Spraberry Trend
... that recovery of the oil in Spraberry Trend, an oil field ranked third in the U.S. by total proven reserves, is so difficult that the area was dubbed "the world's largest unrecoverable oil reserve"?
... that <a href="./Extraction_of_petroleum" id="mwCVI" rel="mw:WikiLink" title="Extraction of petroleum">recovery</a> of the <a href="./Petroleum" id="mwCVM" rel="mw:WikiLink" title="Petroleum">oil</a> in <b id="mwCVQ"><a href="./Spraberry_Trend" id="mwCVU" rel="mw:WikiLink" title="Spraberry Trend">Spraberry Trend</a></b>, an <a class="mw-redirect" href="./Oil_field" id="mwCVY" rel="mw:WikiLink" title="Oil field">oil field</a> ranked third in the <a href="./United_States" id="mwCVc" rel="mw:WikiLink" title="United States">U.S.</a> by total proven <a class="mw-redirect" href="./Oil_reserves" id="mwCVg" rel="mw:WikiLink" title="Oil reserves">reserves</a>, is so difficult that the area was dubbed "the world's largest unrecoverable oil reserve"?