据世界管道11月6日报道，溶解天然气（油井生产的天然气）所占份额越来越大，这是低渗透致密岩层（二叠纪、巴克肯、伊格尔福特、尼奥布拉拉和阿纳达尔科）原油产量增加的结果。2018年，这五个主要原油产区的伴生溶解天然气产量为120亿立方英尺/天，约占这些地区天然气总产量的37%，约占美国天然气总产量的12%。

伴生溶解天然气又称伴生气，是油井产出物中的天然气。相对的，非伴生气是天然气井生产的天然气。根据不同的油气比(GOR)，不同州对油井和天然气井有不同的定义。美国能源信息署（EIA）用6000立方英尺天然气与1桶石油(立方英尺/桶)的油气比来确定探井是油井还是天然气井。如果一年的GOR产量等于或小于6000立方英尺/桶，则该井被定义为油井，从该井生产的任何天然气被称为伴生气。此外，不同州对用来测量天然气的标准压力已转换成14.73磅/英寸的联邦标准，标准温度为60华氏度。

伴生气含有NGPLs，如乙烷，丙烷，正丁烷，异丁烷，和天然汽油。伴生气有时被定性为湿气，因为它必须经过天然气加工厂的处理，以去除杂质和液体，然后才能作为天然气销售。伴生气的增加导致了美国NGPLs产量创造了新记录（NGPLs被用作生产塑料、纤维和其他产品的原料）。

横跨德克萨斯州西部和新墨西哥州东部的二叠纪地区是五大原油产区中伴生天然气产量最高的地区。二叠纪的原油产量创历史新高，随之而来的是大量伴生气。2018年，二叠纪地区的伴生气产量达58亿立方英尺/天，占二叠纪天然气产量的51%，首次超过了该地区的非伴生气产量。二叠纪地区天然气产量的增加，提高了天然气运输管道的运力——需要将天然气运入市场。

巴肯(Bakken)地层主要位于北达科他州，在五大主要产油区中，其伴生气占地区天然气总产量比例最大，达92%。2018年，巴肯页岩伴生气产量为22亿立方英尺/天，超过了伊格尔福特（Eagle Ford）页岩，后者的伴生气产量为21亿立方英尺/天。2018年，尼奥布拉拉和阿纳达尔科页岩伴生气产量均有所增加，伴生气总量为19亿立方英尺/天。

王佳晶 摘译自 世界管道

原文如下：

EIA: associated gas contributes to growth in US natural gas production

A growing share of US natural gas production is associated-dissolved natural gas (natural gas produced from oil wells), which is the result of increased crude oil production from low permeability, tight rock formations – Permian, Bakken, Eagle Ford, Niobrara, and Anadarko. In 2018, associated-dissolved natural gas production in these five major crude oil-producing regions was 12.0 billion ft3/d, or about 37% of total natural gas production in these regions and about 12% of total US natural gas production.

Associated-dissolved natural gas, also referred to as associated gas, is natural gas produced by oil wells. By contrast, non-associated gas is natural gas produced by natural gas wells. Some states define an oil well versus a natural gas well differently based on different gas-oil ratios (GOR). The US Energy Information Administration uses a gas-oil ratio of 6000 ft3 of natural gas to 1 bbl of oil (ft3/bbl) for each year’s total well production to determine whether a well is an oil well or natural gas well. If the GOR for a year of production is equal to or less than 6000 ft3/bbl, then the well is defined as an oil well, and any natural gas produced from this well is called associated gas. In addition, the various state pressure bases used to measure natural gas volumes have been converted to the federal pressure base of 14.73 lb/in.2 absolute and 60°F.

Associated gas contains natural gas plant liquids (NGPLs) such as ethane, propane, normal butane, isobutane, and natural gasoline. Associated gas is sometimes characterised as wet gas because it must be treated at natural gas processing plants to remove impurities and liquids before it can be marketed as natural gas. The increase in associated gas has led to record volumes of US NGPL production. NGPLs are used as feedstocks to produce plastics, fibres, and other products.

The Permian region, which spans parts of western Texas and eastern New Mexico, has the most associated gas production of the five crude oil-producing regions. The Permian region produced 5.8 billion ft3/d of associated gas in 2018, accounting for 51% of the Permian’s natural gas production total and surpassing non-associated gas production in the region for the first time. Record-high crude oil production from the Permian brings with it large volumes of associated gas. Greater natural gas production in the Permian region has led to additional natural gas takeaway pipeline capacity to move the natural gas out of the area to the market.

The Bakken formation, which is mostly in North Dakota, has the largest share of associated gas among the five major oil-producing regions. Associated gas accounts for 92% of the total natural gas production in the region. In 2018, the Bakken produced 2.2 billion ft3/d of associated gas, surpassing the Eagle Ford, which produced 2.1 billion ft3/d of associated gas. The Niobrara and Anadarko Basins both had increases in associated gas production in 2018, and their combined associated gas volume was 1.9 billion ft3/d.