Infill Horizontal Well Placement Optimization and Execution Through Time-Lapse Cased-Hole and Open-Hole De-Risking Efforts Coupled with High Definition Geosteering Frontier Technology
Authors: Goh Jin Wang Arthur , Wahid Ali Nurul Athirah , Chuah Mei Mei Stefanie , Bt M Zaid Siti Nurfarhana , AL Naupa Nagarajan , Ain Sapian Nik Fazril , Bt Rafiuddin Nur Liyana 
Published: October 2022

Managing complex brownfield production and sustainability expectations has become a norm in the oil and gas industry – where opportunities to materialize resources can still be present. This paper covers the constructive practices in Field B, a 50-year-old brownfield offshore Malaysia in understanding uneven fluid movements dynamics via execution of time-lapse data acquisitions to justify planning for infill drilling. This has led to successful four (4) horizontal geosteering well placement in the major oil reservoir units. Time-lapse contact monitoring was made possible through integration of recent open-hole, production, dynamic simulations & cased-hole saturation logs in Reservoir A. Between the year 2014 to 2021, saturation logging campaigns were executed, and phenomena of uneven fluid contacts was observed between the un-faulted western to eastern areas of the field. Eastern area wells have observed shallower gas-oil contact (GOC) and oil-water contact (OWC) by 80 to 100ft-TVD, resultant from gas and water injections, disproportionate production withdrawal, potential gas leaks behind casing and stronger aquifer strength. The combination scenarios of geological structure and fluid contact uncertainties provided a range to drive geosteering pre-job modelling planning to sensitize multiple cases to optimize the well trajectories.

The integrated ranges of current contact derived from saturation logs, recent open-hole logs and reservoir simulation constructed the basis of low-base-high remaining oil opportunity cases for planning and economic evaluations. Coupled with advancement of frontier technology Geosteering-HD, four (4) wells successfully penetrated 35 to 80ft-TVD of oil column in horizontal section and maintained along 1500-2000ft-AHD. Tilted oil-water OWC was observed in three (3) of the wells located at eastern area, where the OWC trends shallower from the heel to toe of the horizontal portion confirming the results from time-lapse contact information and contacts prediction from reservoir model. The other well drilled at western area, observed a mostly flat OWC throughout the horizontal section with slight tilting towards the toe, reflecting weaker aquifer strength at the western flank as observed in recent cased hole and open hole logging. The fluid contacts and structure penetrated in all four (4) wells are within the predicted low-base-high cases from pre-job modelling, leading to an optimum placement of horizonal well in the oil column. These optimizations have led to a successful infill campaign, delivering higher production rates of 5,600BOPD against planned 4,600BOPD for brownfield reserves acceleration.

All data acquisition needs to be exhaustively studied and managed as each holds an important piece of evidence on what the field tries to express. In this field, the timely execution of time-lapse cased-hole logs integrated with open-hole results were vital and principal driver in de-risking fluid contact uncertainties within eastern and western area prior infill drilling for a successful horizontal well campaign.