Method for determining length of plugging section and turning distance of new fracture during temporary plugging fracturing at tip of shale fracture

Abstract

The invention relates to a new process design method of an unconventional oil and gas reservoir repeated fracturing technology, in particular to a method for determining the length of a plugging section and the turning distance of a new fracture during temporary plugging fracturing at the tip of a shale fracture. The method comprises the steps that a temporary plugging agent is injected into the tip of the pressure fracture, and after fracturing fluid enters a main fracture, the pressure of the fracturing fluid in the main fracture forms a stress shadowing effect around the fracturing fluid; the stress state around the original main fracture is affected by the stress shadowing effect; the induced stress is superposed with the original ground stress, and the original ground stress state changes; the tip of the fracture is completely plugged, and new fracture with different direction from the original fracture is generated at the end of the plugging section; and further, at the free surface of the temporary plugging agent, the temporary plugged fractured new fracture extends perpendicular to the original fracture direction until the induced stress difference is equal to the horizontal ground stress difference, and the turning distance of the new fracture is calibrated at the position by giving the actual horizontal ground stress difference. Therefore, the potential resources of shale gas on the two sides of the main fracture surface are reasonably exploited.

Description

technical field [0001] The invention relates to a new process design method for the repeated fracturing technology of oil and gas reservoirs, in particular to a method for determining the length of the plugging section and the turning distance of new fractures during temporary plugging and fracturing at the tip of shale fractures, and belongs to a new type of repeated fracturing The technology mainly focuses on the secondary efficient exploitation of oil and gas resources in unconventional reservoirs such as shale and tight oil layers. Background technique [0002] my country's shale gas resources are very rich, and it is expected to become a new oil and gas growth point. At present, hydraulic fracturing and horizontal drilling technology are the main stimulation methods used in shale gas exploitation at home and abroad. However, the permeability and porosity of shale gas reservoirs are extremely low, and volume fracturing of the reservoir is required to make the fracturing...

AI Technical Summary

Problems solved by technology

[0004] The traditional refracturing methods mostly use 1) secondary fracturing without temporary plugging agent and 2) secondary fracturing with temporary plugging agent plugging the hole. The increase in production is not significant; in the latter case, it is more difficult to completely seal the hole because the subsequent fracturing fluid is easy to break through the original hole roar

In addition, the diversion distance of new fractures caused by the inconspicuous geostress diversion around the wellbore is limited

Both the fluid pressure in the fracture and the formation pressure have a significant effect on the in-situ stress diversion. The fracture tip is the area with the most significant difference in formation pressure reduction, and it is also the significant area where the fluid in the fracture causes the stress shadow effect around the fracture. The temporary plugging agent is pumped at the fracture tip The construction difficulty is relatively small, and the turning distance of new fractures is relatively considerable, but there is still a lack of methods to guide the engineering to determine the reasonable amount of temporary plugging agent and evaluate the turning distance of new fractures

Images