Research On The Rules Of Hydrocarbon Accumulation Of Majiagou 5th Members Of Ordovician In The Eastern Of Sulige Gas Field

This thesis is about the 5th member of Ordovician of Majiagou formation in the eastern of Sulige gas field. Based on the analysis of regional geology, core, thin-section, log, and previous research results, sedimentology, stratigraphic geology, karstology, tectonics are applied to analyze stratigraphic division of the first to fourth sub-member of the 5th member in Majiagou,sedimentary microfacies development , diagenesis and pore texture. The thesis analyzes the characteristics of sedimentary context and through-going tabular surface and the influence of diagenetic and crestal plane tectogenesis on the hydrocarbon accumulation comprehensively, and then serves for the exploration activity. Several achievements could be drawn here:1.Majiagou 5th member of Sulige district can be divided into two sedimentary subfacies and 8 sedimentary microfacies. Among them, dolostone of upper tidal flat, limy dolostone of upper tidal flat and gypsum dolostone of upper tidal flat are the most favorable depositional facies.2.Among the type of diagenesis of the 5th member of Majiagou Formation: dissolution is the most suitable for the development of the reservoirs; compaction and pressolution are unfavorable for the development of the reservoirs; recrystallization, a kind of reconstruction of diagenesis, is beneficial to the enhancement of the reservoirs.3.The study area is low permeability reservoir. porosity and permeability are widely distributed, and the permeability of the storage layers is highly correlated. The areas which have the best physical properties of reservoirs are the third of Majiagou 1st sub-member and the first of Majiagou 4th sub-member, which are also the main gas-bearing stratas, in contrast to the low gas productivity of the left sub-stratas.4.Monadnock and groove are the main kind of landforms in the east, in the southeast and in the south of the study area. The distribution pattern of monadnock alternating with groove is the characteristic of relic landform in this district. The transition areas between monadnock and groove are relevantly favorable for the hydrocarbon accumulation.5.Through analysis on the top of structure, small tectonic doesn't have the ability of traps and disjunctive gas reservoir, but it has certain control of reservoir permeability conditions of gas; under the condition of containing gas, positive tectonic position is conducive to high yield of gas wells.6.Through the profile of gas reservoir and the rules of gas testing drilling distribution, rules of the distribution of hydrocarbon accumulation of the 5th member of Majiagou formation in the eastern of Sulige Gas Field can be drawn here: karstification of Su Dong area developed relatively better. Catoctin and palaeogroove are the main micro geographic unit types. The dolomite and dolomite containing anointed of catoctin are leached and then form the reservoir of high corroded cavity. In the groove of palaeokarst, overlying source rocks of Benxi Formation is up to in the catoctin. In the evolution of geohistory, the oil gas migrated nearby to two flanks of catoctin and conserved, which as cap rock easily forms closed hydrocarbon accumulation of ancient karst circle of ancient landform.