A Bottom Water Injection Method Applicable to Shallow Horizontal Fractured Reservoirs and Its Verification

Abstract

The invention relates to the field of petroleum exploitation, in particular to a water injection method applicable to the bottom of a shallow horizontal fracture reservoir and its verification; calculating the permeability variation coefficient, permeability breakthrough coefficient, and permeability extreme difference of the water injection layer; when the permeability variation coefficient is less than 0.5, when the permeability penetration coefficient is less than 1.5, and the permeability range is less than 5, simulate bottom water injection for the water injection layer; the bottom water injection method in the present invention can effectively supplement the energy of the formation, and at the same time slow down the rapid breakthrough of the injected water along the cracks, and improve the water flow of the injected water. The volume and utilization rate can be reduced, and the water cut rise rate can be reduced, so that the oil field can maintain stable production for a long time.

Description

technical field [0001] The invention relates to the field of petroleum exploitation, in particular to a bottom water injection method suitable for shallow horizontal fracture reservoirs and its verification. Background technique [0002] Researches at home and abroad have shown that the fracturing fractures of oil layers at different depths have complex characteristics. It is generally believed that reservoirs at a depth of 600m are mostly horizontal fractures, and those at a depth of 600-1200m are often complex fractures (vertical fractures, twisted fractures, and horizontal fractures may exist at the same time). Deep fractures above 1200m are vertical fractures; [0003] The East Yanchang Oilfield is located in the eastern part of the northern Shaanxi slope in the Ordos Basin. The main target layer is the Chang 6 oil layer of the Yanchang Formation. Up to now, the accumulated oil-bearing area is 2327Km 2 , the oil reserves in place are 9.64×10 8 t, accounting for 40.5% o...

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Problems solved by technology

This type of reservoir has a shallow burial depth, the average reservoir depth is about 570m, the reservoir physical properties are poor, the average permeability is 0.78mD, and the overlying vertical formation pressure is relatively small. During the fracturing process, artificial fractures extend along the horizontal bedding plane, and the The fracture system is relatively developed, which makes the development of the eastern oilfields have typical characteristics: (1) single well productivity is low, the average daily oil production per well is 0.19, and the comprehensive water cut is high (70%); (3) The heterogeneity of the reservoir is serious, the permeability difference is 112, the breakthrough coefficient is 5.8, and the variation coefficient is 0.82

Due to the existence of horizontal fractures in fracturing, after long-term water injection at constant pressure in the oilfield, the distribution of main lateral pressure in the high and low permeability zone of the oil layer and fractures is extremely uneven. The phenomenon of flooding after one injection, and the water flooding direction is multi-directional and distributed continuously, the lateral oil wells have not been effective for a long time, the utilization rate of injected water is low, the contradiction between injection and production is gradually prominent, the treatment is difficult, and the formation energy is difficult to be effectively replenished. The effect is not ideal, more than 90% of the crude oil in the matrix stays in the formation and cannot be effectively recovered, which seriously restricts the efficient development of the oil field;

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