摘要
塔中地区深层古生界巨厚的碳酸盐岩是当前油气勘探的热点。近年来，在塔中北坡的北西、北东与北东东向断层-裂缝带中取得了油气勘探的重大突破。然而，在其邻近的古城地区断层-裂缝体的研究则一直很薄弱，这一状况严重地制约了该区的油气勘探进程。基于高分辨率三维地震剖面，提出了古城地区古生界垒-扭叠合复合断层-裂缝体模型。其要点是：①剖面上，断层-裂缝体的性质不具有继承性。在深部寒武系、中部中-下奥陶统、上部上奥陶统和顶部石炭系依次发育加里东早期伸展断层-张性裂缝带、加里东中期压扭断层-压剪性裂缝带、加里东晚期张扭断层-张剪性裂缝带和海西早期张扭断层-张剪性裂缝带，它们在垂向上依次叠合。②平面上，自下而上断层-裂缝体的走向发生了明显的顺时针和逆时针旋转。在深部寒武系、中部中-下奥陶统、上部上奥陶统和顶部石炭系断层-裂缝体的走向分别为北东东向、北北东向、北东-北东东向和北东向，它们在横向上依次复合。③剖面上，断层-裂缝体呈现出“上倒锥、下地垒”的形态叠合特点和“上下张性、中间压性”的性质叠合特点。④平面上，断层-裂缝体呈现出“扫帚状”和雁列状的展布特点。
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.
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