Integrated Measurement-While-Drilling and Reservoir Mapping Technologies Enabled Effective and Economical Offshore Marginal Oilfield Development and Broke the ERD Well Records in North China Offshore

Abstract Developing offshore marginal oilfields is an effective way of increasing production, especially for mature oilfields. Due to limitations of waterways and ecological zones, the offshore platform position was restricted to be built as close as the subsurface oilfield, resulting in challenges for well construction. An extended-reach-drilling (ERD) well is recognized as a cost-effective way to develop those reserves. In North China offshore, an ERD campaign in a marginal channel sand reservoir is challenging with up to 6-km horizontal displacements and a 4.1 ratio. Critical engineering challenges include high friction and torque, less weight transfer efficiency, depth uncertainty, etc. Furthermore, uncertain reservoir characterization will enhance the difficulties of accurate trajectory control. To address these challenges, the integrated drilling intelligence service and definitive dynamic surveys synergize with the reservoir mapping service to bring solutions. Real-time drilling intelligence service (DIS) can mitigate risks and improve drilling performance. Real-time weight-on-bit and friction factors information allows the drilling team to proactively manage parameters and avoid drilling risks. Definitive dynamic surveys (DDS) measurement-while-drilling (MWD) tool could take surveys while drilling instead of staying off bottom with the pump off by using advanced signal processing and modeling to remove the effect of the drilling environment. This allows more surveys to be taken along with the trajectory and decreases in depth uncertainty. Meanwhile, the ultradeep directional electromagnetic (EM) resistivity (UDDR) mapping service can provide a real-time 1D longitudinal resistivity inversion with a deep depth-of-detection (DOD) up to 30m from the borehole, which can remotely map the whole sand lobe and thin interlayers for proactive geosteering. The integrated technologies above successfully helped the implementation of this ERD campaign. New ERD records in North China offshore were set with a 6566-m displacement and a 4.1 ratio. The ROP was well controlled by drilling parameter optimization with the DIS. The DDS MWD tool provided high-precision surveys every 10m and reduced TVD errors during the landing section. Within ~20m DOD, novel UDDR service mapped the sand lobes above the target reservoir and provided a precise target position prediction, successfully landed into the target sand lobe 95-m ahead of plan. Meanwhile, during the horizontal section, the UDDR provided a full map of the target sand channel, which tracked trajectory in the sweet spot, impelling actual production exceeding prognosis by 70%. After Well TD, a 3D Ultra-deep Azimuthal Resistivity (3D UDAR) mapping service was applied for a better understanding of the channel sand reservoir. The new technologies display the effectiveness and advantages of drilling and steering ERD wells in challenging marginal fields and establish a solid foundation for the smooth implementation of subsequent completion and production.