Method for assisting gravity drainage by means of solvent and superheated steam

Abstract

The invention provides a method for assisting gravity drainage by means of a solvent and superheated steam. The method comprises the steps that injection-production pattern deployment is conducted; injection-production pattern is preheated, so that hot inter-well communication and pressure communication are built; an SAGD stage is started, wherein the stage comprises the steps of injecting the superheated steam and conducting SAGD initial production; after SAGD initial production is finished, the vaporized solvent and the superheated steam are injected, and SAGD mid-term production is conducted; after SAGD mid-term production is finished, the superheated steam is injected till the SAGD life cycle is finished. According to the technical scheme, the synergistic effects of solvent dilution solution viscosity reduction and permeable mudstone thin interlayer and superheated steam thermal viscosity reduction are fully played, the preheating time is greatly shortened, the oil production is increased, the steam injection and sewage treatment capacity are lowered, and the economic benefit is improved finally.

Description

technical field [0001] The invention relates to a method for assisting gravity oil drainage by using solvent and superheated steam, and belongs to the technical field of petroleum exploitation. Background technique [0002] Steam Assisted Gravity Drainage (SAGD) technology is particularly suitable for the recovery of very heavy crude oil or oil sands with very high viscosity. The most commonly used well layout method is to drill a pair of double horizontal wells near the bottom of the oil layer, and keep the well spacing of 5-10m between the injection and production well patterns. The basic principle of this technology is the combination of heat conduction and heat convection. Steam is injected into the oil layer from the upper horizontal well, and the steam moves upward and sideways, relying on the gravity of the heated bitumen and condensed steam to produce heavy oil through the lower horizontal well. [0003] After the solvent is vaporized, it is mixed with steam and inj...

AI Technical Summary

Problems solved by technology

In the early SAGD development of ultra-heavy oil or oil sand with a burial depth of more than 400m and the fracture pressure not exceeding, the maximum steam injection pressure and steam injection temperature can reach 3.5MPa and 242°C respectively, and wet saturated steam with a dryness of 0.9 or more As an injection medium, it has been able to achieve higher single-well productivity and meet production needs, but as the development progresses, the development of ultra-heavy oil or oil sand SAGD has been expanded to reservoirs with a buried depth of less than 200m, and the maximum steam injection pressure and steam injection temperature As low as 2.0MPa and 212°C, under the same steam quality and dryness conditions, the specific volume increases by 74%, which can only reduce the steam injection rate and restrict the increase of oil production rate

If superheated steam is used as the SAGD injection medium, it can greatly reduce the specific volume of steam, increase the heat enthalpy, and increase the steam injection rate of a single well. Supplemented with a low-concentration mixed solvent that is easier to vaporize under this higher temperature condition, it is expected to improve the shallow formation. Oil sands development effect: Superheated steam is used for deep ultra-heavy oil or oil sands above 400m, which requires auxiliary technical measures such as heat insulation pipes and increases costs, otherwise the superheat will be greatly reduced, resulting in increased specific volume, and higher steam injection speed cannot be used , thus reducing the productivity of a single well

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