Fire-flooding exploitation method used in later period of steam assisted gravity drainage (SAGD) of heavy oil reservoir

Abstract

The invention relates to a fire-flooding exploitation method used in a later period of steam assisted gravity drainage (SAGD) of a heavy oil reservoir. At a steam chamber expansion phase of the SAGD, when steam chambers of adjacent injection and production well pairs are subjected to coalescence, a injection and production well of the middle injection and production well pair is used for injecting air to ignite, a production well of the middle well pair and production wells of the left and right adjacent well pairs are used for producing, and injection wells of the left and right adjacent well pairs are converted into fire-flooding ventilation wells. The exploitation method can utilize a high-temperature fire-flooding front edge to effectively drive remaining reserves at the lower part of an oil layer between the adjacent SAGD well pairs, avoids the steam play of in the later period of the regular SAGD or the gas-assisted SAGD, prolongs the SAGD production time, and obviously improves the oil recovery. The method disclosed by the invention combines the advantages of the SAGD and fire flooding; the output at an SAGD production phase is high, and the oil exploitation speed is high; and the fire flooding is utilized at an output declination phase after the adjacent stream cavities are subjected to the coalescence, so that the injection cost can be reduced, and the heat energy utilization rate and the oil recovery are improved.

Description

technical field [0001] The invention relates to a mining method for heavy oil reservoirs in the field of petroleum exploitation, in particular to a method for converting heavy oil reservoirs to fire flooding in later stages of development using steam-assisted gravity drainage (SAGD) technology. Background technique [0002] Steam-assisted gravity drainage technology was invented by Canada's Bulter in 1978, and has been successfully applied in heavy oil reservoirs in Canada's oil sands mining area, my country's Liaohe Oilfield, Xinjiang Oilfield and other places. The principle is to deploy upper and lower horizontal well pairs in the same oil layer, and inject high-dryness steam into the upper steam injection well. The steam is much denser than crude oil, and the steam overlaps upwards in the formation to form a steam cavity. With the continuous injection of steam , the steam chamber continuously expands upwards and sideways, and exchanges heat with the crude oil in the oil l...

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Problems solved by technology

However, there are three main problems with this inventive method: First, this method only describes the advantages of adding nitrogen to the steam in slowing down the heat loss of the steam upward covering layer and expanding the swept volume of the steam chamber, but does not elaborate on the adjacent SAGD steam chamber After coalescing, how to prevent the steam in one of the steam chambers from entering the other steam chamber because the operating pressure is higher than that of the other steam chamber, causing too much steam in the other steam chamber to cause steam escape Operational technical countermeasures; second, this method only expounds that it is beneficial to the uniform expansion of the steam chamber, but does not elaborate on the specific method of how to effectively develop the reserves in the lower part of the oil layer in the middle of the adjacent steam chamber during the descent of the steam chamber; third, it does not elaborate In the descending stage of the SAGD steam chamber, the risk of gas injected from the steam injection well in a single SAGD well pair entering the lower production well and the risk avoidance countermeasures are described

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