Development and evaluation of an electropositive wellbore stabilizer with flexible adaptability for drilling strongly hydratable shales

• Published in: Petroleum science 2015-08, Vol.12 (3), p.458-469
• Main Authors: Huang, Wei-An, Qiu, Zheng-Song, Cui, Ming-Lei, Zhao, Xin, Liu, Jun-Yi, Wang, Wei-Ji
• Format: Article
• Language: English
• Subjects: Colloids; Compatibility; Earth and Environmental Science; Earth Sciences; Economics and Management; Electropositivity; Energy Policy; Industrial and Production Engineering; Industrial Chemistry/Chemical Engineering; Mineral Resources; Original Paper; Sealing; Shale; Stability; Well drilling; Zeta potential; Zeta电位; 正电性; 水合; 稳定问题; 胶体稳定性; 适应性; 钻井井筒; 页岩地层
• ISSN: 1672-5107; 1995-8226
• DOI: 10.1007/s12182-015-0037-6

In order to overcome serious instability prob- lems in hydratable shale formations, a novel electropositive wellbore stabilizer （EPWS） was prepared by a new approach. It has good colloidal stability, particle size dis- tribution, compatibility, sealing property, and flexible adaptability. A variety of methods including measurements of particle size, Zeta potential, colloidal stability, contact angle, shale stability index, shale dispersion, shale swelling, and plugging experiments were adopted to characterize the EPWS and evaluate its anti-sloughing capacity and flexible adaptability. Results show that the EPWS has advantages over the conventional wellbore stabilizer （ZX-3） in particle size distribution, colloidal stability, inhibition, compatibil- ity, and flexible adaptability. The EPWS with an average particle size of 507 nm and an average Zeta potential of 54 mV could be stable for 147 days and be compatible with salt tolerant or positive charged additives, and it also exhibited preferable anti-sloughing performance to hydrat- able shales at 77, 100, and 120 ~C, and better compatibility with sodium bentonite than ZX-3 and KC1. The EPWS can plug micro-fractures and pores by forming a tight external mud cake and an internal sealing belt to retard pressure transmission and prevent filtrate invasion, enhancing hydrophobicity of shale surfaces by adsorption to inhibithydration. The EPWS with flexible adaptability to tem- perature for inhibition and sealing capacity is available for long open-hole sections during drilling.