Abstract:

The massive carbonate rocks in the deep Paleozoic of Tazhong area are currently a hot spot for oil and gas exploration.Despite several major breakthroughs in oil and gas exploration made along the NW-, NE-, and NEE-trending fault-fracture zones on the northern slope of Tazhong in recent years, the research on fault-fracture bodies in neighboring Gucheng area is yet to be deepened, which has severely restricted the oil and gas exploration in the area.Based on high-resolution 3D seismic sections, this study proposed a Paleozoic superimposed horst-twist fault-fracture body model in Gucheng area, the features of which are summarized as follows.(1) The fault-fracture bodies are not inherited vertically.From the bottom up, i.e.from the Cambrian, Middle-to-Lower Ordovician, Upper Ordovician to Carboniferous, four zones, including the Early Caledonian extensional fault-fracture zone, the Mid-Caledonian transpressional fault-fracture zone, the Late Caledonian transtensional fault-fracture zone and the Early Hercynian transtensional fault-fracture zone are successively developed and superimposed.(2) Horizontally, the strike of the fault-fracture bodies from bottom to top shows obvious clockwise and counterclockwise rotation with those in the deep Cambrian, Middle-to-Lower Ordovician, Upper Ordovician, and top Carboniferous striking NEE, NNE, NE-NEE and NE, respectively and compositely.(3) The fault-fracture bodies feature a superposition that can be roughly described as "an inverted cone in the upper and a horst in the lower", and "being tensile in upper and lower, but compressional in the middle" from a sectional view.(4) The fault-fracture bodies are also distributed in a "broom-shaped" and en echelon arrangement from a map view.

Key words: fault-fracture body model, strike-slip fault, Paleozoic, northern slope of Tazhong Uplift, Tarim Basin