准噶尔盆地石南油气田成藏史分析

History of pool formation of Shinan oil gas field, Junggar basin.

石南油气田位于准噶尔盆地腹部陆西地区的基东鼻凸，中、下侏罗统上、下含油而中部含气。上部原油主要储集在头屯河组的中孔、中渗砂层组，为构造岩性型油藏；中部天然气主要储集在三工河组的低孔、低渗砂层组，为岩性型气藏；下部原油主要储集在三工河组的中孔、中渗砂层组，为构造型油藏。以往认为该油气田的油藏为次生油藏，但其油气未经历任何次生蚀变作用。其原油具有较典型的腐泥型母质成因特征，热演化程度较低；其天然气为腐殖型，热演化程度较高。对石南油气田成藏史的认识为：盆１井西凹陷下二叠统烃源岩主要为腐泥型，在早白垩世晚期大量生、排液态烃，该地区白垩系区域盖层沉积后，液态烃沿侏罗纪发育的张性断裂运移，进入头屯河组和三工河组储集物性较好砂层组中的圈闭聚集，形成原生油藏；该凹陷上二叠统乌尔禾组烃源岩为腐殖型，在第三纪晚期大量生成气态烃，仍沿张性断裂运移，大部分聚集于储集物性较差的三工河组砂层中的“空”圈闭，形成原生气藏。图６表２参５（梁大新摘）

Shinan gas oil field is located on Jidong nose arch, in Luxi region in the centre of Junggar basin. There are oil reservoir in upper and lower part of the section and gas reservoir in the middle parts of Middle Lower Jurassic. Upper oil reservoir is in medium porosity, medium permeability sandstones in Toutun Group, and is a structural lithologic oil trap; middle gas reservoir is in low porosity, low permeability sandstones, and is a lithologic gas trap; and the lower oil reservoir is in a medium porosity, low permeability sandbody in Sangonghe Group, and is a structural oil trap. These oil traps have been considered as secondary oil pools in the past. However, the oil in the pool has not been ed to any alteration. The oil has characteristics of sapropelic origin, and the degree of thermal evolution is rather low. Gas in the reservoir is humic type with rather high thermal evolution. A study of the formation of oil and gas pool indicates that, Permian source rocks in the sag west of well Pen 1 are sapropelic and large amount of liquid hydrocarbons are generated and migrated in Early Cretaceous. Liquid hydrocarbons migrated along the Jurassic tensional faults and entered into sandbodies with rather good petrophysical properties in Toutunhe Group and Sangonghe Group to form primary oil pools. The Upper Permian Urho Group source rocks are humic type and large amount of gaseous hydrocarbons have been generated and migrated along the tensional faults. Most of them were trapped in the sandbodies with inferior petrophysical properties in Sangonghe Group to form primary gas reservoir. Subject