高含硫裂缝性气藏硫沉积预测及对产能的影响研究

发布时间：2018-05-24 15:35

本文选题：裂缝性气藏 + 高含硫　；参考：《西南石油大学》2015年硕士论文

【摘要】：在高含硫裂缝性气藏的开发过程中,由于地层温度压力的变化使得元素硫从气体中析出并沉积,导致气藏物性参数如孔隙度、渗透率等参数的变化,这些物性参数的变化反过来又影响气体的渗流,最终影响气藏的开采效率。目前高含硫裂缝性气藏硫沉积预测研究较少,而且硫沉积预测模型的研究不够完善,大多数预测模型存在不合理的假设条件,不能反应实际地层条件的变化,为了准确预测高含硫裂缝性气藏硫沉积对储层的伤害以及气井产能的影响,在硫沉积机理研究的基础上,针对目前普遍采用的硫饱和度预测模型进行了改进,建立了考虑气藏物性参数及流体参数随压力变化,非达西流以及应力敏感影响的硫饱和度预测模型。针对高含硫裂缝性气藏,改进了考虑双重介质渗流规律的硫沉积预测模型,并且分析了裂缝参数及生产参数对硫沉积的影响。针对地层温度较高,元素硫析出以液态的形式在地层中与天然气形成气-液态硫两相渗流,建立了气-液硫渗流数学模型,数值模拟研究了液态硫对气井产能的影响。通过以上模型的建立以及实例分析完善了高含硫气藏硫沉积预测模型,提高了现有硫沉积预测模型的预测精度,得到了以下结论： (1)通过模型对比发现Roberts模型过低估计了硫沉积的速度,而改进的模型考虑了非达西流与应力敏感的影响以及和压力相关的参数的变化,使计算的结果更准确更具有实际意义。 (2)在硫沉积预测模型中应将储层的应力敏感考虑进去,较强的储层应力敏感会导致硫沉积的速度加快,气井的生产时间也会相应缩短。 (3)与压力相关参数的变化对硫沉积的影响可以归结为压力变化的影响,压力在近井地带变化巨大,因此模型中与压力相关的参数必须对应此处的压力来计算。储层的物性越差,发生硫堵的可能性就越大,发生的时间也越早。 (4)硫沉积污染半径会随着产量和生产时间的增加而增加,给出了有硫沉积污染情况下的气井产量公式,气井产量随着含硫饱和度的升高而迅速降低。 (5)针对高含硫裂缝性气藏,裂缝开度越大,硫沉积的速度越慢；裂缝高度越大,硫沉积的速度越慢；裂缝壁面接触面积越小,硫沉积的速度越慢。 (6)针对液态硫的情况,当元素硫析出并以液态的形式与天然气形成气液两相流时,气井稳产时间缩短并且最终累产气量下降,液硫流动能力越差对气井产能影响越大。
[Abstract]:During the development of fractured gas reservoirs with high sulfur content, the variation of formation temperature and pressure makes elemental sulfur precipitate and deposit from the gas, which results in the change of physical parameters such as porosity and permeability of gas reservoirs. The change of these physical parameters in turn affects the gas percolation and ultimately the recovery efficiency of the gas reservoir. At present, there are few researches on the prediction of sulfur deposition in fractured gas reservoirs with high sulfur content, and the research on the prediction model of sulfur deposition is not perfect. Most of the prediction models have unreasonable assumptions and cannot reflect the change of actual formation conditions. In order to accurately predict the effect of sulfur deposition on reservoir damage and gas well productivity in high sulfur fractured gas reservoirs, the prediction model of sulfur saturation, which is widely used at present, is improved on the basis of the study of sulfur deposition mechanism. A prediction model of sulfur saturation considering the effects of pressure, non-Darcy flow and stress sensitivity on the physical and fluid parameters of gas reservoir is established. The prediction model of sulfur deposition considering the seepage law of double media is improved for the fractured gas reservoirs with high sulfur content, and the influence of fracture parameters and production parameters on sulfur deposition is analyzed. In view of the high formation temperature, elemental sulfur precipitates form gas-liquid sulfur two-phase percolation with natural gas in the form of liquid state, a mathematical model of gas-liquid sulfur percolation is established, and the effect of liquid sulfur on gas well productivity is numerically simulated. Through the establishment of the above model and the analysis of examples, the prediction model of sulfur deposition in high sulfur gas reservoir is improved, and the prediction accuracy of the existing sulfur deposition prediction model is improved, and the following conclusions are obtained: 1) it is found that the Roberts model overestimates the velocity of sulfur deposition, while the improved model takes into account the influence of non-Darcy flow on stress sensitivity and the change of pressure-related parameters, which makes the results more accurate and practical. 2) the stress sensitivity of the reservoir should be taken into account in the prediction model of sulfur deposition. The strong stress sensitivity of the reservoir will lead to the acceleration of sulfur deposition speed, and the production time of gas wells will be shortened accordingly. 3) the influence of pressure related parameters on sulfur deposition can be attributed to the pressure change. The pressure varies greatly in the near well zone, so the pressure-related parameters in the model must be calculated in accordance with the pressure here. The worse the reservoir physical property, the greater the probability of sulfur plugging and the earlier the occurrence time. 4) the radius of sulfur deposition pollution will increase with the increase of production rate and production time. The formula of gas well production under the condition of sulfur deposition pollution is given, and the gas well output decreases rapidly with the increase of sulfur saturation. 5) for the fractured gas reservoirs with high sulfur content, the larger the fracture opening, the slower the sulfur deposition rate, the smaller the contact area of the fracture wall, the slower the sulfur deposition rate. 6) for liquid sulfur, when elemental sulfur precipitates and forms gas-liquid two-phase flow with natural gas in the form of liquid state, the stable production time of gas well is shortened and the final cumulative gas production decreases. The worse the flowing capacity of liquid sulfur is, the greater the productivity of gas well is.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE328

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