Implementing Managed Pressure Drilling Technique in Drilling an Offshore Exploration Well

Abstract

The managed pressure drilling technique has been widely applied in land to solve different technical and well control issues as well as ensuring the safety of field personnel. Offshore exploration drilling is one of the most challenging operations due to its nature of drilling hazards and facing environment. There is a great need of applying managed pressure technique in offshore drilling. A new MPD equipment is developed, which is named as pressure control drilling system (PCDS), and performs its first application in offshore drilling to reach its further potential. The PCDS is applied in an exploration well located in the gulf of Bohai to perform a near-balanced drilling operation for the purpose of reducing the density of drilling fluid. It utilizes the microflux control technique to precisely monitor the wellbore condition and detect the overflow and loss of circulation in time. The technique of constant bottom hole pressure is used by the PCDS to maintain the bottom hole pressure constant and minimize the fluctuations of bottom hole pressure during making connections and round trip, enhancing the drilling performance. The equivalent circulating density of 1.08-1.09 g/cm3 is obtained by the proposed PCDS using the solid-free drilling fluid with a density of 1.03g/cm3. While nearby wells use the drilling fluid with the density of 1.15-1.20 g/cm3 at the same Stratum. Cooperated with the drilling fluid of lower density, utilization of the proposed pressure control drilling system significantly avoids the formation damage. The chip hold-down effect is minimized by the proposed PCDS to increase the ROP. The average ROP of nearby wells is 4.02 m/h. While the average ROP of the well using the proposed PCDS is 7.23 m/h, indicating the increase of 80 percent. With the assistance of the proposed PCDS, the drilling team set a single bit footage record of 312.88 m and daily footage record of 163 m, which demonstrates a great improvement of operation efficiency. No drilling compliancy occurs during drilling in the target stratum. Utilization of PCDS dramatically minimizes the potential of well control and ensures the down-hole safety. This application is a successful attempt of the pressure control drilling system in the offshore operation, demonstrating the wide range of applications of the PCDS. Proper utilization of the PCDS can optimize the offshore drilling operation, prevent drilling issues such as well kick and loss of circulation, minimize the non-productive time and therefore reduce the drilling cost.