Method and Well Pattern Structure of Solvent Improving Heavy Oil Reservoir Recovery by Steam-Assisted Gravity Drainage

Abstract

The invention discloses a method and a well network for improving steam assisted gravity drainage for extracting heavy oil reservoirs by the aid of solvents. The well network comprises SAGD (steam assisted gravity drainage) horizontal well pairs; horizontal sections of steam injection wells are subjected to well completion by the aid of slotted screen pipes; branched well sections are drilled in the horizontal sections of the steam injection wells and penetrate the middles of inner sandwich layers in oil layers; the various branched well sections are subjected to well completion by the aid of tail pipes; first long oil pipes which extend to toes of the steam injection wells descend into screen pipes of the steam injection wells; solvent injection main pipes which are parallel to the first long oil pipes descend into the screen pipes of the steam injection wells and are hermetically connected with the tail pipes in the various branched well sections by tail pipe hangers; second long oil pipes descend into production wells and reach the tail ends of horizontal sections of the production wells; vertical monitoring wells are further deployed in the well network. The method and the well network have the advantages that steam flows into the oil layers to upwardly develop steam cavities, and the hot solvents and steam mixed systems flow into the oil layers on the upper portions of the sandwich layers from the main pipes via the tail pipes, so that heat communication and fluid communication among the oil layers and the steam cavities can be accelerated, the sandwich layers can be forcedly broken through, development of the steam cavities on the upper portions of the sandwich layers can be promoted, and the recovery efficiency can be greatly improved.

Description

technical field [0001] The invention relates to a mining technology for heavy oil reservoirs in oilfields, in particular to a solvent-improved steam-assisted gravity drainage method for mining heavy oil reservoirs and a well pattern structure. Background technique [0002] Steam-Assisted Gravity Drainage (SAGD) 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; its principle is the same Overlapping horizontal well pairs are deployed in the oil layer, and high-quality steam is injected into the upper steam injection well. Because the density of the steam is much lower than that of crude oil, the steam overlaps upwards in the formation to form a steam cavity. With the continuous injection of steam, the steam cavity continues to rise. And lateral expansion, heat exchange with the crude oil in the oil layer; the viscosity o...

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Problems solved by technology

Since the solvent-assisted SAGD technology adopts the same wellbore structure as the steam-assisted gravity drainage technology, its limitation is that it can only accelerate the oil drainage speed of the steam chamber. For the oil layers with a large number of interlayers, the production degree of the horizontal section cannot be improved, resulting in Big loss

[0005] For SAGD heavy oil reservoirs with stable interlayers and contiguous distribution, there is no effective production method for the steam chamber to break through the evenly developed interlayers

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