Distinct Value Realisation from Pulsed Neutron Spectroscopy (PNS) and Subsurface Integration in a Mature Niger Delta field

Abstract

Understanding fluid dynamics is key in optimal well and reservoir management practices in brown fields. This is more apparent in strong water drive reservoirs where water shut-off (WSO), zone change, recompletion and work-over drilling are key well intervention activities usually carried out to optimize the production from these fields. Geologically, the structural architecture of these reservoirs makes it difficult to have uniform fluid movement with time as they are produced. In addition, the interpretation of Carbon/Oxygen (C/O) ratios as derived from Pulse Neutron Spectroscopy (PNS) logs in terms of hydrocarbon saturation is such that, a lot of variables can influence the outcome of the result. Water leg calibration, type of completion, and open hole log interpretation are some of the factors that can affect C/O interpretations negatively. PNS logs when combined with extensive subsurface data integration can become very useful in understanding fluid dynamics and optimization of intervention activities. This has been demonstrated recently in the X Field of SPDC.The two case studies in this paper demonstrate how PNS data and subsurface integration has helped resolve both non-uniform flushing as well as interpretation problems usually associated with PNS logs. Significant cost savings of ca. USD0.5 mln and ca. 2000 bopb have been realized from optimizing the planned well intervention activities on these cases. The result and observation from the study is already being applied to de-risk other similar opportunities in the portfolio while still exploring further understanding to further improve the gains.