Short answers, pulled from the story.
Oil and gas reserves and resource quantification is the process of estimating hydrocarbon volumes in the Earth's subsurface and determining which portion can be economically recovered. Reserves are quantities expected to be commercially recoverable under existing economic, technological, and regulatory conditions. The results govern how petroleum companies report assets to investors and regulators.
Resources represent all estimated hydrocarbons in a subsurface accumulation, including deposits that may not be economically extractable. Reserves are a subset of resources: the volumes that are, or are reasonably certain to be, commercially recoverable. The 2018 Petroleum Resources Management System (PRMS), developed jointly by the Society of Petroleum Engineers and four other professional bodies, defines both terms with precision.
1P designates proven reserves, defined by a 90% statistical probability of meeting or exceeding the stated recoverable volume, also called P90. 2P adds probable reserves to the total, representing a 50% cumulative probability (P50). 3P further adds possible reserves, where there is a 10% probability of delivering or exceeding the combined volume (P10).
Before January 2010, the U.S. Securities and Exchange Commission required oil companies to report only proven (1P) reserves to investors. Since January 2010, companies have been permitted to optionally disclose 2P and 3P estimates, with discretionary verification from qualified third-party consultants.
Reserve growth is the consistent pattern by which a field's estimated ultimate recoverable volume increases over time as more data becomes available. Initial reserve estimates for newly discovered fields are almost always too low. As years of drilling, production, and pressure data accumulate, successive estimates typically rise and their range of uncertainty narrows.
Unconventional oil and gas, including shale gas, tight oil, coalbed methane, and natural bitumen, are bound within the rock matrix rather than held by buoyancy above water, requiring different extraction and estimation approaches. Standard volumetric and performance-based methods are less reliable for these formations; analog-only yet-to-find (YTF) techniques are commonly applied instead. Pilot projects are often required before enough data exists to formally declare any unconventional reserves.