百色探区中三叠统兰木组沉积相研究

Study on sedimentary facies of middle Triassic Lanmu Formation in Baise exploration area

中三叠统兰木组灰岩潜山油藏是百色盆地油气勘探的重要领域,但对其沉积相认识一直存在争议。兰木组地层沉积后经历印支晚期—燕山—喜山运动早期的长期隆升及差异剥蚀,现今残余的灰岩呈孤立块状不均匀分布。为了厘清兰木组沉积相特征,基于岩心和野外露头资料,重新开展了兰木组岩性特征及沉积环境分析。结果表明,兰木组纵向上经历了从浅水陆棚—开阔台地—潮坪/局限台地演化的沉积格局。上部发育更多的颗粒滩与礁(丘),滩体具垂向叠置、横向局部连片特征,叠加后期岩溶改造后,可在局部形成有利的优质储层。

Limestone buried hill reservoirs developed in the Lanmu Formation of the middle Triassic are an important area of oil and gas exploration in the Baise Basin,but the understanding of its sedimentary facies has always been controversial.After the deposition of the Lanmu Formation,it experienced long-term uplift and differential denudation during the late Indosinian—Yanshan—early Himalayan movement,and the remaining limestones are now unevenly distributed in isolated masses.In order to clarify the sedimentary facies characteristics of the Lanmu Formation,based on the core and outcrop data,it was carried out again the analysis of the lithological characteristics and sedimentary environment of the Lanmu Formation.The results show that the Lanmu Formation has experienced a depositional pattern that evolves from a shallow-water shelf to an open platform and finally to a tidal flat/limited platform in the vertical direction.There are more grain beaches and reefs(mounds)in the upper part,and the beach bodies have the characteristics of vertical superimposition and lateral partial contiguousness.After superimposed later karst reformation,favorable high-quality reservoirs can be formed locally.