Parameters optimization in deepwater dual-gradient drilling based on downhole separation

• 作者: HUANG Tao LI Jun LIU Gonghui WANG Jiangshuai YANG Hongwei
• 来源期刊: 石油勘探与开发:英文版
• 学科: 工学
• 关键词: narrow pressure MARGINS DEEPWATER dual-gradient DRILLING DRILLING parameters optimization model maximum DRILLING depth
• 年，卷（期）: 2019,（4）
• 页码范围: 819-825
• 页数: 7页
• 分类号: TE241

摘要

To ensure safe drilling with narrow pressure margins in deepwater, a new deepwater dual-gradient drilling method based on downhole separation was designed. A laboratory experiment was conducted to verify the effectiveness of downhole separation and the feasibility of realizing dual-gradient in wellbore. The calculation of dynamic wellbore pressure during drilling was conducted. Then, an optimization model for drilling parameters was established for this drilling method, including separator position, separation efficiency, injection volume fraction, density of drilling fluid, wellhead back pressure and displacement. The optimization of drilling parameters under different control parameters and different narrow safe pressure margins is analyzed by case study. The optimization results indicate that the wellbore pressure profile can be optimized to adapt to the narrow pressure margins and achieve greater drilling depth. By using the optimization model, a smaller bottom-hole pressure difference can be obtained, which can increase the rate of penetration(ROP) and protect reservoirs. The dynamic wellbore pressure has been kept within safe pressure margins during optimization process, effectively avoiding the complicated underground situations caused by improper wellbore pressure.