Optimizing Horizontal Well Geosteering and Reservoir Evaluation in Complex Marginal Oil Field with Ultra-Deep Reservoir Mapping and Ultra-High-Definition Multilayer Mapping-While-Drilling Technologies
Authors: Wu Donghao , Li Yan , Li Wei , Zhang Lili , Wang Fei , Chen Chengqian , Li Cang , Yu Xiaoning , Wang Chao , Wang Haifeng , Wang Shuai 
Published: February 2024

Abstract
BZ-X field is a marginal field with intensive production for more than 10 years. Although it still has potential to achieve a higher recovery ratio, complex fault systems of the structure with high uncertainty of sand channel connectivity, sand property and structure set major obstacles for the exploration of residual oil and wellbore optimization in this field. Meanwhile with production and water injection, the OWC and flooded zone are lifting year by year. A method to depict the reservoir and locate trajectory precisely in the upper part of the target is crucial to the development team.
Recently, the Phase II of horizontal well campaign to exploit trapped oil were planned in this field. Successful cases in complex fluvial system in Bohai bay convinced the operator to use ultra-high-definition multilayer mapping-while-drilling technology and ultra-deep reservoir mapping technology to effectively optimize the wellbore position and get better understanding of this area after years of production.
With the latest combination of axial, tilted and transverse antennas and significant software enhancements, ultra-high-definition mapping-while-drilling electromagnetic propagation resistivity method could provide larger depth of detection to completely depict the thin sand channel with much more detailed resistivity property inside, fitting for most of challenging scenarios such as severe changing of reservoir structure, local sedimentary character, overlapping sand bodies, and sand pinch out.
Besides the close shot, ultra-deep reservoir mapping technology could provide larger vision of reservoir mapping with OWC detection. With the scale up to 250ft depth of detection, this technology perfected the view of reservoir, unfolding an enlarged sight for more potential development targets.
In total 8 wells were drilled with new reservoir mapping technologies. With ultra-high-definition multilayer drilling-while-mapping technology, trajectories were precisely controlled at the top sweet zone to meet both oil column height and oil property requirement; Local sedimentary characters were clearly portrayed by the latest inversion which help delineate sand channel with rich information to compensate the blur sand property caused by low vertical resolution of seismic profile. It also depicted the pinch out process of single sand and property at the side of the channel.
With ultra deep reservoir mapping technology, OWC was successfully detected precisely to control the nearby planned wells. Different overlapping sand channels and potential new sand channels were detected to provide a possible direction for further planned wells. With the combination of close and full shot of this area, the operator is provided a better understanding to the complex environment which could highly contribute to further development plans.
The production was greatly enhanced compared to original prediction after using the technology and the result exceeded expectations. The combination of two technologies could also benefit current development in North China market for marginal oil exploration.