Tight oil reservoir permeability-increasing oil displacement system and preparation and application thereof

Abstract

The invention discloses a tight oil reservoir permeability-increasing oil displacement system and preparation and application thereof. The permeability-increasing oil displacement system is composed of a surfactant, an oil-soluble substance and water, and is in an oil-in-water droplet state. The outer phase is an aqueous solution containing the surfactant, and the inner phase is the oil-soluble substance; the surfactant comprises one or a combination of more than two of a nonionic surfactant, a nonionic gemini surfactant, an anionic surfactant and an anionic gemini surfactant. The preparationprocess of the permeability-increasing oil displacement system is simple to operate, suitable for industrial production and low in overall cost, and has a remarkable application prospect in the fieldof increasing the recovery ratio of tight oil reservoirs.

Description

technical field [0001] The invention belongs to the technical field of tight oil reservoir exploitation, and in particular relates to a tight oil reservoir permeability enhancement system and its preparation and application. Background technique [0002] my country's unconventional crude oil (tight oil, oil shale, shale oil, etc.) has a huge amount of recoverable resources. In the past five years, the new reserves of low-permeability, tight, and shale oil have accounted for 70%-80% of the proven reserves. Become an important strategic replacement resource for oil and gas exploration and development. The average permeability of unconventional reservoirs such as tight and shale in my country is less than 0.3mD, and the porosity is 6%-15%. Micron-sized pores are the main oil storage space, and the average throat radius is less than 400nm. The fluid saturation is less than 30%, which greatly affects the production efficiency. The tight oil reservoirs in the Ordos, Songliao and J...

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Problems solved by technology

However, the average hydrodynamic radius of linear vegetable gum and slick water molecules is greater than 500nm, which is much larger than the tight and shale throat radius. The water injection start-up pressure is high, and it cannot effectively enter the micro-nano matrix pores, and it does not have the ability to continuously improve the recovery of unconventional oil reservoirs. Ability

[0004] In recent years, the technology of supplementary energy recovery by imbibition displacement has become a research hotspot at home and abroad for the efficient development of unconventional reservoirs, mainly including surfactant huff and puff, carbon dioxide huff and puff, and nanofluid displacement, among which surfactant imbibition huff and puff is a compact The technology has good applicability. Although it has been applied in many tight oil fields (blocks) in North America, the core of imbibition is to maximize the capillary action of the injection medium. For water-wet reservoirs, after reservoir stimulation The injected fluid can effectively enter water-wet fractures or porous media and expand the swept volume of the wet phase. However, most reservoirs in the oil storage space are oil-wet, and the capillary force becomes capillary resistance, which will inhibit the formation of tight and shale matrix. Oil-water imbibition displacement, greatly reducing the degree of recovery

Secondly, the hydrodynamic size of the added surfactant and ion-matching liquid is in the micron level, and part of the surfactant is emulsified in situ with the oil phase, which virtually increases the difficulty of crude oil migration in the matrix; finally, the existing The fluid focuses on improving the wettability of the reservoir to enhance the imbibition effect, but it does not essentially solve the technical problem of low mobility of the crude oil reservoir, and it is difficult to fundamentally greatly increase the oil recovery of tight / shale oil reservoirs

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