A method of gravity drainage assisted steam flooding to enhance the recovery of deep ultra-heavy oil reservoirs

Abstract

The invention relates to a method for improving the oil deposit recovery ratio of deep massive extremely-viscous oil in an extraction mode of gravity drainage assisted steam flooding. In the method, superposition horizontal wells are arranged among wells by combining results of researches on the fine contrast of small geological strata of massive oil deposit, the distribution rule of interlayer, the distribution rule of remaining oil and the like and a fine research on numerical simulation; an upper superposition horizontal well is used for injecting steam, a peripheral vertical shaft is used for production, and a lower superposition horizontal well is used for discharging liquid (crude oil between condensate water and the horizontal wells); and thus, a production-injection ratio of high-speed steam injection of deep oil deposit is improved, the dryness of steam on the well bottom is improved, the pressure of an oil layer is reduced, a steam cavity is easy to expand, the swept volume is improved, a development effect is improved, and the aim of improving the recovery ratio finally is fulfilled.

Description

technical field [0001] The invention belongs to the field of oil reservoir development, and relates to the development of massive or thick-layered super heavy oil reservoirs, in particular to a gravity drainage assisted steam flooding technology. Recovery of heavy oil reservoirs. Background technique [0002] The viscosity of crude oil is a measure of the frictional resistance when one part of crude oil flows relative to another part, and is an important parameter for oil and gas field development. For heavy oil reservoirs, China's current heavy oil classification method is based on the viscosity of degassed crude oil under the condition of reservoir temperature: ordinary heavy oil viscosity 50-10000mPa s; extra heavy oil viscosity 10000-50000mPa s; super heavy oil viscosity The viscosity of crude oil is greater than 50000mPa·s. Super-heavy oil has high viscosity and poor fluidity, making it the most difficult to recover. The development of heavy oil reservoirs is mainly ...

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Problems solved by technology

[0009] (1) Deep heavy oil reservoirs are deeply buried and have large heat loss. Steam flooding and SAGD generally require high bottom well dryness, making it difficult to develop deep heavy oil;

[0010] (2) After the deep heavy oil enters high rounds of huff and puff, the periodic oil production and oil-gas ratio will decrease, and the economic benefits will become worse. If effective development methods are not adopted, the oil reservoir will be abandoned;

[0011] (3) The production degree of the super heavy oil huff and puff stage is low, and the recovery degree of the general huff and puff stage is less than 30%;

[0013] (5) The oil reservoir is deeply buried, the heat loss is serious during the steam injection process, and the dryness of the steam at the bottom of the well is low, so an effective steam cavity cannot be formed

[0014] From the perspective of ultra-heavy oil development technology in the world, for deep heavy oil reservoirs (reservoir buried depth greater than 1300m), due to the large heat loss in the wellbore during the heat injection process, there is no other effective development method except the huff and puff development technology.

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