Research On 3D Architecture Modeling Of Facies-controlled Aquifer And Water Abundance Mechanism

Water disaster has always been one of the main threat to the safety of coal mine.The research of water abundance has the great significance to the prevention of water disasters.The early and middle Jurassic coal-bearing strata of the Ordos basin were sedimented in the inland lacustrine environment.The sand bodies superimposed between each other in space and distributed in a complex way which result in inhomogenous water abundance and frequent facies change.Therefore,it is of great significance to study the spatial distribution law of coal-bearing aquifer.The geological control mechanism of groundwater occurrence and the distribution of water abundance areas is significance to formulate the corresponding water control measures.These measures can ensure the safe production of coal mine and improve the scientific production capacity of coal.Based on the theories of high-resolution sequence stratigraphy,geophysics,sedimentary geology and geostatistics,according to the data of drilling,core,logging,and experimental analysis,this paper applied the theories and methods of high-resolution sequence stratigraphy to carry out fine classification of coal series.The sedimentary characteristics of Zhiluo formation in the study area were analyzed to predict the plane distribution of water-bearing sand-bodies in different stratigraphic frameworks.The architectural structure model of water-bearing rock group was studied under different facies belts,a 3D geological model of architectural structure was established to represent the 3D spatial distribution of aquifer.Combined with the method of stochastic and deterministic modeling,a facies-controlled heterogeneous attribute model was established to predict the potential area of groundwater from macroscopic,mesoscopic,microscopic and three-dimensional perspectives.Finally,the controlling factors of water-abundance in the study area were summarized from two factors of sedimentary and diagenesis.The results show that:(1)Based on the method of lithologic cycle and prediction error filtering analysis,the characteristics of hidden cycles were identified.The Zhiluo Formation was a long-term cycle which upward turns depth.Three medium-term cycles,which correspond to upper,middle and lower member,were identified in Zhiluo Formation.The three medium-term cycles are divided into 6 short-term cycles,namely 6 submembers.(2)According to the result of sequence stratigraphic division,8 typical rock facies types and 6 typical rock facies combinations were identified,different rock facies reflect different hydrodynamic conditions and sedimentary environments.Braided river sedimentary system was developed in the lower member of Zhiluo Formation,including braided river channel,batture,flood plain and channel overflow.The middle member of Zhiluo formation shows the characteristics of the delta front sedimentary system,and the subaqueous distributary channel,estuary bar,sand sheet,front bar,front beach and other sedimentary microfacies were recognized.The plane consecutiveness of sand body in the upper member of Zhiluo Formation is relatively poorly developed in meandering river sedimentary system,the sedimentary microfacies such as channel,point bar,flood fan,natural levee and flood plain are identified by single well facies and logging facies.(3)According to the result of sedimentary characteristics,this paper introduces the concept of architectural structure model,puts forward the aquifer architectural structure method,and summarizes the characteristics of different levels of architectural structure interfaces in the study area.The architectural structure interfaces of each sub-member of Zhiluo formation in Yingpan coalfield are divided into five grades,from the level 1 laminar interface to the level 5 channel filling complex interface.This paper analyzes the lateral aggradation distribution of meandering river point dam,the lens-like distribution of "upper convex lower flat" of estuary dam in delta front,and the distribution of "sand inclusion mud"of braided river bank sand body.In this paper,the contact relation of three types of sand bodies,namely isolated type,connected type and superposed type,as well as the difference identification marks of contact relation of three kinds of sand bodies,including elevation difference,thickness difference and logging curve similarity,are summarized.(4)The sandstone pores of Zhiluo Formation mainly include intergranular pores,Intragrase pores and casting pores,among which intergranular pores are the main pores and the microfractures are allost undeveloped in the study area.Combined with core observation and thin section analysis,there a few fracture developments and the pores are the main water storage space in the sandstones of Zhiluo Formation.The face rate of Zhiluo Formation sandstones is high,and its separation and connectivity are good.The petroelectric relationship of Zhiluo formation in the coalfield is established to evaluate the porosity of the sandstone aquifer in Zhiluo formation.(5)Based on the study of the distribution of sand bodies and the microscopic storage characteristics of aquifer in the study area,the water abundance mechanism of Zhiluo formation aquifer is analyzed from sedimentary genesis and diagenesis.The sedimentary environment and corresponding sedimentary facies affect the plane distribution,longitudinal development thickness,architectural structure model,spatial contact relationship,porosity of the sand bodies and hydraulic relation.In the sedimentary areas such as channel,point bar and batture,the sand bodies are relatively thick and pure,with high porosity and strong water abundance.The sand bodies in the prodelta,flood plain,channel overflow and other sedimentary areas are relatively thin,with high argillaceous content,low porosity and relatively weak water abundance.Diagenesis controls the pore development of aquifers and the potential of groundwater.The grain contact forms are mainly in point contact and point-line contact which indicated weak compaction in the study area.According to the quantitative analysis of the influence degree of diagenesis,diagenesis of sandstones in the study area belongs to medium-low degree compaction,medium-weak degree consolidation and medium-strength degree dissolution.Such kinds of diagenesis degree are important factor that causes more developed pores and better water abundance in the sandstones of Zhiluo Formation.(6)The facies-controlled architectural geological model of water-bearing rock group is established.The 3D spatial distribution of the water-bearing rock group is characterized.Based on the combination of sedimentary factors and rock porosity,the facies-controlled heterogeneous porosity model of water-bearing rock group is established to predict the potential area of groundwater.After analyzing the data of mine water inflow,the prediction results of water-rich area are verified.The hole prediction method provides a reference for the research area with similar geological conditions.