The Application of State of the Art Geosteering in Extending the Oil Production tn Late Life Asset: Case Study from Offshore Peninsular Malaysia
Authors: Khor S. , Azam M. N. H. M. , Aziz M. F. A. , Fadjarijanto A. , Shafie S. H. , Mirto E. , Alang K. 
Published: February 2025

Abstract
Field E, located offshore Peninsular Malaysia and discovered in 1970, was originally regarded as a marginal field development due to its initially estimated low reserves. As part of a recent development campaign aimed at extending and sustaining production, four infill wells were drilled utilizing the ultra-deep resistivity technology to optimize drilling and production. This paper captures and highlights the successful utilization of geosteering technologies, resulting not only in a predicted extension of the well life but also led to production rates that exceeded expectations.
The 2023 infill development campaign encountered several challenges including a thin oil column entirely within an already swept zone, uncertainties in fluid contact due to a large gas-cap, a strong aquifer, significant mobility contrasts between oil and water, as well as laterally extensive shale breaks or sand discontinuities and variations in lateral properties. Drilling extended reach wells longer than 1 km was necessary, with trajectories cautiously positioned near the reservoir top while ensuring optimal separation from the water contact. This approach aimed to enhance the chances of achieving the desired minimum horizontal length that intersects intervals with favorable oil saturation. To achieve these objectives, real-time interpretation based on continuous 1D resistivity mapping was utilized while drilling, requiring a collaborative effort across various disciplines from both the drilling and subsurface teams.
This case study reveals the value of real-time 1D-resistivity inversion results from ultra-deep electro-magnetic measurements to detect the reservoir top during landing, locate the water contact and resolve the thin shale break, thereby enabling accurate geosteering within the reservoir.
This technique was substantiated by well results which intersected a thicker oil column than anticipated through effective geosteering between two sand lobes. Additionally, the thin shale break was distinctly delineated within the two sand bodies, attributed to the high resolution of the inversion. Mapping the high-water saturation and oil-water contact was crucial for ensuring the well path drilled and remained in an unswept zone. Furthermore, main sand channel packages were encountered and mapped with greater confidence, enhancing our understanding of the channel complex's nature. Taking advantage of the tens of meters of depth detection, one of the infill wells successfully navigated a previously undrained structure in the southwest; the well reached a measured depth of more than 4,600 m, making it the longest in the field. This discovery of new oil accumulation has doubled the production rate to over 3,000 bopd, contributing to an incremental peak production of ~10,000 bopd.
The success of this infill campaign, which utilized geosteering LWD technology integrated with advanced high-resolution 1D-resistivity inversion complemented by a well-suited completion strategy, has proven to be an effective solution for addressing the extreme formation challenges in this marginal field. This strategy has revitalized the aging asset, leading to increased production rates and ultimately extending the overall life of the field.