Improving Gas Storage Operations with Horizontal Wells
The Tri-Cities gas field near the city of Athens in Texas was once an important contributor to natural gas production in the region. As a depleted reservoir, it provided a ready-made solution for underground storage of natural gas supplies.
We were engaged to assist with analyzing some reservoir characteristics during an asset integrity review of the wells within the reservoir. We created a complex 3D simulation model to study the reservoir’s dynamic behavior during periods of injection and withdrawal. This allowed our client to assess how it would perform when used for storage. The model also helped to validate new drilling and operational strategies for the site.
It was determined that the existing vertical wells would not drain the field efficiently during operations, and the decision was made to drill a series of new horizontal wells to improve the facility’s long-term operational performance. Optimum locations for five new horizontal wells were identified and verified by the 3D reservoir model. We subsequently provided drilling management services for development of the new wells.
Drilling the wells presented significant technical challenges. After reaching a vertical depth of approximately 7,000 feet, the wells had to be turned 90 degrees to drill the horizontal sections. Russell Bentley, WSP’s project manager, observed: “The work was also being performed within a very restricted natural gas zone that was, in effect, only about two feet thick.” A geosteering technique involving the use of logging-while-drilling tools at the bottom of the drill string allowed the team to receive real-time data about the formation during the project.
The work was performed on a highly accelerated schedule, with two drilling rigs operating continuously for about four months to complete all five wells, while simultaneously adhering to rigorous safety requirements. Our expertise in reservoir and aquifer storage was instrumental in delivering this challenging project successfully.