油田压裂井地电法双参数联合监测技术与仪器研究

目前世界上水力压裂技术是老油田增产和低渗透油气田开发所应用最为广泛、最为有效的技术措施,油气储层裂缝分布规律监测对于油田勘探开发具有重要意义.本文利用压裂液在地层中的低阻特性与极化特性,基于井地电阻率法与激发极化法联合,根据位场理论镜像原理,采用三维有限差分,计算了多种压裂模型的地表传导电位与极化电位;通过非等权值的数据融合算法,计算了地表双参数异常,仿真数据的研究结果表明,双参数融合技术在异常提取方面具有明显优势.在此基础上,基于双波大功率联合发射技术、时分复用低噪声接收技术,研制了井地电法双参数联合监测仪器系统,共模抑制比达110 dB,有效地提取了微弱异常信号.通过陕西省富县华北局油田的压裂野外联合监测试验,表明了井地电法双参数联合监测仪器系统在水力压裂裂缝监测中具有较好的监测效果和较高的分辨率,解决了在低电阻率储层压裂或深井压裂情况下监测困难以及单一方法的监测结果多解性等问题,实现对油田水力压裂裂缝的实时监测.

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.