异常压力与油气分布

ABNORMAL PRESSURE AND HYDROCARBON ACCUMULATION

随着油气勘探活动的不断加深，国内外相继发现了许多异常高压油气田。据不完全统计，全世界已发现超压盆地１８０多个，其中１６０多个为富含油气盆地。异常高压油气田约占全球油气田３０％左右，因此，对异常压力的研究，具有举足轻重的意义。本文介绍了异常地层压力的概念、特征及分类；详细论述了异常压力的成因，即烃类生成作用、欠压实作用、液态烃类的裂解作用、粘土矿物的后生成岩作用、构造作用、温度变化等；系统阐述了世界典型含油气盆地的超压形成机制、超压体系中油气初次运移机理以及超压与油气分布关系；并在此基础上，归纳总结出了五种超压油气藏成藏模式，即：（１）位于超压体系中的低渗超压油气藏；（２）位于超压层系中，以礁灰岩（或浊积砂岩）为储层的高压油气藏；（３）位于超压带上倾方向，以退覆三角洲平原和分流河道砂岩为储层的常压或过渡带超压油气藏；（４）位于超压带上、下部的超压油气藏；（５）位于远离超压体系的泄压区常压油气藏，本文对指导、加深新老油气区勘探具有实际应用价值。

Many abnormal overpressure fields have been found both at home and abroadwith more intensified petroleum exploration. According to statistic results,there are morethan 180 overpressure basins in the world,of which 160 basins are rich in hydrocarbon,abnormal high pressure fields account for 30 percent of the total fields of the world.Thisissue introduces the basic conception,features and classification of formation pressure,discusses in detail the contributing factors of abnormal pressure,such as hydrocarbon gen-eration,under-compaction, cracking of liquid hydrocarbon,epigenesis of clay mineral,tectonism,change of temperature,etc.;systematically explaines the mechanism of over-pressure in typical oil bearing basins worldwide and primary migration of hydrocarbon inoverpressure strata,as well as the relationship between overpressure and hydrocarbon ac-cumulation. On this basis,five kinds of overpressure reservoir models can be concluded:(1)overpressure reservoirs with lower permeability in the overpressure system:(2)reef(or turbidite)reservoirs within overpressure formations;(3)normal and/or overpressurereservoirs in transition zone with the lithology of regressive deltaic plain and branchingchannel sandstone above the overpressure zone,(4)reservoirs above or below the over-pressure zone,(5)reservoirs with normal pressure in drainage zone far away from over-pressure system,This paper can be the guide for further exploration in new or old oil andgas provinces.