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塔里木盆地塔中18井揭示了一个94m厚的侵入岩体侵入到志留系砂岩中,在侵入岩体异常热作用下,砂岩中原来存在的原油变成了黑色的碳质沥青,沥青反射率高达3.54%,已到了非常高的热演化阶段.塔中18井碳质沥青的C27,C28和C29甾烷分布特征与邻近的塔中11,塔中12,塔中45和塔中47井同层位的样品较为一致,仍保留着“V”字型分布的特征,仍能作为有效的油源对比标志,并表明其油源为中-上奥陶统烃源岩;但萜烷类的一些油源对比参数与邻近井相比已经发生了较大的变异,不能再用作油源对比标志.邻近的塔中11,塔中12,塔中45和塔中47井样品氯仿沥青“A”碳同位素δ13C值位于?32.53‰~?33.37‰之间,属于塔里木盆地正常古生界海相原油范畴,但塔中18井异常热作用下形成的碳质沥青碳同位素δ13C值位于?27.18‰~?29.26‰之间,具有明显偏重的特征.饱和烃组分上,塔中18井碳质沥青的饱和烃中含有相对较多轻烃组分(nC14~nC20),轻烃和重烃之比(ΣnC21?/ΣnC22+)位于4.56~39.17之间,而邻近的塔中11等井轻烃和重烃之比(ΣnC21?/ΣnC22+)位于0.85~1.92之间;塔中18井饱和烃还具有强烈的偶碳优势,OEP(奇偶优势指数)值位于0.22~0.49之间,而邻近的塔中11等井不具有明显的偶碳优势或奇碳优势,其OEP值位于0.88~1.05之间.另外,由于异常热作用下含烷基的芳烃化合物的脱烷基化作用和芳环的稠合作用,塔中18井与邻近的塔中11等井相比,含有相对较高的不含烷基取代基的芳烃化合物(如菲等)和相对较高的多环芳烃化合物(如甾蒽、芘、苯并[a]蒽、苯并荧蒽等).
The Tazhong 18 well in the Tarim Basin revealed a 94-m-thick intrusion into the Silurian sandstone. Under the unusual thermal intrusion of intrusion rock, the crude oil originally present in the sandstone turned into a black carbonaceous pitch with a bitumen reflectivity Up to 3.54%, a very high thermal evolution stage has been reached.The C27, C28 and C29 steranes in Tazhong 18 carbonaceous bitumen are similar to the adjacent Tazhong 11, Tazhong 12, Tazhong 45 and Tazhong 47 The samples of the horizon are more consistent and still retain the character of “V” distribution, which can still be regarded as an effective marker of oil source correlation and indicate that the source of oil is Middle-Upper Ordovician source rock. However, Compared with the adjacent wells, some oil source correlation parameters have changed greatly and can no longer be used as oil source contrast markers. Samples of adjacent wells in Tazhong 11, Tazhong 12, Tazhong 45 and Tazhong 47 wells were collected. The δ13C value of carbon isotope δ13C of the “A” is between 32.53 ‰ and 33.37 ‰, belonging to the normal Paleozoic marine oil category in the Tarim Basin. However, the δ13C value of carbonaceous tar formed under the abnormal thermal action of the well Tazhong 18 Located between 27.18 ‰ ~ 29.26 ‰, with obvious biased characteristics.On the saturated hydrocarbon fraction, the saturation of carbonaceous pitch in Well Tazhong 18 The hydrocarbon contains relatively light hydrocarbon components (nC14 ~ nC20), the ratio of light hydrocarbon to heavy hydrocarbon (ΣnC21? /? NC22 +) is between 4.56 and 39.17, while the adjacent light hydrocarbons (ΣnC21? /? NC22 +) is between 0.85 and 1.92. The saturated hydrocarbons in Tazhong 18 well also have a strong carbon-even advantage. OEP (Odd-even Oddness Index) is between 0.22 and 0.49. Does not have obvious even carbon or carbon odd advantages, and its OEP value lies between 0.88 and 1.05. In addition, due to the dealkylation of alkyl aromatic compounds and the aromatic ring condensation due to the abnormal thermal effect, Well Zhong 18 has relatively higher alkyl substituents without aromatic compounds (such as phenanthrene) and relatively higher polycyclic aromatic hydrocarbons (such as sterols, pyrene, benzene, benzene, [A] anthracene, benzofluoranthene, etc.).