Study of Cementing Operations Challenges in High-Temperature High-Pressure Wells in Deepwater Blocks OML 118 and OML 119, Offshore Nigeria

High-temperature high-pressure wells in deepwater Nigerian blocks present unique cementing challenges that can compromise zonal isolation if not carefully engineered. This study examines cementing operation challenges and mitigation strategies for HTHP wells drilled in OML 118 and OML 119, offshore Nigeria, in the South South geopolitical zone. Well completion reports, cement job post-analysis records, and cement bond log results from eleven HTHP wells drilled in water depths exceeding 1,400 metres were reviewed. Temperature profiles derived from distributed temperature sensing measurements confirmed bottomhole static temperatures reaching 205 degrees Celsius, requiring specialised retarder systems to prevent premature cement setting during displacement. Four cement formulations tested under simulated wellbore conditions are evaluated: standard Class G with silica flour, engineered particle size distribution blend, flexible latex-modified system, and an expandable cement composition. Thickening time, compressive strength development, and free water separation measurements confirm that the engineered PSD blend and expandable cement formulations provide the best combination of placement stability and long-term integrity in the HTHP conditions encountered. Micro-annulus prevention through appropriate expansion pressure development is confirmed using ultrasonic cement evaluation tool responses in three post-cement bond evaluation logs. Recommendations include mandatory cement system qualification testing under representative wellbore temperature and pressure profiles before job execution. Keywords: cementing, HTHP wells, deepwater, OML 118, zonal isolation.