アブダビ海域 Neewat Al Ghalan (GA) 油田におけるArab•Hith 層 (ジュラ系) 中のHSTとTST
GA油田における堆積サイクルと積み重なりパターン
1994 年 59 巻 1 号 p. 99-108
詳細
1994 年 59 巻 1 号 p. 99-108
The depositional sequence in the Upper Jurassic Arab•Hith Formations, which is main reservoir zone of the Neewat Al Ghalan (GA) field, offshore Abu Dhabi, is composed of sabkha-nearshore deposits and divided into two systems tracts (transgressive systems tract (TST) and highstand systems tract (HST)) based on the characteristics of parasequence stacking patterns.
Each parasequence in TST shows a shallowing upward cycle which commences from barrier shoal grainstone and terminates in lagoonal mudstone or sabkha anhydrite. Vertical stacking patterns of these parasequences within TST indicate thinning upward cycle and retrogradational/aggradational pattern.
The parasequences in HST are characterized by a shallowing upward cycle from tidal channel grainstone or lagoonal mudstone to sabkha anhydrite. Stacking patterns of both bedsets parasequences within HST show overall thickening upward cycles and progradational pattern.
The stacking patterns in the depositional sequence reflect various orders of sea level fluctuations. During TST deposition the barrier shoal systems accompanied by shoreface erosion developed in the field. In the succeeding HST deposition, the barrier shoal (strand plain) systems were migrating basinward, and the tidal flat-sabkha systems, in turn, were prograding to the field. These environmental changes due to the sea level fluctuations are considered to have affected the reservoir quality (cementation or dolomitization) of the field.
