地学前缘 ›› 2023, Vol. 30 ›› Issue (2): 96-108.DOI: 10.13745/j.esf.sf.2022.2.73

• 沉积作用与沉积环境演化 • 上一篇    下一篇

鄂尔多斯盆地中南部地区延长组砂岩溶蚀增孔模型的建立与应用

刘震1(), 朱茂林1, 潘高峰1, 夏鲁2, 卢朝进1, 刘明洁3, 刘静静4, 侯英杰5   

  1. 1.中国石油大学(北京) 油气资源与探测国家重点实验室, 北京 102249
    2.中国石油大学(华东) 深层油气重点实验室, 山东 青岛 266580
    3.西南石油大学 天然气地质四川省重点实验室, 四川 成都 610500
    4.中国石化石油勘探开发研究院, 北京 102206
    5.中国石油天然气股份有限公司 长庆油田分公司 第五采气厂, 陕西 西安 710018
  • 收稿日期:2021-06-16 修回日期:2022-01-10 出版日期:2023-03-25 发布日期:2023-01-05
  • 作者简介:刘震(1963—),男,博士,教授,博士生导师,主要从事石油地质学基础及应用研究工作。E-mail: liuzhenjr@163.com
  • 基金资助:
    国家自然基金面上项目(41672124);国家油气重大专项子课题“致密气成藏机理与富集规律研究”(2016ZX05047001-002-002)

A dissolution porosity increase model for sandstone reservoir in the Yanchang Formation in central and southern Ordos Basin—model building and model applications

LIU Zhen1(), ZHU Maolin1, PAN Gaofeng1, XIA Lu2, LU Chaojin1, LIU Mingjie3, LIU Jingjing4, HOU Yingjie5   

  1. 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China
    2. Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao 266580, China
    3. Sichuan Natural Gas Geology Key Laboratory, Southwest Petroleum University, Chengdu 610500, China
    4. Petroleum Exploration & Production Research Institute, SINOPEC, Beijing 102206, China
    5. No.5 Gas Production Plant of Changqing Oilfield Branch of PetroChina, Xi’an 710018, China
  • Received:2021-06-16 Revised:2022-01-10 Online:2023-03-25 Published:2023-01-05

摘要:

溶蚀作用作为一种建设性的成岩作用,对于砂岩储层储集空间的扩大以及储层性能的改善具有重要作用。由于现有研究更多的是从定性的角度出发表征溶蚀作用对于砂岩储层孔隙度的影响,对于溶蚀作用产生的孔隙度增加值有多少,对砂岩储层性能的改善效果有多大,目前暂不能定量表征。本文采用化学反应动力学基本原理,基于录井、测井数据,结合砂岩成岩序列、地层埋藏史和热史等资料,采用化学反应动力学基本原理,对鄂尔多斯盆地中南部地区延长组砂岩现今孔隙度特征及成因进行了分析,构建了砂岩溶蚀增孔定量模型,并用该模型对延长组砂岩孔隙度演化进行了模拟,取得以下主要认识:(1)研究区延长组现今砂岩孔隙度剖面总体上可分为正常趋势段和次生溶蚀增孔段两部分,依据次生孔隙形成的起始层位和形态特征,现今砂岩孔隙度剖面可划分为双峰Ⅰ型、双峰Ⅱ型、单峰Ⅰ型和单峰Ⅱ型4种类型;(2)延长组现今砂岩孔隙度主要经历了孔隙度减小和孔隙度增大两种变化效应。其中浅部地层孔隙度减小主要是缘于机械压实作用,深层孔隙度减小则是由于压实和胶结共同作用,而孔隙度增大主要由有机酸溶蚀长石等矿物形成的;(3)建立了砂岩溶蚀增孔定量表征模型,具体包括3个阶段:①地层进入酸化窗口之前,由于酸化溶蚀发生的条件不满足,砂岩溶蚀增孔量为0;②地层进入酸化窗口内,砂岩累计溶蚀增孔量是现今次生增孔量和时间的函数;③地层继续深埋超过酸化窗口后,溶蚀孔隙不再变化。表明砂岩溶蚀增孔模型是一个分段函数,具有明显的窗口效应;(4)运用砂岩溶蚀增孔模型对研究区延长组砂岩孔隙度演化进行了模拟,发现研究区南部镇泾地区红河1井长8砂岩、东部安塞地区丹40井长6砂岩及北部姬塬地区峰12井长4+5砂岩在酸化窗口内溶蚀作用产生的增孔量具有明显的阶段性演化特征,实现了溶蚀作用对于砂岩孔隙度增加值的定量表征。本文建立的砂岩溶蚀增孔模型可以定量计算酸化窗口内溶蚀作用形成的孔隙度增加值,首次实现了砂岩溶蚀增孔的定量模拟,在分析溶蚀作用和砂岩储层性能演化等方面具有比较重要的探索性意义。

关键词: 鄂尔多斯盆地, 延长组, 砂岩, 溶蚀增孔模型, 孔隙度, 定量表征

Abstract:

Dissolution as a constructive diagenetic process plays an important role in expanding reservoir storage capacity and improving reservoir quality of sandstone reservoirs. However, in the existing studies, the influence of dissolution on sandstone porosity is mostly characterized from a qualitative perspective, whilst the amount of dissolution porosity increase in sandstone reservoirs and the effect of dissolution on reservoir quality improvement are not quantitatively characterized. In this paper, based on the mud log and wireline logging data, combined with sequence stratigraphy, burial history and thermal history data, the porosity characteristics and genesis of sandstone of the Yanchang Formation in central and southern Ordos Basin are analyzed by using the basic principle of chemical reaction dynamics, and a dissolution porosity increase model for sandstone is established. Using this model porosity evolution of the Yanchang sandstone is investigated via simulation. The main results are: (1) The present porosity profile for the Yanchang sandstone can be divided into two parts: “normal trend” section and “dissolution porosity increase” section; and, according to the initial horizon and morphological characteristics of secondary pore formation, the sandstone porosity profile can be divided into four types: bimodal I and II, and unimodal I and II. (2) The present Yanchang sandstone mainly experiences two types of porosity changes: porosity decrease in shallow or deep strata by mechanical compaction or by compaction and cementation, and porosity increase by organic acid-induced dissolution of feldspar and other minerals. (3) The dissolution porosity increase model calculates dissolution porosity increase as follows: ① Before the sandstone acidizing condition is reached in the strata, the amount of dissolution porosity increase is zero. ② As the strata condition moves inside the window of acidification, the accumulative dissolution porosity increase is a function of the present secondary porosity increase and time. ③ As the strata continue to be deeply buried post acidification, dissolution porosity does not change. That is, the model defines a piecewise function to calculate dissolution porosity increase. (4) Porosity evolution modeling allows quantitative characterization of dissolution porosity increase in the Yanchang sandstone. It reveals secondary porosity increases of 5.6%, 3% and 6.5%, respectively, in three sandstone reservoirs in the study area, namely, the Chang-8 sandstone of well Honghe-1, Zhenjing area in the south; the Chang-6 sandstone of well Dan-40, Ansai area in the east; and the Chang-4+5 sandstone of well Feng-12, Jiyuan area in the north. The model established in this paper can be used to quantitatively evaluate the amount of secondary porosity increase due to dissolution within the window of acidification. And for the first time quantitative simulation of sandstone dissolution and dissolution porosity increase in sandstone is demonstrated, which is of great significance for quantifying the effect of dissolution on improving reservoir quality of sandstone reservoirs.

Key words: Ordos Basin, Yanchang Formation, sandstone, dissolution porosity increasing model, porosity, quantitative characterization

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