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Petroleum Science Bulletin ›› 2025, Vol. 10 ›› Issue (6): 1130-1151. doi: 10.3969/j.issn.2096-1693.2025.01.027

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Controls on fluid occurrence and classified reserves characterization in tight conglomerate reservoirs of Upper Urho Formation in Mahu Well Block 1

ZHANG Xuyang1,2(), LYU Bingchen3, LI Qing2,3,*(), SONG Zhaojie3, YUE Dali1, FANG Yuxiang3, LI Zhe3, LIU Xiyu3, WANG Jiaqi3   

  1. 1 School of Geosciences, China University of Petroleum, Beijing 102249, China
    2 Xinjiang Oilfield Company of PetroChina, Karamay 834000, China
    3 State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum, Beijing 102249, China
  • Received:2025-07-04 Revised:2025-09-23 Online:2025-12-30 Published:2025-12-30
  • Contact: LI Qing E-mail:zhxy-xj@petrochina.com.cn;liqing688@petrochina.com.cn

玛湖1井区上乌尔禾组致密砾岩油藏流体赋存控制因素及分级储量表征

张旭阳1,2(), 吕柄辰3, 李庆2,3,*(), 宋兆杰3, 岳大力1, 方宇翔3, 李哲3, 刘曦雨3, 王佳琦3   

  1. 1 中国石油大学(北京)地球科学学院北京 102249
    2 中国石油新疆油田分公司克拉玛依 834000
    3 中国石油大学(北京)油气资源与工程全国重点实验室北京 102249
  • 通讯作者: 李庆 E-mail:zhxy-xj@petrochina.com.cn;liqing688@petrochina.com.cn
  • 作者简介:张旭阳(1985年—),博士研究生,主要从事油气藏地质、储层保护研究,zhxy-xj@petrochina.com.cn
  • 基金资助:
    国家科技重大专项“CO2驱大幅度提高采收率与长期封存技术”(2024ZD1406601);国家科技重大专项“砾岩油藏精细分类与CO2驱适应性评价”(2025ZD1408401);中国石油新疆油田公司科技重大专项课题“准噶尔盆地CO2驱地质油藏工程研究与现场试验”(2024XJZX0801);国家自然科学基金项目“坳陷湖盆洪水型湖相重力流沉积演化机理及差异构型模式”(42272186)

Abstract:

The tight conglomerate reservoir in the Junggar Basin exhibit complex multi-scale pore-throat structures, which obscure the dominant controls on fluid occurrence, hinder reservoir classification, and complicate the quantitative evaluation of graded reserves. To clarify the relationship between microscopic pore-throat characteristics and fluid occurrence states and achieve effective evaluation of highly heterogeneous tight conglomerate reservoirs, this study takes the Upper Urho Formation (P3w) in the CO2 flooding pilot area of the Mahu 1 well block as an example, conducting comprehensive workflow of “pore-throat structure-fluid occurrence-reservoir classification-graded reserves”. Integrating methods including cast thin sections, high-pressure mercury intrusion, and nuclear magnetic resonance (NMR) logging were integrated to characterize the lithomechanical properties and pore-throat structure parameters of different sub-layers within the main reservoir interval. Grey relational analysis further identified movable-to-total porosity (weight 0.913) and clay mineral content (weight 0.805) as the key factors controlling effective oil saturation. Based on NMR T2 spectral morphology, three-component index, IB value, and permeability, a classification standard dividing the reservoir into three types (Ⅰ~Ⅲ) was established, A methodology for calculating tiered pore-volume reserves was proposed, achieving a systematic evaluation from pore-throat structure to classified reserves. Results indicate that in the main producing interval P3w22, the lower sublayer exhibits significantly better reservoir quality than the upper. The lower section has a micron-scale pore proportion of 25.48%, an average permeability of 5.59 mD, and an effective oil saturation 15%~20% higher than the upper section. Nano-scale pores (<100 nm) represent the dominant storage space in the pilot area, containing reserves of 784.3 thousand tons (61.7% of the total). From the perspective of reservoir classification, type Ⅰ reservoirs, with the highest proportion of micron-scale pores (25.48%) and excellent oil-bearing capacity. Type II reservoirs show reduced micron-scale pores and moderate oil-bearing capacity; Type III reservoirs suffer from poor oil retention due to strong confinement by nanopores. The results of this study reveal the controlling factors of fluid distribution, establish a classification standard and tiered reserve characterization system for tight conglomerate reservoirs constrained by pore-throat structures, and provide theoretical support and technical support for the optimal selection of CO2 flooding target zones and the identification of “sweet spots” in the Mahu conglomerate oilfield.

Key words: tight conglomerate reservoir, pore-throat structure, fluid occurrence characteristics, NMR logging, graded reserves

摘要:

准噶尔盆地致密砾岩油藏多尺度孔喉结构复杂,导致流体赋存状态主控因素不清、储层分类与分级储量评价困难。为了厘清储层微观孔喉结构特征与流体赋存状态之间的联系,实现强非均质致密砾岩储层的有效评价,本文以玛湖1井区碳驱试验区上乌尔禾组(P3w)为例,开展“孔喉结构-流体赋存-储层分类-分级储量”全流程研究。本研究综合铸体薄片、高压压汞、核磁共振测井等实验手段,揭示了试验区主力层不同小层岩石力学、孔喉结构等参数特征;结合灰色关联分析方法,明确可动/总孔隙度(权重0.913)和黏土矿物含量(权重0.805)为影响有效含油饱和度的主控因素;基于核磁T2谱形态、三组分指数、IB值、渗透率4个参数,建立了试验区Ⅰ~Ⅲ类储层分类标准,提出了分级孔隙储量计算方法,实现了从孔喉结构到分级储量的系统评价。结果表明:试验区主力层P3w22段储层上下部物性与流体赋存状态差异显著,下部储层微米级孔隙占比达25.48%,平均渗透率5.59 mD(上部仅2.35 mD),有效含油饱和度较上部高15%~20%。纳米孔(<100 nm)储量为78.43万t,是该油藏的主要赋存空间(储量占比61.7%);从分类储层来看,Ⅰ类储层微米孔贡献率最高(25.48%)、含油性好;Ⅱ类储层微米孔减少、含油性一般;Ⅲ类储层受纳米孔强束缚作用限制、含油性差。本研究成果揭示了流体赋存状态的控制因素,建立了基于孔喉结构约束的致密砾岩储层分级评价及储量表征体系,为玛湖砾岩油藏CO2驱靶区优选和碳驱甜点识别提供了理论支撑与技术支持。

关键词: 致密砾岩储层, 孔喉结构, 流体赋存规律, 核磁共振测井, 分级储量

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