深部煤层割理空间拓扑构型及基质块几何学定量OA

[Objective]Cleats in deep coal seams are characterized by strong heterogeneity,and their topological config-urations,as well as their topological relationships with matrix blocks,remain poorly understood.On the other hand,the assumptions regarding the size and geometry of matrix blocks adopted in representative reservoir structure models and numerical simulations do not fully reflect actual reservoir conditions.[Methods]Deep coal cores collected from the northeastern Ordos Basin were investigated in this study.Using CT scanning and topological theory,a multi-dimension-al topological parameter system was established to characterize cleats in deep coal seams.Furthermore,four topological configurations of cleats in deep coal reservoirs were identified,and corresponding discriminant models were developed.[Results]Cleats in the deep coal cores exhibited the synergistic development of I-,Y-,and X-type nodes,accounting for average proportions of 59.7％,33.8％,and 6.5％,respectively,in the same sample.Despite representing the lowest pro-portion,X nodes played a key role in driving the evolution of cleats from isolated structures to complex,interconnected networks,thereby enhancing their global connectivity.Based on the clustering of multidimensional topological paramet-ers and convex tessellation theory,four topological configurations of cleats in deep coal seams were identified,primar-ily controlled by the combined effects of cleat development and network connectivity.Among these,the dense reticula-tion type(Type Ⅰ)accounted for 4.18％.This topological configuration was governed by Platonic attractors and exhib-ited extremely developed fracture networks,with the matrix partitioned into highly interconnected,tiny rectangular blocks.The complex branch type(Type Ⅱ)accounted for 23.34％.It was characterized by dense branches accompanied by a large number of ineffective blind ends,with matrix blocks transitioning toward irregular hexagons.The branch transition type(Type Ⅲ)accounted for 55.06％.This topological configuration exhibited fracture networks with a mod-erate scale but efficient connectivity and approached Voronoi attractors,with matrix blocks approximating regular hexagons.The sparse isolation type(Type Ⅳ)accounted for 17.42％and was characterized by a limited number of ef-fectively connected cleats.Accordingly,the matrix remained largely intact,with matrix blocks represented by large circles.The geometrical quantitative characterization of the matrix in deep coal seams indicates that with an increase in the cleat development,the matrix blocks evolved from Type Ⅳ[Smed=2 320.09 mm2;median diffusion distance Lmed=27.18 mm]toward types Ⅲ(Smed=210.76 mm2;Lmed=7.80-9.01 mm)and Ⅱ(Smed=16.87 mm2;Lmed=2.21-2.55 mm),ultimately broking into tiny rectangles(Type Ⅰ;Smed=4.75 mm2;Lmed=1.09-1.54 mm).This transition in topological configuration resulted in dramatic changes in gas desorption and diffusion radii of the matrix.[Conclusions]The results of this study refine the understanding of the topological configurations of cleats in deep coal reservoirs,along with their control over the geometric characteristics and gas diffusion scales of the matrix.The discriminant diagrams developed in this study provide a practical tool for coal reservoir classification and the selection of optimal intervals.Furthermore,the qualitified sizes and gas diffusion radii of matrix blocks provide a basis for numerical simulation and reservoir stimula-tion design.