Texas-based CrystaTech is taking its patented CrystaSulf hydrogen sulfide (H₂S) removal technology downhole, and it is getting some help from multinational energy company Total. In a joint development and commercialization agreement between the two companies, the Downhole Sulfur Recovery (DSR) process will be a regenerable process for continually removing and recovering sulfur deposits in sour gas wellbores.

The DSR process is a modification of the CrystaSulf process, which is designed for the medium-scale (0.1 to 25 tons per day) removal of sulfur deposits. The hydrocarbon-based CrystaSulf process is a modification of the liquid-based Claus process, an industry standard for the removal of large-scale sulfur deposits. CrystaSulf is a one-step, direct treatment for any gas stream that converts gaseous H₂S to solid crystals of elemental sulfur, and avoids the problems of plugging, foaming, and high chemical costs associated with conventional aqueous liquid redox processes, according to the company.

CrystaSulf has been applied in applications ranging from direct treatment of high-pressure natural gas and heavy oil associated with gas production to clean coal syngas cleanup streams and amine offgas. Further, the company states that the technology easily handles gas contaminants (heavy hydrocarbons, carbon dioxide, oxygen, ammonia, sulfur dioxide, etc.), has a 10-to-1 turndown ratio, and is able to ramp up with heavy oil production.

To this point, these applications have all taken place at the surface. The new initiative between CrystaTech and Total will modify CrystaSulf such that it can remove sulfur deposits in sour gas wells (containing 35% H₂S or greater) using a solvent regeneration process. The patented approach will selectively remove elemental sulfur from the wellbore casing, thereby eliminating common sulfur deposition problems of plugging, flow restriction, reservoir impairment, and tar formation.

Existing downhole sulfur removal technologies require producers to shut in gas production while injecting disposable solvents to clear blocked wellbores, to inject nonregenerable solvents continuously, or to use chemical regeneration processes. According to CrystaTech, the DSR process will avoid the need for any of these options, thus providing economic and environmental benefits to the producer.

For its part, Total has been involved in all aspects of the development effort, including a pilot unit demonstration phase of the project that will begin in the near future. In the long term, the energy company plans to incorporate the regenerable technology for the production of its very large sour gas reserves around the world.