Identification and ranging of reservoir boundary in horizontal wells geosteering

To make quantitative measurement of the distance between the drilling tool and the reservoir boundary in horizontal well drilling, this paper presented the method of “layer-detection ranging”, established the physical and mathematic models and designed the circuit supporting the method. Moreover, the simulation experiment was made to verify the method's feasibility. With the method, the reservoir boundary was detected and the distance between it and the drilling tool was measured through transmitting directional high-frequency electromagnetic waves and receiving reflection waves, in process of measurement while drilling (MWD) in the horizontal well drilling. Two “layer-detection ranging” circuits, i.e. high-voltage narrow pulse and single frequency modulating pulse, were designed. Based on the circuit theory, a “layer-detection ranging” system was established and three media were used for simulation experiment. The results show that: more details of the reservoir are acquired from received waveforms using the high-voltage narrow pulse circuit, and the received waveforms are more easily identified and discriminated using the single frequency modulating pulse circuit; under the conditions of different media and distances, the relative error between the true distance and the distance measured with the “layer-detection ranging” method is less than 5%, suggesting that the method is reliable. Key words: geo-steering, horizontal well, MWD, electromagnetic wave, reservoir boundar