Unlocking Gas Production Potential for Ultra-High H2S Reservoirs: Closed-Loop Testing Avoids Flaring and Toxic Gas Release

Flowback operation of ultra-high H2S gas well is a challenging scenario due to complex environmental considerations, equipment limitations and limitations on surface flow management with unstable well conditions. This paper will present an application where flaring impacts were significantly minimized and no H2S gas was released to the atmosphere, unlocking the production potential of high-H2S formations. Then, a new Technology concept is being developed. A brand new Closed-Loop Testing package has been implemented to overcome the flowback limitations with high H2S concentration and minimize flaring during well clean-up. Simulation results of expected wellbore dynamics during well start-up were studied to optimize flowback package fluid handling capacity and perform safe operating conditions. New inline measurement devices were used for H2S, CO2 and inline density measurement were key on providing in-line well monitoring parameters as well as better decision points and control in key elements and including; new control valve metallurgy, new metal-meat seals, new PRV design/metallurgies, new EE-NL pipeline, new approach in low pressure systems, pressurized storage vessels both condensate and water, as well as avoid any human exposure for critical procedure including water, PVT sampling and gas metering validations. This new approach allows to complete this task without releasing toxic gases to the atmosphere. Selected equipment also allowed continuous flow to clean-up the wellbore and safely transfer the fluids to the production line, minimizing flaring while avoiding any environmental impact. Wellbore behavior during well kick-off was as expected based on the transient wellbore and reservoir simulations, which helped achieve a continuous flow to safely flow the wellbore and handle the produced fluids. The selected closed-loop testing set-up in addition to continuous well monitoring with new inline measurement devices allowed remarkable flow management optimization. This reduced CO2 and toxic gas emissions, minimizing environmental impact. Toxic gas release in the flowback area was also avoided by eliminating manual measurements with the closed-loop testing package. The wellbore was cleaned-up to achieve the production tie-in criteria. This implementation acts as a proof of concept to flowback high-H2S wells. This paper presents the new testing equipment and practices to enable safe flowback in high and ultra-high H2S conditions. The example explained in this paper is the first post-stimulation wellbore flowback in Saudi Arabia, including ultra-high H2S conditions being achieve by a new closed-loop well-testing package.