Nitrogen improved oil recovery (N2-IOR) processes have teen used inover thirty-three (33) reservoirs in Canada and the United States. Theaggregate volume of gas injected exceeds 600 MMCFD (million cubic feet perday).
Nitrogen improved oil recovery processes are being used in reservoirs that arein their nearly depleted stage as well as in reservoirs that are in their earlyproduction life cycle. Some of these reservoirs:
are located in harshgeographic am climate environments;
have large or small reserves:
arereservoirs onshore or offshore and
are located in areas which have plentifulor limited quantities of natural gas.
The major purpose of this paper is to discuss the applications of nitrogen, particularly as they apply to three types of oil fields:
large reserves inthe peak of their production;
reservoirs nearing primary or secondarydepletion; and
reservoirs located in remote geographic areas. A secondarypurpose is to update the list of all known nitrogen projects, including thoserecently initiated or expanded.
While most of the current nitrogen projects are in the USA and onshore, it isshown that the concept is applicable to the candidate fields regardless oftheir location.
Primary production, and conventional secondary recovery of oil produces lessthan one-third of the original oil in place. The worldwide oil shortage in theearly 1970's, and resultant increase in world oil prices, spawned the advent of"enhanced" or "improved" oil recovery techniques. Despite the fact that the oilsupply has caught up with the demand. oil producers are still activelyintroducing "improved" oil recovery techniques wherever economics justify them.The literature still contains many references to the projects being initiatedor underway.
The techniques and screening guides for selecting the optimum "improved"recovery process are described in an early publication by the USA's NationalPetroleum Council (Ref. 1). This publication discussed thermal, chemical, andgas displacement techniques. Unfortunately, it did not include one of thefastest growing improved oil recovery techniques, the use of nitrogen.
The lack of N2-IOR screening guides, a paucity of technicalinformation on nitrogen projects, and the unavailability of a definitive listof and data on existing nitrogen projects may have resulted in many oilproducers passing up the opportunity to consider nitrogen as an improved oilrecovery process. In 1983, the authors prepared a paper (Ref. 2) entitled, "Analysis of Nitrogen Injection Projects …", which listed the then knownapplications for nitrogen and presented a screening guide for nitrogenapplications. At that time in the USA and Canada, over 500 MMCFD of nitrogenwas being injected into twenty-nine (29) fields to enhanced the recovery of oilor gas. Subsequent to the aforementioned paper an additional four new fieldsare now receiving nitrogen, and two projects have teen extended. In 1985 thetotal nitrogen injection is greater than 600 MMCFD.
It is the objective of this paper to highlight immiscible displacement, improved gravity displacement, pressure maintenance and the displacement of amiscible slug with nitrogen.