Facies-Controlled Geostatistical Porosity Model for Estimation of the Groundwater Potential Area in Hongliu Coalmine, Ordos Basin, China

Accurate and reliable
evaluations of potential groundwater areas
are of significance in the hydrogeological assessments of coalfields
because water inrush disasters may be caused by unclear groundwater
potential. A three-dimensional geological model of porosity based
on deterministic modeling and a facies-controlled method are used
to determine the groundwater potential of the coal measure aquifer.
The modeling processes are as follows: based on the interlayer and
discontinuity (faults) data extracted from boreholes and geological
maps, an integrated sequence framework model is developed. Using the
results of sedimentary microfacies identification and the method of
deterministic modeling, a sedimentary microfacies model is successfully
established. Finally, based on facies-controlled and sequential Gaussian
methods, an effective porosity model is established that can predict
the groundwater potential. The predicted results show that sandstones
sedimented in channel, point bar, and batture environments possess
high effective porosity and strong groundwater potential; however,
the sandstones sedimented in interdistributary bays, flood plains,
and sand sheets possess low effective porosity. Model validation was
performed based on the hydrological pumping test data collected from
observation boreholes, drainage water inflow data from dewatered boreholes
in the tunnel around workface, and the mine water inflow in tunnels
and the workfaces. The validation analysis results show that the effective
porosity and sedimentary facies were correlated with the actual flux.
The predicted results are consistent with the actual flux data, validating
the predicted model.

精准可靠的潜在地下水区域评价对煤田水文地质评估至关重要，因地下水潜力认知模糊可能诱发突水灾害。本研究采用基于确定性建模（deterministic modeling）与相控方法（facies-controlled method）的孔隙度（porosity）三维地质模型，以确定煤系含水层（coal measure aquifer）的地下水潜力。建模流程如下：基于从钻孔与地质图中提取的层间界面与不整合面（断层）数据，构建综合层序格架模型；结合沉积微相（sedimentary microfacies）识别结果与确定性建模方法，成功建立沉积微相模型；最后，基于相控与序贯高斯（sequential Gaussian）方法，构建可预测地下水潜力的有效孔隙度（effective porosity）模型。预测结果显示，在河道、点坝与边滩环境中沉积的砂岩具有较高的有效孔隙度与较强的地下水潜力；而在分流间湾、泛滥平原与砂席环境中沉积的砂岩有效孔隙度较低。模型验证基于观测钻孔的水文抽水试验数据、工作面周边巷道内疏干钻孔的排水量数据，以及巷道与工作面的矿井涌水量数据开展。验证分析结果表明，有效孔隙度与沉积相均与实际涌水量具有相关性，预测结果与实际涌水量数据吻合，验证了所建预测模型的可靠性。