well diameter and acoustic time difference curves are selected as the basic curves for logging facies analysis,sedimentary facies study and sand body identification.Based on the analysis of core facies and logging facies and the study of the distribution of profile facies and plane facies,it is determined that the sedimentary microfacies in the target section are mainly three types of microfacies: distributary channel,sheet sand in floodplain,sheet sand in leading edge and distributary stream bay.The natural gamma ray amplitude of some well sections is abnormally large,but the well diameter curve is severely enlarged,so the sandstone identified by reading the half-amplitude point of the natural gamma curve is not completely correct.According to the characteristics of formation electrical response,the lithology is identified by combining natural gamma ray with borehole diameter and acoustic time difference curve in the process of sandstone identification,which solves the problems encountered in the process of sandstone identification.