Abstract:
The western margin thrust zone of the Ordos Basin are characterized by the presence of natural fractures at the interface of deep shale formations, with multiple sets of weak pressure-bearing layers coexisting in the long open hole wellbore section, resulting in weak pressure-bearing capacity and frequent lost circulation during drilling, which seriously restricts drilling speed and efficiency. To this end, the pressure-bearing wall protection while drilling technology has been studied to enhance the pressure-bearing capacity of weak pressure-bearing layers in the open hole sections. Precision positioning technology for leak layers in long open hole sections has been employed to achieve accurate positioning of the leak layers. Acid-soluble high-filtration plugging fluid has been developed, which was highly effective in plugging severe loss caused by fractures and thus significantly improving drilling efficiency. These technologies have been integrated into key leakage prevention and plugging technologies for the thrust zone at western margin of Ordos Basin. These technologies have been applied in 14 shale gas wells in the thrust zone at the western margin of Ordos Basin, reducing the special plugging time by 55.25% and shortening the drilling period by 15.5 days. The comprehensive leakage control technologies for the thrust zone at the western margin of Ordos Basin provide technical support for the safe and efficient development of unconventional oil and gas wells in Ordos Basin.