鄂尔多斯盆地大牛地西北部地区古岩溶形成机理

Formation Mechanism of Paleokarst in Northwestern Daniudi Area of Ordos Basin

全球对燃料的需求日益增加,柳杨堡地区构造特征一直备受争议,通过地震解释有着十几公里似断裂并未证实,古岩溶地貌形成成了确凿的证据,通过地震解释方法1×1地震解释、相干体技术、顺层相干体以及时间切片等技术,研究区内存在大量背斜结构构造为岩溶古地貌控制下的盐底辟及太原组-下石盒子组披覆叠加型构造。研究区内向斜主要是岩溶作用控制下的重力负载等叠加型。柳杨堡气田石炭-二叠系内断层发育主要由盐底辟及岩溶塌陷所诱发。揭示出部分地区地震相位错断,岩溶作用导致的古地貌起伏差异所引起的。加里东末期开始发育大规律的岩溶作用,形成了早期初步岩溶古地貌,这期岩溶地貌对太原组沉积有明显的控制作用。加里东末期岩溶地貌在石炭纪岩溶作用进一步作用下地貌差异逐步扩大,进一步加大了古岩溶对太原组的沉积控制。二叠纪早期,岩溶作用逐步减弱。建议下一步重点加强源内气藏评价开发的力度,选取贴近烃源岩层的砂体,进行水平井钻井评价,有利于钻取砂体内的天然气,通过深度压裂手段把烃源岩层内煤层气钻取出来。

In order to study the formation mechanism of more than ten kilometers of similar faults or paleokarst landforms in Liuyangpu area,and by using the traditional method of 1×1 seismic data fine interpretation,coherent body technique,stratified coherent body and time slice,a large number of anticlines are salt diapir and overlying superposed structures of Taiyuan Forms-Xishihehe Formation under the control of karst ancient landforms in the study area.The syncline in the study area is mainly superimposed by gravity load under the control of karstification.The development of faults in the Carboniferous Permian in Liuyangpu gas field was mainly induced by salt diapir and karst collapse.It is revealed that the seismic phase fault in some areas is caused by the difference of paleo-geomorphic relief caused by karstification.In the late Caledonian period,large regularity of karst process began to develop,forming the early preliminary karst paleo-landform,which obviously controlled the deposition of Taiyuan Formation.In the late Caledonian karst landform,the difference of landform gradually expanded under the further action of Carboniferous karst,which further strengthened the sedimentary control of paleokarst on Taiyuan Formation.In the early Permian period,karstification gradually weakened.It is suggested that the next step should focus on strengthening the evaluation and development of in-source gas reservoirs,and select sand bodies close to the source rock strata for horizontal well drilling evaluation,which is conducive to drilling natural gas in the sand and drilling out coalbed methane in the source rock strata by deep fracturing means.