Utilization of Associated Petroleum Gas (APG) —the Norwegian Experience

Abstract

Abstract The goal of any petroleum producing country is to maximise the long-term social value of the hydrocarbon assets. To protect society's interests in development and operation of oil and gas fields, the Norwegian authorities have established frameworks for these activities, which are intended to ensure that the companies makes decisions that are also beneficial to the society at large. In Norway the Norwegian Petroleum Directorate (NPD) has the authority to monitor the development of the different oil and gas fields and to ensure that the fields are being produced in accordance with best practice reflected in regulations and the framework established. As for use of associated gas the regulation pertaining to proper utilization of the petroleum resources has been of paramount importance. In the regulations it is stated that flaring of petroleum is not allowed, unless in quantities needed for safe operation. From day one the oil companies thus had to find a proper way of utilizing the associated gas. In most cases the gas was transported in pipelines and sold to the market, but in some cases there was no pipeline available and re-injection into the reservoir was the only option. Improved recovery has been and still is of great concern for Norwegian authorities. Several initiatives have been made to evaluate the possibilities for improving oil recovery. The results of gas injection have been studied together with other methods for enhancing the oil recovery. For the Norwegian oil fields pressure maintenance by use of associated gas has proved to be very successful. By the end of 2009 and since the oil production started on the Norwegian Continental Shelf in 1971 a total of more than 3526 million Sm3 of oil and 2138 billion Sm3 of gas has been produced. Most of the gas produced has been exported to the European market. Some gas has been used as fuel on the platforms and for transportation purposes and a small amount has been used in Norway as feed-stock for petrochemical plants. Due to strict regulations and economical incentives just a minor part has been flared. However it is reported that gas in the order of 595 billion Sm3 has been re-injected into the reservoirs to sustain pressure and to enhance oil recovery. The average oil recovery factor for fields in production today is estimated to be 46%. It has been estimated that re-injection of gas so far has yielded an extra oil recovery of between 240 and 270 million Sm3 oil and condensate compared to the case without gas injection. If existing plans for further gas injection are executed, the total gains are in the range 320 to 360 extra million Sm3 oil and condensate.