Upstream Stranded Raw Gas Management as Compressed Natural Gas (CNG)

Abstract

Marine compressed natural gas (CNG) has been considered in the past as a means of natural gas transportation but proved to be a non-starter for a number of reasons including long distances or large volumes of gas when compared with liquefied natural gas (LNG). However, marine CNG still figures economically attractive over shorter voyages (up to ~4,000km) and medium volumes of gas. Recent advances in containment systems are poised to provide marine CNG with the best opportunity to be resurrected as a major enabler of new and previously stranded hydrocarbons by becoming an important optimization tool to petroleum well performance. Almost half of offshore natural gas, SEC-type, reserves are considered" stranded" because of the high unit technical cost to harness natural gas in remote locations involving deep-water and/or pre-salt basins, and the lack of are liable and commercially viable market for the natural gas. Most of them do not contain enough gas to justify their own gas transmission solution, floating or onshore LNG production. Furthermore, inoperable gas affects oil production in many adverse ways from the logistics of handling and facilities capacity to the cost of the treatment. Marine CNG used as a wellhead fluid shuttling service for raw gas can generate significant monetary benefits for an operator attributable directly to the new technology and innovative application. Gas viewed like this is no longer a mid-stream product in need of further processing prior to sale, but becomes a potential upstream saleable product. We present here the new technology emphasizing the containment system manufactured with composite materials that are far lighter than metal and yet can withstand the 200-atmosphere pressure and corrosion from hostile raw gas composition straight out of the primary separator. CNG cargo containment system produced with composite materials can reduce overall steel weight by 50–80% and can operate with pressures ranging from 150 to 250 bars, sufficient to accommodate a wide range of gas-oil-ratios without the need of refrigeration.