巨厚盐膏岩蠕变特性实验研究

Experimental Study on Creep Properties of Thick Salt-gypsum Rock

为掌握深层盐膏岩地层受到温度和地应力作用时表现出的塑性特性,针对井眼钻开后发生蠕变引起的阻卡、套管变形等问题,运用室内蠕变实验方法,针对西南油田Y井盐膏岩,重点研究了NaCl含量对盐膏岩瞬态蠕变及稳态蠕变速率的影响。结果表明:盐膏岩瞬态蠕变及蠕变速率与NaCl含量呈幂律递增规律,随着NaCl含量增加,瞬态蠕变和稳态蠕变速率均相应增大。因此NaCl含量差异性是影响盐膏岩蠕变特性的关键因素,这为盐膏岩地层钻井的钻井液体系选择及密度确定提供理论依据,对钻井施工具有重要指导价值。

Grasping creep properties of salt-gypsum is an important foundation to design safe mud density window and select casing materials due to the effect of temperature and in-situ stress, especially in deep salt-gypsum rock layers. Salt-gypsum rock creep after borehole has been drilled, which leads to blockage and casing deformation. The creep experiment was carried on salt-gypsum rocks from well-Y of South-west oilfield, mainly studied effect of NaCl content on the transient creep and steady-state creep rate. The results show that the transient creep and steady-state creep rate have increasing law with NaCl content conforming to power-law creep. With the increase of NaCl content, both transient creep and steady-state creep rate increase, so the difference of NaCl content is the key factor influencing the salt-gypsum rock creep property, which provides theoretical basis for selecting drilling fluid system and determining density for safe drilling of salt-gypsum rock layers, and plays an important guidance value in drilling construction.