Petrophysical Facies Characteristics Of Tight Oil In The W Area Of Ordos Basin

The Chang 6 reservoir in the W area of the Ordos Basin is a typical tight reservoir,and its genetic mechanism is very complicated.In order to clarify the petrophysical facies characteristics of tight reservoir,this paper takes the Chang 6 reservoir of the Yanchang Formation in the W area of the Ordos Basin as the research object,and uses various theories such as sequence stratigraphy,reservoir geology and sedimentology,and combined the data of previous research results,cores observations,the interpretation of logging data and microscopic test analysis to study the sedimentary microfacies and diagenesis in the study area,and to analyze the petrological,physical and microscopic pore structure characteristics of the reservoir,and to summarize the Petrophysical facies characteristics of tight oil in the study area.Finally,the reservoir classification evaluation is demonstrated from the perspective of petrophysical facies.The results show that,the Chang 6 reservoir in the W area is a semi-deep lake-deep lake facies sedimentary environment,mainly developing semi-deep&deep lake mud,turbidite sand et;the lithology is mainly composed of extremely fine-fine grain sandstone with sorting preference and poor roundness.Among various diagenesis,strong compaction,illite cementation and carbonate cementation are the main causes of reservoir densification;feldspar dissolution improves the physical properties of the reservoir;the pores mainly develop intergranular pores,feldspar dissolved pores and micropores,the throat radius is generally small,and the coordination number of pores is low,,mostly 0-2.The study area mainly develops ? and ? petrophysical facies reservoirs,and the reservoirs of the ?reservoirs have relatively better seepage performance.In the plane distribution,due to the turbidity of gravity,there is no obvious sorting of sand bodies and mudstones,and the reservoirs of all levels are cluster-like.However,in general,Class ? is more distribut.ed in the west and south of the study area,and Class ? is more distributed in the east and north of the study area.