Research On Sequence Stratigraphy And Sedimentary Facies Of Putaohua Oil Layer In Xingshugang Region Of Daqing

Xingshugang study area is located in the south of Xingshugang anticline of DaqingPlacanticline in Songliao Basin, of which the oil source bed is Qingshankou Formation. Thetarget layer is the Putaohua reservoir of the first member of Yaojia Formation of lowerCretaceous. Based on achievements of others in previous research, regional sedimentarybackground and characteristics of tectonic evolution, under the guide of sequence stratigraphy,logging geology and sedimentology, this paper studies the characteristics of tectonic evolution,sequence stratigraphy, sedimentary facies and reservoir characteristics of the study areasystematically, combined with the seismic, core and logging data. Thus, this study makes the ruleof sedimentary facies distribution clear and predicts the favorable exploration area. The mainachievements are:1．The structural configuration of the study area is a large nearly north-south anticline, ofwhich the terrain is flat and southward monoclinic, east and west sides develop slope. Generally,this area shows an overall tectonic framework of one uplift-two depressions, with a structuralfeature of bottom fault-middle depress-up reverse. The fault system runs NNW and is enechelon-distributed. The faults develop in the main anticline densely, while relatively less inslopes and depressions.2. With the guidance of sequence stratigraphy, the Putaohua oil layer is divided in threesubsequence sets and eight subsequences, and is a positive cycle sequence with the risingbase-level. Based on the sequence division of Xingshugang region, the isochronous sequencestratigraphic framework of the whole region is set up.3. Analysis of the logging and core data shows that Putaohua oil layer of the study areadevelops delta sedimentary system and its sedimentary subface is delta plain. Under the controlof the sequence stratigraphic framework, the vertical distribution characteristics and evolutionrule of deltaic depositional systems are analyzed. Sq1period belongs to LST deposition, duringwhich the distributary inflows from the northwest and the north direction and the west slopedepression deposits the slough face. Sq2period develops lake transgression, channels distributefrom north or northwest to south and well develop in the main anticline and the gentle slope inthe east, while the slope depression zone in the west deposits the slough and interdistributary bayfacies. With the lake transgression, Sq3period gradually transit to the delta front, distributarychannels are not developed well, while the slough and interdistributary bay depositions increase.4. The Putaohua reservoir is lithic arkose sandstone, which is well sorted and semi-rounded,with moderate degree of weathering. The cementation types have mainly porosity-films, porosity and regenesis-porosity. The Putaohua oil layer belongs to low porosity and permeability and lowporosity-medium permeability reservoir, of which the oil saturation mainly is ten to fiftypercent and the oil storage capacity is general.5. On the base of comprehensive analysis of sedimentary, reservoir characteristics and welltest results, two kinds of favorable facies belts have been selected as follow: the first favorableface belt distributes in the distributary channels in the delta plain, which has thick sand body andgood reservoir physical property and is favorable for hydrocarbon accumulation; the secondfavorable face belt is the crevasse splay and natural levee located in the delta plain, which hasrelatively small sand body and good reservoir physical property. It’s also a favorable explorationzone though it’s sand thickness is small.