A preprocessing method to improve the development effect of sagd

Abstract

The invention provides a pre-treating method for improving the SAGD development effect. The pre-treating method comprises the following steps that two horizontal wells are arranged at the bottom of an oil layer of an oil reservoir; supercritical CO2 is injected into the oil layer for the first round at the operation pressure lower than bursting pressure through the two horizontal wells, soaking is conducted, when the pressure is reduced to be 0.5-1 MPa, the supercritical CO2 is injected into the oil layer for the second round at the operation pressure higher than bursting pressure, and soaking is continuously conducted; stem cycle preheating is conducted through the two horizontal wells; and after preheating is completed, continuous steam injection production is conducted on the horizontal wells. The oil reservoir is pretreated through the supercritical CO2; by greatly reducing the viscosity of crude oil, the seam demand quantity in the SAGD operation process is reduced; the cycle preheating time is shortened, the displacement efficiency of steam zones is improved, and a heavy oil reservoir can be economically and effectively exploited.

Description

technical field [0001] The invention belongs to the technical field of oil field recovery, in particular to a pretreatment method for improving the development effect of SAGD, especially a novel supercritical CO 2 Improve the oil recovery method of SAGD development effect. Background technique [0002] Heavy oil reservoirs refer to reservoirs with a degassed crude oil viscosity greater than 50,000mPa·s at the reservoir temperature. At present, horizontal well technologies are widely used in the development of domestic heavy oil fields, including steam-assisted gravity drainage, horizontal well steam huff and puff, horizontal well technology such as steam drive. The steam-assisted gravity drainage technology requires that the thickness of the oil layer must be greater than 15m, the property of the reservoir is relatively uniform, and the interlayer is discontinuous. In order to promote the thermal communication and fluid flow between the two wells, it is required to deploy t...

AI Technical Summary

Problems solved by technology

Horizontal well steam flooding also has the characteristics of small application range, high requirements on reservoirs, easy steam channeling, and poor production effect.

Horizontal well steam huff and puff can be widely used in heavy oil reservoirs with different conditions, but there are problems such as small huff and puff production range, low recovery rate, and inability to supplement formation energy, etc.

Utilizing the properties of gas with small thermal conductivity and non-condensable gas, a heat insulation layer is formed to reduce the heat transfer rate of steam to the overlying rock layer, reduce heat loss, and improve thermal efficiency; at the same time, the non-condensable gas distributed in the upper part of the steam chamber can maintain The system pressure not only pushes the crude oil downward, but also slows down the steam’s upward overburden velocity, strengthens the lateral expansion capability of the steam chamber, and increases the steam’s lateral swept volume; The non-condensable gas affects the steam injection ability. During the operation, it is found that when the non-condensable gas is injected at the same time, the steam injection rate is reduced by about 30% due to the obvious increase in the steam chamber pressure.

Secondly, the injected gas only has the effect of heat insulation and viscosity reduction, so it can only increase the oil recovery rate, but the effect on improving the oil displacement efficiency is not obvious

[0006] Conventional fracturing technology for horizontal wells has also been applied to the development of heavy oil reservoirs, but conventional fracturing only creates a horizontal fracture at the location of the horizontal well to expand the expansion range of the steam zone