塔中地区泥盆系东河砂岩石油运聚方向研究

Petroleum Migration in Lower Devonian Donghe Formation Sandstone(D_3d),in Tazhong Area of Tarim Basin

筛选有机地球化学参数中不受或者很少受其他地质因素干扰的地球化学指标作为油气示踪的有效参数,探讨塔中地区泥盆系东河砂岩中油气充注方向。泥盆系东河砂岩中地球化学指标(1,3,6-)/(1,3,6-+1,2,5-)三甲基萘(TMNr)、4-甲基二苯并噻吩/1-甲基二苯并噻吩(4-/1-MDBT)、咔唑类化合物含量(W)、C2烷基咔唑的结构类型(G1、G2、G3)存在一定的运移分馏作用。表现为随着油气运移距离的增长,TMNr值、4-/1-MDBT值、W值和G3值呈现出有序的降低;而C2烷基咔唑的结构类型G1值、G2值和C3-咔唑/C2-咔唑值则随着石油运移距离的延伸而逐渐增大。根据对上述地球化学指标的综合分析,塔中东部泥盆系东河砂岩的油气充注表现为自NW向SE方向和自SE向NW方向往构造高部位充注,塔中西段则表现为自NW向SE方向和自NE向SW方向充注。同时研究结果也表明该区的油气可能经历了相当长距离的运移。

We choose some geochemical parameters,which are seldom interfered by geological factors,to trace the hydrocarbon migration and filling in the D3d sandstone,Tazhong area of Tarim basin.A certain migration fractionation exists in the 1,3,6-tri-methylnaphthalenes /（1,3,6-tri-methylnaphthalenes ＋1,2,5-tri-methylnaphthalenes） tri-methylnaphthalenes（TMNr）,4-methyldibenzothiophene/1-methyldibenzothiophene（4-MDBT/ 1-MDBT）,carbazole compounds,G1,G2 and G3 types of C2-alkylcarbazoles.With increase of migration distance,the decrease tendency of TMNr,4-MDBT/1-MDBT,carbazole compounds and G3 type of C2-alkylcarbazoles occurs,in contrast that of the increase of G1 and G2 types of C2-alkylcarbazoles and C3-/C2-alkylcarbazoles is observed.According to the observed results,we consider that the hydrocarbons in the structural high part of eastern Tazhong area were migrated from both northwest to southeast and southeast to northwest,whereas the hydrocarbons in the western Tazhong area were migrated from both northeast to southwest and northwest to southwest.The results also indicate that the hydrocarbons in the D3d sandstone would have undergone long distance migration.