利用地质约束降低天然气概率储量的不确定性

以YL气田山西组2段主力气层为例，利用储集层展布和物性参数的横向和纵向非均质性等地质条件约束建模，降低气藏建模结果的不确定性，从而降低主力气藏概率储量的不确定性。地质约束条件包括：①主力气藏东南部大片地区几乎没有砂岩；②砂岩集中分布在辫状河道中部和底部，气藏物性参数比例曲线显示孔隙度、渗透率、含气饱和度值呈顶部较小、底部较大的特征。比较没有地质条件约束得到的400个建模实现和利用约束1、约束1+约束2分别得到的100个实现和23个实现，并求取了概率储量P90、P50、P10，所得结果说明，应用地质约束后，山西组2段主力气藏的概率储量不确定性明显降低。图7表1参18

Reduction of uncertainty of gas probabilistic reserve by geological constraints

With a major gas reservoir of the second member of Shanxi Formation in YL gas field as an example, reservoir modeling constrained by geological conditions, including distribution of sand bodies and lateral and vertical heterogeneity, is carried out to reduce uncertainty of results of gas reservoir modeling and uncertainty of probabilistic reserves of the major gas reservoir. The geological constraints include: (1) there are almost no sand body in most of the southeastern part in the study area; (2) owing to sand bodies concentrated in the middle and bottom parts of braided channels, the proportion curves of petrophysical parameters of the gas reservoir show that porosity, permeability, and oil saturation present low values on the top and high values on the bottom of the channels. Comparison with 400 realizations obtained without any geological constraints, 100 realizations with constraint No.1, and 23 realizations with constraints No.1 and No.2, and the calculation of the probabilistic reserves P90, P50, and P10 show that owing to the geological constraints, the uncertainty of the probability reserves of the major gas reservoir is reduced significantly.