川中地区寒武系沧浪铺组沉积特征

Sedimentary characteristics of Cambrian Canglangpu Formation in central Sichuan Basin

基于区域构造特征、野外露头、钻井、测井等资料,对川中地区寒武系沧浪铺组沉积特征进行了研究,重建了古沉积环境,明确了各沉积相的横向展布特征并预测了有利储层发育区。研究结果表明:(1)川中地区德阳—安岳裂陷槽内发育深水陆棚相,以碎屑岩沉积为主;裂陷槽以东高磨—龙女寺—北斜坡地区为浅水陆棚相,可细分为3种亚相,碳酸盐浅水陆棚亚相以细晶或颗粒灰岩、细晶或颗粒白云岩为主,见古杯、腕足类等生物,自然伽马和电阻率曲线均呈箱形;碎屑浅水陆棚亚相以粉砂岩或粉砂质泥岩为主,自然伽马和电阻率曲线均呈钟形或漏斗形;混积浅水陆棚亚相表现为砂质白云岩、砂质灰岩和泥岩互层,自然伽马和电阻率曲线均呈齿状。(2)研究区整体上为西高东低的沉积古地貌格局,由西向东水体逐渐加深,地层厚度逐渐增大;高磨—龙女寺—北斜坡地区沧一下亚段主要为混积浅水陆棚,沧一上亚段主要为碳酸盐浅水陆棚;沧二段主要为碎屑浅水陆棚相。(3)研究区沉积相的展布控制着优质储层的发育,沧一上亚段碳酸盐浅水陆棚中,颗粒滩白云岩储层最为有利、灰岩储层次之;平面上优质储层主要沿德阳—安岳裂陷槽边缘的构造高部位发育,呈条带状展布。

Based on the regional structural characteristics,field outcrops,drilling and logging data,the sedimentary characteristics of Cambrian Canglangpu Formation in central Sichuan Basin were studied,the paleosedimentary environment was reconstructed,the lateral distribution characteristics of each sedimentary facies were defined,and the favorable reservoir development areas were predicted.The results show that:(1)Deep-water shelf facies are developed in Deyang-Anyue rift trough in central Sichuan Basin,mainly composed of clastic rocks.Shallowwater shelf facies are developed in the areas of Gaomo-Longnusi-north slope to the east of the rift trough,which can be divided into three sedimentary sub-facies.The lithologies of carbonate shallow-water shelf facies are mainly finely crystalline limestone and finely crystalline dolomite,followed by grainstone and granular dolomite.Archaeocyatha and brachiopods can be observed,and the gamma and resistivity logs are in a box shape.The lithologies of debris shallow-water shelf facies are mainly siltstone or sandy mudstone with the gamma and resistivity logs bell or funnel-shaped.The mixed shallow-water shelf is interbedded with sandy dolomite,sandy limestone and mudstone with the gamma and resistivity logs toothed.(2)The sedimentary palaeogeomorphology pattern of Canglangpu Formation is high in the west and low in the east.The water body gradually deepened from west to east,and the stratum thickness gradually increased.The lower sub-member of the first member of Canglangpu Formation in Gaomo-Longnvsi-north slope area is mainly mixed shallow-water shelf facies,the upper sub-member of the first member of Canglangpu Formation is mainly carbonate shallow-water shelf facies,and the second member of Canglangpu Formation is mainly debris shallow-water shelf facies.(3)The sedimentary facies of Canglangpu Formation in the study area control the development of high-quality reservoirs.The reservoir mainly develops in the carbonate shallow-water shelf of the upper sub-member of the first member of Canglangpu Formation.The granular shoal is the most favorable sedimentary microfacies,among which dolomite reservoir is the best,followed by limestone.On the plane,high-quality reservoirs mainly develop along the high part of the structure at the edge of Deyang-Anyue rift trough,showing a banded distribution.