Method of measuring gas flow

#This invention relates to a method of measuring a gas flow. More particularly, but not by way of limitation, this invention relates to a method of measuring a dry gas flow from hydrocarbon wells.

#As those of ordinary skill in the art will appreciate, the world contains significant natural gas deposits. For instance, according to the National Energy Board (NEB), Canada has about 53 trillion cubic feet (Tcf) of marketable gas supply. The Western Canada Sedimentary basin (WCSB) accounts for more than half. In addition, the magnitude of unconventional gas resources in place is estimated to be quite formidable. However, development of this natural resources require substantial capital expenditures and extensive drilling due mostly to the decline of the know reserve pool sizes and continued high demand for natural gas.

#Even though the economic climate seems favourable, producers continue to face the predicament of developing these marginal pools within budgets and strict regulatory regime. According to the data found within the Alberta Energy and Utilities Board (EUB) publication titled: ST98-2006, production from the WCSB is not up to expectations, especially from unconventional sources.

#FIG. 1A is a prior art differential pressure-type flow meter for measuring flow of fluids and gas.

#FIG. 1B is a prior art schematic illustration of a measurement facility.

#FIG. 2 is a graphical representation of the LGR (liquid-gas ratio) error relationship.

#Referring to FIG. 1A, a prior art differential pressure type flow meter (hereinafter “flow meter”) for measuring flow of fluids and gas will now be described. This flow meter 2 is manufactured by Yamatake Corporation and is commercially available for Zedi Inc. under the name eTube™. Applicant notes that the specification of the flow meter 2 (eTube™) is described in a technical data sheet entitled eTube™ Technical Date Sheet, SDR80A Series. The technical data sheet is incorporated herein by express reference.

#FIG. 1B is a prior art schematic illustration of a measurement facility. In the preferred embodiment, gas and liquid from a wellhead are flown into a separator. It should be noted, however, that the liquid and gas mixture may come from a multi-well battery, gas plant inlet, or gas gathering system. The liquids are directed via a separate path 6, with the liquids being directed to a tank 8 or recombined with the gas after the measurement point. The gas from the gas liquid separator 4 is directed to the measurement system 10, which includes an orifice meter. These prior art orifices type dry gas metering system are well known in the art. The liquid can be combined with the gas as shown at 12, and then placed into a pipeline. From there, the gas and liquids are delivered to a further processing facility for various purposes, including refining and distribution.

#As noted previously, the flow meter 2, model SDR80A series, is Yamatake Corporation's (of Japan) differential pressure-type flow meter for measuring fluids under harsh conditions (see FIG. 1A). With its smooth shaped throat “T”, flow meter 2 is designed to efficiently produce differential pressure, while creating a minimum permanent pressure loss. Referring again to FIG. 1A, the throat “T” is shaped like an ellipse, which is where its original name “elliptical tube” derives from. Unlike other differential style meters, this unique design prevents the entrenched liquid in the flow stream from stagnating at the throat entrance, thereby enabling accurate measurement of the fluid flow. The flow meter 2 is designed especially for measuring flow rate of natural dry gas or wet gas.