古龙凹陷泥岩非构造裂缝的形成

经钻井揭示,松辽盆地古龙凹陷白垩系青山口组泥岩裂缝储集层段的平面分布,与断裂的发育状态没有必然的联系;与褶曲的曲率大小也没有相关性。在纵向上,泥岩裂缝储集层段与地层应力大小并没有对应关系。这些特征表明,泥岩的裂缝不是构造因素形成的。通过对埋藏史,流体形成等地质过程的模拟,结果表明,古龙凹陷泥岩裂缝是封闭在泥岩中的粘土矿物脱水收缩和烃类受热增压作用形成的非构造缝。明水期形成的流体超压使这些裂缝得以保持和扩大,并形成一些新的裂缝。

FORMATION OF NON-TECTONIC FRACTURES IN MUDSTONES IN GULONG DEPRESSION

Gulong depression in Songliao basin is a major hydrocarbon generating area, where the mudstones have well- developed fractures and abnormally high fluid pressure. Some of these fracture reservoirs have produced commercial oil and gas. Drilling results reflect that the lateral distribution of these mudstone reservoirs in Cretaceous Qingshankou Formation is neither related directly to growth of faults, nor related to the fold curvature ; the vertical distribution of these mudstone fracture reservoirs is not corresponding to the stress in the formation, too. These features indicate that fractures would not be the result of tectonic force. After modeling geological processes concerning the sedimentary burial history and the fluid generation, it is concluded that these mudstone fractures in Gulong depression are non-tectonic fractures ,including the shrinking rocks caused by clay mineral de-hydration and pressure boost fracturing caused by heating of hydrocarbon. And these fractures have continuously been developed and expanded further by fluid overpressuring during Mingshui period, and some new fractures have also been produced in this period.