塔中地区鹰山组碳酸盐岩储层水平井轨迹优化研究

针对塔中地区鹰山组碳酸盐岩的储层特征和目前水平井钻探过程中遇到的问题,综合考虑地应力控制下的井壁稳定性和后期压裂增产等因素,对水平井井眼轨迹进行优化。通过有限元数值模拟计算,分析不同井眼轨迹下的水平井稳定性和压裂缝形成难易程度,得到最优的井眼轨迹方向。对塔中某井的分析结果表明:所分析水平井的井周地应力状态为潜在走滑型,基于地应力状态和岩石力学特征,从井壁稳定性的角度考虑,当井筒延伸方向与水平向最大主应力夹角为20°~40°时井壁较为稳定,有利于安全、高效钻井;从压裂缝形成的难易程度考虑,当井筒延伸方向靠近水平向最大主应力方位时,井周张应力最大,压裂过程中较容易形成张裂缝。综合井壁稳定和后期压裂增产,分析得到塔中地区最为有利的水平井井眼轨迹方向为与水平向最大主应力夹角20°左右,并通过现场验证得到该方向既能保证安全钻井又能通过后期的压裂获得较高的产能。

Study on horizontal well track optimization of carbonate reservoir in Tazhong region

The main content of the thesis is about the feature of carbonate reservoir in Tazhong region and the problem occurred in the process of horizontal well drilling, and optimizing the well track under the consideration of borehole stability under the control of ground stress, fracturing stimulation in the later period, etc. The paper concludes the optimal direction of well bore path by using finite elements software to analyze the stability and the difficulty level of making fracturing fracture in the present in-situ stress, potential strike-slip type, in the Tazhong region. The consequence indicates that, in the present ground stress state in Tazhong region and the feature of rock mechanics, from the view of well bore stability, for the safe drilling, the appropriate included angle between well hole and maximum principal stress is from 20° to 40°,from the side of creating fracturing crack, the smaller angle can have the maximum tensile stress to make fracture much easily. In the compromise of bore well stability and fracturing stimulation, the most optimal included angle between wellbore and maximum principal stress in the Tazhong region is approximate 20°. And in field application, drilling in that angle can guarantee the safe drilling and satisfied production in the fracturing.