In discussing the handling or oil and gas it would seem advisable to define what areas this discussion will dwell on. No attempt will be made to discuss the detailed mechanical aspects or production handling. Instead, some of the effects of customs, codes, and regulations on production handling will be pointed out. Since the discussion bears on both oil and gas handling, the two cannot be properly related unless they are spoken of in common terms. If both oil and gas production are viewed from a common reference plane, some striking similarities in magnitude can be Been.
In order to view the two phases of production from a common reference point, a conversion to common units is necessary. The approximate daily oil production in the United States is 7,400,000 bbl. The gas production is about 36,400 MMcf/D. Converting to tons, the daily oil production is about 1 million tons and the daily gas production is about 800,000 tons. This may be somewhat startling at first to realize the tonnage of oil and gas produced is so nearly the same. One barrel of oil weighs about 300 lb, or roughly 1/7 ton/bbl. Natural gas weighs roughly 44 lb/Mcf, or about 22 tons/NMcr. what may be equally startling is the price of oil and gas on a perpound basis. Crude oil is priced at about $5/bbl, or $0.01/lb. Natural gas, if priced at $0.20/Mcf, is about 1/2 cent/lb. On a heat basis, methane has a heat of combustion of about 25,900 BTU/lb while an average oil has about 19,000 BTU/lb. So, changing into common units presents a picture somewhat different from the usual one.
This picture of similarity or close relationship in oil and gas production, however, fades completely when the concepts of handling and measurement are considered, First, the oil side of this picture is much older than the gas side. It is only in comparatively recent years that gas production has grown to be a major part of the picture. Oil production has years of history and tradition behind it and, as a consequence, has had a longer period in which operating customs could solidify into general practices, standards, and codes. Second, gas by its very nature must be, processed and handled continuously, as it is produced while oil has traditionally been handled by batch methods. With oil being handled in batches, measurement of quantity and quality, while carried out according to certain standards, is basically a manual procedure subject to human interpretation.
However, when the handling of oil is placed on a continuous or semi continuous basis and production is measured by continuous metering, there is no room for human judgment, particularly in quantity measurements. A meter displays a set of digits which is not subject to interpretation. Therefore, since no human judgment is involved, the measuring device is governed by codes or standards and tolerances which become quite rigid. In fact, cases arise where the code measurement tolerances are so much closer by meter than by previous methods that metering cannot be done and still abide by the tolerances without unreasonable checking and proving. In attempting to maintain meter accuracies at 0.1 per cent, proving equipment becomes costly and proving periods so frequent that the installations may become 50 costly to install and operate that they cannot be justified.
Most codes or recommended practices include in their wording such phrases as "where mutually agreeable" when dealing in measurement practices. It is proposed here that, where mutually agreeable, codes can be relaxed or new methods used provided satisfactory accuracies can be obtained. As one example, most LACT installations include one or more tanks where are or can be strapped to acceptable accuracy. This lease tank should be an acceptable proving means for a positive displacement meter if accurate gauging practices are followed. In fact, this is being done in at least three instances and accuracies achieved are comparable to other means of proving. In another instance, in a remote area where no proving service is readily available and a distillate which is difficult to gauge is being handled, a permanently installed master meter is used for proving. This is considerably less expensive than a prover tank or pipe-prover type of system and achieves satisfactory accuracy.
