Pressure Systems And It's Relation To Distribution Of Natural Gas In The Upper Paleozoica Of Daniudi Gasfield, Ordos Basin

Abnormal pressure is an import global geological conditions in petroliferous basins, more and more researchs indicate that abnormal pressure's formation is intimate relation to migration and accumulation of oil—gas. There lie prevalent subnormal pressure and compactness reservoir and simple ectonic, but the gas-bearing reservoir disperse, under the background, 200 wells are researched and rock pressure's distributional characteristics are analysed in order to illuminate in natural gas's regularities of distribution in Daniudi gasfield. Our research discover:1. There are low-pressure gas reservoir—normal pressure gas reservoir, reservoir pressure's value affect productive capacity largely, every interval include multi-pressure systems which reflect different hydrocarbon generation's characters and accumulation processes in each gas pool.2. In the Upper Paleozoicln Daniudi Gasfield in Daniudi gasfield there are three kinds of overpressures which include singlet gradual change kind and split-blip gradual change kind and singlet or split-blip mutant kind, singlet gradual change kind is the best preferably in accumlating of natural gas, split-blip gradual change kind is the better preferably in accumlating of natural gas, singlet or split-blip mutant kind is the worse in accumlating of natural gas. In cross-sectional views natural gas is apparent relate to overpressure, at same stratigraphic position gas sand develop avail where overpressure is relatively small, different stratigraphic positions need different overpressures to close over gas sand, local abnormal pressure volume affect accumlations of natural gas underneath local abnormal pressure volume, natural gas give priority to migrate vertically, small overpressure's gradient in vertical orientation is in favor of hydrocarbon generation to third and second member of Shihezi formation. In flat surfaces relatively small overpressure lie in region which gas reservoir develop availly, overpressure's value of hydrocarbon source rock represent hydrocarbon expulsion's level, high overpressure indicate that hydrocarbon retent largely, smallness overpressure indicate that hydrocarbon expulsion's environments are well and hydrocarbon is expulsed adequacally to supply favorable material basis for hydrocarbon generation, the region of best productive capacity's distribution is where hydrocarbon source rock congruence the least overpressure.3. Natural gas lie complementarity in distribution, productive capacitys of six layers distribute underlaply. Hydrocarbon generation have no choice but to prior select the best reservoir to pour. While sandy—ground ratio in vertical orientation decide stratigraphic position to be poured.