Standards Development

Scope

This technical specification provides the adaptable reservoir conditions and recommended application methods of multi-component thermal flooding for heavy oil reservoirs. NOTE: This technical specification is only applicable to heavy oil reservoirs. 

Purpose

The multi-component thermal flooding development technology is a thermal recovery method, which could drive the crude heavy oil to the production well by injecting multi-component medium of steam, chemical agent and gas from injection well according to a certain injection-production well pattern. Aiming at the difficulties of steam cavity expansion and disequilibrium displacement in the steam flooding process, this technology could expand the steam cavity volume, reduce heat loss and improve thermal sweep range using the synergistic effect of steam, chemical agent and gas. It would greatly improve the heavy oil recovery, reduce thermal recovery cost and carbon emission at the same time. Global reserves of heavy crude oil and bitumen are approximately 8.9 trillion barrels, and they occupy 53.6 percent of recoverable crude oil reserves according to the annual report from USGS (United States Geological Survey) 2007 and ASG (American Society of Geosciences) 2018. Steam flooding is an effective means of significantly enhancing oil recovery in heavy oil reservoirs, and the field applications have shown that the oil recovery rate of steam flooding can be increased to more than 50% (such as Kern River oilfield in the United States, Duri oilfield in Indonesia, Liaohe oilfield in China). After decades years of pilot and filed tests, the reservoir application conclusion have been summarize for steam flooding method. It is generally suitable for heavy oil reservoirs with buried depth less than 914 meters, reservoir pressure less than 7MPa, API higher than 8° (viscosity lower than 20000mPa·s) and effective formation thickness greater than 9m according to PetroWiki of SPE. For heavy oil reservoirs with deeper burial depth, the heat loss of injected steam in the well bore would get larger and the steam dryness at bottom hole will be lower than 0.4. For heavy oil reservoirs with formation pressure greater than 7MPa, the underground steam specific volume would get lower, and the steam cavity is difficult to expand during the steam flooding process. For heavy oil reservoirs with a thickness of less than 9 meters, more heat would loss to the top and bottom layer during steam cavity expansion, which results in low oil-steam ratio of 0.1~0.2 in the steam flooding stage, and then leads to relatively poor economic benefit. Therefore, difficulty of steam cavity expansion, disequilibrium displacement, huge heat loss and other problems result in limited technical and economical feasibility of single steam flooding technology in thin and deep heavy oil reservoirs. 

In order to solve these problems, different oil fields tried to develop the multi-component thermal combined flooding method in recent years. Different chemical agents and gas were injected with steam into the formation to reduce the heat loss and increase thermal sweep range. Pilot tests and field-wide applications have been carried out in about 60 oilfields (according to C&C database). In North America, multi-layer heavy oil reservoir of Kern River adopts the method of reducing injection heat and high concentration foam flooding, which effectively slows down the steam channelling and oil production decline, increases the oil-steam ratio by about 0.1 and improves oil recovery rate by 5.5-15.6% compared with single steam flooding. For heavy oil reservoir in Liaohe Oilfield, they adopt a combined steam flooding method with foam, displacement agent and plugging agent; The oil viscosity limit of steam flooding was increased to 100000 mPa·s, and the depth limit was lowered to 1400 ~ 1600m. While Shengli deep heavy oil reservoirs adopts the combined steam flooding method of nitrogen gas, foam agent, displacement agent and viscosity reduction agent, which could increases steam dryness and displacement efficiency in the formation. This method improved the applicable reservoir pressure to more than 7MPa and the daily oil production by 56%, while the thickness limit reduced to 6 meters. In most cases, the development effect and economy of heavy oil thermal recovery have been effectively improved, and the multi-component thermal flooding technology has gradually become the key technology to greatly improve recovery efficiency of heavy oil reservoirs.

Due to the significant differences in the characteristics of buried depth, oil viscosity and pressure of heavy oil reservoirs in different oil regions, the mainly development contradictions faced during the thermal recovery process and the developed multi-component thermal flooding medium are different. As the results, the applicable heavy oil reservoir range, multi-component medium function and the production increase effect of thermal flooding have obvious differences. The international unified technical standard and specification have not been established, which limits the application and popularization of this technology in the world. Therefore, it is necessary to establish a general technical specification of multi-component thermal combined flooding method to provide technical guidance for thermal recovery and development in different types of heavy oil reservoirs. In view of the significant advantages of this technology in improving heavy oil recovery efficiency, reducing development cost and increasing production, the technical specification and scale application can assist international oil companies jointly to improve the development level of heavy oil. Finally, it would make contribute to increase the international heavy oil production and oil recovery to meet the growth demand of crude oil in the international market