Multi stage Frac & Testing of High Angle HPHT Ultra Sour Exploratory Well: Challenges Encountered & Mitigated

Abstract

Reservoir production challenges are always escalated when the concentration of H2S and CO2 are extremely high. This paper highlights the challenges encountered, mitigation techniques used to overcome hurdles, and remaining tasks in testing the first deep high angle High Pressure High Temperature (HPHT) exploratory well completed with Multi-Stage Completion (MSC) in the presence of ultra-sour fluid (H2S-31% and CO2-38%) in Kuwait. The subject Jurassic well is drilled at a highly deviated angle up to 19,000 ft in measured depth (MD). The completion installed is composed of an open-hole MSC and three stages of frac ports tied back with a Liner Hanger to the upper 4.5 inch tubing. After setting the completion, the 15.8 ppg oil base mud (OBM) completion fluid was displaced with 11.6 ppg brine. DataFrac treatment and analyses were followed by acid fracturing treatment in all three stages. Post-fracturing well clean-up is achieved by continuously pumping Hydrogen Sulfide (H2S) scavenger to protect the entire surface test equipment set up. Employing self-containing breathing apparatus for personnel safety and having two flare pits permitted uninterrupted well testing for 13 days. During the well clean-up, the very high H2S and Carbon Dioxide (CO2)concentrations in knocked out fluid were 31% and 38%, respectively. However, due to the extremely high sour nature of reservoir fluid and limitation of separator metallurgy, the flow rate measurement is limited to only 2 hours. Various technical and operational safety challenges were safely handled during the well preparation, acid fracturing, testing, and flaring operation without any HSE incident. Moreover, continuous flow rate measurements are not achieved due to equipment limitations. Currently, a multi-phase flow meter (MPFM) which can handle high H2S and CO2 is under evaluation to conduct long term well testing to ascertain the production potential. The completion of three stage acid fracturing treatments and safely testing the high sour deviated well in HPHT conditions of an exploration well for the first time in the State of Kuwait is a remarkable success, paving the way for future field development in similar well conditions. However, production and processing of this highly sour fluid will be challenging for field development.