Method for improving recovery ratio of super heavy oil reservoir

Abstract

The invention provides a method for improving the recovery ratio of a super heavy oil reservoir. The method for improving the recovery ratio of the super heavy oil reservoir comprises the following steps of: 1, preheating two horizontal wells in parallel distribution; 2, injecting steam into the upper part horizontal well, and maintaining the original stratum pressure in the lower part horizontal well for production; 3, simultaneously injecting steam, carbon dioxide and viscosity reducers into an oil layer through the upper part horizontal well, and maintaining the original stratum pressure in the lower part horizontal well for production; and 4, stopping the injection of the carbon dioxide and the viscosity reducers, continuously injecting the steam into the upper part horizontal well and maintaining continuous production of the lower part horizontal well. The method for improving the recovery ratio of the super heavy oil reservoir has the advantages that the viscosity of crude oil is greatly reduced; the heat loss of top and bottom cover layers is reduced; the steam enthalpy is improved; the elasticity energy of the stratum and fluid is increased; the flow seeping capability in near bore zones is improved; and the crude oil is recovered through the gravity effect so as to improve the recovery ratio of the super heavy oil reservoir.

Description

technical field [0001] The invention relates to the technical field of oil field development, in particular to a method for increasing the recovery rate of ultra-super heavy oil reservoirs by using steam + viscosity reducer + carbon dioxide to assist gravity drainage. Background technique [0002] Shengli Oilfield currently has proven heavy oil geological reserves of 6.4×10 8 t, of which the proven heavy oil in place in the eastern oil region is 5.89×10 8 t, currently used 4.69×10 8 t; Chunfeng and Chunhui oilfields were successively discovered in the western oil region, with proven geological reserves of 5128×10 4 t, currently used 2471×10 4 t. With the popularization and application of new theories and technologies, the annual output of Shengli heavy oil continues to grow, reaching 475×10 in 2012. 4 t is one of the main positions for the stable and increased production of Shengli Oilfield. [0003] In 2011, the Chunhui Oilfield in Shengli Western Oilfield reported 53...

AI Technical Summary

Problems solved by technology

Due to the large seepage resistance of steam injection and the small heating radius, the conventional steam huff and puff cannot break through the production capacity

[0005] 2. The thickness of the oil layer is not large (10-25m), which is at the lower limit of the conventional steam-assisted gravity drainage technology (15m). Steam injection leads to a large heat loss in the top and bottom cap layers, and the formed steam chamber is small in volume, which affects the development effect

The heterogeneity of Chunhui Oilfield is relatively large, and the horizontal permeability is 41-1790×10 -3 μm 2 , lower permeability and strong reservoir heterogeneity will affect the steam rising speed and the lateral expansion of the steam chamber, affecting the development effect

In addition, the viscosity of formation crude oil is extremely high, close to 2000×10 4 mPa·s, which is much larger than similar foreign oil reservoirs, resulting in large steam injection seepage resistance and small heating radius, it is still difficult to effectively develop oil reservoirs with such a high viscosity by conventional SAGD development technology

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