A Study On Recognition For The Subtle Reservoir Of Nanpu Sag And Its Distribution Law

The subtle reservoir discovered in the Dong 1st group of Gaonan-Dulin area in Nanpu sag characters with bad distribution and complicated reservoir-forming mechanisms.Therefore,this thesis,which is based on the amount of material about geology and 3D seismic data,uses the sequence stratigraphy,the seismic interpretation,the depositional analysis,high-resolution seismic inversion to research the sequence of layers,fine structural interpretation,sedimentary context as well as depositional system for the Dong 1st group,analyze the mechanisms of sedimentary evolution predict reservoir.And then,the subtle reservoir is identified and evaluated.Finally,it concludes the distribution law.Use the sequence stratigraphy analyze the structural features of the Dong 1st group in the Gaonan-Dulin area of Nanbao depression.By the integrated sequence stratigraphy method,it is the first time to find the high base-level cycle and set up the high resolution sequence stratigraphic framework.It concludes the fouth sequence boundary,the characteristics of seismic profile,drilling and logging on the lake flooding surface.The Dong 1st group is a third-order sequence and includs three fourth-order sequence for three sand formations(Ed11,Ed12,Ed13).The largest-lake-flood period was in the Ed12 period.Based on the sequence interface and the largest-lake-flood face in the fourth-order sequence,the Dong 1st group is divided to 6 formations.Research the sedimentary system distribution characteristics of the fourth-order sequence in the Dong 1st group in the Gaonan-Dulin area of Nanbao sag.Firstly,there is a fan sedimentary system.Two source systems from Laoyemiao area and Gaoliu-fault upside are found by the restoration of the palaeo geomorphology and the seismic attribute analysis.Secondly,it studies the sedimentary system and evolution characteristics in 6 formations by the analysis of single well facies,logging facies and seismic facies.Laoyemiao Fan-delta distributes laterally large scale,while Gaonan Fan-delta distributes includes several small fan-deltas.Sedimentary system,sourcedirection and developing places in different periods have inheritances.Because the bottom interfaces of Dong 1st group is the third-order sequence,the effective accommodation space reduced substantially.Therefore,Ed13 rising period sedimentary system moves forward to the lack basin obviously.The fourth cycles in declining period move towards to the lack basin more than rising period.Study the reservoir prediction.It analyzes basic materials and the petrophysical features.Sand layer and mud formation cannot be identified by sonic wave,density,spontaneous potential and wave impedance.However,GR is sensitive to sand-shale stone.For the difficulties of reservoir prediction,it suggests following methods: 1excavate seismic data,geology and logging materials to research the feasibility of every technology by multiple-attribute analysis.2 Use the post stack migration material and drilling result to study the inversion of the poststack wave impedance.The reservoir thickness and distribution are predicted.3 Interpret the lithology and fluid by the inversion of prestack wave impedance.4 Integrate prestack inversion,poststack inversion and hydrocarbon detection to evaluate lithology,physical property and hydrocarbon potential.Identification and evaluation to the subtle reservoir.First,evaluate the geology conditions of the Dong 1st group.Classify and analyze the subtle reservoir.Considering tectonic factor,the lateral change of sedimentary system,the angle between sedimentary and structure,the angle of sequence stratigraphy,the angle of position of trap to classify the subtle reservoir of research area.Finally,it concludes the hydrocarbon enrichment law: hydrocarbon is located in the thin sand layers of lake flooding surface within the Dong 1st group.Oil&gas is controlled by the distribution of sedimentary facies and structural background in the plane.The law of lake flooding surface control reservoir is given.By this method,identify and evaluate subtle trap in the Dong 1st group by getting the inversion of lake flooding surface.It make sure the exploration area of the subtle reservoir.