Method for improving recovery ratio of sensitive heavy oil reservoir

Abstract

The invention provides a method for improving the recovery ratio of a sensitive heavy oil reservoir. The method utilizes combined application of a high-temperature clay stabilizer, a sustained-release acidizing fluid system, an efficient oil-displacing agent and carbon dioxide in the development of the sensitive heavy oil reservoir to improve the single-well development effect and the recovery ratio of the sensitive heavy oil reservoir. The technical scheme is that the method comprises the steps of first utilizing the temperature-sensitive sustained-release acidizing fluid system to treat a polluted treat near-well-bore zone, then injecting the liquid carbon dioxide, utilizing the high-temperature clay stabilizer to protect an oil layer before steam injection and injecting a high-temperature oil-displacing agent system while the steam injection; then performing well shut-in for soaking and well opening for gushing and putting a pump into a well to perform continuous oil extraction. A field test shows that the oil-steam ratio of an average period of a vertical well reaches to 0.4, the oil-steam ratio of an average period of a horizontal well reaches to 0.6, and the periodic oil yield exceeds 1000t. A laboratory test shows that the final recovery ratio can reach to higher than 35% by adopting a process related to the method for improving the recovery ratio of the sensitive heavy oil reservoir.

Description

technical field [0001] The invention relates to an oilfield exploitation technology, in particular to a combination application of a high-temperature clay stabilizer, a slow-release acid solution system, a high-efficiency oil displacement agent and carbon dioxide in the development of sensitive heavy oil reservoirs to improve the development effect of a single well and increase the sensitivity A new method for the recovery of heavy oil reservoirs. Background technique [0002] With the massive consumption of conventional oil and gas resources and the rising demand for oil, heavy oil resources have become the main potential for lower development due to their wide distribution, huge reserves, and low reserves utilization rate. Domestic heavy oil resources are very rich, and the estimated proven reserves are 8 billion tons. Of the 2.06 billion tons of proven heavy oil reserves, 701 million tons are unused geological reserves. A considerable part of the undeveloped heavy oil re...

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Problems solved by technology

[0003]⑴ High clay content, strong water sensitivity, difficult oil layer protection

[0005] (2) The oil layer is thin, the net-to-total ratio is low, and the heat utilization rate of steam huff and puff is low

[0006]Because the oil layer is thin, the heat loss of the steam injected into the oil layer from the upper and lower cover layers increases, the lateral sweep volume of the oil layer becomes smaller, and the heat utilization rate decreases; in addition, the net total The heat ratio is also an important factor affecting the heat utilization rate. Due to the existence of the thin muddy interlayer, the heat loss in the oil layer increases, and part of the heat is consumed in the interlayer.

When the effective oil layer thickness and steam injection rate are the same, as the thickness of the interlayer increases, that is, the net-to-total ratio decreases, the oil-steam ratio becomes significantly lower, mainly because the heating radius of the oil layer becomes smaller, the heat utilization rate is low, and the throughput effect becomes smaller. Difference

[0007](3) Crude oil has high viscosity, insufficient natural energy, and poor fluid supply capacity of oil wells

Both chemical cold recovery and conventional thermal recovery will produce a large amount of liquid entering the well, and the serious water sensitivity of the reservoir will lead to a huge loss of permeability. The failure of injection and production is an important system of this contradiction. Even if the anti-swelling hand is used before the process , the permeability damage caused during the drilling and completion process cannot be restored

In addition, the oil layer in the block is thin, the net-to-gross ratio is low, the heat loss is huge during thermal recovery development, and the thermal efficiency utilization rate is less than 40%. In addition, the reservoir energy is scarce and the recovery pressure is insufficient, resulting in a short thermal recovery production cycle and poor economic benefits.

[0010]Therefore, among the above-mentioned undeveloped sensitive heavy oil reserves, especially sensitive heavy oil reservoirs with a water sensitivity index greater than 90% and a layer thickness less than 6m are scarce It is of great practical significance to alleviate the conflict of crude oil demand and ensure the development of the national economy to explore the economic development mode of this type of oil reservoir with mature and supporting production technology, and to increase the degree of production and recovery of the corresponding reserves.

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