焉耆盆地博湖坳陷八道湾组底部层序(SQ1)地震相研究

SEISMIC FACIES STUDY OF BADAOWAN FORMATION BASAL SEQUENCE(SQ1) IN BOHU DEPRESSION OF YANQI BASIN

博湖坳陷是焉耆盆地的主要油气勘探区域,但长期以来,该地区都以寻找构造圈闭为主要勘探目标,随着勘探程度的加深,寻找构造油气藏的难度不断加大,为进一步打开油气勘探局面,故迫切需要寻找隐蔽圈闭。为此,通过对八道湾组底部层序(SQ1)开展地震相-沉积相分析,结合已有钻井岩性资料,预测油气富集相带。研究表明,研究区主要存在山前复合扇体、主水道、扇三角洲;废弃的三角洲平原、沼泽、三角洲平原;强制水退、低位三角洲;滨浅湖、半深湖等相带。强制水退期间沉积的倾向湖盆的前积砂泥互层,极有可能发育孤立砂体,形成隐蔽的岩性圈闭,是最为有利的勘探目标。

Bohu depression is the main hydrocarbon exploration area in the Yanqi basin.However,for a long time,structural traps are searched as its main exploration target in this area.With the further exploration,finding structural reservoirs is becomong harder and harder.In order to breakout the situation of hydrocarbon exploration,it is urgent to find the subtle traps.according to the seismic internal reflection and external geometry,continuity,amplitude,frequency and other seismic facies parameter,7 seismic facies are identified in the study area.Combined the logging data and sedimentary tectonic background,lithofacies distribution charts of SQ1 sequence are compiled.Piedmont complex fans,main stream channels,fan-deltas,abandoned delta plain,swamp,and delta plain,forced regression,lowstand delta,shore-shallow lake facies develop in the study area.Progradation sand-mud alternations which trend to the lake basin during the force regression,probably develop separated sand-body,and form a concealed lithologic trap.This is the best exploration target.