Unlocking Ultra-Sour Gas Reservoirs by Mitigating Elemental Sulphur Deposition While Maintaining Sale Gas Quality

Unlocking ultra-sour gas reservoirs in brownfields presents many surface and sub-surface operational challenges that must be overcome. Ultra-sour well testing carries risks due to reservoir uncertainties and sour gas handling at surface. During high H2S reservoir exploration, a novel approach was used to analyze elemental sulfur content in produced solvent samples and validate laboratory results. Various potential elemental sulfur solvent chemicals were tested in the laboratory to determine the most cost-effective choice to prevent elemental sulfur deposition during well testing. A new chemical was evaluated specifically in ultra-sour reservoirs. A custom-built, portable High Pressure Liquid Chromatography (HPLC) apparatus was used for continuous sulfur content analysis in gas and liquid with net zero emissions, and portable H2S sweetening technologies were assessed. A specialized oil-based chemical was obtained from the in-country refinery to mitigate surface and subsurface elemental sulfur deposition during ultra-sour gas production. Laboratory tests on samples of the selected chemical indicated improved elemental sulfur solubility compared to diesel over the range of temperature expected to be encountered in the production process. A completion design was chosen to enable downhole delivery of this solvent. Samples of the produced solvent were analyzed at the surface using custom, portable HPLC equipment to determine the optimal solvent injection rate. An advanced ultra-sour gas analyzer was installed at the manifold station to monitor the blended gas and prevent any integrity and corrosion issues while testing the ultra-sour to comply with the blending study. A new portable H2S sweetening unit technology was also evaluated under various flow conditions.