Nano-magnetic fluid huff and puff oil recovery method and well pattern structure in extra-heavy oil and super-heavy oil reservoirs

Abstract

The invention discloses a nano-magnetic fluid huff-and-puff oil extraction method and well network structure for extra-heavy oil and super-heavy oil reservoirs. A huff-and-puff well, magnetic source wells and monitoring wells constitute a huff-and-puff well group in an oil reservoir exploitation area; electromagnets are fed into shafts of the huff-and-puff well and the magnetic source wells; a nano-magnetic fluid dispersing solution is injected into the huff-and-puff well; the downhole electromagnets of the magnetic source wells are started, and the magnetic flux is adjusted, so that a large magnetic field is formed in a target oil layer by the magnetic source wells; the electromagnets of the magnetic source wells are shut off, meanwhile, the electromagnet of the huff-and-puff well is started, and the magnetic flux is adjusted, so that nano-magnetic fluids which enter the deep oil layer flow back under the action of the magnetic force of the huff-and-puff well; and the huff-and-puff well is opened for production. According to the nano-magnetic fluid huff-and-puff oil extraction method and well network structure, the nano-magnetic fluids are injected into the oil layer and then spreads in a wide range outwards under the action of the magnetic field of the magnetic source wells, the viscosity of crude oil is reduced, and the nano-magnetic fluid huff-and-puff oil extraction method and well network structure has the advantages of being wide in huffing and puffing range of oil reservoirs where injected media are used, high in oil extraction rate during huff-and-puff recovery, high in huff-and-puff recovery rate and the like.

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 nano-magnetic fluid huff and puff oil recovery method and well network structure for extra-heavy oil and super-heavy oil reservoirs. Background technique [0002] According to the classification standard of heavy oil reservoirs, extra-heavy oil reservoirs refer to heavy oil reservoirs with a degassed crude oil viscosity of 10,000 centipoise to 50,000 centipoise at the reservoir temperature, and super heavy oil reservoirs refer to the degassed crude oil viscosity at the reservoir temperature. Heavy oil reservoirs greater than 50,000 centipoise. Since the steam huff and puff technology has the advantages of small periodic injection of steam, long recovery period, high periodic oil-steam ratio, and good economic benefits for ordinary heavy oil reservoirs, the above-mentioned extra heavy oil and super heavy oil reservoirs are usually...

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Problems solved by technology

Since the steam huff and puff technology has the advantages of small periodic injection of steam, long recovery period, high periodic oil-steam ratio, and good economic benefits for ordinary heavy oil reservoirs, the above-mentioned extra heavy oil and super heavy oil reservoirs are usually carried out by conventional steam huff and puff. However, during the steam huff and puff development process, due to the high viscosity of the underground crude oil, the steam injected into the oil layer is greatly resisted by the high-viscosity crude oil, making it difficult for the steam to enter the deep part of the oil layer to heat a large-scale oil layer. The steam huff and puff heating and mobilization radius of oil reservoirs is small, usually no more than 20 meters; according to incomplete statistics, after 3 to 5 rounds of steam huff and puff, it enters a period of rapid decline, and the huff and puff mobilization radius is difficult to continue to expand, and the cycle of steam injection is invalid. The economic benefit drops sharply, and there is no obvious economic benefit to continue huffing and puffing, and the recovery rate of steam huffing and puffing is low, usually less than 20%

[0003] Ordinary heavy oil reservoirs are usually replaced by steam flooding technology after steam huff and puff. For extra heavy oil and super heavy oil reservoirs, laboratory experiments and field pilot tests have shown that during steam flooding, due to the injection of steam condensate The oil-water viscosity ratio between the oil and the high-viscosity heavy oil is too large. Therefore, the steam channeling of the water vapor and its condensed water relative to the high-viscosity heavy oil due to the high flow rate will cause premature steam channeling of the steam-driven production well. Steam flooding has a limited range of enhanced oil recovery and poor economic benefits

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