Study On The Water Production Rule Of Sulige Tight Sandstone Gas Reservoir

As the rapid development of the economics in China, the consumption of oil and gas is accelerating. It is not surprised that the Sulige gas field in the north of the Ordos basin, which is the largest natural gas field found in China, is attracting more and more attention. The Sulige gas reservoir is characterized as sandstone with low porosity, tight permeability, and high water-cut. The higher gas production of its main reservoir leads to huge potential for development. After comprehensively analyzing the conventional log interpretation data of the movable water saturation the gas well production data, and the characteristics of the water production, some following conclusion can be obtained.Summarized the impact of water production wells on production capacity. By compare the gas reservoir production of the three gas stations in northwestern Sulige gas reservoir, before the water has broken through in the gas well, the gas productivity is lower than other gas wells. The gas production decrease quickly, after water produced from the gas well (the annual decline rate is 60%, the region decline rate is 20%), and the production of a gas well is only 1/3～1/4 of the well which that the water hasn’t broken through in the gas well. Comparing the current cumulative gas production wells and the final cumulative gas production, it can be seen that once the water has broken through in the gas well, the subsequent gas production will be weak, the final cumulative gas production is less than the economic limit of gas production (1400 ×104m3).According to the gas well production data, two rapid methods have been summarized for determining whether the gas well has produced water. According to the wellhead pressure and the gas productivity, we can effectively predict the reservoir water production characteristics. Once the water has been produced from the gas well, the gas production decrease quickly, and the production curve showed that the slope of curve between the cumulative gas production and the production time suddenly become smaller. There will be a significant turning point. In addition, the gas-liquid immiscible flow in a gas reservoir will cause negative effects on gas flowing, and in turn, reduce the gas well deliverability.In this article, the conventional log interpretation method of measuring the movable water saturation is concluded by combing the nuclear magnetic resonance (NMR) method and the lab experiment of the core measurement. Finally, according to the experimental results, obtain the relation curve between the irreducible water saturation and the porosity. Based on the formula, "Movable water saturation= original water saturation-irreducible water saturation", calculate the movable water saturation for each depth point, and then generate the log interpretation curve of the movable water saturation. According to the analysis of the testing results of the movable water saturation, the higher the movable water saturation, the higher the water production of the gas well. The threshold value of the movable water saturation is concluded as 6%.Based on the log interpretation data of the movable water saturation, the distribution map of the movable water saturation in the target block in the Sulige tight gas reservoir is drawn. In this map, the darker the color of that figure, the higher the movable water saturation. The distribution map may preferably guide in designing the pattern of the well location and optimizing the selection of the production layer.