| The exploration potential of Ordovician weathering crust reservoir is huge in Ordos Basin.Hangjinqi area is located in the northern Ordos Basin,upper Majiagou group of the main rock types for dolomite,dissolved pore reservoir space is mainly epigenic karstification and burial dissolution formed products,karst palaeogeomorphology is one of the main factors of controlling supergene leaching solution strength.But Hangjinqi area Paleozoic is still in lack of system integrated geological research stage,the understanding of karst landforms in the area of development is insufficiency,the studying in lower Paleozoic reservoir distribution characteristics and the understanding of specific groove direction is fuzzy,and development potential,there is no research result.Through a large amount of field and laboratory work,stratigraphic division and correlation and Lithofacies and paleo geographic features of the lower Paleozoic in Hangjinqi area,especially through a variety of methods in Hangjinqi area late Caledonian stage of palaeo geomorphology restoration characterizations.Based on the investigate karst palaeo landform of the area of Paleozoic carbonate rock oil and gas into accumulation,carries on the analysis to the lower Paleozoic carbonate rock oil and gas exploration potential and to investigate the hidden rules,points out the favorable exploration area,mainly made the following results and understanding:(1)Hangjinqi area Ordovician stratigraphic division was established,and the stratigraphic correlation,the preparation of the each layer of stratum distribution maps,reproduces the strata spatial and temporal distribution.Variation of formation thickness,horse four segments are kept relatively better and the distribution area is the largest,relatively poor Ma 5 member,horse three segments are kept only distribution in the southeastern part of the study,the Ordovician strata of early(a horse,Ma Erduan)in no deposition in the study area.(2)The sea is the main Majiagou land supplemented by intermittent period,change transgressive depositional period.In the sea area of period during M1,M3 and M5,a variety of clouddolomitic flat,paste the Salt Lake development is Majiagou transgression period relative regression;open sea is wide in the period of M2,M4 and M6 and is also the relative transgression,period of M4 is the largest transgression.(3)Hangjinqi area deposition of Ordovician Majiagou group is mainly evaporation tidal flat facies period.Majiagou Formation sedimentary phase partitioning scheme are put forward,and that Majiagou is mainly the drought has evaporated tidal flat facies zone and in the tidal flat environment mainly supratidal zone,intertidal depositional.(4)The overall geomorphic features in the study area before deposition of Carboniferous is : the terrain is generally high in the north and low in the South,southeast is high and northwest is low,strata thickness distribution is not uniform,the lowest lying area is located in the southeast of the study area,the highest lying area is located in the north of the study area of Yimeng uplift.The ancient slope(slope)area,ancient monadnock(beam)and the ancient groove which extend to the southeast area constitute the time level of the main geomorphic units which is in the south part in Hangjinqi area at the Ordovician.(5)The Paleozoic carbonate rocks is mainly controlled by palaeogeomorphology,paleokarst control into reservoir combination mode and tip arc type lithologic gas used two types.Controlled by palaeogeomorphology,palaeo rock solution control model is the main accumulation model of reservoir in the study area,the Ordovician Majiagou formation containing gas area is controlled by the weathering crust slope platform and the monadnock. |
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