A Natural Gas Transportation System for Wells With No Pipeline Connection
Authors: Burns Jack M. 
Published: December 2007

Petroleum reservoirs containing marginal gas reserves Petroleum reservoirs containing marginal gas reserves located remote from gas transmission lines represent a serious challenge in gas resource management. Often the revenue from gas sales based on the estimated reserves in such fields will not justify the cost of pipeline construction and, as a result, many such wells are never produced commercially. This paper describes the patented process of transporting compressed natural gas (CNG) by truck as an alternative to pipeline construction. It can be used to transport gas to commercial markets until either the reserve estimates are amended upward, thus encouraging pipeline construction, or until the field is depleted. It pipeline construction, or until the field is depleted. It also can be used as an alternative to flaring gas during short-term well tests, or for tong-term production of associated gas in oil wells.

Introduction

With the advent of higher natural gas prices in recent years, it has become economically feasible to lay gathering and transmission pipelines to many of the smaller and more remote gas-producing wells and fields that traditionally have been deemed noncommercial because of their limited or unknown reserves. Those higher gas paces increase the total revenue expected from such paces increase the total revenue expected from such fields to a point commensurate with the risk of installing the pipeline system. Many other fields, however, are so small or remote or ill-defined that the value of the gas known to exist is insufficient to pay for the cost of installation and operation of the pipeline, thus those fields remain shut in. Numerous alternative schemes have been proposed for recovering and transporting the natural gas energy in these shut-in fields, but thus far only one has proved economically feasible in a wide range of operating conditions. That technique is the transportation of CNG at ambient temperature in high-pressure cylinders mounted on appropriate transport vehicles. This process, pioneered and patented by Texas Gas Transport Co. in pioneered and patented by Texas Gas Transport Co. in 1975, now is used by Pressure Transport Inc. as an exclusive licensee in the U.S. Approximately 15,000 loads of gas have been moved by these companies using the CNG transport process, and ongoing operations involve movement of about 1,000 loads per month. CNG transportation is a simple system applicable to either onshore truck and rail transportation or to offshore barge transportation, and it can accommodate a wide range of natural gas compositions. CNG transportation has relatively low sunk-capital costs but relatively high operating costs, which makes it especially competitive with pipelines in those specific circumstances where the high capital costs of pipelines should be amortized over a known reserve life that is only a short time period. Fundamental laws of physical science are the basis for the primary economic advantage of CNG transportation over other pipeline alternatives such as LNG. CNG transportation (at high pressure) minimizes the total change in the thermodynamic state of the natural gas (as characterized by the property entropy), and the costs of transportation are directly related to the cost of mechanical equipment required to perform such changes of state.

JPT

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