Research On Sedimentary Facies Features Of The Middle-upper Jurassic In Sumatou Structure And Its Main Factors Analysis Of High-yield Gas Wells, In Western Sichuan Depression, Sichuan Basin

I apply sedimentology and petroleum geology theory, basing on the analysis of previous studies, a large amount of drilling, logging, cores and core samples of a variety of experimental tests, the multi-direction complement, perfect combination of macro and micro methods, to analyse the Sumatou Middle-Upper Jurassic gas field in the sedimentary system and sedimentary facies, reservoir characteristics, formation water characteristics and gas and water distribution and gas accumulation pattern systematically. Meanwhile, I investigate the Terminal secondary reservoir gas wells yield controlling factors of the Sumatou structure.According to the characteristics of the Sichuan Basin in the Middle-Upper Jurassic strata and the classified scheme about each, we divide the Shaximiao formation into three sections, the Suining formation into two sections, and the Penglaizhen formation into five sections. Relying on the core observation, log analysis, the Shaximiao formation in the Sumatou gas fieldis mainly terminal area delta front depositions and part of it is the delta plain. While the Suining formation is mainly shallow lake deposition and a small quality of delta sediment. The Penglaizhen formation is mainly delta front and a small part of it is the delta plain and shallow lake deposits.Penglaizhen of Sumatou gas fieldregion formation is mainly feldspathic lithic sandstone, and secondly is the lithic quartz sandstone and lithic sandstone; Suining formation rocks are mainly feldspathic lithic sandstone and lithic sandstone. The destructive diagenesis of work area includes compaction, cementation and replacement; constructive diagenesis includes the formation and dissolution of early rim illite (chlorite); the dissolution of acid water formed by the mix of underlying hydrocarbon formation formed the main reservoir consisting of intergranular dissolved pore in the work area.The analysis of Core properties showed us that the gas reservoir properties of Sumatou gas field reflects low porosity - permeability, extremely low porosity - low permeability reservoir, high water saturation of the "two low and one high" features. The storage space was constituted by the original intergranular pore and secondary intergranular pores, which was mainly formed by primary and secondary bore hole and has micro-fracture occasionally.According to logging, characteristics of formation water chemistry and the test data, we analyse the the surface layer water in the Penglaizhen, Suining and Shaximiao formation of the micro and macro distribution of water causes. The study found the relativity between the closure of the Sumatou gas field and layer depth, that is, the deeper the layer, the better sealing.Sumatou structure of the Upper Triassic source rocks provided the material foundation for the Jurassic gas gathering; mutually superimposed sandy body supplied the favorable reservoir conditions for the formation of gas reservoir. The controlling factors of high-yield wells in Sumatou structure attributed to:â‘ the high position closer to the fault is conducive to gas accumulation and gas abundance;â‘¡the sand under high-quality thick mudstone is conducive to hydrocarbon accumulation and preservation;â‘¢the sand body with thick and high porosity and permeability is the prerequisite for high-yield wells there.