The device most commonly used for measurement of natural gas in the upstream sector of the oil and gas industry is the orifice meter. With a broad variety of measurement equipment from which to choose, the orifice meter is most often preferred in this segment of our industry for many reasons, including:

• With no moving parts, the orifice meter is durable as well as relatively easy to maintain and operate, even in a harsh upstream environment where physical contaminants such as paraffin, sand, dirt, and liquids are often present.
• The rangeability or turndown ratio (i.e., the ratio of maximum accurately measured flow rate to minimum accurately measured flow rate under given conditions) is greater than that for most other devices since, by periodically changing the orifice plate/diameter as conditions vary, the effective turndown ratio may be as high as 180:1.
• Orifice measurement standards are well established by the AGA, API, and GPA and, for the most part, readily accepted by both sellers and purchasers throughout the industry.
• Orifice measurement can produce accurate, accountable volume and energy results which are vital due to their bottom-line impact on sales gas allocations, royalty payments, cash flow, productivity, performance, reservoir engineering, as well as regulatory and contractual compliance.