Crack-type dense oil reservoir water-injection energy replenishing method

Abstract

The invention discloses a crack-type dense oil reservoir water-injection energy replenishing method. The crack-type dense oil reservoir water-injection energy replenishing method comprises the steps: 1, whether oil reservoir cracks are developed or not is determined; 2, if the cracks of an oil reservoir are not developed, same-well synchronous injection and production are adopted, one-section injection and multi-section production are conducted firstly, water is injected to root perforation sections, oil is produced from toe perforation sections, after the toe sections are flooded, packing points gradually move downwards to the toe perforation sections till all the perforation sections are flooded, after daily fluid and oil output of an oil well is increased and the comprehensive water content is stable, multi-section injection and multi-section production are conducted, water is injected to the cracks of the odd sections, and meanwhile oil is produced from the even sections till all the perforation sections are flooded; and 3, if the cracks of the oil reservoir are developed, same-well asynchronous injection and production are adopted, after water injection sections of the same well complete water injection, the well is closed and soaked for a period of time, the pressure is increased to be reasonable and then kept to be level, then the well is opened, and oil is produced at oil production sections till all the perforation sections are flooded. Effective replacement is conducted, formation energy is effectively replenished, and the development effect is improved.

Description

technical field [0001] The invention belongs to the field of oil field development and relates to a method for supplementing energy by water injection in fractured tight oil reservoirs. Background technique [0002] With the increasingly prominent contradiction between the world's oil supply and demand and the gradual shortage of high-quality oil resources, the development of ultra-low permeability reservoir resources (surface air permeability is less than 1.0mD) has become a new topic for the development of my country's petroleum industry. Reservoir production practices have shown that horizontal wells are an effective way to develop this type of reservoir. In foreign ultra-low permeability reservoirs, the formation pressure coefficient is high (the formation pressure coefficient is greater than 1.2), and the viscosity of the formation crude oil is low. Basically, long horizontal wells are used for depletion production. Although the single well production has been greatly in...

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Problems solved by technology

However, with the prolongation of production time, the single-well production of some fracturing wells gradually declines, decreasing by 20% to 30% in half a year and 30% to 50% in one year, and the reservoir pressure maintenance level is less than 80%.

There are three main reasons for the large decline: First, the ultra-low permeability reservoirs in the Ordos Basin developed fractures, and some reservoirs developed multiple groups of natural fractures, and the extension direction of the natural fractures was inconsistent with the artificial fracture direction of the production well, and the injected water seeped along the natural fractures , leading to rapid water breakthrough and large decline in horizontal wells; second, some reservoirs are developed by water injection with a row spacing of about 150 meters. The production well pattern only deploys water injection wells at the root and toe of the horizontal well. Due to the long horizontal section of the horizontal well (600-1200 meters), the artificial fractures in the middle of the horizontal section can only rely on elastic solution gas flooding for oil production. Low pressure coefficient, low original dissolved gas-oil ratio, insufficient natural energy

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