华北地区古生界海相油气潜力分析

华北地区自早元古代结晶基底形成以后的沉积盖层发育演化可划分为五个阶段:拗拉槽—克拉通边缘(Pt_2—Pt_3);克拉通—被动大陆边缘(∈—T_1);裂谷盆地(T_2—K);拉张断陷盆地(E);坳陷盆地(N—Q)。中、上元古界—古生界海相碳酸盐岩和碎屑岩为该区海相油气勘探提供了多套勘探层系和广阔空间,并以二次生烃(再生烃)为特征,构成再生烃油气系统。海相油气勘探的有利地区,一般古生界保存完好,二次生烃强度大,且为晚期成藏。划分出了13个古生界二次生烃的有利区块,它们一般位于中一新生代沉积凹陷区,海相烃源岩主要为奥陶系碳酸盐岩和石炭系一二叠系煤系地层,二次生烃强度在5×10~8～70×10~8 m~3/km~2范围。作为多种沉积盆地类型并存的叠合盆地,具有多旋回构造运动、多套生储盖组合、多阶段生烃的特征,使同一区域内有多种油气系统的叠合,构成复合油气系统。区内存在古生古储再生烃油气系统、古生新储再生烃油气系统、新生古储油气系统等几种基本类型的油气系统。对华北地区海相油气的勘探应重视印支运动和燕山运动的破坏作用及后期沉降导致的二次生烃作用,尤其是在中—古生界地腹保存较完整、且晚白垩世—早第三纪再次埋藏发生二次生烃作用的地区应该具有良好的勘探前景,是天然气勘探的重要地区。

Hydrocarbon Potential of Paleozoic Marine Sequence in Northern China

In northern China, evolution of the sedimentary sequences since formation of the early Proterozoic crystal basement can be divided into five stages,i.e.aulacogen-craton margin (Pt_2-Pt_3),craton-passive continental margin(∈-T_1),rift basin(T_2-K),extension and fault-depression basin(E)and depression basin(N-Q).Middle-Upper Proterozoic to Pale- ozoic marine carbonate rocks and clastic rocks offered several sets of prospective strata for petroleum exploration in marine strata in this region, in which petroleum system of re-generated hydrocarbon was constituted through the secondary generation of hydrocarbon(regenerated hydrocarbon).In the areas that are favorable for exploration,Paleozoic strata are generally well preserved and reservoirs with high secondary HC-generat- ing intensity were the late hydrocarbon accumulation.Thirteen favorable plot areas are sketched out,which are commonly lo- cated in the Mesozoic-Cenozoic sedimentary depressions where the marine source rocks are mostly Ordovician carbon- ate rocks and Carboniferous-Permian coal measures strata with the secondary HC-generating intensity of 500×10~6～ 7,000×10~6m~3/km~2.That there are multicycle movements, several source-reservoir-cap assemblages and multistage hy- drocarbon generations in the northern China leads to the super- position of several petroleum systems,which comprises petroleum multisystems.It is suggested that the plot areas where the Paleozoic-Mesozoic hinterland was perfectly re- mained and the secondary hydrocarbon generation ever hap- pened during Late Cretaceous- Paleogene re-burial should be the important prospective gas exploration areas.