玉北古近系膏泥层地应力分布规律探索

Study on In-Situ Stress in Paleogene Gypsum Mudstone in Yubei Area

塔里木盆地玉北地区地质构造运动剧烈,古近系地层压力高、地应力异常,膏泥岩蠕变缩径导致套管挤毁变形。为了明确膏泥岩蠕变特性,从区域构造演化史入手,结合区域内断层发育情况,依据实钻资料和测井资料,针对古近系发育灰白色泥膏岩、石膏岩、含泥石膏夹薄层灰色含泥质白云岩以及非均质性较强的特点,选用黄氏"七五"地应力计算模型,求取了膏泥岩地层垂向应力和水平方向最大、最小主应力,并依据3个主应力间的大小关系,明确了断层、断裂带的类型及分布情况,分析了各井地应力特征,在此基础上得出了玉北地区古近系地应力分布规律和异常地应力梯度,能够指导后期井位布置、套管程序优化、钻井施工方案等设计。

Complex and atrocious geological conditions result in high formation pressure and abnormal iwsitu stress in Paleogene, which were causes of casing collapse in several wells. In order to clarify the creep characteristics of gypsum mudstone, considering the tectonic evolution and the fault distribution in Yubei Area, Huang＇ s＂seventh-five＂model was used. With actual drilling and logging data, this model could determine vertical and horizontal maximum and minimum principal stress in gypsum mudstone layers. Based on the relations among three principal stresses, the types and distribution of faults and fault zones were identified. In addition, in-situ stress characteristics of each well were analyzed. Finally, the distribution of in-situ stress and gradient of abnormal in-situ stress were obtained in Paleogene, which may help guide future well deployment, optimization of casing program and the drilling program.