基于等离子体技术的新型高分辨率远探测声波测井声源研究

Remote-exploration acoustic reflection logging technology has a very significant application prospect in those aspects like fine description of reservoirs, identification and evaluation of unconventional reservoirs, optimization and adjustment of well trajectory for drilling. Unfortunately, the radial exploration depth of this tool is only tens of meters without taking high resolution into consideration at present, which greatly limits its wide application. Increasing the effective energy of directional radiation from the transmitter is the most effective way to improve the radial exploration depth and ensure the resolution. In this project, three aspects of the plasma source will be studied: acoustic and electrical characteristics with their influencing factors, method of downhole directional cumulative radiation, acoustic reflection logging response of geological structure near the well. We aim to develop a downhole plasma source which has features of high power, wide band, good performance of three-dimensional directional radiation, stability and controllability. Using this source replace current piezoelectric transducer could obviously improve the comprehensive performance of the transmitter. Based on the remote-exploration logging technology proposed in this project, future multi-frequency logging can not only increase the exploration depth to hundreds of meters, but also make high-resolution imaging of fractures near the wellbore zone, which could better serve the exploration and development of hydrocarbon reservoir. Retrieval result shows that the remote-exploration logging technology based on the plasma source proposed in this project has not been reported at home and abroad.

远探测声波反射测井技术在储层精细描述，非常规油气藏识别与评价，钻井井眼轨迹的优化与调整等方面有着非常重要的应用前景。但是，目前该类仪器的探测深度只有数十米且不能兼顾高分辨率，这极大地限制了该技术的广泛应用。提高发射源定向辐射的有效能量是提高仪器的径向探测深度同时保证分辨率的最有效途径。本项目拟研究等离子体声源的声电特性和影响因素，声源的井下定向聚能辐射方法，井旁地质构造的声反射测井响应3个方面的内容，开发一种大功率、宽频带、三维定向辐射性能好、稳定可控的井下声源，代替当前的压电换能器声源，从而提高远探测测井声源的综合性能。使用本项目拟发展的等离子体声源远探测测井技术进行多频率测井，有望将仪器的探测深度提高到数百米，而且能够对近井带的裂缝等构造进行高分辨率成像，可以更好地服务于油气勘探与开发。经检索，本项目提出的等离子体声源远探测测井技术在国内外尚未见报道。

远探测反射声波测井在大范围储层描述、非常规油气藏识别、钻井地质导向等方面有重要的应用潜力。目前该类仪器的探测深度浅且不能兼顾高分辨率，限制了该技术的进一步发展。提高发射源向井旁地质体定向辐射的有效能量是一种有效的解决方法。本项目探索了等离子体声源的声电特性与影响因素、声源的井下定向聚能辐射方法、井旁地质构造的声反射测井响应、等离子体远探测声波测井数据的井下处理这4个方面的内容，为将等离子声源应用到高分辨率远探测反射声波测井进行了前期的理论和应用研究。研究结果表明，等离子体声源能够产生大功率、宽频带的冲击波，导电介质、温度和静水压等因素对声源的声电特性影响较大；仪器内小尺寸旋转抛物面反射罩能够改变声源向井孔和地层中辐射声场的三维指向性，将反射罩轴线附近小角度内的声压提高2倍；声源反射罩将井旁地质体转换反射波和横波反射波的信号提高到2倍以上，而井壁模式波和纵波反射波仅为1.1倍，反射波的信噪比（尤其是横波反射波）得到很大提高；基于轴向不同源距的线性阵列和周向不同方位的圆弧阵列接收到的信号，含声源反射罩的等离子体远探测方法能够有效判断井旁反射体的方位、距井距离和倾向倾角等特征，从而提高仪器性能；井下数据处理是等离子体远探测声波测井探测深度和精度提高趋势下的关键技术，基于DPCM算法的井下数据压缩能够将远探测声波测井的电缆传输效率和测井速度提高至2倍。本项目的研究成果有望加快等离子体声源在远探测声波测井中的应用，使其更好地发挥井下 “望远镜”和“显微镜”的优势，为油气勘探与开发服务。