Abstract
Due to the impact of the geological nature of the Tengiz field, which is dominated by high fracture areas and has associated drilling challenges such as lost circulation, a first development trial well named as a "High-Pressure Lower Slope Development" (HPLSD) project well was initiated. The well was designed by the engineering team of Tengizchevroil to be horizontal producer with the longest lateral section in Kazakhstan. This paper describes Managed Pressure Drilling (MPD) and Managed Pressure Cementing (MPC) aspects of the HPLSD project.
MPD was utilized on 12 ¼ × 13 ½", 8 ½", and 6" sections to improve drilling performance. The system was used to control bottom hole pressure and manage background gas, it was further applied to minimize loss/gain scenarios and allow drilling through the "narrow" margin between pore and fracture pressures, along with decreasing the wellbore instability and differential sticking risks.
Constant Bottom Hole Pressure (CBHP) technique helped to successfully cement the 7 ¼" liner avoiding any losses of cementing fluid into the wellbore. The primary cementing of the 8 ½" hole section compiled of reservoir embedded with the layers of anhydrite and limestone has been associated with the risks of losing the cement slug, and therefore creating the risk of not achieving adequate cementation. The MPD system helped to successfully run in hole the 7 ¼" liner, cement it and finalize the 6" hole section running the Lower Completion in constant bottom hole pressure mode.
MPD results examined in this paper provide the proof that MPD system is as reliable tool not only for drilling, but also for managed pressure cementing, compensation of swab effect, managing small volumes of influx, and circulating associated gas while drilling. The additional capabilities offered by MPD technology in effectively controlling wellbore pressure profiles has led to MPD tools becoming a commonplace in Tengiz drilling operations.
