| The third member of the Shahejie Formation in the Liuzhong area belongs to a complex fault block reservoir,with rapid sedimentary microfacies transformation.The development law,recovery degree,and influencing factors of oil sand bodies are unclear,resulting in poor effectiveness of oilfield development adjustment measures,which restricts the further improvement of development efficiency in the Liuzhong area.This article integrates core,logging,seismic,and dynamic data to establish a precise isochronous stratigraphic framework,solving the problems of sand body channeling,oil-water contradiction,and dynamic contradiction.It clarifies the characteristics of low-level fault layers and microstructures in the study area,characterizes the distribution characteristics of sedimentary microfacies in the study area,identifies single sand bodies and describes the stacking style of sand bodies,and identifies and describes oil sand bodies,The oil sand bodies were classified and analyzed for their genesis and reservoir properties,as well as the influencing factors on the recovery degree of different levels of oil sand bodies.The paper achieved the following results:(1)Reconstruct logging curves to identify sedimentary cycles,comprehensively consider the logging interpretation of oil and water results,fully consider the actual situation of low water and high oil,and conduct stratigraphic isochronous comparison.The Sha-3 section of Liuzhong area is divided into 10 oil formations,22 sand formations,and 111 small layers,solving 218 sand body channeling problems,eliminating 91 oil-water contradictions,resolving 28 dynamic contradictions,and adding 36.01×10~4t new reserves。(2)Utilizing fault profile and plane analysis techniques to implement and adjust faults,resulting in an additional reserve of 14.98×10~4t;By compiling 111 micro structural maps of the top surface of small layers,215 new structural highs and 107structural lows were identified,resulting in an increase of 43.23×10~4t reserves。(3)Based on the analysis of core,well logging,and seismic data,it is concluded that the Shasan Formation in the Liuzhong area mainly develops fan delta front underwater distributary channel microfacies,estuarine bar microfacies,distributary channel flank microfacies,and inter distributary bay microfacies.Along the source direction,the distributary channel and estuarine bar microfacies extend forward in a finger like manner,and the distributary channel microfacies are superimposed on the estuarine bar microfacies,presenting a sedimentary pattern of finger like"river above the dam".(4)A total of 597 oil sand bodies have been identified in each sub layer of the third member of the Shahejie Formation in the entire region.The distributary channel microfacies are the most favorable microfacies for the development of oil sand bodies in the study area.Due to strong compaction and cementation,the physical properties of the riverway wings are poor,and dry layers are mostly developed.The underwater distributary channel sand bodies and the combination of river mouth bars are the main types of oil sand bodies in the third member of the Shahejie Formation in the Liuzhong area.(5)According to the scale of reserves,the oil sand bodies in the third member of the Shahejie Formation in the Liuzhong area are divided into four levels,with Class I oil sand bodies having large reserves(>5×10~4t)is a"dam river connected"lithologic fault oil sand body formed by overlapping river channels,with moderate oil saturation;The reserves of Grade II oil sand bodies are relatively large(2×10~4t～5×10~4t),located far from the high point of the fault block structure and controlled by lithology,is a"single river dam stacked"strip-shaped oil sand body with high reserves,which is affected by poor physical properties of the mouth dam and flank microfacies sand body,and has low oil saturation;Grade III oil sand body has moderate reserves(1×10~4t～2×10~4t)is a strip shaped lithological oil sand body with a"single river dam overlay"on the edge of the fault.The area controlled by the fault is small,the oil saturation is high,and the reserves of Grade IV oil sand bodies are small(<1×10~4t)is a channel microfacies oil sand body controlled by the microstructure at the fault edge,with the highest oil saturation.(6)The Grade I oil sand body in the third member of the Shahejie Formation in the Liuzhong area has improved connectivity due to sand body cutting and stacking,resulting in a good injection production relationship and the highest degree of recovery;The injection and production wells of Grade II oil sand bodies are far away,and the contact connectivity between the river channel and the mouth bar sand body is poor,resulting in low water drive control of the mouth bar sand body,uneven water drive in the plane,and the overall recovery rate of the oil sand body is the lowest;The connectivity of Grade III oil sand bodies is moderate,the injection production relationship is moderate,the proportion of sand bodies in river mouth dams is small,and the degree of oil sand body recovery is moderate;Grade IV oil sand bodies are underwater distributary channel microfacies oil sand bodies with good connectivity,good injection production relationship,and high recovery degree. |
