Analysis of Nitrogen-Injection Projects to Develop Screening Guides and Offshore Design Criteria

Abstract

Analysis of Nitrogen-Injection Projects to Develop Screening Guides Projects to Develop Screening Guides and Offshore Design Criteria Summary In 1982 more than 500 million cu ft/D [ 14 ⨯ 10–6 M3 /d] of nitrogen was injected into oil or gas reservoirs. To date, 30 fields have used nitrogen for enhanced oil or gas recovery (EOR/EGR), In this paper, 29 nitrogen EOR/EGR projects are listed. Some pertinent reservoir, rock, and fluid data, as well as historical information and injection rates, are given for each field. On the basis of the literature and the analysis of these 29 fields, five applications of nitrogen are indicated: immiscible displacement, miscible displacement, gravity drainage enhancement, pressure maintenance, and as a driving fluid for a miscible slug. No single nitrogen application, however, is mutually exclusive in any field; two or more mechanisms (applications) may be involved, For each application, a specific field was chosen as an example and more detail was provided. A screening guide has been developed for each application. Most of the 29 fields fall within these guidelines for the respective nitrogen applications. As nitrogen EOR/EGR technology matures in onshore projects, operators will attempt to transfer this technology projects, operators will attempt to transfer this technology to offshore fields. To date, three barge-mounted nitrogen plants have been used in near-shore fields. Air plants have been used in near-shore fields. Air separation plants can be installed on platforms to supply nitrogen. Some offshore nitrogen supply parameters are presented and discussed. presented and discussed. Introduction Primary production and secondary recovery methods Primary production and secondary recovery methods (waterflooding or reinjection of produced natural gas) on the average produce less than one-third the original oil in place (OOIP). Enhanced recovery techniques (such as thermal, chemical, or gas injection) can be used to recover additional hydrocarbons. The literature is replete with information on thermal, chemical, and CO2 miscible displacement. Several publications, including the Natl. Petroleum Council publications, including the Natl. Petroleum Council (NPC), contain screening guides for most enhanced recovery processes. However, these screening guides and their respective reports are generally silent with respect to two processes, nonhydrocarbon immiscible displacement and nitrogen miscible displacement, both of which are considered by the U.S. DOE as EOR techniques ' 2 In the U.S. and Canada more than 500 million cu ft/D 14 × 10–6 m3/d] of nitrogen is being injected into reservoirs to enhance the recovery of oil or gas, In reviewing the literature, several facts are apparent:more than 30 fields have used nitrogen for EOR;no comprehensive list of the various nitrogen projects is available, andno screening guides for nitrogen are available or have been proposed. A comprehensive list of nitrogen-EOR projects and screening guides should be helpful to field operators who are considering enhanced recovery projects. For the most part, EOR has been limited to onshore fields. As the state of the art of EOR processes develops and as our offshore fields mature, operators will be using EOR processes offshore. Platform space and supply constraints will limit the operator's EOR options. Nitrogen injection, however, may not be as technically and economically constrained as other EOR options. Gas Injection-Historical Perceptions. Before 1970, natural gas (rich or lean) was the primary choice of operators for gas injection (miscible or immiscible). In the 1960's and 1970's, operators began seeking nonhydrocarbon sources of gas because natural gas was unavailable in some geographic areas or natural gas was becoming too expensive for reinjection. CO2 and nitrogen started to emerge as substitutes for natural gas. In the 1960's and early 1970's, operators seeking additional volumes of gas generated inert gas (mostly nitrogen, but containing some CO2 and other combustion products) by burning natural gas in boilers or internal combustion engines; processing the flue gas or engine exhaust gas, respectively, to remove water, heat, and undesirable combustion byproducts; and compressing the resultant processed gas using steam-driven compressors or the internal combustion engine. A more detailed description of these processes is contained in Refs. 3 and 4. In the mid- 1970's, operators sought a source of nitrogen that had no corrosion potential, had high reliability, and had economy of scale potential. In 1977 the first air separation plant appeared in the oil fields. JPT P. 1097