Unlocking Reservoir Potential with Logging-While-Drilling Technologies in Mature Fields

Abstract

Abstract Wireline logging has been the preferred primary formation evaluation tool commonly used for decades for assessing reservoir quality. However, where the complexity of the well plan and uncertainty in formation pore pressure may necessitate decision making in real time, logging while drilling (LWD) has become more commonplace. Assessing the reservoir properties of previously drilled laterals presents a challenge due to hole condition deterioration over time. Even if the borehole is stable and competent while drilling, it might be subject to time-dependent deterioration that could be due to reservoir pressure depletion. LWD tools can be used to re-evaluate previously drilled wells as well as log new wells while drilling. In some wells it is required to measure the formation pressure to be able to log, deepen, and consequently drill several laterals from existing wellbores. The uncertainty in formation pressure depletion can result in operational delays due to difficulties in optimizing the mud weight window based on available data. LWD tools, including formation testers, can be utilized in real time to acquire formation pressure and mobility information, which are key measurements for mud-weight optimization and confirming the feasibility of drilling deeper. LWD tool strings, including formation testers, have been used to acquire real time formation evaluation and reservoir pressure measurements in formations which had previously limited success due to the relatively low mobility, decreasing the likelihood of obtaining a reliable measurement. Lessons learned have been developed to implement best operational practices in successfully testing in these low mobility environments. Gamma Ray, Resistivity, density, neutron, and NMR LWD sensors were also used in the bottom hole assembly (BHA) to replace wireline logging due to the risks associated with wireline deployment under these unfavorable hole conditions. Measurement integrity and data quality provided by LWD sensors have been evaluated and used for the design of multilateral wells. This paper presents the effective utilization of LWD technologies to address operational risks of logging highly deviated well while facilitating robust formation evaluation for this development re-entry drilling program.