胜北构造粘土矿物纵向分布及演变规律

为探求吐哈油田胜北构造粘土矿物纵向分布规律与井眼稳定性的关系，以台参２井为例系统分析了本构造泥页岩地层中高岭石（Ｋ）、绿泥石（Ｃ）、伊利石（Ⅰ）、蒙脱石（Ｓ）和伊蒙混层（Ｉ／Ｓ）矿物的分布及演变特征，测定了粘土矿物中各种阳离子（Ｋ＋、Ｎａ＋、Ｃａ２＋、Ｍｇ２＋）的可交换容量（ＣＥＣ）．研究表明，胜北构造上部地层是以Ｓ（约４０％）为主的高活性泥岩，中部大段硬脆碎泥页岩以Ｉ／Ｓ（约５０％）为主，下部地层Ｉ／Ｓ渐减至消失．Ｋ、Ｃ、Ｉ纵向分布较为均匀，基本与井径扩大率无相关性．井径扩大率与Ｉ／Ｓ含量呈明显正相关，但与Ｉ／Ｓ中的Ｓ含量却呈负相关，Ｉ纵向变化小但总含量较高（约５０％）且其中裂隙、解理发育，因此认为井眼的失稳主要是Ｉ及Ｉ／Ｓ含量较高的硬脆碎泥页岩在释放构造应力时，各种综合工程因素诱发地层崩裂和剥蚀而引起的，具有明显的时敏性．由于这种地层的ＣＥＣ特别是ＥＫ较低，因而必须主要靠封堵裂缝而不是提高钻井液中的Ｋ＋浓度来抑制井眼垮塌

Longitudinal Distribution and Evolution Law of the Clay Mineral in Shengbei Structure

For studying the relationship between the distribution of clay mineral and borehole stability in Shengbei structure, taking TC2 well as an example, the authors systematically analysed the longitudinal distribution and the evolution of kaolinite(K), chlorite(C), illite(Ⅰ), smectite(S) and illite/smectite mixed layer(I/S)in mud shale formation of the structure, and measured the cation exchange capacity(CEC)of K +,Na +,Ca 2+ ,Mg 2+ in the clay mineral. It is shown that in top formation is active mud shale, the content of S in it is about 40%; in middle is hard, brittle and shatter(HBS)long mud shale, I/S is about 50%; in bottom formation, I/S decreases gradually and disappears. K,C and I are well distributed in longitudinal direction, and they are not correlative to the rate of hole enlargement (RHE). RHE has a positive correlativity with I/S content in clay, but it has a negative correlativity with the S content of I/S. I in clay is more than 50%. The fractures and cleavages in I are developed. So it is held that the failure of borehole stabilization is due to the formation cracking and slabbing caused by some engineering factors when HBS mud shale contained more I and I/S releases tectonic stress. This type of hole collapse has obvious time sensitivity.The main measures for inhibiting well sloughing must be plugging fractures instead of increasing K + concentration in drilling fluids because CEC especially EK in clay mineral is very small in Shengbei structure.