Study Of Sequence Stratigraphic And Reservoir Prediction Of Carboniferous Huanglong Formation In Sichuan Basin

After nearly thirty years of exploration and development, we have achived a great gain in oil and gas of carboniferous Huanglong formation in Sichuan basin. With high steep structure based exploration of access to a large number of natural gas discovery,but with strtum and lithology based exploration just begun.Because lack of overall,system and sophisticated research of stratigraphy and sedimentary facies,which directly dominate reservoir development and hydrocarbon accumulation, Oil and gas exploration of the field have been restrainted. Therefore, it is important theoretical and practical significance to research sequence stratigraphy and reservoir characteristics. This paper, based on the consolidated results of previous studies, with a large number of single well, outcrop sequence stratigraphy and sedimentary facies research-based,have combined with a comprehensive study of seismic and regional data, Huanglong reservoir development on the characteristics of a system of in-depth research, The understanding of the following:(1) Huanglong formation can be divided into a three layer sequence by lithology, lithofacies and sedimentary evolution.As the initial flooding surfaces and the sea flooding surface is bounded system can be divided into three domains:Lowstand system tract (LST), transgression system tract (TST) and high system tract (HST), respectively correspondence one section (C2hl1), two section (C2hl2) and three sections (C2hl3) of Huanglong formation.(2) The main rock type of research area is micrite-microlite limestone(dolomite rock), crystal powder-cryptomere dolomite rock, dolomitic(grey matter) karst breccias and resid granule dolomite rock, through statistical analysis of a large number of rock flakes. Inter alia, The main rock type of one section (C2hl1) is grey matter karst breccias and micrite-microlite limestone; two section (C2hl2) is dolomitic karst breccias and resid granule dolomite rock, the reservoir layers in this horizons is better; three sections (C2hl3) of Huanglong formation is in maximum transgression, the limitations of the shallow bay to the normal transition zone, The main rock type is micrite-microlite limestone,some places visible bioclastic limestone and nodular limestone.(3) According to the depositional environment and palaeogeo graphical background, Sichuan basin carboniferous mainly developed a tidal flat-shelf sedimentary system. Integrated regional depositional background and lithologic characteristics, tidal flat system is mainly developed tidal flat facies, continental shelf system is mainly developed bay shelf facies. According to the sedimentary facies logo, Huanglong formation can be divided into10kinds of sub-phase and four types of micro facies.(4) Through thin slice identify and core observe,Huanglong formation of Sichuan Basin effective reservoir space is intercrystal pore, inter crystal pore, intergranular pore, intragranular dissolved pore, early diagenetic fracture and tectonic fracture etc. Huanglong Formation reservoir is controlled by the lithology, sedimentary facies, paleo karstification and tectonic activity etc. Dolomite karst breccias, Grain dolomite and crystalline grain dolomite are the best reservoir. shallows microfacies is the most favorable reservoir facies belt; Dolomitization and ancient karst action is the key factor in Huanglong formation reservoir formation. The dolomitization is the most common andmost important diagenesis in carbonate rock of Huanglong formation,and is the basis of pore development; distribution of ancient karst reservoir is controlled by paleokarstification and paleotopography.(5) According to the distribution of the reservoir development characteristics of Huanglong formation,comprehensive dolomite reservoir distribution,karst development law, distribution of natural gas reservoir,Huanglong formation have been determined17favorable reservoir development area, correspond to Ⅰ、Ⅱ、Ⅲ、Ⅳtypes of reservoir, by the comprehensive evaluation for class I as the most favorable reservoir development areas and class Ⅱ for the favorable reservoir development areas, it should be the focusof rolling exploration optimum target area in the future.