Peak production of 15 MMCFD was restored in a sour well (17% H2S) drilled and completed near-

balance to prevent reservoir damage. The ACG #6B well is in the Whitney Canyon Gas Field located in southwest Wyoming. The Mission Canyon formation is the primary reservoir. The current bottom hole pressure is less than 1100 psi at 12,457 feet TVD. Severe damage occurred to the original ACG #6A wellbore and the reservoir during an attempted work-over to replace production tubing.

Recently drilled wells suffered massive lost circulation. Continued pressure depletion raised concerns that the ACG #6B sidetrack was undrillable using conventional overbalance drilling techniques. lf drilling was successful, setting and cementing production casing through the reservoir carried high risk of getting stuck. Failure to get casing to bottom would result in a poor performing well as the highly damaged rock left open hole would be unproductive.

Formation damage from the expected loss of 50,000 barrels of drilling fluid would require a fracture stimulation to regain productivity. To prevent these massive fluid losses while drilling and completing the well, the asset team considered near balance drilling and open hole completion the best option. This technique, if successful, would maximize the well productivity and eliminate casing across the reservoir, perforating, and massive acid stimulation. Drilling near balance would also significantly improve the drilling ROP and reduce nonproductive time caused by massive losses

Utilizing near-balance drilling and an open hole completion, allowed a simplified acid wash stimulation vs. a typical acid frac on offset wells. Near-balance drilling was preferred to underbalance drilling to manage the risk of produced sour gas at surface.

Production results from the well exceeded the prediction of 10 MMCFD. Current well production is in excess of 11 MMCFD and peak production rates were nearly 15 MMCFD. Minimizing formation damage provided the productivity and resulted in decreased completion costs.

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