Downhole Sampling of Geopressured Gas Wells

摘要

Under a previous GRI supported project, LBL designed and built a downhole fluid sampler for use in geopressured gas wells. This report describes engineering tests performed on the sampler, and the design and fabrication of auxiliary tools needed to use the sampler effectively. The fluid inside the sampler exchanges with ambient fluid in a few minutes; therefore, fluid exchange rate is no problem. The sample extraction system allows brine and gas to be removed from the sampler and packaged for shipment, all without exposure to air. Wellhead samples of gas condensate, oil, and brine from geopressured gas wells were analyzed. The condensates are derived from oil dispersed in the reservoir rock. The unusual aromatic condensates represent the relatively water soluble fraction of the oil. The paraffinic condensates represent production of oil by solution in dense, high pressure gas downhole. Geopressured brines contain carboxylic acid anions, which cause them to have high B.O.D. These anions may be chemical precursors to the gas dissolved in the brine.