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Fault-controlled dolostone geometries in a transgressive-regressive sequence stratigraphic framework
Sedimentology ( IF 3.5 ) Pub Date : 2020-05-30 , DOI: 10.1111/sed.12739
Shuqing Yao 1, 2 , Enrique Gomez‐Rivas 1, 3 , Juan Diego Martín‐Martín 3 , David Gómez‐Gras 4 , Anna Travé 3 , Albert Griera 4 , John A. Howell 1
Affiliation  

This study investigates the geometries of fault-controlled dolostone geobodies and their structural and sequence stratigraphic controls, which provide new insights for the prediction and production of fault-controlled dolomitized hydrocarbon reservoirs. A very thick succession (>1600 m) of Aptian-Albian shallow-marine carbonates of the Benassal Formation that crop out in the Benicàssim area (Maestrat Basin, eastern Spain) is partly replaced by dolomite, resulting in dolostone geometries ranging from massive patches to stratabound bodies. Detailed mapping, systematic logging and correlation were carried out to characterize the structural, sedimentary and sequence stratigraphic framework of the area and to constrain the principal controls on the full-range of dolostone geometries. The results show that carbonate sediments accumulated in a half graben stacked in three transgressive-regressive (T-R) sequences. Large-scale massive dolostone patches (with up to kilometre extension) formed near large-scale faults indicating that they acted as entry points for warm dolomitizing fluids into the basin. These dolostone patches laterally pass to large stratabound bodies that extend for long distances (at least 7 km) away from feeding faults, forming a continuum. The presence of a regional unconformity and a clastic fine-grain low-permeability unit (Escucha Formation) on top of the Benassal Formation likely constrained the dolomitization fluids to an up to 580 m thick interval below the base of the Escucha Formation. Thus, only limestones within this interval, corresponding to the two uppermost T-R sequences, were dolomitized. There is a clear relationship between the stratigraphic framework and the preferred replaced beds. Dolomitization preferentially affected sediments deposited in inner to middle ramp settings with predominant wackestone to packstone textures. Such facies are laterally most abundant in the east of the study area (i.e. basinwards) and vertically in layers around the maximum flooding zone of the top sequence, which is preferentially affected by dolomitization.

中文翻译:

海进-海退层序地层格架中断层控制的白云岩几何形态

这项研究调查了断控白云岩地质体的几何形状及其结构和层序地层控制,为断控白云岩化油气藏的预测和生产提供了新的见解。在 Benicàssim 地区(西班牙东部 Maestrat 盆地)出产的 Benassal 组的 Aptian-Albian 浅海碳酸盐岩层很厚(>1600 m)部分被白云岩取代,导致白云岩的几何形状从大块斑块到分层机构。进行了详细的绘图、系统测井和对比,以表征该地区的构造、沉积和层序地层格架,并限制对全范围白云岩几何形状的主要控制。结果表明,碳酸盐沉积物堆积在三个海侵-海退 (TR) 层序中的半地堑中。在大型断层附近形成了大规模的块状白云岩斑块(长达数公里),表明它们是温暖的白云岩化流体进入盆地的入口点。这些白云岩斑块横向传递到远离馈送断层延伸很长距离(至少 7 公里)的大型层状体,形成一个连续体。Benassal 组顶部的区域不整合面和碎屑细粒低渗透单元(Escucha 组)的存在可能将白云石化流体限制在 Escucha 组底部下方高达 580 m 的层段。因此,只有在这个区间内的石灰岩,对应于两个最上面的 TR 序列,被白云石化。地层格架和首选的置换层之间有明显的关系。白云石化优先影响沉积在内部到中间斜坡环境中的沉积物,其中主要是泥灰岩到灰岩纹理。此类相在研究区东部(即盆地向)横向最丰富,在顶部层序最大洪水带周围垂直分层,优先受白云石化影响。
更新日期:2020-05-30
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