苏丹六区KCl/硅酸盐钻井液体系的研究与应用

苏丹六区出于节约成本的考虑,将部分三开井身结构改为两开结构,不同压力系数和特性的地层处于同一裸眼段内,造成原有的钻井液技术已经不能满足钻井作业的需要,容易发生井塌和井漏的问题。为此,根据地层特性,对原有的钻井液技术进行改进,通过大量的室内实验和现场试验,研发出一种实用的KCl/硅酸盐钻井液体系。新体系可将上部地层的承压能力提高至1.25 g/cm3,实现了窄密度安全窗口下的安全钻进;通过有效控制钻井液固相含量,克服了硅酸盐钻井液流变性难以控制的缺点,实现了钻进过程中钻井液体系的稳定转化。新的KCl/硅酸盐钻井液体系解决了井身结构改变后长裸眼段内不同地层性质和不同压力体系下出现的井塌和井漏的问题,减少了体系转化所需时间,大大降低了废弃钻井液的排放量,缩短了钻井周期,节约了材料成本。

Research and application of KCL/silicate drilling fluid in block 6 of Sudan

In consideration of saving costs in block 6 of Sudan, the operating company changed the structure of some wells to ‘two-section’ instead of ‘three-section’. Thus formation with different pressure factors and characteristics is in the same bore hole which would cause complex problems in the hole such as lost circulation and borehole collapse and under which the original drilling fluid technology could not meet the demand for drilling. Thus, the original drilling fluid technology is improved according to the formation characteristics. The practical KCL/silicate drilling fluid system is developed based on a lot of experiments in lab and on site. The new drilling fluid can increase sustainable pressure of upper formation to 1.25 g/cm3 and can drill safely with a narrow safety density window. The effective control of solid concentration of drilling fluid can overcome the difficulties in control the rheological property and realize the stable conversion of drilling fluid system in drill process. The new KCL/Silicate drilling fluid solves the potential risk of caving and lost circulation problems in long bore hole with different formation properties, pressures after the wellbore structure changes, reducing, system conversation time and the drainage of waste drilling fluid significantly, propenties, shortentingthe drilling period and cuuting costs of drilling fluid materials.