阅读说明：本技术 一种改善页岩孔渗条件的新方法 (Novel method for improving shale hole permeability condition ) 是由 赵金树 于 2021-07-27 设计创作，主要内容包括：一种改善页岩孔渗条件的新方法,涉及油井提高采收率技术领域,包括以下步骤：a.页岩井水平段依次注入液态二氧化碳、废三甘醇液、清水；b.注入地层的二氧化碳进入地层远端孔喉半径较小的孔隙及裂缝中；c.完成注入量后,井口快速降压,使井口与地层形成大压差,在大压差的作用下,已经形成的细小颗粒桥堵就会被冲破、冲碎,变成单一颗粒或较小的颗粒团,由大量返排的超临界二氧化碳携带到井筒；d.页岩中大量的钙、镁在近井周围与注入的二氧化碳、废三甘醇液发生反应,生成三甘醇、二甘醇、二氧化碳络合物,生成物破坏了近井地带的岩石上吸附的油膜,将油膜改造成油滴,在快速返排过程中,油滴被携带出来,改善了近井周围的孔渗条件。(A new method for improving the shale hole permeability condition relates to the technical field of oil well enhanced oil recovery, and comprises the following steps: a. liquid carbon dioxide, waste triethylene glycol liquid and clear water are sequentially injected into the horizontal section of the shale well; b. injecting carbon dioxide into the stratum into pores and cracks with smaller pore throat radius at the far end of the stratum; c. after the injection amount is finished, the wellhead is quickly depressurized to form a large pressure difference between the wellhead and the stratum, and the formed fine particle bridge plug can be broken and broken under the action of the large pressure difference to become single particles or smaller particle clusters which are carried to a shaft by a large amount of flowback supercritical carbon dioxide; d. a large amount of calcium and magnesium in the shale react with injected carbon dioxide and waste triethylene glycol liquid around a near well to generate a triethylene glycol, diethylene glycol and carbon dioxide complex, the product destroys an oil film adsorbed on rocks in a near well zone, the oil film is reformed into oil drops, and the oil drops are carried out in the rapid flow-back process, so that the pore permeation condition around the near well is improved.)

1. A novel method for improving shale permeability conditions is characterized by comprising the following steps:

a. injecting 500 tons of liquid carbon dioxide and 100m per 1000 meters of horizontal section of the shale well³Waste triethylene glycol liquid and 100m³Clean water, which is sequentially filled with liquid carbon dioxide, waste triethylene glycol liquid and clean water;

b. the carbon dioxide injected into the stratum is in a supercritical state and enters pores and cracks with small pore throat radius at the far end of the stratum due to strong liquidity and penetrability;

c. after the injection amount is finished, the wellhead is quickly depressurized to form a large pressure difference between the wellhead and the stratum, and the formed fine particle bridge plug can be broken and broken under the action of the large pressure difference to become single particles or smaller particle clusters which are carried to a shaft by a large amount of flowback supercritical carbon dioxide;

d. a large amount of calcium and magnesium in the shale react with injected carbon dioxide and waste triethylene glycol liquid around a near well to generate triethylene glycol, diethylene glycol and carbon dioxide complexes, products destroy an oil film adsorbed on rocks in a near well zone, the rocks with the oil film adsorbed smoothly are transformed into rocks with rough oil drops, and granular shale oil deposited on the surfaces of the rocks is carried out in the rapid flowback process, so that the hole seepage condition around the near well is improved;

e. hydration after the injected water permeates, improves the page structure and improves the permeability.

2. The novel method of improving shale permeability conditions of claim 1, wherein: and (b) adding no anti-swelling agent into the clear water injected in the step (a).

Technical Field

The invention belongs to the technical field of oil well recovery efficiency improvement, and particularly relates to a novel method for improving shale hole permeability conditions.

Background

The content of the Daqinggulong shale clay is high, but because the shale is positioned at the structural depression, the reservoir is buried deeply and has high temperature, a large amount of clay minerals are converted into illite to form secondary quartz, the brittleness is increased, and the advantage condition is provided for the effective exploitation and development of shale oil. Due to the brittle nature of the gulong shale and the addition of the shale development, after large-scale close cutting and fracturing, the rock is severely crushed and a large amount of fine particles are generated. Along with the continuous production in the later period, the part of fine particles can gradually move to the bottom of the well and become larger particle groups in a bridging mode, effective pores and cracks around the bottom of the well are blocked, the permeability of a reservoir is reduced, the yield of the oil well is forced to be reduced, and the blowout stopping stage is started in advance. In addition, along with the extension of exploitation time, the oil saturation of near-well surrounding zone constantly reduces, some zone areas are close to the constraint oil saturation, because the wettability of gulong shale reservoir is partial oleophylic, when far-end underground crude oil flows to the shaft bottom in-process from the stratum distal end, in the zone area that is close to the constraint oil saturation, some shale oil will be adsorbed by stratum rock granule secondary, isolated oil film can constantly tile all around, the thickening, the effective pore space of reservoir has been reduced, the effective permeability of reservoir has been reduced, lead to the rapid decline of oil well output. In view of the above-mentioned two problems of plugging, a new method is needed to solve the problem of plugging shale oil, improve the conditions of pore permeation around the near well, and further increase the ultimate recovery rate of shale oil.

Disclosure of Invention

In order to solve the problem of blockage formed under two conditions in the background technology, the invention provides a novel method for improving the shale pore permeation condition.

The technical scheme provided by the invention is as follows: a novel method for improving shale permeability conditions, comprising the steps of:

a. injecting 500 tons of liquid carbon dioxide and 100m per 1000 meters of horizontal section of the shale well³Waste triethylene glycol liquid and 100m³Clean water, which is sequentially filled with liquid carbon dioxide, waste triethylene glycol liquid and clean water without adding any anti-swelling agent;

b. the carbon dioxide injected into the stratum is in a supercritical state and enters pores and cracks with small pore throat radius at the far end of the stratum due to strong liquidity and penetrability;

c. after the injection amount is finished, the wellhead is quickly depressurized to form a large pressure difference between the wellhead and the stratum, and the formed fine particle bridge plug can be broken and broken under the action of the large pressure difference to become single particles or smaller particle clusters which are carried to a shaft by a large amount of flowback supercritical carbon dioxide;

d. a large amount of calcium and magnesium in the shale react with injected carbon dioxide and waste triethylene glycol liquid around a near well to generate triethylene glycol, diethylene glycol and carbon dioxide complexes, products destroy an oil film adsorbed on rocks in a near well zone, the rocks with the oil film adsorbed smoothly are transformed into rocks with rough oil drops, and granular shale oil deposited on the surfaces of the rocks is carried out in the rapid flowback process, so that the hole seepage condition around the near well is improved;

e. hydration after the injected water permeates, improves the page structure and improves the permeability.

The invention has the beneficial effects that:

1. the invention enters pores and cracks with smaller radius of the pore throat at the far end of the stratum by virtue of the fluidity and penetrability of the carbon dioxide in a supercritical state, after injection is finished, the pressure of a wellhead is quickly reduced to form large pressure difference between the wellhead and the stratum, and the formed fine particle bridging plug can be broken and broken under the action of the large pressure difference to become single particles or smaller particle clusters, and the single particles or the smaller particle clusters are carried to a shaft by a large amount of returned supercritical carbon dioxide.

2. Because the shale contains large content of calcium and magnesium, the invention generates a complex of triethylene glycol, diethylene glycol and carbon dioxide by reacting the calcium and magnesium components with injected carbon dioxide and waste triethylene glycol liquid, the product destroys an oil film adsorbed on rocks in a near well zone, the rocks with smooth adsorbed oil films are transformed into rocks with rough adsorbed granular oil drops, and granular shale oil deposited on the surfaces of the rocks is carried out in the process of quick return discharge, so that the pore permeation condition around a near well is improved.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more apparent, the present invention is described in further detail below.

The invention comprises the following steps:

a. 500 tons of liquid carbon dioxide, 100m3 waste triethylene glycol liquid and 100m3 clean water are injected into the horizontal section of the shale well every 1000 m, the liquid carbon dioxide, the waste triethylene glycol liquid and the clean water are sequentially injected, and no expansion-preventing agent is added into the clean water, because the gulong shale has low water sensitivity, and due to hydration, the shale can improve the page structure and is beneficial to improving the permeability.

b. Carbon dioxide injected into the formation is in a supercritical state and enters pores and fractures with small pore throat radius at the far end of the formation due to high fluidity and penetrability.

c. After the injection amount is finished, the wellhead is quickly depressurized to form a large pressure difference between the wellhead and the stratum, and the formed fine particle bridge plug can be broken and broken under the action of the large pressure difference to become single particles or smaller particle clusters which are carried to a shaft by a large amount of flowback supercritical carbon dioxide; because the supercritical carbon dioxide has higher density and obvious carrying effect, the fine particles can be finally taken out of the ground, and the problem of inorganic blockage caused by large-scale dense cutting can be solved.

d. A large amount of calcium and magnesium in the shale react with injected carbon dioxide and waste triethylene glycol liquid around a near well to generate triethylene glycol, diethylene glycol and carbon dioxide complexes, products destroy an oil film adsorbed on rocks in a near well zone, the rocks with the oil film adsorbed smoothly are transformed into rocks with rough oil drops, and granular shale oil deposited on the surfaces of the rocks is carried out in the rapid flowback process, so that the hole seepage condition around the near well is improved.

Due to the comprehensive effects of the two aspects, the problem of blockage in the shale exploitation process is solved, the permeability is improved, and finally the shale oil well yield is improved.

Successful examples: GL1-1 well horizontal segment length 1200 m, 600 tons of liquid carbon dioxide and 120m are injected into the well in sequence³Waste triethylene glycol liquid and 120m³The average injection pressure of the well mouth is kept at about 20 MPa. After the injection amount is finished, the quick backflow is carried out within 10 hours, and the backflow liquid contains a large amount of fine rock debris particles and oil stains, so that the blockage removing effect is achieved. When the pressure of the well mouth is reduced to 1MPa, the well is organized to be opened for production, after the well is opened, the average daily oil increment of the well is 5 tons, the accumulated oil increment is 870 tons, the blockage removing effect of the carbon dioxide composite liquid is obvious, and the effect of effectively improving the blockage removing effect of the carbon dioxide composite liquidThe pore permeation condition of the reservoir obtains obvious oil increasing effect.