玛湖凹陷百口泉组扇三角洲群特征及分布

玛湖凹陷下三叠统百口泉组为平缓斜坡背景下的浅水扇三角洲沉积，发育重力流、牵引流双重流体机制下形成的岩相类型。凹陷周缘主要发育夏子街、黄羊泉、中拐、克拉玛依、玛东和夏盐等6大扇三角洲体系，根据古坡度、物源供给方式分为山口陡坡型、山口缓坡型、靠山缓坡型、靠山陡坡型和靠扇陡坡型等5类扇三角洲。扇三角洲前缘相带紧邻玛湖富烃凹陷，前缘砂体分布范围广，延伸距离远，交互叠置覆盖玛湖凹陷中、下斜坡带，有通源断裂沟通下伏油源，侧翼及上倾方向有扇三角洲平原相致密带形成有效遮挡，侧向和顶、底板湖相泥岩封隔层发育，成藏条件优越，控制着斜坡区油气垂向与平面的分布与富集，具备大面积成藏的宏观地质背景，三角洲内部及扇体间的沉积相带立体配置关系为凹陷斜坡区岩性油藏提供了成藏条件。

FanDelta Group Characteristics and Its Distribution of the Triassic Baikouquan Reservoirs inMahu Sag of Junggar Basin

The Triassic Baikouquan formation in Mahu depression belongs to shallow?water delta deposits under the background of gentle slope, in which gravity?flow lithofacies and fluid?flow lithofacies are developed. There exist six fan dalta systems in peripheral Mahu sag,they are Xiazijie, Huangyangquan, Zhongguai, Karamay, Madong and Xiayan fan dalta systems. According to the ancient slope, provenance supply way, such five types of fan deltas are classified as mountain?pass steep slope, mountain?pass gentle slope, near?mountain gentle slope, near?mountain steep slope and near?alluvial fan steep slope types. The fan?delta front has advantageous hydrocarbon accumulation conditions for the following reasons. It is adjacent to the Mahu sag; its sand bodies are widely distributed and extended to a large distance, and superposed in covering the mid?lower slope areas of the sag; there exist faults connecting underlying oil source rocks; the fan?delta plain facies tight belts on the sides and updip directions can shape effective shielding layers and the lateral and top?bottom lacustrine mudstone is developed as barriers, etc. All these can control the distribution and enrichment of oil and gas in vertical and areal directions.Hence the Mahu slope area possesses a macroscopic geological background for large?scale hydrocarbon accumulation, and the above research results can provide guidance for the lithologic reservoir exploration in Mahu sag