Abstract

The first discovery of commercial hydrocarbon in India was in 1889 in a structural trap at Digboi in Assam. Ever since the discovery, geologists have mapped and modeled the subsurface structure of this 50 km long anticlinal fold-thrust belt. However, never before, the existence of a hanging wall syncline north of Jaipur anticline, near the Kusijan oil and gas field, was considered. In this paper, we have proposed a structural model for the regional fold-thrust structures that successfully explains the existence of this syncline adjacent to the Naga thrust. Trishear Fault Propagation folding followed by a complex breakthrough pattern of the thrust at later stages is proposed as most suitable model to explain the outcrop pattern and sub-surface data. We have prepared two northwest-southeast trending balanced structural cross sections using this kinematic model. Total shortening percentages across the southern and northern cross sections are estimated to be 44 and 30 respectively. A complementary play with locations of prospective boreholes is suggested. Based on the dip data in the hanging wall structures of Naga thrust, we predict medium- to small-scale concealed imbricate structures in the sub-thrust. These zones of local thrust imbrications may prove to be prospective leads for concealed petroleum traps.

中文翻译：

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Digboi‒Dilli Ghat含油结构（印度）的地下建模的二维移动

摘要

印度的第一个商业化碳氢化合物发现于1889年，位于阿萨姆邦Digboi的一个结构圈闭中。自发现以来，地质学家就对这条长达50公里的背斜褶皱冲断带的地下结构进行了制图和建模。但是，从未考虑过在斋浦尔背斜以北的库西扬油气田附近存在上垂线。在本文中，我们提出了区域褶皱-冲断构造的结构模型，该模型成功地解释了与纳迦逆冲相邻的该向斜线的存在。提出了三剪切断层传播折叠，随后在后期形成了复杂的冲断模式，是解释露头模式和地下数据的最合适模型。我们使用这种运动学模型准备了两个西北-东南走向的平衡结构剖面。南部和北部断面的总起酥油百分比估计分别为44和30。建议与预期井眼位置互补。根据纳迦逆冲断层悬挂壁结构中的倾角数据，我们预测了亚推力中的中小规模的隐伏岩性结构。这些局部推力振动带可能被证明是隐藏式油气藏的潜在线索。我们预测了亚推力中的中小规模的隐蔽的辫状构造。这些局部推力振动带可能被证明是隐藏式油气藏的潜在线索。我们预测了亚推力中的中小规模的隐蔽的辫状构造。这些局部推力振动带可能被证明是隐藏式油气藏的潜在线索。