Research On Sedimentary Characteristics In The Upper Es₄ Of The Central Fault Zone In Bonan Sag

The structure and the reservoir of upper of Es4 in Bonan Sag is very complicated.The exploration practice indicates that the region has enormous potential.In order to improve the geological understanding and exploration in the study area and improve the total oil production,we make full use of seismic and logging data to carry out stratigraphic classification and correlation,to research characteristics of sedimentary facies and reservoir characteristics,and to analyse accumulation pattern of hydrocarbon.Provide a basis for oil and gas exploration in the next step.Through stratigraphic classification and correlation of 33 Wells in the study area, look for mark layer of upper of Es4 respectively,divide step by step according to the period- the period- sand formation,and divide upper of Es4 formation into four sand layer groups.And according to the characteristics of the research block, set up nine stratigraphic section,compare the whole study area,and find that the first and second sand group develop stably,and the third and fourth sand group change significantly.Through observing the 6 coring Wells, analyzing the characteristics of lithology, color, sedimentary structure, paleontology, granularity and logging curve, and combining previous research results, we think it mainly develop fan delta, nearshore submarine fan, sublacustrine fan, beach bar, half deep lake- deep lake and salt lake sedimentary facies types in upper of Es4 in Bonan Sag.Research single well facies and sedimentary section facies, in combination with sedimentary facies marks, to determine the change in vertical. Explain the plane distribution characteristics of sedimentary facies and sedimentary system combined with sandstone thickness figure and sandstone content diagram. The fourth sand group mainly develop fan delta, nearshore subaqueous fan sedimentary facies types,and with the increase of water area, the third sand group mainly develop fan delta, nearshore subaqueous fan, beach bar and sublacustrine fan sedimentary facies types; the first and second sand groups mainly develop half deep lake- deep lake and salt lake sedimentary.The water depth of the lake in the second sand group is maximum.The reservoir of upper of Es4 in the study area mainly develop in the third and fourth sand group, which is the main study object. The reservoir rock types of upper of Es4 is mainly lithic feldspar sandstone,and the compositional maturity and structure maturity of reservoirs are low. The reservoir types include gray beach dam reservoir and glutenite reservoir. Predict the favorable reservoir areas through the distribution characteristic of reservoir property.Due to the fault, structural reservoirs develop well in upper of Es4 in the study area. Reservoirs are mainly distributed in the northern fan delta front and southern beach bar facies zones on the plane.Because of its good physical condition, the development of the fault, fracture and unconformity surfaces and the high-pressure, it develop multiple thin layer and oil layer in vertical.The influence factors of reservoirs of upper of Es4 in the study area are mainly hydrocarbon generation ability, sedimentary facies,development of paste strata and tectonic position.