Abstract: The good outcrops exposed along the California orogenic belt as well as successful exploration & development provide examples for the study of sandstone injections (injectites). Sandstone injections are widely developed in a variety of sedimentary systems from the Late Proterozoic to the Holocene of which deep-water systems are the most common ones. The lithology of injection is more frequently fine to medium-grained sandstone in turbidite fans, and the host layers are mainly mudstone and shale. Sand injections are comprised of 4 components including parent units, host strata, sand intrusion/extrusion, and the fracture systems and 5 types of sand dikes, sand sills, and columns/sand pillars, sand volcanos and injection complexes. The geometries of sand injection mainly consist of 3 types like saucer-wing shaped, conical shaped and crestal complex, and the top of the intrusion often develops mound shape. The interior part of sand injection is often structureless or laminated, with erosion boundaries and mass mud clasts, like a jigsaw. The formation conditions of intrusion include unconsolidated sand body, low-permeable overlain layers, pore fluid overpressure and dominant channel of the sand body. Seismic liquefaction, disequilibrium compaction, overburden, regional tectonic stress, and fluid flow are the most common triggering mechanisms. The formation process of intrusive body includes 5 processes:pore fluid overpressure, sand liquefaction, hydraulic fracturing and fluidization, sand injection and redeposition. Sand injections increase reservoir volume, link sand bodies together like conduits, and form injection traps. Sand injections can also be used to predict regional stress fields, but may also lead to failure of seals and water channeling. The determination of injecting time, geological process after injection and the deterministic study of triggering mechanisms are facing challenges. Interdisciplinarity, virtual outcrop, simulation experiments, and numerical simulation technology will be the future development direction.

Key words: sand injection, deep-water deposition, North Sea field, trigger mechanisms, seismic liquefaction, injection reservoirs, hydrocarbon exploration

摘要： 北美加利福尼亚地区良好的露头和北海油田的成功勘探与开发为砂岩侵入体研究提供了范例。砂岩侵入体广泛发育于晚元古代-全新世的多种沉积体系中，以深水环境居多。侵入体岩性以浊积体的中砂岩-细砂岩最为常见，宿主层以泥岩、页岩为主。侵入体系统包括供源砂体、侵入（出）体、宿主层和断裂体系4个构成要素和砂岩脉、砂岩床、砂岩柱、侵出体和复合体5种类型。侵入体外部呈碟状-翼状结构、锥形结构和顶梁复合结构3种类型，侵入体顶部发育丘型变形，内部块状或类层理状，常见侵蚀边、泥岩撕裂屑和各种软变形构造，呈拼图状。侵入体形成条件包括未固结供源砂体、低渗透—非渗透覆盖层、孔隙流体超压和砂体优势通道4部分，地震液化、差异压实、沉积负载、区域构造应力、流体流动是最常见的触发机制。侵入体形成过程包括孔隙流体超压、供源砂体液化、水力压裂与流化、砂体充注和砂体再沉积5个过程。侵入体增加了储层体积，沟通了砂体，可形成侵入型圈闭，还可用于恢复区域古应力场，但也可能导致盖层封闭性破坏和水窜。侵入时间确定、侵入后地质过程以及触发机制确定性等研究面临挑战，多学科交叉、虚拟露头、物理模拟及数值模拟技术将是砂岩侵入体研究未来的发展方向。

关键词: 砂岩侵入体, 深水沉积, 北海油田, 触发机制, 地震液化, 侵入油气藏, 油气勘探