石油学报 ›› 2012, Vol. 33 ›› Issue (5): 859-863.DOI: 10.7623/syxb201205017

• 油田开发 • 上一篇    下一篇

高温高压气藏地层水盐析引起的储层伤害

汤 勇 1 杜志敏 1 蒋红梅 2 孙 雷 1   

  1. 1 西南石油大学油气藏地质及开发工程国家重点实验室 四川成都 610500;2 中国石化胜利油田公司河口采油厂 山东东营 257200
  • 收稿日期:2012-03-12 修回日期:2012-06-18 出版日期:2012-09-25 发布日期:2012-11-27
  • 通讯作者: 汤 勇
  • 作者简介:汤 勇,男,1975年10月生,2004年获西南石油大学博士学位,现为西南石油大学石油工程学院副研究员,主要从事油气相态理论及测试、气田及凝析气田开发和注气提高采收率的研究。
  • 基金资助:

    国家自然科学基金项目(No.50604011)资助。

Reservoir damages caused by formation-water salt precipitation in high-pressure and high-temperature gas reservoirs

TANG Yong 1 DU Zhimin 1 JIANG Hongmei 2 SUN Lei 1   

  • Received:2012-03-12 Revised:2012-06-18 Online:2012-09-25 Published:2012-11-27

摘要:

针对高温高压气藏烃水互溶加大,降压开采过程中近井带地层水的大量蒸发极易导致盐析产生,进而堵塞储层、降低气井产能的问题,通过室内实验进行了地层水蒸发盐析对储层物性影响研究,分析了地层水蒸发导致盐析前后岩心渗透率的降低程度。利用扫描电镜观测析出的结晶盐在孔道中的产状,通过流动孔隙结构实验研究岩心中发生盐析后孔隙分布的变化特征。结果表明:盐析致使地层孔隙度最大降幅约15%,渗透率最高降幅达83%;地层水矿化度越高,地层渗透率降低程度越大;地层原始渗透率越低,降低程度越大;不同水型的地层水,其盐析产物不同,以NaCl为主。盐析后,结晶盐填充了岩心中的小孔隙,小孔喉在岩心中的比例明显减少,渗流通道减小,有的甚至完全被堵塞;盐析对小孔径岩心所造成的影响远远大于大孔径岩心。因此,高温高压高矿化度地层水的气藏开发中必须考虑地层水的蒸发以及盐析可能造成的伤害。

关键词: 高温高压气藏, 地层水蒸发, 盐析, 储层伤害, 产能

Abstract:

A high mutual solubility of hydrocarbons and formation waters in a high-temperature and high-pressure gas reservoir may readily cause salt precipitation when formation waters in the immediate vicinity of wellbore evaporate largely during the blowdown process, which may further plug the reservoir and impair gas-well productivity. The effect of formation-water evaporation and salt precipitation on physical properties of reservoirs was studied through laboratory experiments and the reducing level of core permeability before and after salt precipitation was analyzed as well. The occurrence of crystal salt in pore passages was observed using scanning electron microscopy and variation features of the pore distribution in cores after salt precipitation were studied by means of flow micro-pore structure experiments. The result shows that porosity reduces about 15% and permeability decreases about 83% at maximum because of salt precipitation. The higher the salinity of formation waters, the more greatly the level of formation permeability reduces, and the lower the initial permeability of formations, the greater the permeability reduction. Different types of formation waters produce different salt crystals, though mainly with NaCl. After salt precipitation, fine pores are often filled with salt crystals and the proportion of small pore throats in cores reduces significantly, resulting in seepage passages narrowing down and even occasionally being blocked completely. Moreover, the impact of salt precipitation on fine pores in cores is generally greater than that on large pores. Therefore, the formation damage caused by formation water evaporation and salt precipitation must be taken into consideration in the exploitation of HP/HT gas reservoirs with high-salinity formation waters.

Key words: high-temperature and high-pressure gas reservoir, formation water evaporation, salt precipitation, formation damage, deliverability