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.