石油与天然气地质 ›› 2021, Vol. 42 ›› Issue (6): 1354-1364.doi: 10.11743/ogg20210610

• 油气地质 • 上一篇    下一篇

埋藏过程中膏岩封闭有效性演化特征——以塔里木盆地寒武系深层膏岩盖层为例

林潼1(), 王铜山1, 潘文庆2, 袁文芳2, 李秋芬1, 马卫1   

  1. 1. 中国石油 勘探开发研究院, 北京 100083
    2. 中国石油 塔里木油田分公司 勘探开发研究院, 新疆 库尔勒 841000
  • 收稿日期:2020-08-17 出版日期:2021-12-28 发布日期:2021-12-16
  • 作者简介:林潼(1980-), 男, 博士、高级工程师, 油气地质研究与实验。E-mail: lintong1980@163.com
  • 基金资助:
    国家科技重大专项(2017ZX05008006-001);中国石油天然气集团有限公司科技项目(2021DJ0604)

Evaluation of sealing effectiveness of gypsolyte during burial: A case study of the gypsolyte caprock in deep Cambrian, Tarim Basin

Tong Lin1(), Tongshan Wang1, Wenqing Pan2, Wenfang Yuan2, Qiufen Li1, Wei Ma1   

  1. 1. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
    2. Research Institute of Exploration and Development of Tarim Oilfield Branch Company Ltd., PetroChina, Korla, Xinjiang 841000, China
  • Received:2020-08-17 Online:2021-12-28 Published:2021-12-16

摘要:

膏岩作为优质的油气盖层已经得到了普遍认同,但并非所有的膏岩层都具有封闭油气的能力,膏岩作为油气的封盖层需要一定的地质条件。以塔里木盆地膏岩盖层为研究对象,对采自井下岩心和露头的膏岩样品开展了显微观察、物性分析、突破压力测试以及三轴应力试验。研究结果认为:①初始形成的膏岩和盐岩都具有非常强的物性封闭能力,但是在埋藏演化过程中石膏发生脱水作用后逐渐向硬石膏转化,转化过程中形成的孔隙空间使得物性封闭能力减弱;②塔里木盆地台盆区内石膏向硬石膏转化的最大深度在2 000 m附近,脱水后的硬石膏抗剪切能力与未脱水的石膏相比存在显著差异;③膏岩在埋藏演化过程中受地层温度和围压的影响封闭性发生动态变化,最终能否成为优质盖层取决于埋藏条件下膏岩的封闭能力与抗剪切能力。

关键词: 脱水作用, 突破压力, 封闭性能, 三轴应力试验, 石膏, 硬石膏, 膏岩盖层, 塔里木盆地

Abstract:

Gypsolyte has been widely accepted as a superior caprock for oil and gas reservoirs. However, not all gypsolytes are of effective sealing capacity, to which certain geological conditions are in need. The core and outcrop gypsolyte samples taken from the Tarim Basin are applied to carry out scanning electron microscopy (SEM), physical property analysis, breakthrough pressure test and triaxial stress test. The results suggest that (1) both gypsolyte and saline rock initially formed are of strong sealing capacity, which tends to grow weaker as the gypsum under dehydration transforms into anhydrite during evolution under burial, and the spaces formed thereby undermine its sealing performance; (2) The maximum burial depth at which gypsum-to-anhydrite transformation occurs is about 2000 m in the Tarim Basin, and the anhydrite developed under dehydration is significantly different from the initial gypsum in terms of shear resistance; (3) During the evolution process under burial, the sealing properties of gypsolyte are constantly changing under different formation temperatures and confining pressures, and it all depends on the sealing capacity and shear resistance of the gypsolyte under burial whether the gypsolyte can be eventually developed into effective caprock.

Key words: dehydration, breakthrough pressure, sealing capacity, triaxial stress test, gypsum, anhydrite, gypsolyte caprock, Tarim Basin

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