酸性气藏地下储气库采出气组分变化规律研究——以鄂尔多斯盆地陕224储气库为例

在酸性气藏改建地下储气库方面,国内外尚无相关成熟经验可供借鉴,研究酸性气体在地下储气库注采生产过程中的组分变化规律对指导该类储气库生产运行具有重要意义。为此,以鄂尔多斯盆地陕224储气库为例,简要阐述了研究区块内酸性气体的成因,建立了酸性气体组分模型,预测了酸性气体在注采过程中的组分变化规律,并通过直井和水平井注采试验对组分预测结果进行验证。结果表明:①直井和水平井注采试验验证了组分模型预测酸性气体含量的变化趋势,注采试验对研究区块酸性气体进行淘洗,使该区块酸性气体含量整体下降,在今后的注采周期内采出气酸性气体含量会越来越少,最终能达到国家二类商品气标准;②同一周期采气初期,酸性气体含量较低,随着采气量的增加,酸性气体含量也会增加;③在第1个注采周期酸性气体含量下降较多,在不同注采周期采气初期会有一定时间的安全生产期;④注采气量的差异导致了酸性气体分布的不均衡性,注气量多的地方采出气酸性气体含量较低,注气量少的地方,采出气酸性气体含量高。

Compositional variation laws of produced gas from underground gas storage tanks rebuilt from sour gas reservoirs: A case study of Shaan 224 UGS in the Ordos Basin

So far, there has been no mature experience at home and abroad that can be used as reference for the rebuilding of underground gas storages (UGS) from acid gas reservoirs. Therefore, the research on the variation law of acid gas in the process of UGS injection and production is of great significance to guiding the production and operation of UGS of the same type. In this paper, Shaan 224 UGS in the Ordos Basin was taken as an example. The origin of acid gas in this block was described briefly. The compositional model of acid gas was established to predict the variation law of acid gas in the process of gas injection and production. And the composition prediction results were verified by performing an injection–production test in vertical wells and horizontal wells. Based on the analysis and simulation, the following results were obtained. First, by virtue of the injection–production test in vertical wells and horizontal wells, the changing trend of acid gas content predicted in the compositional model is verified, and the acid gas in the target block is cleaned, so the acid gas content of this block drops and the acid gas content of the gas produced in the subsequent injection–production cycles will be lower and lower and ultimately reach the national standard of Class 2 commercial gas. Second, in one cycle, acid gas content is lower in the initial stage and then increases with the increase of gas production. Third, acid gas content drops more in the first injection–production cycle and there is a period of safe production in the initial stage of each injection–production cycle. And fourth, the difference between gas injection rate and gas production rate leads to an unbalanced distribution of acid gas. The acid gas content of produced gas is lower in the areas with higher gas injection and higher in the areas with lower gas injection.