小直径双模式阵列感应测井仪设计

为了解决小井眼以及水平井电阻率测量的需要,设计了仪器外径为70mm的小直径阵列感应测井仪。直井和斜井可采用电缆直传测井的方式,水平井可采用泵出或钻具输送的存储式测井方式。仪器采用5组线圈,3个工作频率同时测量井下地层的感应信号,通过数字信号处理技术消除各种环境影响,测井仪一次下井可以同时获得3种纵向分辨率、5种径向探测深度合成电阻率曲线。电路以FPGA+DSP高集成度电路为核心,采用高温元器件,无保温瓶设计。FPGA负责逻辑控制和采样处理,DSP负责通讯和数学运算。高集成度、高温器件的选用,满足了仪器的小型化和水平井长时间测量的要求。仪器工作温度指标为150℃/30h,最大工作压力140MPa,测量精度±2mS/m或3%,测量范围为0.2~2000Ω·m。

The Design of a Small-diameter Dual-mode Array Induction Logging Tool

In order to meet the need of resistivity measurement in slim holes and horizontal wells,a small diameter array induction logging tool is designed with an outer diameter of 70 mm.Cable conveyed logging tools are available to vertical wells and deviated wells.Pipe conveyed or pumping logging tools are available to horizontal wells.The new tool uses five groups of coils and three frequencies to measure the induced signals from downhole formation at the same time,and eliminates various environmental impacts by digital signal processing.Three kinds of vertical resolution and five kinds of radial depth can be obtained simultaneously,and synthesized to a resistivity curve in a run.The circuit is based on FPGA+DSP(highly integrated),and is composed of high-temperature parts without vacuum flask.FPGA is responsible for logical control and sampling.DSP is responsible for communication and mathematical operation.The highly integrated and high-temperature parts meet the requirements of miniaturization of the tool and long-term measurement in a horizontal well.The tool can work for 30 h at 150℃.Its maximum working pressure is 140 MPa,measurement accuracy is±2 mS/m or 3%,range is 0.2Ω·m to 2 000Ω·m.