Research on borehole-surface joint electrical double-parameter monitoring for the hydraulic fracturing in oilfields

Hydraulic fracturing is one of the most widely used and the most effective methods in EOR enhancement for old oilfields and in low-permeability oilfield exploitation. So fracture monitoring is critical for oilfield exploration and exploitation. In terms of low resistivity and high polarizability of fracturing fluids in strata, this work adopts the joint method of borehole to surface resistivity and induced polarization to monitor the hydraulic fractures in the oilfield. Based on the mirror principle, the abnormal potentials of conduct current and polarized current are computed for any geometry of fractures via three-dimensional finite time difference. The fusion abnormal of double parameters is derived through non-equal weight fusion to improve the ability of anomaly identification. Simulations show the data fusion for double parameter electrical methods has the advantage of extracting anomalies. Based on the forward modeling, we developed the borehole-surface joint electrical instrument for fracture monitoring with double waveforms transmitter and time division multiplexing receiver. It achieves the common-mode rejection ratio of 110 dB and extracts weak abnormal signals effectively. The oilfield test in Fuxian proves the borehole-surface joint electrical instrument has better ability and higher resolution for hydraulic fracture monitoring. This consequently solves the problems encountered when fracturing is in oil reservoirs of low resitivity or in deep reservoirs. It can realize real-time monitoring of hydraulic fractures in oilfields.