Anadarko Petroleum Corp. confirmed Wednesday it approached Apache Corp. about a potential buyout but was rejected, with no “discussions of substance” occurring.

The decision to pursue the Houston-based exploration and production giant is because Anadarko, itself one of the largest independents, is “constantly striving” to create a better company, CEO Al Walker said.

“As part of these efforts to enhance value, and after extensive analysis of public information, we recently sent Apache Corp. a nonbinding offer to acquire the company. The proposed all-stock transaction, which included a modest premium, would have been highly accretive to Anadarko on a cash flow per-share basis, even before synergies.

“Further, based on public information and Apache’s historic financial and operating underperformance, the proposed transaction offered shareholders of both companies numerous value-creation opportunities given Anadarko’s demonstrated success at building value through operational excellence, proven capital allocation, and active portfolio management.”

Anadarko’s efforts to obtain a “mutually acceptable confidentiality agreement” to explore the merits of a potential transaction “were summarily rejected,” Walker said. No “discussions of substance occurred.”

The Houston area independent is “unwilling to pursue the transaction without access to detailed nonpublic information, and based on our analysis, which shows that Apache appears to trade at or near full value currently, the offer was withdrawn,” he said.

After rumors surfaced that Apache was being considered as a takeover target for about $18 billion, analysts had puzzled about what producer might be interested, often citing BP plc as the most likely buyer, since it is building its North American operations. However, most analysts said the possible $18 billion offer was too low and would be rejected. That Anadarko was the potential buyer puzzled some analysts.

Anadarko has “multiple decades of high quality inventory” in Colorado’s Wattenberg field and in the Permian Basin’s Delaware sub-basin, “which will likely expand in 2016…as the company delineates additional zones and proves up downspacing potential,” said Tudor, Pickering, Holt & Co. (TPH) on Wednesday. “There is little need, in our view, to add a large, scattered footprint, much of which is outside the core unconventional fairways, as we believe the current Delaware asset base already has the potential to reach similar size and scale to the Wattenberg.”

Anadarko’s management team also recently stated it had little interest in buying international assets, preferring to grow through organic exploration and development, TPH analysts said. Like Anadarko, Apache has a substantial international portfolio.

“Being a top quality explorer is one thing, but we would be hard pressed to see how buying large mature fields internationally would strategically fit and how it would be accretive for the organization given Apache has done a great job efficiently running both Egypt and the North Sea,” the TPH team said.

BMO Capital Markets analyst Phillip Jungwirth said Tuesday Anadarko was the more likely takeover candidate, not Apache.

“While a deal looks attractive on paper, the possibility is clearly negative for the Anadarko story, in our view, given the perception of a higher-quality asset base in which Apache’s assets (outside of Egypt and Tier 1 Midland/Delaware Basin) would have difficulty competing for capital,” Jungwirth said. “Also, many view Anadarko as a takeout candidate in itself…Anadarko shares have underperformed Apache by 2,500 basis points in the past three weeks or 2,700 basis points over the past six weeks.”