Abstract Logging while drilling (LWD) has been gaining preference over conventional e-line logging in complex well trajectories for operational reasons associated with well-safety and delivery efficiency. Earlier such operations lacked some key measurements due to limitations of high-temperature, high mud salinity etc. that can be overcome with technological advances now, thereby extending the operational envelope for formation evaluation while drilling. This work presents a case study illustrating this in offshore China from a condensate reservoir. Highly heterogeneous, fractured, high-resistivity deep basement reservoirs are drilled with hyper-saline water-base mud (WBM) through high-angle and horizontal well trajectories that suffer well stability issues jeopardizing the wireline logging options. Advances in LWD, especially that of ultra-high resolution borehole images in high-temperature and high salinity conditions have helped with unique engineering design; helping eventually with quantitative interpretation of fracture network. High-temperature logging conditions were further made difficult with high contrast of formation resistivity and mud resistivity in addition to expectations of higher rate of penetration (ROP) for efficient well delivery. To align the downhole temperature with LWD advanced tools specification and effectively manage the associated risks, a tailored process including stimulating borehole temperature changes, redesign staging-in course based on nearby wells drilling process is also implemented. Ultra-high-resolution image (UHRI) data was acquired on drill string with natural GR, propagation resistivity, laterolog resistivity, array acoustics, density & neutron, caliper, which conventionally would take 3 runs for wireline logging amidst deteriorating borehole conditions and operational risks. Data from more than 40 successful runs covering formation resistivity upwards of 10,000 ohm-m and mud resistivity downwards of 0.015 ohm-m in slim-hole operations was analyzed and is being presented. The working scope covered a variety of conditions including maximum formation temperature up to 190 degC, maximum logging speeds up to 300 ft/hr, and large formation-to-mud resistivity contrast exceeding 3 million. The LWD results were comparable to wireline logs deployed in the same campaign in two low inclination wells. This work presents an innovative approach to develop a deep-seated reservoir using advanced LWD tools, extending the operating envelope in the pursuit of economically valuable condensates. This also serves as a guideline for similar campaigns having a requirement to extend the operating envelope.
Zhu et al. (Mon,) studied this question.
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