Talos Energy Inc. will move ahead with an updip penetration in the Zama reservoir offshore Mexico following initial phase results that help to derisk Zama and the remainder of the Block 7 inventory, the company said (OGJ Online, Dec. 4, 2018).
On Jan. 20, the first of three appraisal penetrations to better define the resource potential of the Zama discovery—the Zama-2—was drilled in a downdip location 1.3 miles north of the Zama-1 discovery well to confirm the geological model and define the oil-water contact. This phase was completed Jan. 20, about 28 days ahead of schedule and 25% below initially projected costs. The well reached the top of the Zama reservoir at 10,759 ft TVD and encountered the following:
• A contiguous Zama sandstone interval of 1,676 ft of gross TVD sand, materially thicker sand than the Zama-1 discovery well and slightly thicker than the predrill estimates for the Zama-2 well. The well also encountered several other thick, wet sands of similar age directly beneath the main Zama horizon for an aggregate total of 2,350 ft TVD of high quality Upper Miocene sands with rock properties analogous to Upper Miocene sands in the US Gulf of Mexico.
• The Zama-2 penetration logged 581 ft of gross TVD oil pay before reaching the oil-water contact, preliminarily estimated at 11,254 ft TVD, about 100 ft, deeper than the anticipated depth of the oil-water contact based on the geophysical signature called a “flat-spot.” The preliminary net-to-gross factor in this pay interval ranges 68-73%, with rock properties in line with those at the Zama-1 location.
• Preliminary pressure data helped confirm the oil-water contact depth, complementing the traditional logging results. The pressure data also indicates that this northern section of the reservoir is connected to the Zama-1 discovery well. The Zama-2 vertical sidetrack and the Zama-3 well will provide additional information about the reservoir connectivity and consistency.
The last objective of the Zama-2 well was to test a deeper exploration prospect called Marte. Marte was designed to inexpensively test a higher risk stratigraphic trap, and although it encountered high quality sands of consistent geological age, pressures and quality, they were not hydrocarbon bearing. However, the information gathered helps the consortium with the evaluation of the aquifer support of the main Zama reservoir and other possible prospects on Block 7.
Testing of Marte, initially expected to cost $10 million but totaled $2.5 million.
The company achieved its primary goals of “understanding the depositional environment and the presence of thick sand bodies needed for robust aquifer support, both of which help with ultimate recovery,” said President and Chief Executive Officer Timothy S. Duncan. “We also confirmed that this section of the reservoir has similar or better rock properties as compared to the Zama-1 discovery well and that the pressure information indicates connectivity to Zama-1. Perhaps most importantly, the oil-water contact was encountered at the predicted depth, if not slightly deeper,” he said. “These results provide us with confidence that our geological and reservoir modeling can be used as a predictive tool for the Zama development, just as we've been successfully using them on the US side of the Gulf of Mexico. It helps to de-risk not only Zama, but the remainder of the Block 7 inventory.”
The appraisal program is expected to be complete by midyear with the goal to achieve initial production by second-half 2022.
The appraisal program will continue next with an updip vertical penetration in the Zama reservoir from the main bore hole of the Zama-2 well, which will be cored and a drillstem test performed. The second appraisal well, Zama-3, will be drilled south of the original discovery well and will help delineate the reservoir continuity and quality in the southern part of the field and will be cored to be better understand the reservoir geology.
Block 7 interests are held by operator Talos 35%, Sierra Oil & Gas 40%, and Premier Oil PLC 25%. In December, DEA Deutsche Erdoel AG (DEA) agreed to acquire Sierra, giving it access to six exploration and appraisal blocks in Mexico, including the Zama discovery (OGJ Online, Dec. 5, 2018). Upon completion, expected in the first half of the year, Sierra will be integrated into Deutsche Erdoel Mexico, a fully owned subsidiary of DEA.
