Diagenesis and its impact on the reservoir quality of Miocene sandstones (Surma Group) from the Bengal Basin, Bangladesh
Diagenesis and its impact on the reservoir quality of Miocene sandstones (Surma Group) from the Bengal Basin, Bangladesh
复制标题
DOI：
10.1016/j.marpetgeo.2016.07.027
复制
发表时间：
2016-11
影响因子：
4.2
通讯作者：
M. J. Rahman;R. Worden
中科院分区：
文献类型：
--
作者：
M. J. Rahman;R. Worden
与埋藏较慢的老砂岩相比，1000‘S中新世和上新世沉积物的快速供应和沉积往往会导致对储集层质量的一套不同的控制。在这里，我们利用岩石学、地球化学和岩石物理相结合的方法，研究了孟加拉盆地苏尔马群至3,000米和110℃埋藏的中新世河流-三角洲布班组砂岩，以了解对中新世砂岩储层质量的控制，从而有助于改进孔隙度和渗透率的预测。研究的主要结论是，尽管早期方解石的生长导致了一些砂岩中局部可忽略的孔隙度，但机械压实过程是孔隙度损失的主要控制因素。机械压实以颗粒重排、韧性颗粒压实和脆性颗粒破碎为主。方解石胶结物占晶间体积的41%，是由溶解和重结晶的生物碎屑、有机二氧化碳的涌入和斜长石蚀变共同形成的。粘土矿物有蒙皂石-伊利石、高岭石和绿泥石。近晶粘土可能局限于低能沉积环境，其局部渗透率降低程度与孔隙度损失程度不成比例。高岭石可能是有机二氧化碳流入长石蚀变的结果。尽管温度相对较高，但由于这些年轻砂岩中可用时间有限、包裹颗粒的绿泥石以及这些含气储层砂岩中的低含水饱和度，仍存在少量的石英水泥。现在可以通过考虑原生沉积物供应和原生沉积环境、碎屑生物碎屑分数的大小和有机衍生二氧化碳的流入来预测储集层的质量。
Rapid supply and deposition of 1000's of meters of Miocene and Pliocene sediment tend to lead to a different set of controls on reservoir quality than older, more slowly buried sandstones. Here we have studied Miocene fluvial-deltaic Bhuban Formation sandstones, from the Surma Group, Bengal Basin, buried to >3,000 m and >110 °C, using a combination of petrographic, geochemical and petrophysical methods in order to understand the controls on Miocene sandstone reservoir quality to facilitate improved prediction of porosity and permeability. The main conclusions of the study are that mechanical compaction processes are the dominant control on porosity-loss although early calcite growth has led to locally-negligible porosity in some sandstones. Mechanical compaction occurred by grain rearrangement, ductile grain compaction and brittle grain fracturing. Calcite cement, occupying up to 41% intergranular volume, was derived from a combination of dissolved and recrystallized bioclasts, an influx of organic-derived carbon dioxide and plagioclase alteration. Clay minerals present include smectite-illite, kaolinite and chlorite. The smectitic clay was probably restricted to low energy depositional environments and it locally diminishes permeability disproportionate to the degree of porosity-loss. Kaolinite is probably the result of feldspar alteration resulting from the influx of organic-derived carbon dioxide. Quartz cement is present in small amounts, despite the relatively high temperature, due to a combination of limited time available in these young sandstones, grain-coating chlorite and low water saturations in these gas-bearing reservoir sandstones. Reservoir quality can now be predicted by considering primary sediment supply and primary depositional environment, the magnitude of the detrital bioclast fraction and the influx of organic-derived carbon dioxide.