Detailed Study On Gas-water Relative Flow Of Tight Gas Sandstone

This paper takes tight gas sandstone as the study object. Many such advanced core analysis experiments as sandstone thin section identification, cast thin section, scanning electronic microscope, particle analysis, image pore, constant-rate mercury intrusion, nuclear magnetic resonance of moveable fluid saturation tese, water-gas relative flow have been used to make a better understanding of reservoir characteristics about petrography, diagenesis, property and other fundamental features for the He8formation of southeast Sulige area. Based on those detailed knowledges, the T2spetrum features of NMR and water-gas two phase flow law are mainly interest and further analyzed, which point out the following conclusions:1. The rock types mainly consist of quartz lithic sandstone. With the common deepe bury of He8formation, serious compaction and silicon cementation has caused a significant decreasing of intergranular pore. Dissolved pore and intercrysalline pore are the mainly pore gernes, of which the quality of former gerne is the main factor influencing the reservoir quality. It is not the difference of sedimentary but dissolution that makes the existence of discrepancy of reservoir quality.2. T2spetrum of NMR presents with a bimodal shape and as a whole the average moveable fluid saturation is around30%not so high. The major characterizing parameters of controlling moveable fluid saturation include surface porosity, pore body, dissolved pore while the secondary controlling factors are reservoir property, throat body and intracrystalline pore.3. According moveable fluid saturation the samples have been divided into four kinds: Ⅰ、 Ⅱ、Ⅲ、Ⅳ and their corresponding average values are about58%、29%、17%、2%respectively. In He8below part2, it average moveable fluid saturation is about40%mainly consisting of Ⅰ、Ⅱ. Both in the He8upper part1and He8below part1, their average moveable fluid saturations are about16%and18%respectively mainly made up of Ⅲ Ⅳ.4. In water-gas two phase flow, the jamming effect has something to do with mixture of two phase and much serious water-gas mixture will lead to highly strong jamming effect. Once gas enters and colonizes flow space, the flow radius will sharply declines and water relative permeability then decreases rapidly; strong water wettability results in gas’s existence in discontinueous phase and gas relative permeability accerates slowly in the initial stage of gas-flooding-water.5. In the southeast of Sulige gas field, the reservoir quality of H28xia2is most favorate which has the I type of gas-water flow curve, and also has the mose serious hetegeneity. The secondary favorate formation is He8shang2with the main type III of gas-water flow curve and the worst formation is He8xial with main type III and IV of gas-water flow curve.6. Irreducible water saturations from two phase flow experiments are generally smaller than irreductable fluid saturation from NMR T2and between them there is relative much big discrepancy. Two resaons have been figured out:①the distrainage pressure in two phase flow is not always equelable to centrifugual pressure of NMR, which results in variation of minimus drianange radius;②clay minerals and paragramatic minerals can turn the relaxation time of fluid from moveable fluid saturation into irreductable fluid saturation, which leads to a wrong results about moveable fluid saturation.