Faults And Their Control Effects On Hydrocarbon Accumulation In Middle-shallow Strata In The East Of No.2Structure Of Nanpu Sag

In order to study the role No.2structure of Nanpu Sag played in the process ofhydrocarbon accumulation, on the basis of making full use of the drilling, logging,three-dimensional seismic, geochemical and other geological data, combined with thegeological background of the study area, we analyze the structural characteristics of thestudy area systematically. On the basis of the study of fracture geometry and kinematics,using fault growth index profile, faulting rate, profile extensional deformation intensityand tectonic evolution profile analysis, etc., we study the formation and evolution historyin the study area, divide fault system, and determine conducting-type fracture andblock-type fracture on this basis. And on the basis of the type division of oil and gasreservoirs and the study of oil and gas distribution, combined with accumulation factorssuch as distribution of hydrocarbon source rocks, developmental characteristics of sand,distribution of cover, etc and their spatial configuration relationship, we start from thecontrol of fracture acting on the distribution of oil and gas in the plane and the vertical,analyze fault control function, summarize main controlling factors ofhydrocarbon-containing of fault traps, ultimately prefer favorable zones and traps. Studiesindicate that the study area is composed by three tectonic units of the uplift, deep-lyingarea and ramp area, the faults here experienced three evolution characteristics of earlystretch, medium-term strike-slip stretch and late tension-twisting, and can divide into sixsets of fault systems: type I-early stretch fault system, type II-medium-term strike-slipstretch fault system, type III-late transtensional fault system, type IV-early stretch-medium-term strike-slip stretch fault system, type V-medium-term strike-slip stretch-latetranstensional fault system, type VI-early stretch-medium-term strike-slip stretch-latetranstensional fault system. Type V and type VI fault system are oil source faults, can befurther divided into two types of communicating Es3-Es1and communicating Es1, and theformer is more beneficial to communicate source rocks and overlying reservoirs in thevertical, in fracture-caprock matching, critical caprock thickness of fault connections ofthe second section of Dongying formation is35-38m, When the caprock thickness of faultconnections of the second section of Dongying formation in the east of No.2structure ofNanpu Sag is less than35-38m, Oil is distributed both on and under the caprock of thesecond section of Dongying formation, and when the caprock thickness of fault connections is more than35-38m, oil is only distributed under the caprock. the resultshows that beneficial sandstone ratio of oil and gas lateral diversion from the fault to thereservoir should be greater than32%, in terms of fault sealing, the lateral seal type oftrap-controlling fracture in study area is mainly fault rocks, and using the reservoir datafrom the fault traps that have been drilled successfully we build functional relationship toevaluate the sealing capacity of faults in each oil layers of No.2east structure of NanpuSag quantitatively, and evaluate lateral sealing capacity of trap-controlling fault in faulttrap of the study area quantitatively, the result shows that the average height that can sealoil column of trap-controlling fault in No.2east structure of Nanpu Sag is49.9m, theaverage fulling extent is78.8%. The analysis above indicates that trapped formation ofNo.2east structure of Nanpu Sag must meet the following three major conditions:(1) inaccumulation position of oil and gas: palaeostructure of the footwall traps of reverse faultin ramp structure should be inherited high positions, out of intensively faulted zone,(2) inaccumulation layers of oil and gas: when the thickness of fault connections is more than35~38m, they accumulate under the second section of Dongying formation, on thecontrary both on and under may they accumulate,(3) in migration-accumulation andconservation: type V and type VI fault system, dual-source and single-source fault areadvantageous transporting fault of oil and gas, and fracture intersections and transitionzones are favorable positions for transporting oil and gas. Lateral sealing capacity of faultmay affect the degree of enrichment of the hydrocarbon in traps. And the footwall ofreverse fault in ramp tectonic background, the thickness of fault connections and thelateral sealing capacity of fault are main controlling factors of hydrocarbon accumulation,on this basis, by the compare between these main controlling factors and hydrocarbonpotential, we evaluate and prefer the target traps in study area, delineate three favorablezones, identify thirteen beneficial traps and design eight favorable wells.