Hydraulic fracturing ground stress measuring system suitable for confined water stratumand method of hydraulic fracturing ground stress measuring system

Abstract

The invention provides a hydraulic fracturing ground stress measuring system suitable for a confined water stratumand a method of the hydraulic fracturing ground stress measuring system. The hydraulicfracturing ground stress measuring system comprises a water-isolating stratum equipment group and a confined water stratum equipment group which are connected in series to a central steel pipe; a borehole penetrates through a water-isolating stratum and extends to a to-be-measured crustal stress position of a confined water stratum; the water-isolating stratum equipment group is installed at theposition, on the water-isolating stratum, on the central steel pipe; and the confined water stratum equipment group is installed at the position, on the confined water stratum, on the central steel pipe. The hydraulic fracturing ground stress measuring system has the advantages that (1) a closed space can be formed on the lower part of the water-isolating stratum through the used water-isolating stratum equipment group, the phenomenon that the excess pore water pressure in the hole wall of the confined water stratum dissipates can be avoided, and thus the pore water pressure in the confined water stratum is accurately measured; and (2)after the water-isolating stratum equipment group forms the closed space on the lower part of the water-isolating stratum, continuous high-pressure water inrush from the hole wall of the confined water stratum can be avoided, thus the confined water stratum at the measured position is always in the original natural crustal stress environment, and the measurement accuracy is ensured.

Description

technical field [0001] The invention belongs to the technical field of geostress measurement, and in particular relates to a hydraulic fracturing geostress measurement system and method suitable for confined water formations. Background technique [0002] Hydraulic fracturing is currently the only feasible method for measuring the deep crustal stress. Therefore, it has a very important application in seismic crustal stress measurement and large tunnel engineering ground stress measurement. [0003] At present, the hydraulic fracturing method is mainly used to measure the ground stress of the unconfined water formation. The measurement method is as follows: first, drill a borehole to reach the position where the ground stress needs to be measured; read the natural head pressure of the measured position at this time; Then, install an upper packer and a lower packer on the upper and lower parts of the borehole where in-situ stress needs to be measured. After the upper packer a...

AI Technical Summary

Problems solved by technology

[0008] (2) If the traditional hydraulic fracturing method is used, that is, to drill a borehole reaching the confined water formation, and install the upper packer and the lower packer in the confined water formation, at this time, due to the upper packer The borehole above the reservoir is connected to the external atmosphere, and there is an excess static pore water pressure P′ in the confined water formation 0 , therefore, the pore water in the confined water formation will continuously break into the borehole above the upper packer, forming a continuous high-pressure water inrush phenomenon on the hole wall; the high-pressure water inrush will make the ultra-static pore water pressure in the rock near the borehole P' 0 Dissipation causes the effective stress on the rock particle skeleton to increase, which leads to the destruction of the original stress distribution state in the hole wall rock, that is, the measurement object is destroyed, making the measurement invalid; therefore, in confined water formations, the traditional The measurement of ground stress by hydraulic fracturing technology will have the potential problem of the measurement object being destroyed by disturbance. If a pressure sensor is arranged in the isolated space between the upper packer and the lower packer at this time, and the When injecting high-pressure water for hydraulic fracturing, the pressure change curve with time collected by the pressure sensor at this time is the pressure change curve with time of the destroyed confined water formation, not the original undamaged pressured water formation. Therefore, it is impossible to obtain accurate in-situ stress values ​​by analyzing the pressure-versus-time curve of the destroyed confined water formation.

[0010] It can be seen that the traditional hydraulic fracturing method is not suitable for in-situ stress measurement in confined water formations, so as to realize the in-situ stress measurement suitable for confined water formations is an urgent need to solve

Images