End Speculative Oil and Gas Leasing Act of 2021 This bill specifies requirements for the leasing of oil and gas resources on federal lands. The Bureau of Land Management (BLM), with respect to certain federal land that is covered by a reasonably foreseeable development scenario (i.e., a long-term projection of oil and gas development) shall not offer the land for lease until such scenario includes an assessment of the land's oil and gas potential that specifically identifies the potential for all acres subject to decisions on availability for leasing. If certain federal land that is otherwise available for leasing of oil and gas resources is not covered by a reasonably foreseeable development scenario, the BLM shall complete such a scenario in accordance with the requirements and factors described in this bill. In general, the BLM shall not offer for lease certain federal land otherwise available for leasing of oil and gas resources if such land is designated in the applicable reasonably foreseeable development scenario as having low or no potential for the development of oil or gas resources. However, the bill provides for a variance process. With respect to each of these requirements, exceptions apply for federal land that is leased for the purpose of preventing oil or gas drainage or that meets specified requirements related to size and proximity to an oil- or gas-producing well.