LAUSR

Abstract Density, aperture and developmental position are key parameters of tectonic fractures in carbonate reservoirs for oil and gas exploration and development. The analysis of fracture development and distribution in interbedded bioclastic and biological limestone and mudstone of Carboniferous and Ordovician age in the Hetianhe area of the Bachu uplift, central Tarim Basin reveal that mudstone thickness, mechanical parameter properties and interlayer frequency are significant factors. A new simulative geo-mechanical modeling method was used to quantitatively calculate the 3D fracture distribution, development and to evaluate fracture penetration behavior through the interlayered mudstone in the vertical. Fractures were deduced from the stress and strain distribution. Interlayered limestone-mudstone models were established, and simulated results were compared with drill core and well logs. The results show that the mechanical parameters (Young's Modulus, Poisson's ratio) are primary factors controlling fracture development. Fracture development and distribution is mainly influenced by the limestone/mudstone thickness ratio where limestone was interbedded with multiple mudstone layers of variable thickness. Pressure is an important control on the generation of fractures, and the nature of lithological surfaces highly influences fracture penetration in interlayered limestone-mudstone. Where the limestone/mudstone thickness＞10 (a critical value), the limestone fracture easily penetrated along the contact surfaces. The simulated fracture linear density and aperture are consistent with the observations from drill core and geophysical well logs, and average accuracy was better than 80% in single wells.