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落基山地区最大的气田均发现在压力异常的储层中。这些气藏与位于盆地中心部位常见的气藏不同,它们分布在含水层的下倾部位,并且都是超压或低压的低渗透储层。我们认为这类超压和低压气藏其有共同的成因。在具有超压气藏的盆地内,热成气聚集的速率超过气体逸散的速率,进而造成流体(气体)压力超过区域静水压力。在超压气体生成带内,迫使较大孔隙中的自由水从气体生成带排出,并进入上覆的和上倾方向压力正常的含水层。残余饱和度降低了的束缚水,不能除去溶解物,所以使具有重要意义的渗透率和孔隙度提不高。因此,当其他成岩过程不断进行时,就发育成渗透率很低的孔隙网。在这些低渗透率储层中气体就以高于逸散的速率聚集起来了。在具有低压气藏的盆地中,气体产生和聚集的速度均低于逸散的速度。这些盆地都经历过明显的抬升和侵蚀过程和或短暂的古地温变化,尽管有这些影响,但盆地中央的气藏继续存在。这是由于盆地内动力的变动,使超压气藏演变成低压系统。
The largest fields in the Rocky Mountains are found in abnormally stressed reservoirs. Unlike the gas reservoirs commonly found in the center of the basin, these reservoirs are located on the dip below the aquifer and are either overpressured or underpressured reservoirs. We think this kind of overpressure and low pressure gas reservoirs have common causes. In basins with overpressured gas reservoirs, the rate of accumulation of thermites exceeds that of gas, resulting in fluid (gas) pressure exceeding hydrostatic pressure in the area. In an overpressured gas formation zone, the free water in the larger pores is forced to exit the gas generation zone and into the overlying and upwardly pressured aquifer. Residual saturation reduced irreducible water, can not remove dissolved matter, so that the permeability and porosity of great significance. Therefore, as other diagenetic processes continue to develop, pores develop into very low permeability. In these low-permeability reservoirs, gas accumulates at a higher rate than escape. In basins with low-pressure gas reservoirs, gas production and accumulation rates are lower than the rate of escape. In spite of these effects, the gas pools in the central part of the basin continue to exist, both of which experience significant uplift and erosion processes and short-lived changes in paleobrages. This is due to the dynamic changes in the basin, the overpressure gas reservoir evolved into a low pressure system.