Study On Three-dimensional Geostress Determining Method With Hydraulic Fracturing Technique In Single Borehole

Relying on "the Tanlu fault zone in situ information repeated observation andseismogenic mining research" project of the Institute of Crustal Dynamics, ChinaEarthquake Administration, this paper aims to analyze error and verifyaccuracy ofhydrofracturing test systembased on classical two and three-dimensionalhydrofracturing measurement method, and seeks a perfect and applicable evaluationsystem and analysis method in practice.Firstly, based on the domestic and foreign research data, the hydraulic fracturingtheory and method were investigated, and the existing problems in these theory andmethod were analyzedand the improvement methods were proposed.Secondly,standardized hydraulic scientific fracturing measurement system wasestablishedinthree aspects: the measuring instruments, measuring software andcomputing software. The old R232serial port data acquisition instrument wasimprovedusing the USB data collector and the height of wave filter module. A set ofcomplete three-dimensional single hole hydraulic fracturing measurement system wascompiled in Visual Basic language so as torealize the automatic measurement ofhydraulic fracturing treatment and reduce human error. Finally, based the geo-stressdata in Red River town,Changle County,Shandong province,the applicability andaccuracy of hydraulic fracturing interpretation method was analyzed, thethree-dimensional hydraulic fracturingimprovement methods was inspected, and thereliability of hydraulic fracturing in-situ stress measurement system was checked.Based onthe above research, the following new understanding was obtained:(1) Hydraulic fracturing method developed well and changed from the originaltwo-dimensional plane stress measurement intothe three-dimensional in-situ stressmeasurement technology.The measurement accuracy and technological level alsoimproved constantly. Based on the analysis of new three-dimensional hydraulicfracturing in-situ stress measurement methods, this paper suggests that the shear stressshould not be0, and presents the calculation method of the shear rupture stress strength using crack surface friction.(2) The difficulty in hydrofracturing is how to interpret its attenuation curve.Fivekinds of interpretation methods to identify the shut-in pressure were summarized, andthe analysis method ofaverage slope changing rate was proposed.Better results weregotten in practice.(3) Considering the standard fracturing cure, the dt/dp method and Maskatmethod were suggested to interpret results and other methods were used to reviseresults for classical hydrofracturing.While for the HTPF, the rock of test section wasaffected by crustal stress rupture. Therefore, rock structure is loose and the fracturingcurve is more complex. This condition has a great effect on Maskat method, and thereliability of interpretation is relatively low. It also has a big influence on the usingofdt/dp method which will induce a larger range of error. The HTPF shouldinterpretby using single cutting method ordp/dt method, which also should beproofread and corrected by dt/dp.