A Case Study on Open-Hole Logging While Tripping LWT Through Drill Pipes, as a New Technology for Risk Mitigation and Cost Optimization in Abu Dhabi Onshore Fields

Abstract

Abstract The ability to measure formation petro physical properties thru drillpipe has always been a challenge. It requires unconventional approaches to remove the effects of metal and borehole fluids on both the transmitted and received logging signals. This paper will present a proven technology executed in more than 1,000 wells all over the world and a first two successful trail case study from ADNOC Onshore wells in the Middle East. The main objective is to acquire triple combo data (resistivity, density, neutron, gamma ray, spectral gamma ray & caliper) using the LWT conveyance and acquisition technology where there is a high risk of downhole triple combo Logging While Drilling (LWD) and or wireline (WL) tools getting stuck and the risk of losing radioactive sources. The new patent pending technique was executed by using a slim downhole measurement tools inside specially designed drill collars invisible to the measurement sensors. LWT collars can be used for drilling and reaming as with normal drill collars. Propagation resistivity and neutron measurements are mostly like conventional techniques in tools physics. Density and nuclear caliper are measured by modelling the responses of three detectors short, medium and long distance away from the cesium source. The measured LWT log data has been validated through back to back comparisons with WL & LWD) logs showing almost one to one correlation considering the effects of mud invasion due to lapsed time between runs, different wellbore condition and different depth of investigations. Measured caliper, resistivity, density, neutron from LWT showed respectable match with WL or LWD tool. The differences in log responses are explained by differences in tool physics, logging speeds and environmental conditions. Similarly, the computed porosity from LWT tool comparison with WL and LWT porosity has almost the same statistics. The Quality LWT data was acquired in both wells at virtually zero LIH risk and minimum extra drilling rig time. Introducing the new LWT technique to measure accurate Open Hole formation evaluation data from inside the drill-string is a cost-effective solution in various challenging scenarios, Exploratory/ Appraisal/ Development risky & challenging wells with unknown reservoir pressures or unsystematic depletion scenarios, complex downhole in-situ stress regimes, challenging tectonically faulted or fractured areas & unstable shales and many more, posing challenge to drill stable holes and a threat to LWD/ WL radioactive tool stuck.Unplanned deviated 8-1/2’ hole section geo-steered by MWD-GR, where at last minute triple combo is desired.