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Chemical spalling fracture forming method for shale core

A shale core and chemical technology, applied in the preparation of test samples, etc., can solve the problems that cannot meet the experimental requirements of fractured shale samples, and achieve the effects of controllable process, fast growth and rapid dissolution

Inactive Publication Date: 2018-09-07
SOUTHWEST PETROLEUM UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
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Problems solved by technology

[0005] In order to solve the technical problem that the existing rock core fracturing method cannot meet the experimental requirements of fractured shale samples, the object of the present invention is to utilize shale carbonate mineral components (i.e. calcite, dolomite)-sulfuric acid or containing sulfate ion The chemical reaction between acid fluids promotes shale fracture, forming multi-scale and complex fractures

Method used

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  • Chemical spalling fracture forming method for shale core
  • Chemical spalling fracture forming method for shale core
  • Chemical spalling fracture forming method for shale core

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] Embodiment 1: reaction solution is the acid solution containing sulfate ion, and raw material percentage is formed as follows:

[0030] Ammonium sulfate: 10%,

[0031] Hydrochloric acid: trace amount, keep the pH value of the reaction solution below 3;

[0032] Deionized water: 90%.

[0033] Experimental results ( figure 1 ) showed that after the acid solution containing sulfate ions reacted with the shale core, a large number of dense fractures appeared, and with the prolongation of soaking reaction time, the number of fractures increased and the fracture network became more complex; the low-resolution CT scan image ( figure 2 Left) It is confirmed that after the reaction, a large number of millimeter-scale fractures with fracture widths appeared in the shale core, and there is a certain connectivity between the fractures; the high-resolution CT scan image ( figure 2 Right) It is confirmed that after the reaction, a large number of fractures with micron-scale frac...

Embodiment 2

[0034] Embodiment 2: reaction solution is dilute sulfuric acid, and raw material percentage is formed as follows:

[0035] 98% concentration of sulfuric acid: 10%,

[0036] Deionized water: 90%.

[0037] The shale core soaking reaction time is 10 days.

[0038] Soaking test results ( image 3 ) shows that after dilute sulfuric acid reacts with shale cores, a large number of dense fractures appear, and the effect of chemical expansion of fractures is very prominent.

Embodiment 3

[0039] Embodiment 3: reaction solution is respectively dilute sulfuric acid, dilute hydrochloric acid, and raw material percentage composition is as follows:

[0040] Raw material ratio composition of dilute sulfuric acid solution: 98% sulfuric acid-10%, deionized water-90%;

[0041] Dilute hydrochloric acid solution raw material ratio composition: 37% concentration hydrochloric acid-25%, deionized water-75%;

[0042] The shale core soaking reaction time is 10 days.

[0043] Soaking test results ( Figure 4 ) shows that after dilute sulfuric acid reacts with shale cores, the amount of mercury intrusion increases significantly in the range of 20 to 5000 nm, which may be due to the formation of a large number of nano-scale and micron-scale cracks or pores after the carbonate mineral dissolution-gypsum precipitation reaction; However, after dilute hydrochloric acid reaction, only carbonate minerals are dissolved, no gypsum precipitates, and the amount of mercury intrusion only ...

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Abstract

The invention discloses a chemical spalling fracture forming method for a shale core. The chemical spalling fracture forming method comprises the following steps of selecting the shale core in which the total volume of calcite and dolomite ores is 1% to 10%, and soaking the shale core by a sulfuric acid solution with mass concentration of 1% to 10% or an inorganic acid with sulfate mass concentration greater than 1%; observing the formation and spalling process of a fracture in real time when a shale core sample is soaked; when the facture of the rock core sample reaches the specified experiment requirements, fetching out the shale core, flushing, and drying for further use. The chemical spalling fracture forming method has the advantages that the feature requirements of the real reservoirfracture system, such as coarse fracture surface, multiple fracture widths and network shape, can be met; the limitation by the size and shape of the shale core is avoided.

Description

technical field [0001] The invention relates to the technical field of petroleum and natural gas exploitation, in particular to a method for creating fractures by chemical expansion of shale cores. Background technique [0002] Fractures are the main seepage channels of tight shale oil and gas reservoirs, so it is very important to simulate the real fracture conditions of reservoirs to carry out fluid (oil, gas, water, drilling fluid, etc.) seepage experiments. Shale has high content of brittle minerals and well-developed bedding. The fractures in real reservoirs are mainly characterized by multi-scale (nanoscale, micron-scale and millimeter-scale) and network. Under the existing drilling technology conditions, it is difficult to obtain representative core samples of shale fractured intervals by drilling and coring methods on site, so artificial fractures are generally used in the laboratory to prepare fractured core samples. [0003] In the prior art, the core artificial f...

Claims

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Application Information

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IPC IPC(8): G01N1/28
CPCG01N1/28
Inventor 陈强游利军康毅力许成元豆联栋程秋洋闫霄鹏
Owner SOUTHWEST PETROLEUM UNIV
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