Research On Hydraulic Fracturing Monitoring Based On Surface-Borehole Potential Method

Hydraulic fracturing technology is an important mean to increase the production of oil fields currently.The monitoring of fracture morphology during fracturing is an important technical problem.Line current model is widely used to simulate subsurface fracture in current well-ground potential method fracturing inversion research which makes the fracture shape inversed quite different from the actuality.Also,the widely used Gaussian Newton method in the inversion solution requires calculating Hessian matrix in each iteration step which reduces the speed of the solution.The factors like the slope of the surface topography of the surveyed ground can also affect the measurement result which causes errors in fracturing monitoring.Conventional theoretical models are mostly single homogeneous resistivity models which generally lack adaptability facing complex stratigraphic structure.In order to solve the above problems,the paper constructs an isosceles triangular surface current source fracture model which makes the inversion result more in line with the actual fracture morphology.At the same time,the Quasi-Newton algorithm is used to invert the bottom,height,depth and current s hunt coefficient of the triangular fracture model.The Quasi-Newton algorithm replaces calculating the time-consuming Hessian matrix by solving a positive definite matrix similar to the Hessian matrix which ensures the accuracy of the solution,the convergence speed and significantly reducing the calculation time.The paper also conducts a detailed research of the effect of ground slope on the measurement results.By adding the slope factors in the inversion formula,the effect of the ground slope on the inversion result can be corrected.The influence of different stratigraphic structures on the measurement results is also studied,including the geological models with multiple layers of different resistivity distributions in the vertical direction.The research results have certain guiding significance for the actual fracturing monitoring.The sink experiment device for potential method fracture monitoring was built in the laboratory,and the potential method instrument developed by the project team was used to get the potential method monitoring data of fractures of different depth,length,thicknesses,azimuth and number.The data obtained is used to verify the inversion algorithm and summarize relevant laws.