成都理工大学学报（自然科学版）2025，Vol.52Issue(4)：658-673,16.DOI:10.12474/cdlgzrkx.2024032501
川北旺苍—南江地区龙王庙组颗粒滩储集层特征及致密化机理
Characteristics and densification mechanism of shoal reservoirs in the Longwangmiao Formation in the Wangcang-Nanjiang area of northern Sichuan
摘要
Abstract
In this work,we show that shoal facies led to the favorable development of reservoirs in the Longwangmiao Formation of Sichuan Basin.In the Wangcang-Nanjiang area of northern Sichuan,shoal facies have widely developed,although high-quality reservoirs have not formed over a large scale.To clarify the characteristics and densification mechanism of the shoal reservoirs,this article conducts systematic research on four outcrops and two new drillings of the Longwangmiao Formation.Based on the outcrop data and thin section observations,coupled with porosity,permeability,and lithological analyses,the potential reservoir rock types and diagenetic sequences are identified.On this basis,carbon and oxygen isotopes and in situ trace rare earth element geochemical analyses are further conducted.This study indicates that peloidal limestone(dolostone)and ooidal limestone(dolostone)are potential reservoir rock types,with an average porosity of 1.75%and an average permeability of 0.022 7×10-3 μm2,generally belonging to class Ⅲ-Ⅳ low porosity and low permeability reservoirs.Many of the test samples have relatively high w(Al)(0～8 458×10-6),w(Si)[(451～32 784)×10-6],and high content of ∑REY[(3.7～271.0)×10-6],reflecting the significant influence of terrestrial sources on the Longwangmiao Formation.The calcite samples generally have carbon and oxygen isotopic values(δ13C and δ18O)that fall within the marine range,while high w(Sr)[(76～628)×10-6],relatively low w(Fe)[(172～12 215)×10-6]and w(Mn)[(88～922)×10-6]and a notably negative Ce anomaly are found.These characteristics confirm that the original depositional particles and intergranular fibrous-granular calcite cements formed in a marine environment.Similarly,the dolomite samples also have carbon and oxygen isotopic values within the marine range,but with a significant decrease in w(Sr)[(20～92)×10-6],an increase in w(Fe)[(1 367～17 493)×10-6]and w(Mn)[(245～2 124)×10-6],and the absence of a negative Ce anomaly.This suggests that dolomitization was mainly related to a shallow burial environment marine with water infiltration and reflux.The densification of reservoirs in the Wangcang-Nanjiang area of northern Sichuan area is due to strong cementation and underdeveloped dissolution,coupled with the sedimentary background near the oldland,where terrestrial material input occupied a large amount of intergranular porosity.Therefore,exploration of the Longwangmiao Formation should first avoid oldland and littoral facies areas,and further move towards the high points of the central Sichuan uplift core that are more favorable for karstification and hydrocarbon charging.关键词
龙王庙组/川北地区/颗粒滩相/储层/致密化机理Key words
Longwangmiao Formation/northern Sichuan/shoal facies/reservoir/densification mechanism分类
能源科技引用本文复制引用
CHEN Rongqing,DING Yi,LIU Shugen,SONG Jinmin,LI Zhiwu,ZOU Haowen..川北旺苍—南江地区龙王庙组颗粒滩储集层特征及致密化机理[J].成都理工大学学报（自然科学版）,2025,52(4):658-673,16.基金项目
国家自然科学基金项目(42130809,42372301). （42130809,42372301）
