Characteristics of energy fields and the hydrocarbon migration-accumulation in deep strata of Tahe Oilfield, Tarim Basin, NW China

Abstract

Deep energy fields in the Tahe Oilfield are studied and the relationship between energy fields and hydrocarbon migration and accumulation is discussed through the comprehensive analyses of energy field characteristics. Multi-phase tectonic stresses are the main controlling factor of the developmental morphologies of the present fractures. The characteristics of the present regional tectonic stress indicate that the Tahe Oilfield is a favorable area for hydrocarbon collection. The present pressure field of the Ordovician is a slightly low abnormal pressure system. The fluid potential characteristics show that there are two hydrocarbon migration trends: one is from east to west in part of the eastern area, and the other is from south to north in the whole southern area. The present formation water is of typical CaCl2 type. According to the formation water geochemistry, the Tahe Oilfield has a good seal capability, favorable for hydrocarbon accumulation and preservation. Aqueous inclusions indicate that homogenization temperatures are mainly 80–100°C, 120–130°C, and 150–170°C, therein, 80–100°C and 120–130°C represent two large scale hydrocarbon accumulation phases, Early Hercynian and Himalayan, and 150–170°C is controlled by tectonic event and Permian magmatic activities, representing a partial hydrocarbon accumulation event. 摘 要: 以塔河油田深层能量场为研究对象，通过系统分析能量场特征来探讨其与油气运聚的关系。研究认为，多期构造应力作用是塔河油田现今断裂发育形态的主控因素，现今区域应力场特征表明塔河油田是油气运移的有利指向区；奥陶系现今压力场整体上属于略偏低异常的压力系统，流体势特征显示油气运移存在东部自东向西局部性运移趋势以及南部由南向北区域性运移趋势；奥陶系现今地层水离子构成符合典型的CaCl2型水特征，地层水地化指标显示塔河主油区具有良好的封闭性，是油气聚集保存的有利区；盐水包裹体均一温度测试结果主要集中在80～100 ℃、120～130 ℃和150～170 ℃等3个温度段，前两个温度段分别对应于塔河油田2次大规模的油气成藏期：海西早期和喜马拉雅期，而最后一个温度段主要受控于构造变动和二叠系岩浆活动，代表了一期局部油气成藏事件。图7参22 Key words: Tahe Oilfield, deep carbonates, energy field, hydrocarbon migration, hydrocarbon accumulation