The Study Of Sedimentary And Reservoir Characteristics For 5-5th Sub-member Of Majiagou Formation Of Ordovician In The Eastern Of Sulige Gas Field

The Lower Ordovician Majiagou₅ member occurring in eastern Sulige area is the newly explored gas layer in lower palaeozoic erathem.Althrough great breakthrough had been made in exploration and development of Majiagou formation stratums,but the research of Majiagou₅ member has fallen behind relatively,so that study on its characteristics of sedimentary reservoir is particularly urgent.Based on reservoir sedimentology,petroleum geology,geophysics and carbonate reservoir geology,combined with Core observation,microscopic identification,log information explanation and seismic data interpretation,this research has analyzed the Sedimentary characteristics,tectonic evolution and reservoir characteristics of Majiagou₅ member in eastern Sulige area.The main understanding made by this paper is as follows:The Majiagou₅ member of eastern Sulige area was formed in carbonate platform facies,the semi open platforms and semi restricted platforms are mainly developed,according to the sedimentary microfacies and rock types,Majiagou₅ member was divided into four sub-facies:dolomitic flats,lime flats,dolomitic lime flats and lime dolomitic flats.The rock type include dolomite,limestone,dolomitic limestone and calcareous dolomite.The sedimentary environment plays a decisive role in the development of beneficial reservoirs of Majiagou₅ member,and the mainly reservoirs are dolomite rocks.Diagenesis can form advantageous space for preserving,especially dolomitization.At the same time,tectonization provide geomorphic condition for the development of favorable reservoirs.The putty crystal dolomite and powder crystal dolomite are the major rock type of Majiagou₅ member.Research on interspace and permeability of this area indicates that the beneficial reservoirs are located in northern Yulin,Wushen Banner near the erosion line in West China and A195 well in northern region.