Sedimentary Evolution And Reservoir Characteristics Of The Longwangmiao Formation In The Lower Cambrian In Western Sichuan

The longwangmiao formation of the lower Cambrian in western sichuan is one of the main reservoirs of oil and gas resources in sichuan basin.Many times of carbonate formation in central sichuan basin studied,but under the western sichuan Cambrian correlation set of sedimentary evolution process and the change of the sedimentary facies belt reservoir characteristics and controlling factors of reservoir development remains to be further research.On the basis of previous studies,this paper is guided by the theory of structural geology sedimentary sequence stratigraphy and reservoir geology,Using the combination of macro research and micro analysis,this paper refers to the seismic core drilling log and various advanced test and analysis data,to study the sedimentary evolution and reservoir characteristics of the longwangmiao formation of lower Cambrian in western sichuan area.Based on the tectonic background to recover its lithofacies paleogeographic evolution figure,finally through to the correlation set of reservoir characteristics research,combined with the controlling factors of reservoir development,determine the favorable facies belt in the study area,provide geological basis for western sichuan correlation areas favorable exploration area.This article mainly obtains the following understanding:(1)The tectonic movement of the sedimentary evolution of longwangmiao formation mainly includes the tung wan movement,the xingkai movement and the ancient upheave of sichuan in the late sinian and early Cambrian.:First,Late sinian and the group of the mangrove bay movement due to the episodic movements,make the group of the strata denudation exposed,with the upper Cambrian stratigraphic unconformity,which affects the follow-up period of strata,including correlation group of sedimentary strata;Second,the formation and distribution of early high quality reservoirs in the longwangmiao formation were controlled by the ancient geomorphic heights on both sides.Third,the preliminary development of the ancient uplift in sichuan province controls the palaeogeomorphologic pattern and the ancient geomorphic elevation of the longwangmiao period,thus controlling the spreading of the sedimentary facies of the longwangmiao formation.(2)The sedimentary facies of the longwangmiao formation in the lower Cambrian in western sichuan province can be divided into the mixed tidal flat facies and the restricted platform facies.(3)The evolution of lithofacies paleogeography in the longwangmiao formation of the lower Cambrian in western sichuan is defined.At the first period of longwangmiao age,the high part of the ancient uplift in sichuan was located west of ya 'an in the southern part of western sichuan,and extended eastward to nanchong and guang 'an.The water from the east to the west,at this time the west of the west of the denudation,most of the development of the mixed tidal flat phase,to the east of the limited platform facies.The granule formation is formed during the period of the pull of the two large underwater uplifts--ziyang and the grinding stream.At the second periods of longwangmiao age,the north rim began to uplift the western margin of sichuan basin and become the ancient terrain is relatively high,the water continued to deepen,the thickness of sedimentary rocks,extended their restricted platform facies,tidal flat facies in western sichuan and part of chuanbei distribution,area of narrow but tends to be stable.At this time,the granule beach is not only in the development of the original shingle,but also in the nanjiang section.During the thied periods of the longwangmiao age,the water slowly retreated,and the water became shallow,and the ancient terrain rose to the surface of the water,becoming a granule,and the water between the grains beach was called the beach sea.(4)The reservoir rock types in longwangmiao group mainly include granule(oolitic sand chip)pellets of pellets,and 4 types of micrite and dolomite,and the pores and fissures of intergranular pores in the intergranular pores are developed.Among them,the fracture-hole type reservoir is the main reservoir type of longwangmiao formation,the reservoir has a good overall porosity,and the permeability is not strong,which belongs to the second class reservoir.(5)Favorable reservoir facies mainly for grain beach facies,so the western sichuan basin phase correlation favorable reservoir facies belt distribution area of hubei vying-from-an yue-nanchong-female base well a line to the north to sichuan and deep Wells,1 dragon agent-horse deep a line to the south of yilong.